Air, Water and Land Pollution
Chapter 5:
Investigating the Environment
Copyright © 2009 by DBS
Contents
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Monitoring
Types of monitoring
Sampling methods
Modeling of environmental dispersion
Duration and extent of survey
Prerequisites for monitoring
Remote sensing
Monitoring:
A Systematic Investigation of the Environment
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•
•
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Existence and concentration of substances in the environment is found via
measurement
Single measurements not very useful…why?
Environment is variable
(sampling strategy needs to account for this)
Require knowledge of temporal and spatial variations
e.g. NO3- in river water
Different results would be found a few km
downstream due to physical, chemical and
biological transformