Trace Element Contamination of the
Rio Colorado in Argentina
by
David Frederic Ashcroft
A DISSERTATION SUBMITTED TO THE DEPARTMENT OF
PHYSICS,
UNIVERSITY OF SURREY, IN PARTIAL FULFILMENT OF THE
DEGREE OF
MASTER OF SCIENCE IN RADIATION AND ENVIRONMENTAL
PROTECTION
Department of Physics
Faculty of Electronics & Physical Sciences
University of Surrey
September 2009
© David Frederic Ashcroft 2009
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ABSTRACT
Trace element contamination in the surrounding Argentinean area of the Patagonia region has
been acknowledged and published in various reports relating to the agricultural industry, petro
industry, water treatment, sewage and other affiliated industrial activities. In this study samples
of water, sediment and plant material were collected from various locations spread along the
Rio Colorado, which is situated north the Rio Negro and Grande Canal, in part to copy the
sampling regime implemented by Paddock, 2006 and Arribere et al., 2002. The sampling sites
were specifically targeted to highlight areas of contamination and were located in four primary
sites: Rincón de los Sauces; Catriel; Embalse Casa de Piedra dam; and the town of Rio
Colorado. These sites house fruit orchards, petrochemical plants, potash industry, sewage
discharge and water treatment plants. All water samples were filtered (using 20 micron filter)
and analysed for trace elements using inductively coupled plasma mass spectrometry (ICPMS), ion chromatography and inductively coupled plasma atomic emission spectrometry (ICPAES). The sediment and plant material were dry-ashed using a muffle furnace (550oC) and
acid dissolved using HNO 3 :HF digestion method, with the resultant digests analysed using ICPMS.
Flame atomic absorption spectrometry (FAAS) was also implemented to ascertain trace
element concentrations in the samples. In addition, sediment sub-samples, maintained in a wet
state, were prepared and analysed for some seventeen USEPA priority polycyclic aromatic
hydrocarbons (PAHs).
The highest river trace element levels in water samples are seen at Catriel on the sewage
discharge site with selected trace elements exceeding the guidelines for Vida Acuática.
Similarly, the sewage discharge site at Rio Colorado possesses high levels of an abundance of
chemicals all associated to this anthropogenic process. Sites at Rincón de los Sauces and
Catriel contain significantly high levels of selected trace elements, many of which are attributed
to oil products (namely V, Sb, Cr, Cd, Mn & Pb) with several elements (Cr, Cd, Pb & As)
exceeding guidelines for Vida Acuática.
Nitrates levels were found to be high at all four
sampling locations with values above the drinking water guidelines as prescribed by WHO and
UK guidelines. Predominantly, industrial and sewage processes are responsible. Drinking
water from the faucets at all four sampling areas is generally deemed well within drinking water
guideline quality standards, although there a couple of areas of concern. Drinking water from
faucets in Rincón de los Sauces and Rio Colorado possess very high lead concentrations with
values typically above the WHO drinking water guidelines. A possible explanation for this trend
may be due to lead pipes being used for domestic distribution. Similarly, drinking water from
faucets in Rincón de los Sauces and Rio Colorado also possess high concentrations of
sulphate that may be associated to the use of metal sulphates in local chemical water treatment
processes.
Sediment samples from both Catriel and Rio Colorado show clear evidence of heavy metal
contamination and show elevated levels above those quoted in the Dutch Adjusted and UK
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CLEA guidance limits. Likewise for aquatic plant samples, with Rincón de los Sauces being
contaminated with the most trace elements measured.
In summary, it must be stressed that two of the Rio Colorado sites are highly contaminated from
industrial and sewage discharge which may be of significance in comparing the two regions.
More sediment samples need to be collected from the Rio Colorado at all sampling areas,
especially Rincón de los Sauces, where no sediment samples were taken in this study, and
Catriel in order to assess the long-term impact of industrial activities (oil extraction and
processing).
ACKNOWLEDGEMENTS
Firstly I would like to take the pleasure in thanking and acknowledging Prof Neil Ward for his
support and assistance during the compilation of this report. I would also like to thank Jenny
O’Reilly for all of her help with the sample analysis using the ICP-MS and FAAS instruments.
Finally I would like to thank Dr P Regan and Miss A Smith for their contribution and assistance
throughout ambiguous times.
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CONTENTS
Page No
1. Rio Colorado Valley and Heavy Metal Contamination ......................................................... 7 1.1 Introduction to the Rio Colorado Basin System .................................................... 7 1.2 Pollutant Model – Pathways.................................................................................. 8 1.2.1 Irrigation Water ..................................................................................................... 8 1.2.2 Agricultural Soils and Aquatic Plants .................................................................. 10 1.3 Environmental Trace Elements and Heavy Metals ............................................. 11 1.4 Pollution Sources ................................................................................................ 15 1.4.1 Oil Products ........................................................................................................ 16 1.4.2 Fruit Orchards ..................................................................................................... 16 1.4.3 Water Treatment ................................................................................................. 17 1.4.4 Drinking Water .................................................................................................... 17 1.4.5 Potash Industry ................................................................................................... 18 1.5 International Regulatory Constraints................................................................... 18 1.5.1 Cadmium ............................................................................................................ 19 1.5.2 Arsenic ................................................................................................................ 19 1.5.3 Manganese ......................................................................................................... 20 1.5.4 Chromium ........................................................................................................... 21 1.5.5 Vanadium............................................................................................................ 22 1.5.6 Antimony ............................................................................................................. 22 1.5.7 Lead.................................................................................................................... 22 1.5.8 Mercury ............................................................................................................... 23 1.5.9 Polycyclic Aromatic Hydrocarbons...................................................................... 24 1.6 Aims and Objectives ........................................................................................... 25 2. Materials and Methods....................................................................................................... 26 2.1 Background......................................................................................................... 26 2.2 Materials and Methods ....................................................................................... 27 2.3 Sample Preparation ............................................................................................ 29 2.3.1 Surface Water ..................................................................................................... 29 2.3.2 Sediment and Plant Material............................................................................... 30 2.3.3 Analytical Technique........................................................................................... 30 2.3.4 Inductively Coupled Plasma Mass Spectrometry (ICP-MS)................................ 30 2.3.4.1 Instrumentation ................................................................................................... 32 2.3.4.2 Optimisation ........................................................................................................ 33 2.3.4.3 Calibration........................................................................................................... 33 2.3.4.4 Interferences ....................................................................................................... 35 2.3.4.5 Detection Limits .................................................................................................. 35 3545105
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2.3.5 Flame Atomic Absorption Spectrometry (FAAS)................................................. 36 2.3.5.1 Instrumentation ................................................................................................... 37 2.3.5.2 Calibration........................................................................................................... 38 2.4 Summary ............................................................................................................ 38 3. Results and Discusion........................................................................................................ 39 3.1 Surface and Drinking Waters .............................................................................. 39 3.1.1 pH and Conductivity Levels ................................................................................ 43 3.1.2 Trace Elements and Anion/Cation Levels........................................................... 43 3.2 Sediments ........................................................................................................... 45 3.2.1 Trace Element Levels ......................................................................................... 45 3.2.2 Polycyclic Aromatic Hydrocarbons...................................................................... 48 3.2.3 Aquatic Plants ..................................................................................................... 49 3.3 Comparative Data ............................................................................................... 51 4. 4.1 Conclusions........................................................................................................................ 53 Further Works ..................................................................................................... 55 References................................................................................................................................. 57 3545105
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LIST OF TABLES
Table 1:
Sampling Sites along the Rio Colorado
Table 2:
Certified Reference Results for the ICP-MS Calibration
Table 3:
Theoretical and Calibrated Detection Limits in the ICP-MS
Table 4:
Hollow Cathode Lamp Operating Conditions
Table 5:
Water Sample Results from Rincón de los Sauces and Associated UK
Regulatory Organisations’ Requirements
Table 6:
Water
Sample
Results
from
Catriel
and
Associated
UK
Regulatory
Organisations’ Requirements
Table 7:
Water Sample Results from Rio Colorado and Associated UK Regulatory
Organisations’ Requirements
Table 8:
COIRCO – Guideline Values for the Different Water Uses
Table 9:
Sediment Results for Heavy Metals
Table 10:
Comparison of Metals/Metaliods for COIRCO
Table 11:
Polycyclic Aromatic Hydrocarbons in Sediment
Table 12:
Heavy Metal Levels in Rio Colorado Plant Samples and Associated Literature
Requirements
LIST OF FIGURES
Figure 1:
Multimap Map of the Study Area
Figure 2:
Photographs of Potential Pollution Sources and Receptors along the Rio
Colorado
Figure 3:
Source Pathway Receptor Consequence Schematic for the Rio Colorado
Figure 4:
Template Source Pathway Receptor Consequence Model
Figure 5:
Sampling Sites Mapped along the Rio Colorado
Figure 6:
Inductively Coupled Plasma Source
Figure 7:
Processes that occur when Sample Aerosol reaches Plasma
Figure 8:
Flame Atomic Absorption Spectrometry
Figure 9:
Contaminants within the Areas of the Rio Colorado that are above Associated
International Regulatory Organisations’ Limits
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TRACE ELEMENT CONTAMINATION OF THE
RIO COLORADO IN ARGENTINA
DEPARTMENT OF PHYSICS
UNIVERSITY OF SURREY
1.
1.1
RIO COLORADO VALLEY AND HEAVY METAL CONTAMINATION
Introduction to the Rio Colorado Basin System
The study location is situated in the south of Argentina along the route of the Colorado River.
The river has its sources on the eastern slopes of the Andes in the latitude of the Chilean
volcano Tinguiririca, and pursues a general east-southeast course to the Atlantic Ocean, where
it discharges through several channels to a delta in the Union Bay. Its total length is about
1000 kilometres, of which about 300 kilometres, from the coast to Pichi Mahuida, are negotiable
for vessels that draw up to 2 metres.
Various literature describes the river as being formed by the confluence of the Grande and
Barrancas, but as the latter is only a small stream compared with the Grande it is more aptly
described as a tributary, and the Grande as a part of the main river under another name. After
leaving the surrounding area of the Andes, the Colorado flows through a barren, arid territory
and receives no tributary of note except the Salado from La Pampa Province, and is considered
to be a part of the ancient outlet of the now defunct Lacustrine basin of Urre Lauquen. The
bottom lands of the Rio Colorado in its course across Patagonia are fertile and wooded, but
their area is too limited to support more than a small, scattered population. The Rio Colorado
marks most of the political boundary between the provinces of Neuquen and Mendoza.
Urban and industrial development in the province of Tucumán, North West Argentina, was
historically associated with its water resources. Rivers such as the Salí runs in a north to south
direction along main cities and industries before filtering into the Rio Colorado via headwater
catchments from the Aconquija range.
The foothills of the Aconquija range comprise of
industrial development (citrus, paper mill, candy factories). The central and lower basins of the
Salí River (Galindo and others 2001) as well as the lower basin of its tributaries are polluted by
urban sewage, and effluents from industrial and agricultural activities.
The assessment of the chemistry, and quality of surface and ground waters of the province has
been underway since the last decade as part of a systematic study (regional project) (Padilla
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Torres and others, 1996; Perondi and others, 1999; García and others, 2001). The hydrological
network was subdivided into small basins that were monitored yearly (Vece and others, 1997).
This report looks at the chemical composition of various samples spread the length of the Rio
Colorado and subsequent chemical contamination patterns are derived, and compares any
evidence of pollution against the chemical contamination of the Rio Negro (Paddock, 2006).
Figure 1: Multimap Map of the Study Area
1.2
Pollutant Model – Pathways
The diverse pollutant pathways are found in both the area water courses of the Rio Colorado
and pollution of the surround soils in the agricultural areas, as a result of using water from
tributaries for irrigation and from the historic use of arsenic based pesticides, and through
sewage discharge, petro exploitation and water treatment plants.
1.2.1
Irrigation Water
The Rio Colorado is used for a variety of both irrigation and disposal purposes, along with being
a major source of drinking water. The waters are used for the irrigation of a diverse range of
orchards, crops and plants. Due to both illegal and legal disposal of chemical and domestic
wastes, the water course may potentially be contaminated like its neighbouring river, the Rio
Negro (Paddock, 2006). As the illegal disposal of waste into the Rio Colorado is uncontrolled,
potentially this possesses a larger threat than legal discharges.
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The legal discharges into the Rio Colorado contain chemicals stemming from potash plants,
petrol-chemical plants, other process waters and treated sewage (Marcilla, 2006). In addition,
suspicion also indicates the possibility of pollution arising from illegal discharges from origins
such as municipal, untreated sewage and unauthorised discharges from industries along the
path of the water course off the Rio Colorado.
Possible sources for potential pollution of the Rio Colorado are humans, insects, animals,
plants and fauna that may be both directly and indirectly exposed to the contaminants in the
water course. There are several communities littered along the Rio Colorado and its water
course that use the aquifer for drinking, fishing, water sports and irrigation of crops/plants.
The sources of pollution, their pathways and potential receptors for any contamination of the
Rio Colorado water course are illustrated in the schematic in Figure 3, which represents the
Source-Pathway-Receptor Conceptual Model for the Rio Colorado.
Figure 2: Photographs of Potential Pollution Sources and Receptors along the Rio Colorado
La Pampa Salt Lakes
Rio Colorado Dam above Rio Colorado
Rio Colorado Lake above dam
Rio Colorado orchards
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Rio Colorado basin
Salt lakes near Rio Colorado’s dam
Natural gas burner near Neuquen
1.2.2
Rio Neuquen
Agricultural Soils and Aquatic Plants
Historical data have highlighted the extensive use and potential for accumulation of arsenic
based pesticides in soil in lands adjacent to the banks of the Rio Colorado. A potential pollutant
pathway has been predicted between the soil contamination and consumers of fruit and
vegetables through the uptake of the soil contaminants into the produce (Paddock, 2006).
Significant inorganic compounds that have been historically used in the Rio Colorado regions
are Paris Green (Cu 3 (AsO 3 ) 2 ) and lead arsenate (PbHAsO 4 ) (Peryea, 1998). Indeed, research
conducted on soil contamination found that the use of inorganic arsenic pesticides has led to
increased concern over a potential ‘chemical cocktail’ resulting in the accumulation of the
counter-ions of arsenates/arsenites associated to lead, copper, calcium and sodium in soil
(Broadway et al., 2004).
The use of river sediments is considered to provide the best stable sample media to identify any
long term deposition of chemical contaminants, as sediments act as reservoirs for insoluble
heavy metals contaminants (Ward, 2000), especially mercury (Hissler, 2005). Aquatic plants
also provide a good stable media to identify any long term deposition of trace elements, but are
restricted solely to calendar seasons.
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This report will also permit investigation of a potential pollution relationship between any of the
Rio Colorado water and the water course’s use for irrigation of agricultural land surrounding the
Rio Colorado leading to an uptake of contaminants within harvested produce, namely grapes.
This study shall also compare the levels of pollution between the Rio Negro (Paddock, 2006)
and the Rio Colorado.
Possible sources of pollution, their pathways and potential receptors for any contamination of
the Rio Colorado water course are illustrated in the schematic in Figure 3, which represents the
Source-Pathway-Receptor Conceptual Model for the Rio Colorado.
1.3
Environmental Trace Elements and Heavy Metals
Heavy meals are one of the more serious pollutants in our natural environment due to their
toxicity, persistence and bioaccumulation problems (Tam & Wong, 2000). Trace metals in
natural waters and their corresponding sediments have become a significant topic of concern
for scientists and engineers in various fields associated with water quality, as well as a concern
of the general public.
Direct toxicity to man and aquatic life, and indirect toxicity through
accumulations of metals in the aquatic food chain are the focus of this concern.
The presence of trace metals in aquatic systems originates from the natural interactions
between the water, sediments and atmosphere with which the water is in contact.
The
concentrations fluctuate as a result of natural hydrodynamic chemical and biological forces.
Man, through industrialisation and technology, has developed the capacity to alter these natural
interactions to the extent that the very waters and the aquatic life therein have been threatened
to a devastating point. All of these issues are explored further in the following studies.
The activity of trace metals in aquatic systems and their impact on aquatic life vary depending
upon the metal species. Of major importance in this regard is the ability of metals to associate
with other dissolved and suspended components. Most significant among these associations is
the interaction between metals and organic compounds in water and sediment. These organic
species, which may originate naturally from process such as vegetative decay or result from
pollution through chemical discharge from municipal and industrial sources, have a remarkable
affinity and capacity to bind to metals. This phenomenon would naturally alter the reactivity of
metals in the aquatic environment. (Singer, 1974).
Many human activities (e.g.; mining, overuse of chemicals, industrial waste from ports and
refineries) have a negative impact on several biological processes and there is no doubt that
these will continue to affect the functioning of highly productive coastal ecosystems.
Contamination caused by trace metals affects rivers and their environments (Guzman & Garcia,
2002).
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Trace metals, including those defined as ‘heavy’, arising from industrial and mining activities are
discharged into rivers at many sites. The term heavy metal refers to any metallic chemical
element that has a relatively high density and is toxic, highly toxic or poisonous at low
concentrations. These anthropogenically derived inputs can accumulate in local sediments (up
to five orders of magnitude above the overlying water (Bryan & Langston, 1992) and
invertebrates living on or in food, and the rate of accumulation caries widely between species
and heavy metal concentration found in ‘clean’ conditions. Less is known of the uptake of these
metals by ingestion with food or from close contact with contaminated sediments (Harris &
Santos, 2000).
For some time, there has been serious concern about the simultaneous input of unwanted trace
elements, present in these mineral fertilizers, (Cd, Hg, As & Cr). These trace metals are much
more likely available to biota than those amounts bound to the soil (Sager, 1997).
Approximately 80% of total chromium from mineral fertilizers emanates from basic slag and
basic slag potash. Regional differences in application rates and crops lead to differences in
trace element loads per farmed area up to 6-fold. Further on, inputs from fertilizers have been
compared with input by atmospheric deposition. As a source of lead and cadmium, long-range
transport via the atmosphere supersedes the input from mineral fertilizers, whereas in case of
chromium it is reverse. It is widely recognised that marine ecosystems can become
contaminated by trace metals from numerous and diverse sources. However, anthropogenic
activities, such as mining, petro plants, and industrial processing of ores and metals, still remain
the principal cause of the increased amount of heavy metals which have been dumped into the
rivers (DeGregori et al., 1996).
There is now considerable evidence in the scientific literature that contaminates such as trace
metals, phosphorous, pesticides, PCBs and polycyclic aromatic hydrocarbons, can be taken up
and concentrated by sediments and suspended matter in aquatic systems. Transportation of
these contaminants in association with particulate matter represents a major pathway in the
biogeochemical cycling of trace contaminants (Allen, 1979. quoted in Hart, 1982).
Heavy metals belong to the group of elements whose hydro-geochemistry cycles have been
greatly accelerated by man. Anthropogenic metals emissions into the atmosphere such as Pb,
Hg, Zn, Cd and Cu are 1:3 orders of magnitude higher than natural fluxes. As a consequence
these elements are expected to become increasingly accumulated in the natural environment.
An increase in trace metal concentrations in river is not obvious since earlier data on the trace
metals concentrations in these systems suffer from inadequacy of sampling technique as well
as from a lack of reliable analytical tools (Schindler, 1991).
In order to capture all environmental pathway routes, environmental samples during this case
study were water, river sediment and plant material.
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represent potential monitors impacted by primary chemical contamination in the River Colorado.
In the scope of this investigation, other pathways, that exist, were considered to be less
influential media due to the complexity of identifying chemical causes and seasonal variations,
i.e. human hair and nails from the local populations (Steindel & Howanitz, 2003; Hammond,
2002; Ward, 2000; Ward et al., 2005).
Running water may only indicate a recent or continued pollution incident as the contaminant will
be diluted with fresh water flow passing the point of the pollution source. Surface water could
be used as a monitor for longer periods of pollution, but in order to make any valid assessment
of the contamination levels, there is a requirement for further physical measurements of the
water, such as the inflow and outflow, and the residual time in the water body. Plants are a
reasonable source of data relating to soil, water and air pollution, however, to make any
comparison then the same species of plant must be sampled and the plants must be collected
and analysed together, keeping all variables such as humidity and temperature identical for
each plant sample. The length of the record of pollution determined by plant analysis is only as
long as the last growing season, as the plants die back and shed foliage the record is lost, thus,
plant samples must be collected at the same time of year (Ward, 2000; Paddock, 2006).
Sediment samples indicate the build up of metal contamination with a specific environmental
receptor, such as the build up of trace elements in river sediment and the soils beneath historic
industrial sites through a process of sorption of the elements to the soil particles (Hester, 2001).
It is indicated that the contamination of river sediment will be influenced by local pollution
events, however, the chemical fractionation of this contamination may be altered by a change in
redox conditions when the sediment is excavated, which could change the bio-availability and
leachability of the contaminants (Stephens et al., 2000; Paddock, 2006).
In order to understand the linkage between the hazard and risk of a potential contaminant, it is
useful to consider the commonly adopted Source – Pathway – Receptor - Consequence Model.
This is, essentially a simple conceptual model for representing systems and processes that lead
to a particular consequence. In order for a risk to arise there must be hazard(s) that comprise
of a ‘source’ event (e.g. chemical spill), a ‘receptor’ (e.g. plant sediment) and a ‘pathway’ that
acts as an interface between the source and receptor (e.g. the river), as illustrated in Figure 4.
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Figure 3: Source Pathway Receptor Consequence Schematic for the Rio Colorado
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Figure 4: Template Source Pathway Receptor Consequence Model
The predicted receptors, sources and pathways for any pollutants in and around the Rio
Colorado are illustrated in the Source Pathway Receptor Consequence Model in Figure 3 and
the Template Source Pathway Receptor Consequence Model in Figure 4.
1.4
Pollution Sources
Pollution sources arise from a variety of man-made and naturally occurring processes. This
chapter talks about the potential sources of pollution and the associated detrimental effects to
the environment. In addition to the intensity of the pollution source, concentrations of chemical
pollutant may also depend on some of the factors as follows:
Season of the year;
Retention efficiency of plant parts;
Collection efficiency of plant parts;
Wind direction and speed;
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Local precipitation;
Particulate size of pollutant;
Solubility in water; and
Topography.
1.4.1
Oil Products
Although much of the world depends on the production or the trade of oil to fuel to its
economies, these activities can cause severe damage to the environment, either knowingly or
unintentionally. Oil production, and/or transportation, can disrupt the human population and the
animal and fish life of a region. Oil waste dumping, production pollution, and spills may present
hazards to the surrounding wildlife and habitat.
Furthermore, environmental releases
potentially threaten the extinction of plants and animals/birds from the residing area.
Petrochemicals are chemical products made from raw materials of petroleum or other
hydrocarbon origin. Although some of the chemical compounds that originate from petroleum
may also be derived from coal and natural gas, petroleum is the major source.
The effects of petrochemicals on river life are caused by either the physical nature of the
petrochemical, physical contamination and smothering, or by its chemical constituents such as
the toxic effects and accumulation leading to tainting.
These effects may be induced by
either/both the petrochemical or/and additive. River wildlife may also be affected by clean-up
operations or indirectly through physical damage to the habitats in which plants, fish and
animals live. The plants, fish and animals most at risk are those that could come into contact
with a contaminated river-bed’s sediment and plant life (Corbett Dabbs W, 1996).
The industrial sites at Rincón de los Sauces and Catriel both contain oil exploitation and
processing facilities, which may provide a potential source for chemical contamination.
In
addition to the obvious threat of organic chemical pollution, these facilities also tend to use
heavy metals in the manufacture of petrochemicals and other oil products, which include
elements such as V, Sb, Cr, Cd, Mn and Pb. Contamination from such sites may be via liquid
discharge and/or spillage, gaseous discharge, and leaching from solid discharge. Additional
chemical contamination may arise from petro industry is in the form of polycyclic aromatic
hydrocarbons that also arise from vehicle pollution.
1.4.2
Fruit Orchards
A diverse range of studies have been conducted in recent years to examine orchard soil
concentrations of key contaminants related to the accumulation of pesticides such as lead
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arsenate and Paris Green, whose chemical constituents are namely arsenic, lead and copper.
However high concentration of counter ions, such as sodium and calcium, are not considered to
be a chemical hazard in comparison to these studies (Broadway, 2004; Paddock, 2006; Ward,
2006; Embrick et al., 2005; Gaw, 2002; Merwin et al., 1994; Merry et al., 1983; Gaw, 2003;
Peryea, 1998; Peryea, 1999; Wolz et al., 2003; and Yokel and Delistraty, 2003).
Recent studies have highlighted an increase in arsenic concentrations in contaminated fruit
orchards in the Grande Canal and neighbouring regions (Paddock, 2006 and Broadway, 2004).
These studies revealed that a large percentage of arsenic in the near surface soils collected
from the fruit orchards soils was in the residual form, signifying that the arsenic was in a matrix
bound geochemical form.
Indeed, it was observed that the mobile exchangeable arsenic
fraction was made up of between 8% and 68% of the total concentration, varying with depth,
suggesting a significant anthropogenic source of arsenic was present in the region (Broadway,
2004).
1.4.3
Water Treatment
Water treatment is the process of removing undesirable chemical contaminants from raw water.
Most water is purified for human consumption but water purification may be designed for a
variety of other purposes, which leads to a diverse range of chemicals being used in the
purification process. Amongst the chemicals used in water treatment processes, the most
common are: iron(III) hydroxide; lime; hydrochloric acid; soda-ash; sodium hypochlorite; Iron(III)
chloride; aluminium hydroxide; aluminium sulphate (coagulant); chlorine dioxide; hydrogen
peroxide; and chloramines.
Although these chemicals are relatively innocuous in trace
amounts, large quantities of these compounds are stored on water treatment sites, possessing
the potential to leak into the environment and cause environmental ramifications.
The
discharge of untreated sewage is equally a threat that may cause detrimental effects to
animals, fish and plant material.
1.4.4
Drinking Water
Lead is a metal commonly found in the environment. In the past, it was widely used in paint, as
a petrol additive and for plumbing materials.
Although no longer used in Argentina, most
properties may have lead pipes somewhere between the tap in the kitchen and the main in the
street outside. Water that leaves water treatment plants contains virtually no lead, but it may be
picked up travelling through lead pipes. The two commonest forms of lead are soluble lead and
particulate lead. Fortunately there are only two forms of soluble lead: lead nitrate; and lead
acetate, and soluble lead concentrations decrease dramatically depending on water quality,
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integrity of lead piping and water use. In general, lead is only an issue in drinking water when
lead pipes are disturbed, releasing the particulate lead.
Although there are no lasting ill-effects of trace amounts of lead, lead may become harmful to
humans, fish, animals and plant materials if accumulated over a period of time. Children and
babies are particularly at risk due to the potential of effect on mental development, and lead is
deemed to be teratogenic and mutagenic.
1.4.5
Potash Industry
Potash is the common name given to potassium carbonate and various mined and
manufactured salts that possess the element potassium in water-soluble form.
Potash is
traditionally used in the manufacture of glass, soap, and fertilizer. The name derives from the
old method of making potassium carbonate by leaching wood ashes and evaporating the
solutions collected in large iron pots, leaving a white residue called ‘pot ash’. Later, potash
became the term widely applied to naturally occurring potassium salts and the commercial
product derived from them. The rich salt lands in the La Pampa region of Argentina provide
potash ore for the thriving Potash Industries. In addition to the potash process waste, there are
also a diverse range of chemicals used within the plants that possess the potential to leak into
the environment and cause environmental concerns.
1.5
International Regulatory Constraints
The Environment Agency (EA) published a series of reports in 2002, which provide a
scientifically based framework for the assessment of risks to human health from land
contamination. The reports, model and associated soil guideline values which make up the
framework are valid for use throughout the United Kingdom. This framework, for similar land
uses along the Rio Colorado, suggests that specific contaminants may consist of the elements
including V, Sb, Cd, Mn, Pb, B, Cr, Ni, Cu, Zn, As and Hg. In addition, significant levels of
polycyclic aromatic hydrocarbons (PAH) may exist using the Environment Agency’s model.
Other guidelines that may be used as comparisons, for water, sediment and aquatic samples,
are as follows: Dutch Adjusted, WHO, COIRCO, CLEA (UK) and Guidance Values for Different
Water Use and Guideline Values for PAHs for the Protection of Aquatic Life (Argentina).
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1.5.1
Cadmium
Cadmium poisoning is, in general, an occupational hazard associated with industrial processes
such as petro exploitation, metal plating and the production of nickel-cadmium batteries,
plastics and other synthetics.
The primary route of exposure in industrial settings is via
inhalation of cadmium containing fumes. Cadmium is also a potential environmental hazard
and human exposures to environmental cadmium are primarily the result of the burning of fossil
fuels and domestic wastes. However, there have been notable occurrences of toxicology as
the result of long term exposure to cadmium in contaminated food and water. In Japan, during
the sixties, cadmium accumulated in rice crop due to mining operations. Subsequently, the
local population who consumed the rice developed Itai-itai disease and renal abnormalities,
including proteinuria and glucosuria. Indeed, cadmium is one of six substances banned by the
European Union’s Restriction on Hazardous Substances directive, which bans certain
hazardous substances in electronics (A Wallace et al, 2001).
Current research has discovered that cadmium toxicology may be carried into the body by zinc
binding proteins (in particular, proteins that contain zinc finger protein structures). Zinc and
cadmium are in the same group in the periodic table, contain the same common oxidation state
(+2), and when ionised are almost the same size. Due to these similarities, cadmium may
mimic and subsequently replace zinc in many biological systems, in particular, systems that
contain ligands such as sulphur.
It may be of interest for any future studies to note that the absorption of cadmium from the lungs
is much more effective than that of the gut, hence smokers may contain 4-5 times higher blood
cadmium concentrations and 2-3 times higher kidney cadmium concentrations than nonsmokers (L Friberg, 1983).
1.5.2
Arsenic
Arsenic and many of its compounds are especially potent poisons, as both elemental arsenic
and arsenic compounds are classified as toxic and deemed dangerous to the environment. The
European Union lists some arsenic compounds as Category 1 carcinogens (Klassen et al,
2003).
Arsenic disrupts adenosine-5-triphosphate (ATP) production through several mechanisms. At
the level of the citric acid cycle, arsenic inhibits pyruvate dehydrogenase and by competing with
phosphate it uncouples oxidative phosphorylation, thus inhibiting energy-linked reduction of
NAD+, mitochondrial respiration, and ATP synthesis. Hydrogen peroxide production is also
increased, which might form reactive oxygen species and oxidative stress. These metabolic
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interferences lead to death from multisystem organ failure probably from necrotic cell death
(Croal et al, 2004).
Exposure to arsenic can occur from the environment and food consumption. The two forms of
arsenic can be absorbed and accumulated in diverse tissues and body fluids (Ueki et al, 2004).
In the liver, the metabolism of arsenic involves enzymatic and non-enzymatic methylation, in
which the most frequently excreted metabolite (≥ 90%) in the urine of mammals is
dimethylarsinic. The remaining non-excreted arsenic accumulates in cells, which over time may
lead to skin, bladder, kidney, liver, lung and prostate cancers. Other forms of arsenic toxicology
in humans have been observed in blood, bone marrow and cardiac. Central nervous system,
gastrointestinal, gonadal, kidney, liver, pancreatic and skin tissues.
The human liver after
exposure to therapeutic drugs may exhibit hepatic non-cirrhotic portal hypertension, fibrosis and
cirrhosis. Arsenic is also known to cause arsenicosis due to its manifestation in drinking water,
with the most common species being arsenate and arsenite. The ability of arsenic to undergo
redox conversion between As3+ and As4+ makes its availability in the environment more
abundant. What stimulates As3+ oxidation and limits As4+ reduction may well be relevant for
bioremediation of contaminated land (J Vigo et al, 2006).
Analysing multiple epidemiological studies on inorganic arsenic exposure suggests a small but
measurable risk increase for bladder cancer at 10 parts per billion. Roughly 80 million people
worldwide consume between 10 and 50 parts per billion arsenic in their drinking water
(Ravenscroft, 2008). If they all consumed exactly 10 parts per billion arsenic in their drinking
water, the previously cited multiple epidemiological study analysis would predict an additional
2000 cases of bladder cancer alone. This may indeed presents a clear underestimate of the
overall impact, since it does not include lung or skin cancer, and explicitly underestimates the
exposure (J Vigo et al, 2006).
1.5.3
Manganese
Manganese compounds are less toxic than those of other widespread metals such as copper
and nickel. Manganese poses a particular risk for children due to its ability tendency to bind to
CH-7 receptors. Manganese poisoning has been linked to impaired motor skills and cognitive
disorders. In 2005, a study suggested a possible link between manganese inhalation and
central nervous system toxicity in rats (Oak Ridge National Laboratory, 1995).
It is
hypothesised that long-term exposure to the naturally occurring manganese in shower water
puts up to 8.7 million Americans at risk. In addition, a form of neurodegeneration similar to
Parkinson’s disease called ‘manganism’ has been linked to manganese exposure amongst
miners and smelters since the early 19th Century (R Elsner, 2005).
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Manganese may affect liver function, but the threshold of acute toxicity is very high. On the
other hand, more than 95% of manganese is eliminated by biliary excretion. Any existing liver
damage may slow this process, increasing its concentration in blood plasma (Oak Ridge
National Laboratory, 1995).
The exact neurotoxic mechanism of manganese is uncertain but there are clues pointing at the
interaction of manganese with Fe, Zn, Al and Cu. Based on the number of studies, disturbed
iron metabolism could underlie the neurotoxic action of manganese. It participates in Fenton
reactions and could thus induce oxidative damage, a hypotheses corroborated by the evidence
from studies of affected welders (Los Alamos National Laboratory, 2003).
A study on the exposed workers showed that they have significantly fewer children. This may
indicate that long-term accumulation of manganese affects fertility.
Pregnant animals
repeatedly receiving high doses of manganese bore malformed offspring significantly more
often compared to controls (Los Alamos National Laboratory, 2003).
1.5.4
Chromium
Hexavalent chromium may be transported into human cells via sulphate transport mechanisms,
taking advantage of the similarity of sulphur and chromate with respect to their structure and
charge. Trivalent chromium, which is the more abundant variety chromium compounds, is not
usually transported into cells.
Inside the cell, Cr (VI) is reduced first to metastable pentavalent chromium (Cr(V)), then to
trivalent chromium (Cr(III)). Trivalent chromium binds to proteins and creates haptens that
trigger immune response. Once developed, chrome sensitivity can be persistent. In such
cases, contact with chromate-dyed textiles or wearing of chromate-tanned leather shoes can
cause or exacerbate contact dermatitis. Vitamin C and other reducing agents combine with
chromate to give Cr(III) products inside the cell (K Sanikow & A Zhitkovich, 2008).
Hexavalent chromium compounds are genotoxic carcinogens. Chronic inhalation of hexavalent
chromium compounds increases risk of lung cancer and maybe deficiencies in the kidneys and
intestine.
It appears that the mechanism of genotoxicity relies on pentavalent or trivalent
chromium. According to some research, the damage is caused by hydroxyl radicals, produced
during reoxidation of pentavalent chromium by hydrogen peroxide molecules present in the cell.
Zinc chromate is the strongest carcinogen of the chromates used in industry.
Soluble
compounds, like chromic acid, are much weaker carcinogens (K Sanikow & A Zhitkovich,
2008).
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1.5.5
Vanadium
All vanadium compounds should be considered to be toxic. Tetravalent, e.g. VOSO 4 , has been
reported to be over five times more toxic than trivalent V 2 O 3 . The most dangerous compound
is vanadium pentoxide. Vanadium compounds are poorly absorbed through the gastrointestinal
system (N Ress, 2003; K Kaern, 2007; A Scibior, 2006). Inhalation exposures to vanadium and
vanadium compounds result primarily in adverse effects on the respiratory system. Quantitative
data are, however, insufficient to derive a subchronic or chronic inhalation reference dose.
Other effects have been reported after oral or inhalation exposures on blood parameters (A
Scibior, 2006), on liver (Gonzalez-Vilalva et al, 2006), on neurological developments (K
Kobayashia et al, 2006) and other organs.
There is little evidence that vanadium or vanadium compounds are reproductive toxins or
teratogens. Vanadium pentoxide was reported to be carcinogenic by a national study, although
the interpretation of the results has recently been disputed (J Duffus, 2007).
1.5.6
Antimony
Antimony compound is only weakly absorbed by the digestive system, and the main route of
exposure is by inhalation of the dust. The elimination of antimony from the body is slow,
leading to a risk of chronic toxicity in the form of pneumoconiosis with repeated inhalation
exposures. Acute poisoning is very rare, and the signs are fairly non-characteristic (vomiting,
abdominal pain, irritation of the mucous membranes).
These symptoms are more often
associated with ingestion of other more water soluble compounds (A Wells, 1984). Chronic
poisoning by antimony trioxide is also rare. The main signs are irritation of the respiratory tract
and of the skin and a characteristic pneumoconiosis, which is visible on chest X-rays (A Wells,
1984).
Antimony trioxide is known to pass into breast milk and to transverse the placenta only in very
small amounts. One study of exposure with regard to female workers suggested a higher
incidence than usual of menstrual problems and of late-term miscarriages. Also, their children
may have developed slower than usual during the first twelve months of life, although this study
is considered inconclusive (A Wells, 1984).
1.5.7
Lead
Lead has no known physiologically relevant role in the body. The toxicity of lead comes from its
ability to mimic other biologically important metals, most notably Ca, Fe and Zn, which act as
cofactors in many enzymatic reactions. Lead is able to bind to and interact with many of the
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same enzymes as these metals but, due to differing chemistry, does not properly function as a
cofactor. This interference hinders the enzyme’s ability to catalyse its normal reactions.
Lead is removed from the body extremely slowly, normally at a rate of 0.5 µmol/L, causing
accumulation in the tissues. 95% of the absorbed lead is deposited as a lead phosphate
complex in the bones (Scotland NHS, 2009).
Most lead poisoning symptoms are thought to occur by interfering with an essential enzyme
delta-aminolevulinic acid dehydratase (ALAD).
ALAD is a zinc-binding protein which is
important in the biosynthesis of heme, the cofactor found in hemoglobin. Lead poisoning also
inhibits the enzyme ferrochelatase which catalyses the joining of proporphyrin IX and Fe2+ to
form heme.
Genetic mutations of ALAD cause the disease prophyria.
Lead poisoning is
sometimes mistaken for porphyria but the distinction is that lead poisoning usually causes
anemia while true porphyria does not.
Lead also interferes with excitatory neurotransmission by glutamate, which is the transmitter at
more than half the synapses in the brain and is critical for learning. The glutamate receptor
thought to be associated with neuronal development and plasticity is the N-methyl-D-aspartate
(NMDA) receptor, which is blocked selectively by lead. This disrupted long-term potentiation,
which compromises the permanent retention of newly learned information (Holstege, 2007).
Outside of occupational hazards, the majority of lead poisoning occurs in children under age
twelve. The main sources of poisoning are from ingestion of lead contaminated soil (leaded
gasoline) and from ingestion of lead dust or chips from deteriorating lead based paints. This is
particularly a problem in older houses where the sweet-tasting lead paints is likely to chip, but
deteriorating lead-based paint can also powder and be inhaled.
Lead has also been found in drinking water. It can come from plumbing and fixtures that are
either made of lead or have trace amounts of lead in them (Water Webster, 2007). Lead may
even migrate into wells and waterways from nearby industrial plants (petrochemicals) (EPA &
NYSDEC, 2006).
Exposure to lead and lead compounds may occur through inhalation, ingestion and dermal
contact. Lead exposure in the general population occurs primarily through ingestion, although
inhalation also contributes to lead body burden. However, lead from petrochemical additives
may be absorbed directly through the skin (USCDC, 2007).
1.5.8
Mercury
Mercury poisoning is a disease caused by exposure to mercury or its compounds. Mercury is a
heavy metal which occurs in several forms, all of which can produce toxic effects in high
enough doses. Its zero oxidation state exists as vapour or as liquid metal, its mercurous state
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Hg+ exists as inorganic salts, and its mercuric state Hg2+ may form either inorganic salts or
organomercury compounds, with these three groups varying in effects. Toxic effects include
damage to the brain, kidney, and lungs (J C Clifton, 2007).
Mercury poisoning can result in several diseases, including acrodynia (pink disease), HunterRussell syndrome and Minamata disease (PW Davidson, 2004).
Symptoms typically include sensory impairment (vision, hearing, and speech), disturbed
sensation and a lack of coordination. The type and degree of symptoms exhibited depend upon
the individual toxin, the dose, and the method and duration of exposure.
Common symptoms include peripheral neuropathy (presenting as paresthesia or itching,
burning or pain), skin discolouration, edema (swelling) and desquamation (peeling dead skin).
Because mercury blocks the degradation pathway of catecholamines, epinephrine excess
causes hyperidrosis (profuse sweating), tachycardia (persistently faster than normal heart
beat), mercurial pytalism and hypertension (high blood pressure).
Mercury is thought to
inactivate S-adenosyl-methionine, which is necessary for catechoamine catabolism by catecholo-methyl transferase.
Affected children may show red cheeks and nose, erythematous lips (red lips), loss of hair,
teeth and nails, transient rashes, hyptonia (muscle weakness) and photophobia.
Other
symptoms include kidney dysfunction or neuropsychiatric symptoms (memory impairment,
insomnia).
Human generated sources such as coal plants emit approximately half of atmospheric mercury,
with natural sources such as volcanoes responsible for the remainder. An estimated two-thirds
of human-generated mercury comes from stationary combustion, mostly of coal.
Other
important human-generated sources include non-ferrous metal production, cement production,
waste disposal, crematoria, caustic soda production, production of steel and pig iron, mercury
production for batteries, and biomass burning (L R Goldman, 2007).
Mercury and many of its chemical compounds, especially organomercury compounds, can also
be readily absorbed through direct contact with bare skin. Mercury and its compounds are
commonly used in chemical laboratories, hospitals, dental clinics and establishments that
fabricate batteries, fluorescent light tubes and explosives (USEPA, 1997).
1.5.9
Polycyclic Aromatic Hydrocarbons
Polycyclic Aromatic Hydrocarbons (PAH) toxicity is very structurally dependant, with isomers
varying from being non-toxic to extremely toxic. Thus, highly carcinogenic PAHs may be small
or large. Although PAH is not very well known to the general public, everyone can be exposed
to them through many different routes. PAHs are molecules made from carbon and hydrogen.
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PAH is generated when materials are burned. Several PAHs are probable human carcinogens:
benz[a]anthracene,
benzo[b]fluoranthene,
benzo[k]fluorathene,
chrysene,
dibenz[a,h]anthracene, and indeno[1,2,3-cd]pyrene (B Larsson, 1983).
Constant, long-term exposure of PAHs can cause cancer to the lungs and problems with the
reproductive and organ systems. It is common for smokers or second hand smokers to get
lung cancer because of the PAH molecule in cigarette smoke. Industrial workers are also at a
high risk for exposure manifesting in birth defects occurred to unborn babies. As for our organ
system, lungs, liver, skin and kidneys can be damaged by exposure. However these effects are
dependant on an individual’s health, heredity, previous exposure, and to chemicals and
medicine, so each individual may be affected differently (B Larsson, 1983).
For people who believe that they have been exposed to PAHs for a prolonged period, there is
now a means of testing for the toxin via blood and urine samples (B Larsson, 1983).
1.6
Aims and Objectives
The aim of this study is to determine the trace element (Al, Sb, As, B, Ba, Ca, Cd, Co, Cr, Cu,
Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Se, Sr and V) levels of surface waters, plants and sediments
taken along the Rio Colorado in Northern Patagonia and evaluate the impact of chemical input
from anthropogenia (such as oil and petrochemical extraction and agricultural activities on
water quality). Another aim is to undertake a comparison study between the Rio Colorado and
a neighbouring river, Rio Negro, to ascertain any trace element trends.
The project objectives are as follows:

To collect and store for transport to the United Kingdom, surface water, plant and sediment
samples from the two river systems (Rio Colorado, Patagonia – Argentina);

Develop analytical techniques to chemically prepare water, plant and sediment samples for
trace element analysis by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and
Flame Atomic Absorption Spectrometry (FAAS);

Develop techniques for the determination of trace element levels in samples by
optimisation, calibration and validation of both ICP-MS and FAAS instruments;

To statically evaluate the trace element results and compare with affiliated literature, other
Rio Colorado database values and water quality standards;

Determine levels of trace elements and the geochemical phase of these metals in the Rio
Colorado sediments, to assess the bioavailability, mobility and potential source of
contaminants, and compare them to the Rio Negro, especially levels of trace elements
reported by Paddock, 2006.
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
To interpret the data, so as to assess the input of human activities on the water quality of
Rio Colorado and evaluate the effect on abstraction of water for drinking and agricultural
purposes in the region.
2.
MATERIALS AND METHODS
This chapter will provide a summary of the geosphere of the Rio Colorado regions, specifically
describing the natural drinking water, and detail the sample media and analytical methods used
for analysis.
2.1
Background
The Rio Colorado flows generally east-southeastward across the arid terrain of northern
Patagonia and the southern Pampas, and is a border for four provinces. The arid conditions
support widespread but relatively sparse vegetation, which species have evolved methods of
coping with lack of water and extreme heat. The barren terrain’s soil is typically weathered and
lacking in humus, with saline accumulation at high levels. Therefore water resources in these
dryland areas are of vital importance. Irrigation in drylands is essential for the many aspects of
agriculture that rely upon the Rio Colorado, as water is sourced from the river.
Due to the arid climate, complex geological conditions and human activities, some problems of
ecological environmental geology occur, such as lack of water resources, desertification,
salinisation, and biogeochemical endemic diseases, etc.
These problems occur in fragile
regions of the environment that seriously restrict the development of the local economy and
cause harm to human health.
Although the Rio Colorado originates from the Andes, as the river flows downstream it
potentially may uptake contaminants from agriculture and human industry.
Recent studies
undertaken suggest that pesticides and phenolic derivatives have been reported to be found in
drinking water in rural areas. It is a trend that water quality rises significantly as you go from
rural to urban areas. This fact may be especially alarming as rural healthcare is drastically
more sparse compared to urban medical resources.
Ground-water quality has deteriorated where the main economic activity is cattle breeding (J.D.
Paloni et al, 2002).
Overgrazing and deforestation have resulted in detrimental effects to
vegetation that has in turn produced a more arid environment.
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Materials and Methods
2.2
In 2007-2008, a study was commissioned to investigate the chemical (trace elements, anions
and polycyclic aromatic hydrocarbons) levels in surface waters, sediments and aquatic plants
(at selected sites depending on availability) along the Rio Colorado.
Samples consisting of plant material, sediments and water were collected along the length of
the Rio Colorado by representatives of the Rio Negro newspaper. Specific instructions were
given for the collection and storage of all samples before shipment to General Roca, Rio Negro,
where all sediments and plant samples were sub-divided to remove plant debris/stones
(sediments) or sediment particulate (plant leaves and stalks) and fractions air-dried at ≈ 30
O
C
before transport to the ICP-MS facility, Chemical Sciences, University of Surrey, Guildford,
United Kingdom for chemical analysis. Four sampling areas were selected, namely:

Rincón de los Sauces – five water samples (RSW) from a Petro exploitation area, water
treatment facility and drinking water from a domestic faucet, and one plant sample (RSP)
from the Petro exploitation area;

Catriel – six water samples (CAW) from Peñas Blancas, the water treatment and sewage
outflow facilities and drinking water from faucets, three plants (CAP) from the first three
water sites, and river sediments (CAS) from Peñas Blancas and Puente Dique;

Embalse Casa de Piedra Dam – two water and sediment samples from the lake adjacent
to the northern entrance road to the dam; and

Rio Colorado – five water samples (RCW) from El Viñedo that is 15 km upstream from the
town, the water treatment and sewage facilities, and drinking water from faucets.
In
addition three sediments (RCS) from the first three water sites and two plants (RCP) from
El Viñedo and the water treatment works area bank of the river.
The sample locations are illustrated in Figure 5. The samples from the locations were uniquely
labelled and the specific details of each sample location are presented in Table 1.
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Table 1: Sampling Sites along the Rio Colorado
Site
Date
Sampled
Site Name
Details
Sample
Types*
RCW20070701
20/07/07
Rio Colorado
El Viñedo
15 km upstream from town.
WSP
RCW20070702
20/07/07
Rio Colorado
Water Treatment
Plant
50 metres upstream from water
treatment plant
WSP
RCW20070703
20/07/07
Rio Colorado
Sewage
Discharge
80 metres downstream from
sewage discharge. There is no
treatment plant.
WS
RCW20070704
20/07/07
Rio Colorado
Water Treatment
Plant
Drinking water 300 metres away
from the Water Treatment Plant.
W
RCW20070705
20/07/07
Rio Colorado
Water Treatment
Plant
Drinking water from the Water
Treatment Plant
W
CAW25070701
25/07/07
Catriel
Peñas Blancas
WPS
CAW25070702
25/07/07
Catriel
Point “in
between”
WPS
CAW25070703
25/07/07
Catriel
Water Treatment
Plant
Chanel were water is taken to the
Water Treatment Plant
WP
CAW25070704
25/07/07
Catriel
Sewage
Discharge
Sewage Discharge Pipe
W
CAW25070705
25/07/07
Catriel
Water Treatment
Plant
Sample taken from a faucet close
to the Water Treatment Plant.
W
CAW25070706
25/07/07
Catriel
Water Treatment
Plant
Sample taken from a faucet close
to the Water Treatment Plant.
W
RSW17070701
17/07/07
Rincón de los
Sauces
Petro exploration
region on the
river
In this area there is oil in the water
as the water is used to purge the
wells
W
RSW17070702
17/07/07
Rincón de los
Sauces
Middle point
between petro
region and town
In this area there is construction
work for an irrigation channel. It is
not uncommon to spot oil spills.
W
RSW17070703
17/07/07
Rincón de los
Sauces
A few metres
away from where
water travels into
the Water
Treatment Plant
Area of oil spill due to filtration in
wells
W
RSW17070704
17/07/07
Rincón de los
Sauces
First faucet after
the water is taken
into the Water
Treatment Plant
Rural housing. The inhabitants do
not report any health complications
WP
RSW17070705
17/07/07
Rincón de los
Sauces
Water faucet in a
house in the
centre of the town
A house in the town that is close to
an industrial park.
W
Sample Number
*Note:
Sample Location
W = Water sample
P = Plant material sample
S = Sediment sample
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Figure 5: Sampling Sites Mapped along the Rio Colorado
Rincoñ de los Sauces
Catriel
Embalse Casa de
Piedra Dam
Rio Colorado
2.3
Sample Preparation
All water samples were filtered (using a 20 micron filter), and analysed for trace elements using
Inductively Coupled Plasma Mass Spectrometry, Flame Atomic Absorption Spectrometry and
anions by Ion Chromatography.
Major cations were also analysed by Inductively Coupled
Plasma Atomic Emission Spectrometry.
Water samples were also measured for pH and
conductivity. All sediments and plant material dry-ashed using a muffle furnace (500 OC) and
acid dissolved using a hydrofluoric-nitric acid digestion method. The resultant digests were
analysed for about 20 trace elements using ICP-MS. Sediments sub-samples, maintained in a
wet state, were prepared and analysed for some 17 USEPA priority polycyclic aromatic
hydrocarbons (PAHs).
All determinations by atomic spectroscopy were validated using an internationally recognised
method, matrix-matched certified reference materials, so as to ensure that the values tabulated
for interpretation were within the error of the certified value. As an example, for surface water
analysis, two certified reference water samples were analysed, namely TMDA-54.4 and NIST
1643e, and the validation results are shown in Table 2.
2.3.1
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On receipt to the University of Surrey, the water samples were decanted into PTFE sample
container and refrigerated to await analysis. Prior to analysis, all surface water samples were
filtered using a 20 micron filter.
2.3.2
Sediment and Plant Material
Sediment and plant materials were prepared in an identical fashion prior to analysis. Generally,
all of the samples in the literature are first oven dried at varying temperatures ranging from 35 105C from between 24 hours up to 3 days to ensure that there is no moisture present in the
sample. The samples were sieved into different size fractions, for example <63 m and 63-250
m (Rauch et al., 2000), and other studies sieved them into <2mm, 0.5mm, 74 m, 600-250
m, 250 – 90 m and <90 m (Al-Chalabi and Hawker, 1996).
The sediment and plant material samples were transferred into paper bags and oven dried for
12 hours at ~90˚C. Once the samples had been partially dried, they were then sieved into five
different size fractions - <75, 75-105, 105-125, 125-250 and >250 m. The most abundant
fraction, of sediment/plant materials sample, over the whole range of samples was identified for
analysis, which was found to be 105-125 m. The samples were then transferred into crucibles
and placed in a muffle furnace for 12 hours at 400C to be dry-ashed. Samples were then
weighed before and after dry ashing to establish the organic content present, then transferred
into polypropylene squat beakers in preparation for the digestion process.
Once in the
polypropylene beakers, the samples were digested with 2 ml (1:1) mixture of HF:HNO 3
suspended in a water bath at 90 oC. A further 1 ml of HNO 3 was added to the dried samples.
The samples were then removed from the water bath and made up to 20 ml with distilled
deionised water and transferred into ‘Sterilin’ containers. Further dilution or decanting was then
performed on the digested sediment/plant materials sample prior to FAAS/ICP-MS analysis.
2.3.3
Analytical Technique
Historically, a diverse range of techniques have been implemented for the determination of
trace element concentrations in environmental samples, with the oldest techniques including
simplistic wet chemical titrimetry analysis. Over the last 60 years, the use of instrument based
techniques has increased to take control of environmental analytical chemistry (Fifield &
Haines, 1996).
All heavy metal analysis was undertaken on the ICP-MS, with the exception of Na, Mf, Ca and
Fe which were analysed using the FAAS.
2.3.4
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Inductively coupled plasma mass spectrometry is a technique that is widely used in trace
element analysis because of its capability of easily detecting elements at a ng/g (part per billion)
level.
Method development (e.g. hydride generation, laser ablation, electrothermal
vaporisation) has expanded the use of ICP-MS enabling over 50 elements to be determined in
environmental, biological and clinical samples.
The principle behind ICP-MS is the ionisation of the analyte atoms by inductively coupled
plasma at atmospheric pressure, followed by extraction via a series of cones into a mass
spectrometer. In order for ionisation to occur, the analyte must be supplied with sufficient
energy to permit the removal of an outer electron (M → M+ + e-). This amount of energy is
known as the first ionisation energy, and is unique to each element. The Saha equation allows
the degree of first ionisation to be calculated and is shown in Equation 1 and Equation 2. The
Saha equation demonstrates that at the operating temperature of the plasma (≈ 800 k) and with
an electron density of 1015 cm-3.
The resulting energy supplied is enough to form singly
charged positive ions for more than fifty elements in the Periodic Table, with an ionisation
efficiency > 90%.
Equation 1
Note:
n M + is the number of M+ ions per cm3;
K i is the ionisation constant;
n e is the number of free electrons per cm3; and
n M is the number of M atoms per cm3
Equation 2
Where: Z M + is the partition function for the ionic state;
Z M is the partition function for the atomic state;
K is the Boltzmann constant;
T is the absolute temperature; and
E ion is the ionisation energy (eV).
Once inside the mass spectrometer, the ions are separated accordingly to their mass-to-charge
ratio (m/z) and then detected by either the channel electron multiplier or the Faraday cup (the
detector is chosen accordingly to the intensity of the ion beams produced).
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2.3.4.1 Instrumentation
The ICP-MS instrument used for this study (Finnigan MAT SOLA ICP-MS) consists of a sample
introduction system, and inductively coupled plasma (interfaced to a quadrupole mass
spectrometer. An illustration of an Inductively Coupled Plasma Source is shown in Figure 6.
Figure 6: Inductively Coupled Plasma Source.
The sample introduction system is a pneumatic solution nebuliser (PSN), which makes use of a
peristaltic pump to ensure that the sample is delivered at a constant rate to the nebuliser. After
nebulisation, the sample passes through the spray chamber, where larger droplets are
separated out, resulting in the production of an aerosol of fine droplets. This aerosol is then
carried to the ICP by the carrier gas, argon. The ICP behaves as the ion source. Argon flows
through a quartz torch which has a coil wound around the end that induces radiofrequency
magnetic fields. A high voltage spark that introduces electrons into the argon stream ignites the
plasma – the collision of the electrons with argon atoms causes their ionisation, leading to
ignition of the plasma by inductive coupling (Vandecasteele and Block, 1993). Figure 7 outlines
the processes that take place once the sample aerosol reaches the plasma.
Figure 7: Processes that occur when Sample Aerosol reaches Plasma.
Solvent evaporated
from each droplet to
produce anhydrous salt
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are vaporised
into gas phase
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Gas molecules
atomised into
free ions
Atoms are
ionised
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The aim is to provide the plasma sampling position with the maximum density of ionised atoms
(this can be optimised by adjusting instrument parameters, see Section 2.3.4.2). The plasma
sampling position is situated in the central channel of the plasma. This section is extracted into
the mass spectrometer as a result of a pressure differential between the plasma (atmospheric
pressure) and the pressure behind a series of three cones. The first cone through which the
gas (carrying the singly charged ions) passes is the sampling cones. Its orifice has a diameter
of 1.1 mm, situated approximately 14 mm from the end of the torch and behind this cone the
pressure is 2-3 mbar. It is the lower pressure that causes the gas to be extracted through the
cone from the plasma region, and also to expand once it has passed through the sampling cone
aperture. Because of the expansion, only a tiny amount of the extracted ions pass through the
second cone, known as the skimmer. The skimmer is situated 8 mm beyond the sampling cone
and has an aperture of 0.8 mm. The instrument used in this study is unusual in that it makes
use of a third cone, known as the accelerator. The accelerator, positioned 8 mm behind the
skimmer and with a 1 mm sampling orifice, has a negative charge applied to it, which focuses
the positive ions into a beam that passes into the mass analyser, repels the negative ions and
allows neutral species to diffuse to the vacuum pump. The space between the cones and the
analyser housing is evacuated to a pressure of ≈ 1 x 10-3 mbar by a turbomolecular pump
(Dudding, 2000).
2.3.4.2 Optimisation
As discussed in Section 2.3.4.1, certain parameters affect the properties of the sampling part of
the plasma. To gain the highest ion count, the plasma sampling position must contain the
highest density of ionised atoms. Obtaining the maximum analyte count intensity is mutually
dependent on the forward power and nebuliser flow rate. Forward power governs the amount
of time (residence time) the analyte solution will spend in the plasma before ionisation occurs.
Nebuliser flow rate determines the distance travelled in the plasma by the analyte solution
before ionisation occurs. Too high a forward power will cause the highest density of ionised
atoms to occur too far away from the sampling cone (because the residence time will be lower
when maximum ionisations occurs); too high a nebuliser flow rate will cause the analyte
solution to reach the sampling cone before maximum ionisation has occurred. A balance must
be struck so that the forward power and nebuliser flow are together providing a region of
highest density of ionised atoms that is as close to the sampling cone as possible. Optimisation
experiments were carried out to gain the best balance of forward power and nebuliser flow rate
for the two elements being used as internal standards, cobalt and indium.
2.3.4.3 Calibration
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After optimisation of the instrument parameters, calibration of the ICP-MS was performed using
the same technique as for the FAAS. A series of calibration standards were prepared in 1%
HNO 3 using Plasma Emission Standard Solutions (BDH Laboratories, Poole, England)
possessing element concentrations of either 1000 or 10000 µg/ml. The calibration standards
were prepared with concentrations ranging across the linear dynamic range of the instrument.
It should be noted that for many elements analysable via ICP-MS, the linear dynamic range
extends across more than six orders of magnitude (Vandecasteele and Block, 1993).
Multielemental calibration standards were prepared (containing Ca, Cd, Cu, Fe, Pb, Se and Zn)
and run on the Finnigan MAT SOLA instrument. The isotopes used were as follows:
112
Cd;
65
Cu;
54
Fe;
208
Pb;
82
Se; and
44
Ca;
66
Zn. Isotope selection was based on the extensive work
undertaken by Stovell (1999) using this instrument for the analysis of blood serum.
Two international certified reference materials (CRM) were used to validate the water analysis
measurements. Both samples were run after the ICP-MS calibration and the calculated values,
in Table 2, were compared against the Reference Range (certified values). In most cases good
agreement was obtained for levels of accuracy (good agreement between measured mean and
certified value) and precision (RSD % below 15%).
Table 2: Certified Reference Results for the ICP-MS Calibration.
Elemental Concentration (µg/l)
Element
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CRM TMDA-54.4
CRM 1643e
Reference
Measured
Reference
Measured
Range
Value
Range
Value
Lithium
25.7  0.5
23.3
17.4  1.7
17.1
Aluminium
394.0  5.0
384.9
141.8  8.6
182.7
Chromium
438.0  4.0
383.7
20.4  0.2
23.1
Manganese
275.0  2.0
309.9
39.0  0.5
39.7
Iron
382  5
655.2
98.1  1.4
103.5
Nickel
337.0  3.0
369.2
62.4  0.7
63.6
Copper
443.0  4.0
492.6
22.8  0.3
22.1
Zinc
537.0  6.0
571.5
78.5  2.2
75.2
Arsenic
43.6  0.8
48.0
60.5  0.7
61.6
Selenium
33.0  0.7
35.9
12.0  0.1
14.8
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Antimony
25.7  0.5
23.1
58.3  0.6
50.5
2.3.4.4 Interferences
One of the drawbacks over the use of the ICP-MS in the analysis of trace elements is its
susceptibility to a range of interferences, both spectroscopic and non-spectroscopic. However,
in most areas, these interferences can be either eliminated or overcome through the careful
selection of parameters such as the solvents used to introduce the sample into the ICP or the
isotopes measured.
2.3.4.5 Detection Limits
The detection limit is the lowest concentration of an analyte that can be confidently reported as
being distinguishable from the blank level (Vandecasteele and Block, 1993). Equation 3 shows
how the background signal and its standard deviation are related to provide the smallest signal
that is required to show that the analyte signal is significantly different to the blank signal.
ỹ B + ks B
Equation 3
Where: ỹ B is the mean background signal; and
s B is the standard deviation of the background signal.
The value of k is generally assigned a number of 3 as this is deemed to be high enough to
prevent signals from being incorrectly assigned to the analyte when they are in fact blank
signals, and low enough to prevent analyte signals from being incorrectly attributed to the blank
signal (Vandecasteele and Block, 1993). The detection limit (D L ) for a given analyte, using a
specific technique, can easily be calculated using Equation 4, where b is the slope of the
calibration curve from the least squares line equation (y = bx + c).
Equation 4
Table 3 reports the detection limits calculated for the Finnigan MAT SOLA ICP-MS instrument
used in this work.
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Table 3:
Theoretical and Calculated Detection Limits in ICP-MS
Element
Theoretical Detection
Limit* (µg/l)
Calculated Detection
Limit (µg/l)
Copper
0.077
2.8
Iron
2.5
5.3
Selenium
1.1
2.3
Zinc
0.15
3.5
*Adapted from Table 9.5, p221 – Vandecasteele and Block, 1993
2.3.5
Flame Atomic Absorption Spectrometry (FAAS)
Atomic absorption spectrometry is a popular technique, useful for the analysis of trace metal
levels in solutions. It has been applied to the analysis of a variety of sample matrices and is
frequently used in the analysis of trace elements in fluids. The technique can be used to
analyse the concentration of over 70 different metals in a solution. Although atomic absorption
spectrometry dates to the nineteenth century, the modern form was largely developed during
the 1950s by a team of Australian chemists.
The technique makes use of absorption spectrometry to assess the concentration of an analyte
in a given sample and relies heavily on the Beer-Lambert law.
The electrons of the atoms in the atomiser can be promoted to higher orbitals for a short
amount of time by absorbing a set quantity of energy (i.e. light of a given wavelength). This
amount of energy is specific to a particular electron transition in a particular element, and in
general, each wavelength corresponds to only one element. This provides the technique its
elemental selectively.
As the quantity of energy imparted into the flame is known, and the quantity remaining at the
other side, at the detector, can be measured from the Beer-Lambert law to calculate how many
of these transitions took place, and thus receive a signal that is proportional to the
concentration of the element being measured.
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In order to analyse a sample for its atomic constituents, it has to be atomised. The sample
should then be illuminated by light. The light transmitted is finally measured by a detector. In
order to reduce the effect of emission from the atomiser, in the form of black body radiation, a
spectrometer is normally used between the atomiser and detector. The schematic in Figure 8
illustrates its basic principles.
Figure 8: Flame Atomic Absorption Spectrometry
2.3.5.1 Instrumentation
The FAAS consists of:

A hollow-cathode lamp (which must be changed for each element) that emits the radiation
that is absorbed by the analyte atoms;

An atom cell, where the sample solution is nebulised into an aerosol and dissociated into
free atoms by the flame;

A monochromator;

A photomultiplier detector; and

A means of displaying data.
Flames can vary both in the constituent and in the component ratios. The flame used for this
study pre-mixed air-acetylene, which is capable of reaching temperatures of approximately
2400 oC. The instrument used in this study was a Perkin Elmer Model 5000 Spectrometer
(Perkin Elmer, Beaconsfield, Bucks, UK) with single element cathode lamps; the wavelength
and applied currents are shown in Table 4.
Table 4: Hollow Cathode Lamp Operating Conditions
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Analyte
Wavelength
nm
Applied Current
mA
Calcium
422.7
6
Copper
324.8
5
Magnesium
285.2
6
Zinc
213.9
10
2.3.5.2 Calibration
The instrument was calibrated using a series of calibration standards (prepared from Plasma
Emission Standards of either 1000 or 10000 µg/ml, BDH Laboratory Supplies, Poole, Dorset,
England). These were prepared over a range of analyte concentrations, spreading across the
linear dynamic range of the instrument.
The concentration range over which linearity is
maintained in FAAS depends on the analyte of interest, but usually is that which provides
absorbance signals over 0.5 - 1.0 arbitrary absorbance units (Vandecasteele and Block, 1993).
For zinc analysis by FAAS, then this range is quite low, with the zinc signal forming a plateau at
approximately 6 µg/ml Zn. After plotting the analyte signal against the concentration for each of
the standards, the least squares line equation (y = bx + c) was used to calculate the slope and
intercept, y. Note that b = the slope and c = the y intercept.
All of the standards were prepared in a 1% HNO 3 solution, which was particularly important for
the analysis of serum samples. Momcilovicacute et al., (1975) found that if standards were
prepared in distilled water, the results for the analysis of zinc in serum samples were artificially
elevated.
2.4
Summary
To achieve the study aim and objectives methods of sample preparation and determination of
the trace element contaminant concentrations of environmental samples, namely, water and
soil/sediment, have been designed and developed using published and original procedures.
The data is to be employed in giving an insight into the source of any contamination and its
effects on prescribed receptors. Further procedures have been designed and developed for the
preparation and determination of the geo-chemical phase of any trace elements within the
surface water, aquatic plant and river sediment samples to provide an insight into the
bioavailability of any environmental condition.
The analysis of all prepared samples was
undertaken using ICP-MS and FAAS techniques. Quality control and validation procedures
were designed and implemented, including: blank sample analysis; ICP-MS instrument drift
analysis and duplicate sample analysis.
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RESULTS AND DISCUSION
3.
In this chapter, the results obtained for the analysis conducted during this project will be
illustrated and discussed.
3.1
Surface and Drinking Waters
The trace element and anion/cation values for surface waters, and regulatory values set by the
World Health Organisation (WHO) and United Kingdom Drinking Water Standards are recorded
in the tables as follows:

Table 5 illustrates water sample results from Rincon de los Sauces expressed as µg/l or
*mg/l;

Table 6 illustrates water sample results from Catriel expressed as µg/l or *mg/l; and

Table 7 illustrates water sample results from the Rio Colorado River as µg/l or *mg/l.
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Table 5: Water Sample Results from Rincon de los Sauces and Associated United Kingdom Regulatory Organisations’ Requirements.
µg/l or *mg/l
Element
pH
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Rincon de los Sauces - Elemental Concentration
RSW01
RSW02
RSW03
RSW04
RSW05
Petro Explot
Mid petro town
Water extract WTP
Faucet WTP
Faucet town
6.78
7.12
7.87
7.12
7.02
WHO certified
levels
UK DWS
200
Conductivity (µS)
456
562
873
786
883
Aluminium
10.3
14.1
19.7
27.4
64.8
100
Antimony
45.6
24.1
22.8
1.6
1.2
20
5
Arsenic
5.8
11.5
5.7
3.5
3.8
10
10
Boron*
0.09
0.09
0.09
0.14
0.27
0.5
1
Barium*
0.026
0.026
0.026
0.024
0.021
0.7
1
Calcium*
91.0
91.6
92.3
137.9
135.6
-
250
Cadmium
3.32
0.51
0.88
0.35
0.31
3
5
Cobalt
<0.1
<0.1
<0.1
<0.1
<0.1
-
-
Chromium
39.23
6.39
6.23
3.29
2.08
50
50
Copper
9.31
6.46
2.81
18.59
17.14
2000
2000
Iron
51.1
5.4
5.6
2.7
2.2
-
200
Potassium*
2.81
2.88
2.85
3.05
3.51
-
12
Magnesium*
7.29
7.35
7.42
10.77
9.32
-
50
50
Manganese
243
15
4.3
2.1
1.8
400
Molybdenum
4.1
1.4
0.24
1.8
1.9
70
-
Sodium*
105.3
105.5
33.7
28.9
28.9
-
200
Nickel
16.07
0.08
1.25
0.09
0.16
70
20
Phosphorus*
0.031
0.038
0.028
0.028
0.029
-
2.2
Lead
42.4
7.02
7.62
26.11
58.34
10
25
Selenium
4.2
1.3
<1.0
<1.0
<1.0
10
10
Sulphate*
172
175
174
298
597
-
250
Strontium*
0.65
0.66
0.67
0.96
0.59
-
-
Vanadium
25.79
1.65
4.27
0.37
0.28
-
-
Zinc
78.4
25.54
27.98
28.7
28.8
-
5000
Chloride*
138.0
136.5
139.3
128.2
137.2
250
250
Nitrate*
133.0
156.8
114.2
32.2
27.3
50
50
Bromide*
0.40
0.37
0.34
0.13
0.17
10
-
Fluoride*
8.0
8.8
7.6
3.2
2.8
1.5
1.5
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Table 6: Water Sample Results from Catriel and Associated United Kingdom Regulatory Organisations’ Requirements.
µg/l or *mg/l
Catriel - Elemental Concentration
CAW 01
CAW 02
CAW 03
CAW 04
Penas Blancas
Between Point
Channel WTP
Sewage discharge
Element
CAW 05
Faucet Close WTP
CAW 06
WHO certified
Faucet Far WTP
levels
UKWDS
pH
6.88
7.67
7.23
6.32
7.34
7.28
Conductivity (µS)
1288
897
873
653
983
872
Aluminium
15.2
16.9
12.0
109.6
26.2
22.12
100
200
Antimony
0.9
1.1
0.9
12.2
0.8
1.0
20
5
10
Arsenic
8.5
11.1
12.0
37.9
2.3
2.1
10
Boron*
0.11
0.11
0.09
0.15
0.10
0.08
0.5
1
Barium*
0.028
0.028
0.028
0.441
0.030
0.021
0.7
1
Calcium*
97.4
100.5
88.0
173.8
108.8
72.1
-
250
Cadmium
0.84
1.45
1.33
8.03
0.24
0.31
3
5
Cobalt
<0.1
<0.1
<0.1
6.4
<0.1
<0.1
-
-
Chromium
0.77
6.13
9.15
35.45
3.66
2.13
50
50
Copper
0.40
0.85
1.50
9.38
0.40
0.46
2000
2000
Iron
3.2
2.7
8.2
14.7
1.4
0.9
-
200
Potassium*
2.94
2.92
2.76
7.54
3.05
3.14
-
12
Magnesium*
8.07
8.67
7.39
13.96
8.55
7.20
-
50
Manganese
21
14
3.3
58.3
1.5
1.1
400
50
Molybdenum
4.1
3.7
0.3
5.9
1.9
1.4
70
-
Sodium*
110.3
116.7
43.1
154.7
25.5
22.7
-
200
Nickel
0.05
0.03
2.99
2.17
0.21
0.18
70
20
Phosphorus*
0.043
0.022
0.024
2.859
0.026
0.021
-
2.2
Lead
0.6
4.16
2.45
13.71
0.86
0.98
10
25
Selenium
<1.0
<1.0
<1.0
<1.0
<1.0
<1.0
10
10
250
Sulphate*
187
200
169
288
197
195
-
Strontium*
0.7
0.73
0.64
1.15
0.74
0.73
-
-
Vanadium
0.22
0.15
0.74
0.55
0.18
0.19
-
-
Zinc
17.4
25.2
21.5
322.4
24.7
28.2
-
5000
Chloride*
138.3
155.2
143.2
218.3
166.2
123.2
250
250
Nitrate*
178.2
166.2
123.2
267.3
34.2
23.3
50
50
Bromide*
0.32
0.24
0.21
0.99
0.23
0.16
10
-
Fluoride*
6.4
7.3
4.5
12.4
2.3
1.8
1.5
1.5
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Table 7: Water Sample Results from Rio Colorado and Associated United Kingdom Regulatory Organisations’ Requirements.
µg/l or *mg/l
Element
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Rio Colorado - Elemental Concentration
RCW01
RCW02
RCW03
RCW04
El Vinedo
50m WTPl
Sewage Discharge
Drinking close WTP
RCW05
Drinking 2800m WTPl
Lake
Dam mean 2 samples
WHO certified
levels
UKDWS
pH
7.89
8.01
6.76
7.56
7.43
7.23
-
-
Conductivity (µS)
786
887
563
872
809
776
-
-
Aluminium
13.1
13.4
118.2
60.8
42.6
24.3
100
200
Antimony
8.2
3.0
33.2
1.7
1.7
12.2
20
5
Arsenic
3.2
3.0
3.8
2.8
2.1
1.8
10
10
Boron*
0.14
0.14
0.14
0.13
0.19
0.15
0.5
1
Barium*
0.046
0.046
0.145
0.030
0.031
0.045
0.7
1
Calcium*
94.8
94.8
95.5
99.8
118.1
89.2
-
250
Cadmium
4.79
4.08
13.48
1.77
0.23
0.22
3
5
Cobalt
1.03
3.88
4.05
<0.1
<0.1
<0.1
-
-
Chromium
6.69
9.34
19.98
0.68
3.01
2.89
50
50
Copper
0.44
0.73
8.78
1.23
0.64
0.75
2000
2000
Iron
4.7
2.7
28.2
1.1
0.9
1.1
-
200
Potassium*
3.29
3.33
3.42
3.49
3.87
2.89
-
12
Magnesium*
9.06
9.08
9.22
9.67
7.18
6.29
-
50
Manganese
11.5
8.7
56.9
2.8
3.8
6.7
400
50
Molybdenum
0.6
1.7
8.3
1.3
2.9
0.9
70
-
Sodium*
102.1
102.2
103.9
23.9
24.8
139.7
-
200
Nickel
1.58
1.92
18.94
0.15
0.19
0.18
70
20
Phosphorus*
0.042
0.029
0.166
0.018
0.020
0.038
-
2.2
Lead
1.87
5.18
19.18
9.79
12.27
1.79
10
25
Selenium
<1.0
<1.0
2.78
<1.0
<1.0
<1.0
10
10
250
Sulphate*
206
205
489
251
250
198
-
Strontium*
0.74
0.76
1.73
0.67
0.59
0.54
-
-
Vanadium
0.41
0.42
3.77
0.24
0.29
0.23
-
-
Zinc
31.92
23.85
315.26
26.27
24.34
18.96
-
5000
Chloride*
138.0
132.2
167.4
123.3
115.2
138.2
250
250
50
Nitrate*
113.4
113.6
189.3
49.2
22.3
112.4
50
Bromide*
0.37
0.40
0.56
0.23
0.18
0.32
10
-
Fluoride*
7.8
8.1
14.5
2.3
2.8
7.8
1.5
1.5
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3.1.1
pH and Conductivity Levels
The measured pH and conductivity values in Tables 5, 6 and 7 range from 6.32 to 8.01 and 456
to 1288 µS, respectively, with the lowest pH values associated with sewage outflow or industrial
sites. All drinking water/faucet samples are about pH ≈ 7. The lowest conductivity level is at
Rincón de los Sauces (456 µS) and is associated with the surface water collected near the
petro exploitation site.
The highest conductivity value is for Catriel (1288 µS) as Peñas
Blancas. Values are in good agreement with the comparative data reported by COIRCO: pH
7.10 to 8.04 (Rincón de los Sauces), 6.97 to 8.08 (Catriel), 7.60 to 8.20 (Casa de Piedra) and
7.74 to 8.25 (Rio Colorado); conductivity 427 to 984 µS (Rincón de los Sauces), 444 to 1445 µS
(Catriel), 722 to 865 µS (Casa de Piedra) and 746 to 891 µS (Rio Colorado).
3.1.2
Trace Elements and Anion/Cation Levels
Tables 5, 6 and 7 shows that various sites have numerous chemicals at elevated levels in the
river surface waters, with values exceeding the regulatory guidelines for drinking water. A more
realistic interpretation of these values may be obtained by comparing the river samples against
irrigation, livestock watering or aquatic life standards, as stated by COIRCO (Table 2.29, page
62) in Table 8. The following observations may be deduced:

The highest river water trace element occurs at Catriel, especially the sewage discharge
(CAW04) site, with selected trace elements (As, Cd, Cr, Cu and Pb) exceeding the
guidelines for Vida Acuática Irrigción, as illustrated in Table 8;

The sewage discharge point at Rio Colorado (RCW03) also possesses high levels of many
chemicals (Cd, Cr, Mn, V, Pb, sulphate and nitrate) that may be attributed both to sewage
treatment/discharge;

The industrial sites at Rincón de los Sauces (RSW01 and RSW02) and Catriel (CAW01), to
a certain degree, contain high levels of selected trace elements. The elements include V,
Sb, Cr, Cd, Mn and Pb, and are associated with oil products. Several of these elements
(Cr, Cd, Pb and As) exceed the regulatory guidelines for Vida Acuática and Irrigción as
shown in Table 8;

Nitrate levels are high at all four sampling areas, with values above the drinking water
guidelines (WHO and UK Regulations). This statistic is due to the industrial and sewage
discharge sites that continue to impart detrimental effects on the environment. The specific
locations of nitrate contamination are Rincón de los Sauces (RSW01-03), Catriel (CAW0103), Casa de Piedra and Rio Colorado (RCW01-03);

Drinking water from faucets at all four sampling areas are generally within drinking water
guideline quality standards, although a couple of areas are of concern;
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
Drinking water from faucets in Rincón de los Sauces (RSW04-05) and Rio Colorado
(RCW04-05) have very high lead levels, with values typically above the WHO drinking
water guideline of 10 µg/L Pb. A possible explanation for this may be due to lead pipes
being used for water distribution; and

Drinking water from faucets in Rincón de los Sauces (RSW04-05) and Rio Colorado
(RCW04-05) contain high levels of sulphate, at values above the UK drinking water
standard of 250 mg/L sulphate.
A possible reason for this may be chemical water
treatment using metal sulphates of either aluminium or iron.
Table 8: COIRCO – Guideline Values for the Different Water Uses.
Value Guide (µg/L)
Element
Drinking Water
Irrigation Water
Cattle Breeding
Aquatic Life
Arsenic
10
100
25
5
Cadmium
3
5.1
80
0.017
Zinc
3000
1000-5000
50000
30
Copper
2000
200-1000
500-5000
2-4
Chromium
50
4.9-8.0
50
1.0
Mercury
1
-
3
0.026
Molybdenum
70
10-50
500
73
Nickel
20
200
1000
25
Lead
10
200
100
1-7
Selenium
10
20-50
50
1
A comparison of the trace element levels of river water samples in this report with those of a
previous study of the Grande Canal and Rio Negro (Paddock, 2006) show some interesting
differences. In general, the petro exploitation site at Rincón de los Sauces (RSW01), and the
sewage discharge sites at Catriel (CAW04) and Rio Colorado (RCW03) have much higher trace
element levels than the maximum values along the Grande Canal (especially the fruit
processing plant and disused chloro-alkali plant at Cipolleti). Zinc levels are much higher in
most samples of the Rio Colorado (ranging from 17.4 to 322.3 µg/L Zn) relative to the Rio
Negro (0.52 to 15.5 µg/L Zn), and the petrochemical exploitation and sewage sites have much
higher levels of antimony (Rio Colorado maximum 45.6 µg/L Sb: Rio Negro maximum 1.6 µg/L
Sb) suggesting oil-based chemical release to the environment. Only boron and arsenic seem to
be higher in the Rio Negro, associated with industrial and irrigation canal locations.
The
presence of higher lead levels in faucet drinking water in Rincón de los Sauces and Rio
Colorado was not noted in the drinking water samples from Rio Negro.
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3.2
Sediments
3.2.1 Trace Element Levels
Sediments are often considered to be better monitors of chemical contamination of a river as
they are long-term reservoir of trace elements and heavy metals, whereas surface waters are
subjected to constant variation due to water flow, volume, etc.
Table 9 reports the trace
elements for a limited number of sediment samples. Unfortunately, no sediment samples were
available at Rincón de los Sauces.
Table 9: Sediment Results for Trace Elements
CAS 01
CAS 02
CLEA UK
Dutch Adjusted
Target
Penas
Blancas
Point in
Between
mg/kg
*( )
Aluminium %
4.33
4.12
-
-
Antimony
6.5
7.8
-
-
Arsenic
8.5
11.1
-
29
(40)
Boron
23.2
27.3
3
-
(3)
Barium
266
198
-
Cadmium
2.87
1.23
7.65
Cobalt
2.1
1.3
-
Chromium
134.2
89.3
111
100
(600)
Copper
67.3
42.3
-
36
(130)
Iron %
5.43
5.19
-
-
Manganese
356.7
319.2
-
-
Mercury
1.23
0.78
6.51
Molybdenum
0.78
0.73
-
Nickel
45.5
38.2
52.7
Lead
18.9
12.3
450
Selenium
1.8
0.93
-
Strontium
289.4
267.5
-
-
Vanadium
187.4
203.4
-
-
Zinc
134.2
98.3
-
Element
mg/kg
200
0.8
(3)
20
0.3
(1)
10
35
(70)
85
-
140
(3)
(300)
Units (values expressed as mg/kg - ppm)
nd
* ( ) ICRCL 59/83 Guidance on the assessment and redevelopment of contaminated land 2 Ed. July 1987
{Rio Colorado: Rio Colorado Sediment RCS01-03 (values mg/kg dry weight)}
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{Rio Colorado: Catriel Sediment CAS 01-2 (values expressed as mg/kg dry weight)}
Table 9: continued: Sediment Results for Trace Elements
Element
RCS01
El Vinedo
RCS02
RCS03
50m
WTPl
Sewage
Discharge
CLEA
UK
Dutch
Adjusted
Target
mean 2
samples
mg/kg
*( )
Casa de
Piedra
Dam
mg/kg
Aluminium %
3.45
4.12
5.34
3.66
-
-
Antimony
0.8
0.83
3.44
0.67
-
-
Arsenic
7.8
6.6
23.4
8.4
-
29
(40)
Boron
24.4
22.1
55.6
27.1
3
-
(3)
Barium
342
378
569.3
283
-
Cadmium
0.23
0.33
13.8
0.23
7.65
Cobalt
0.56
1.02
8.22
0.59
-
Chromium
45.2
32.8
166.2
41.8
111
100
(600)
Copper
28.3
21.2
89.3
27.3
-
36
(130)
Iron %
4.34
4.77
6.34
5.12
-
-
Manganese
289.3
277.6
428.3
278.3
-
-
Mercury
0.19
0.23
3.27
0.34
6.51
Molybdenum
0.32
0.25
2.33
0.25
-
Nickel
18.3
12.3
65.3
12.3
52.7
Lead
9.3
6.5
31.2
5.4
450
85
Selenium
0.78
0.65
3.22
0.54
-
-
Strontium
234.3
271.4
319.3
211.4
-
-
Vanadium
98.3
76.3
432.1
112.3
-
-
87.3
65.3
223.8
56.9
-
Zinc
200
0.8
(3)
20
0.3
(1)
10
35
(70)
140
(3)
(300)
Units (values expressed as mg/kg - ppm)
nd
* ( ) ICRCL 59/83 Guidance on the assessment and redevelopment of contaminated land 2 Ed. July 1987
Sediment samples were analysed from Catriel (CAS01-02), Peñas Blancas and a point
between that site and the water treatment facility, Csas de Piedra and Rio Colorado (RCS0103, El Viňedo, water treatment plant and sewage discharge respectively).
Values are
compared with environmental quality guidance limits set by the United Kingdom CLEA, Dutch
Adjusted target values for soils and IRCL 59/83 limits for the assessment and redevelopment of
contaminated land (1987). The findings are as follows:

Two sediments show clear evidence of trace element contamination, namely Peňas
Blancas (Catriel, CAS01) and the sewage discharge (Rio Colorado, RSC03);
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
Both sites show elevated levels of many trace elements above either the Dutch Adjusted or
UK CLEA guidance limits; and

In general, Casa de Piedra shows no significant levels of chemical contamination, which
may in part be due to the dilution effects of the lake.
Comparison of the sediment data for this study with trace element values reported in 2006
(Paddock, 2006) for the Rio Negro and Grande Canal confirm that the Rio Colorado (for these
limited number of sediments) has higher levels, especially for As, Cu, Hg, Ni, Pb and Zn.
Interestingly, arsenic is a serious concern in regions of Argentina, especially in La Pampa (north
of the Rio Colorado) which is the southern border, and the Rio Colorado sediments range from
6.6 to 23.4 mg/kg As compared with the Rio Negro (1.4 to 7.4 and Grande Canal 3.4 to 6.1
mg/kg As). Similarly, concern has been raised about mercury levels in the Grande Canal (Rio
Negro) as a result of industrial discharge from the chloro-alkali plant in Cipolleti. However,
mercury levels in the Grande Canal ranged from 0.12 to 0.17 mg/kg Hg compared with 0.19 to
3.27 mg/kg Hg in the sediments from the Rio Colorado. Overall, it must be stressed that two of
the Rio Colorado sites are highly contaminated from industrial and sewage discharge which
may be of significance in comparing the two regions. In summary, more sediment samples
need to be collected from the Rio Colorado at all sampling areas, especially Rincón de los
Sauces and Catriel in order to assess the long-term impact of industrial activities (oil extraction
and processing).
Table 10: Comparison of Metals/Metalloides for COIRCO (table IV.4 p177 – 2006)
Element
This study
COIRCO
As
8.4
2.6-12
Ba
283
120-279
B
27.1
8.5-58
Cd
0.23
<0.5-2.1
Cu
27.3
17-53
Cr
41.8
6-38
Hg
0.34
<0.05-0.07
Ni
12.3
6.7-25
Pb
5.4
3.2-20
Se
0.54
0.7-1.3
V
112.3
41-191
Zn
56.9
28-105
{and this study (Casa de Piedra dam) – mg/kg dry weight}
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A limited amount of data on the levels of metals/metalloids is reported by COIRCO (2006),
which makes historical comparisons hard to conclude.
Data for thirteen elements are
presented in Tables IV.4 (p177-8), mainly for Casa de Piedra over the period 2000 to 2005.
Comparison with the mean values of two sediment samples taken from Casa de Piedra in this
study are in very good agreement for all elements, as illustrated in Table 10.
3.2.2
Polycyclic Aromatic Hydrocarbons
Table 11 reports the levels of polycyclic aromatic hydrocarbons (PAH) in sediment samples
from Catriel, Casa de Piedra and Rio Colorado sampling areas.
Table 11: Rio Colorado: Polycyclic Aromatic Hydrocarbons (PAHs) in Sediment
PAH
CAS01
CAS02
RCS01 El
RCS02
RCS03
Casa de
Adjusted
Penas
Between
Vinedo
50m WTPI
Sewage
Piedra Dam 2
Dutch
Blancas
point
mean
Target Soil
Discharge
samples
Naphthalene
0.073
<0.002
<0.002
<0.002
<0.002
<0.002
0.015
Acenaphthene
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
0.050
Acenaphthylene
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
-
Fluorene
0.056
<0.002
<0.002
<0.002
<0.002
<0.002
-
Phenanthrene/Anthracene
0.223
<0.002
<0.002
<0.002
<0.002
<0.002
-
Methylnaphthalene
0.022
<0.002
<0.002
<0.002
<0.002
<0.002
-
Dimethylnaphthalene
0.012
<0.002
<0.002
<0.002
<0.002
<0.002
-
Methylphenanthrene
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
-
Dimethylphenanthrene
0.187
0.013
<0.002
<0.002
<0.002
<0.002
-
Fluoranthene
0.226
0.036
0.008
<0.002
<0.002
<0.002
0.015
Pyrene
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
-
Benzo[b+k]fluoranthene
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
0.025
Crysene +
0.034
0.011
0.012
<0.002
<0.002
0.012
0.020 +
benzo[a]anthracene
0.020
Benzo[a]pyrene
0.018
<0.002
0.008
<0.002
<0.002
0.009
0.020
Dibenzo[a,h]anthracene
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
Benzo[ghi]perylene
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
0.020
Indeno[1,2,3-cd]pyrene
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
0.025
Total 1.0
{(values expressed as µg/g or mg/kg dry weight)}
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The combustion of fuel (oil, petrol and diesel) is considered to be one of the main contributors
of PAHs to the environment. In Particular pyrene, benzo(a)anthracene, benzo(b)fluoranthene,
benzo(a)pyrene and benzo(ghi)perylene are serious health hazards due to their carcinogenic,
mutagenic and teratogenic properties. The Rio Negro study (2006-2007) reported two sites
adjacent to out of action roadways, especially at Villa Regina (RUTA 22) that possessed PAH
levels of benzo(a)pyrene of 11.9 and 38.2 mg/kg.
Unfortunately, only a couple of Rio Colorado sediment samples were collected from possible
sites where fuel combustion would be expected. However, some conclusions may be deduced:

Peňas Blancas (Catriel, CAS01) and the point between that site and the water treatment
facility (CAS02) show some evidence of PAH input, but the levels are low compared with
the Rio Negro roadside samples; and

However, the levels of fluoranthene, chrysene(+)benzo(a)anthracene are above the
Adjusted Dutch target guidance limits for PAHs in soils.
PAH values are also reported by COIRCO (Table V.1 to V.4 p181-4) over the period of 2000 to
2005 for Csas de Piedra that concluded that most sites PAH levels to be below the levels of
detection.
Traces
of
naphthalene,
methylnaphthalene,
dimethylnaphthalene
and
dimethylphenanthrene were detectable at about 0.012 to 0.230 mg/L.
COIRCO (2006) also provides a list of Valores guía de HAPs para la protección de la vida
acuática (Table 2.30 p62) in which selected PAHs are listed with limits (µg/L): acenaphthylene
5.8; anthracene 0.012; benzo(a)anthracene 0.018; benzo(a)pyrene 0.015; fluoranthene 0.04;
fluorene 3.0; naphthalene 1.1; phenanthrene; and pyrene 0.025.
Clearly, the sediment sample collected from Peňas Blancas (Catriel, CAS01) has several PAHs
above these limits.
3.2.3
Aquatic Plants
Table 12 reports the trace element levels for several aquatic plants that were collected at
Rincón de los Sauces (RSW01), Catriel (CAP01-03), Casa de Piedra and Rio Colorado
(RCP01-02).
The values compares with literature ranges for non-contaminated plants as
follows:

The sites with high trace elements levels in surface river waters and sediments also have
contaminated plants, with Rincón de los Sauces (RSW01 – petro exploitation) being
contaminated with most trace elements measured;

Interestingly, all three plant samples from Rio Colorado have elevated sodium levels, which
may reflect the release of salt from the Rio Salado; and

No plant materials were provided from the sewage discharge sites.
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Table 12: Heavy Metal Levels in Rio Colorado Aquatic Plant Samples and Associated Literature Requirements.
Element
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CAP 01
CAP 02
CAP 03
RCP01
RCP02
Casa de Piedra Dam
mean 2 samples
Literature
Petro Explot
Penas Blancas
Between Point
Channel WTP
El Vinedo
50m WTPl
Aluminium
896
435
109
156
28.9
32.8
189
8 - 200
Antimony
1.67
0.29
0.11
0.06
1.09
1.16
0.09
0.02 – 0.26
Arsenic
3.3
1.5
1.8
0.6
1.3
2.8
1.1
0.009 – 1.5
Boron
11.2
7.6
5.2
4.8
2.1
1.3
6.5
1.0 – 30.0
Barium
356
167
154
103
89.3
113.8
127
1 - 198
Calcium
5623
4578
4239
3899
2897
3299
3544
6000 - 10000
Cadmium
1.77
0.56
0.21
0.13
0.13
0.17
0.09
0.03 – 0.25
Cobalt
0.66
0.27
0.18
0.12
0.18
0.26
0.11
0.01 – 0.40
Chromium
3.89
1.65
1.22
0.56
1.19
1.78
0.63
0.02 – 3.00
Copper
123.9
56.2
23.2
11.7
4.56
1.28
18.7
2.0 – 25.0
Iron
3655
1288
345
322
234
168
278
18 - 400
Potassium
8122
7688
5689
6133
5692
5299
6523
5000 - 20000
Magnesium
3566
2566
2198
1899
1892
2377
2782
1500 - 3000
Manganese
623
345
213
128
67
112
98
20 - 350
Molybdenum
3.22
3.62
1.66
0.78
1.34
1.18
1.10
0.33 – 1.50
Sodium
2836
1345
1189
1245
3872
3287
2788
60 - 1500
Nickel
12.9
6.7
2.3
1.8
1.2
2.1
0.9
0.8 – 5.0
Lead
42.4
23.4
17.2
6.5
3.2
6.2
5.3
0.5 – 10.0
Selenium
29.6
0.15
0.19
0.06
0.12
0.09
0.07
0.001 – 0.21
Strontium*
673
458
128
233
189
218
309
6 - 1500
Vanadium
10.9
5.9
1.2
0.8
1.19
1.23
0.7
0.1 – 0.5
Zinc
256
67.2
71.3
33.6
45.3
67.3
29.8
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Typical values
3.3
Comparative Data
A detailed report is available for comparing the experimental data of this study. The COIRCO
(Comité Interjuisdiccional del Rio Colorado) report Program Integral de Calidad de Agus del Rio
Colorado is available – Calidad del Medio Acuático, 2006, 218pp, on www.coirco.com.ar. The
report provides a comprehensive overview of sampling procedures and analytical methods and
lists data at similar sites along the Rio Colorado at: Rincón de los Sauces; Catriel; Casa de
Piedra dam and Rio Colorado. Chemical measurements for trace elements were conducted
using less sensitive methods of atomic spectroscopy (when compared with ICP-MS) and
therefore many elements are reported as less than values. The COIRCO report provides trace
element data for water and sediments, and HAPs for sediment, with values compared against
selected standards, i.e. ‘valores guía para diferentes uses del agua’ and ‘valores guía de HAPs
para la protección de la vida acuática’, which translates to ‘guideline values for different water
use and guideline values for PAHs for the protection of aquatic life’. The schematic in Figure 9
illustrates the contaminants within the areas of the Rio Colorado that are above associated
International Regulatory Organisations’ guidelines.
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Figure 9: Contaminants within the Areas of the Rio Colorado that are above associated International Regulatory Organisations’ Guidelines*.
Catriel
Water: Al, Sb, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Se,
SO Sr, V, Zn & NO 4
3
Sediment: B, Ba, Cd, Cr, Cu, Hg & Ni (PAH: Fluoranteno &
Criseno(+)benzo(a)antraceno
Plant: Al, Sb, As, Ba, Cd, Cu, Fe, Mg, Mo, Ni, Pb, V & Zn
Rincón de los Sauces
Rio Colorado
Water: Sb, Cd, Mn, Pb, V & NO 3
Sediment: B, Ba, Cd, Cr, Cu, Hg, Ni & Se
Water: Al, Sb, As, Cd, Cr, Mn, Ni, P, Pb, SO , V, Zn & NO 4
3
Sediment: B, Ba, Cd, Cr, Cu, Hg, Ni, Se & Zn
Plant: Al, Sb, As, Ba, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Na, Ni,
Plant: Sb, As, Na, V & Zn
Pb, Se, V & Zn
Embalse Casa de Piedra Dam
Water: As, Ba, B, Cr, Hg, Ni, Pb & Na
Plant: Na
*The guidelines include: Dutch Adjusted; WHO; COIRCO; CLEA (UK); and Guidance Values for Different Water Use and Guideline Values for PAHs for the Protection of Aquatic Life (Argentina).
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4.
CONCLUSIONS
As defined in an earlier section of this report, the main objective was to highlight the levels of heavy
metals and other contaminants along the Rio Colorado through a systematic sampling strategy
using plant, surface water and sediment samples.
This section will attempt to summarise the
conclusions resulting from this report and ascertain whether the aims and objectives were fulfilled.

Samples consisting of plant material, sediments and surface water were collected along the
path of the Rio Colorado by representatives of the Rio Negro newspaper, with specific
instructions being issued for the collection, storage and conditioning (sediment and aquatic
samples required drying) prior to shipment.
The samples were analysed using ICP-MS,
FAAS, with sediments and plant material dry-ashed, and acid dissolved using hydrofluoricnitric acid digestion method.
No further preparatory works were undertaken before the
samples were analysed using the FAAS and ICP-MS;

Analytical techniques to chemically prepare water, aquatic plant and sediment samples for
trace element analysis by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and
Flame Atomic Absorption Spectrometry (FAAS) was successfully developed using proven
analytical techniques;

Techniques for the determination of trace element levels in samples by optimisation,
calibration and validation of both ICP-MS and FAAS instruments were developed and
implemented successfully using proven analytical techniques;

This report statically evaluates the trace element results and compares them with affiliated
literature and water quality standards;

Comparisons and trends were successfully highlighted between similar reports;

The data was interpreted successfully, in order to assess the input of human activities on the
water quality of Rio Colorado and evaluate the effect on abstraction of water for drinking and
agricultural purposes in the region.
This study has highlighted areas of Rio Colorado that possess higher concentrations of heavy
metals than the regulatory values set by the World Health Organisation and the United Kingdom
Drinking Water Standards. The causes of such contamination are mainly due to anthropogenic
activities undertaken in affected areas. Leaks from water treatment works, sewage plants, potash
plants and petrochemical industries appear to have all been attributed to the induced levels of
contamination along the environs of the Rio Colorado.
Comparisons of heavy metal contamination between the Rio Colorado and Rio Negro show that the
Rio Colorado possesses much higher concentrations of contamination. The Rio Negro possesses
contaminants associated to agriculture and chloro-alkali industry, whereas the Rio Colorado
contains contaminants that may be attributed to petrochemical, potash, agricultural, sewage and
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water treatment plant processes.
Nevertheless, both reports have highlighted significant
concentrations of heavy metals levels that are above international guidelines.
There appears to be numerous similarities with the Rio Negro and Rio Colorado in relation to heavy
metal contamination. Hypothetically speaking, the two rivers’ areas should contain significant levels
of arsenic due the similar historical agricultural processes, which is supported by the presence of
arsenic in samples. The historical use and accumulation of arsenic based pesticides has been
documented in previous studies as the predominant heavy metal contaminant in the Rio Negro
Valley (Broadway, 2004; Paddock, 2006). The pathway to the human food chain was thought to be
through plant uptake from the soil and then human consumption of the contaminated produce. The
inorganic pesticides used historically used in the vicinities of the Rio Colorado and Rio Negro were
Paris Green and lead arsenate.
The actual levels of heavy metal contamination in the Rio Colorado may be spurious as
considerably fewer samples were taken from along the Rio Colorado, compared to the Rio Negro.
On this basis, it is capable to conclude that the Rio Colorado trace element levels detailed in this
report may not be a true presentation of heavy metals contained within its sediments, surface waters
and aquatic plant life. However, based on this report, it is feasible to suggest that parts of the Rio
Colorado are heavily contaminated with a variety of trace elements.
A comparative report to the effects of sewage irrigation in Beijing, China, (Wen-hua Liu et al, 2005)
identifies similar heavy metal contaminants (Cd, Zn, Pb, Cu & Cr) to those found close to the
sewage plant close to Catriel. Both studies also reveal increased concentrations of the inorganic
nutrient, nitrates, in sediment and plant samples, which is attributed to nitrate based fertilizers.
Indeed, the significant presence of nitrates and sulphates in the samples indicates that they are
derived from anthropogenic processes such sewage, water treatment, agricultural and potash
industry activities. The Chinese report suggested that heavy metal transfer from sediment/soils to
plants may be a key pathway to human health exposure to heavy metal contamination.
Soil
inhalation and ingestion may also become important pathways to human exposure to heavy metal
contamination.
Reports from Brazil have also identified increased concentrations of PAH compounds close to a
Brazilian petro industry (Monica C Rojo Camargo et al, 2002). Likewise with the Rio Colorado,
contamination was found predominantly in sediment samples. The Brazilian report also stated that
raised levels of organic solvents were found in the sediment samples, with examples including
benzene, toluene and xylenes. These organic compounds are used predominantly as preservatives
in the petrochemical industry and are classified as carcinogenic due to their aromatic ring structure.
Furthermore, a report from the UK highlighted heavy metal contaminants found close to a municipal
incinerator in Newcastle that burns organic liquids amongst other waste (D Rimmer et al, 2006).
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Both this incinerator site and the petro plant along the Rio Colorado possess similar heavy metals in
the specific localities (Cd, Cr, Ni & Zn). However, the presence of Cd and Cr, along with Hg and As,
may also be due to use of pesticides.
It should be noted that the presence of PAH compounds in sediment samples may also be a
contributor to traffic pollution from trains and vehicles (Kamalakkannan R et al., 2004).
The presence of Cu, Zn, Pb and Cd within samples from the Catriel and Rincón de los Sauces
locations may be attributed to traffic pollution as these four elements were highlighted to be the main
pollutants commonly associated to the combustion engine (Picken, 2006).
4.1
Further Works
Further studies that may be undertaken should focus on sediment and plant samples. Both reports
on the Rio Negro and Rio Colorado have illustrated that surface water samples were not the best
media for sampling due to the extreme dilution factors, as plant and sediment samples tend to
provide a more comprehensive assessment of heavy metals in the environment over longer periods
of time.
However, surface water should be continued to be undertaken as the Rio Colorado
provides a source for irrigation, cattle breeding and, most importantly, drinking water for humans.
Sites containing higher levels of heavy metal contamination from the various anthropogenic
processes and industries are mapped along the Rio Colorado.
Further studies should be
undertaken on those locations with significant levels of chemical contamination. These sites should
include Penas Blancas and El Vinedo that are situated close to petrochemical, sewage, water
treatment and drinking water locations.
Furthermore, a more extensive and systematic river
sampling strategy may be designed and implemented for those particular areas of interest, in order
to compile a more comprehensive report detailing environmental impact assessments.
Factors such as global warming have resulted in river levels dropping which may potentially result in
detrimental effects to biodiversity in relation to fish population. This indeed may also be attributed to
a variety of other parameters such as heavy metal pollution and physical habitat variation. Further
studies may be undertaken to study affects the biodiversity of aquatic creatures in the Rio Colorado.
As reported in Brazil (Monica C Rojo Camargo et al, 2002), organic compounds were found in
sediment samples close to a petrochemical plant.
Further work may include larger chemical
analysis suites to include GC/FID, GC/PID and GC/MS, enabling researchers to test for organic
compounds close to the petrochemical plant in Rincón de los Sauces and neighbouring Catriel.
Although, there is an abundance of reports regarding various countries’ river water quantity,
conversely, the literature available on Argentinean river water quantity is exceptionally sparse.
Further work should be researched using a greater diversity of sampling sources, with examples
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including workers at anthropogenic environments and members of local communities situated to
areas to potentially the greatest threat to human health.
Further work might be carried out on regions of the Rio Colorado that are situated close to main
road networks in order to account for any PAHs and heavy metals such as Cd, Pb, Cu and Zn could
be generated by traffic pollution.
The findings in this report have shown that there is a significant quantity of contamination along the
Rio Colorado. Obviously it not tangible to state that there will or will not be any detriment effects to
the environment from the heavy metal/chemical contamination in and around the Rio Colorado.
Future work could well be carried out on air quality and any trends in medical conditions/diseases on
local human and animal populations.
Overall, it must be stressed that two of the Rio Colorado sites are highly contaminated from
industrial and sewage discharge which may be of significance in comparing the two regions. In
summary, more sediment samples need to be collected from the Rio Colorado at all sampling areas,
especially Rincón de los Sauces, where no sediment samples were taken in this study, and Catriel
in order to assess the long-term impact of industrial activities (oil extraction and processing).
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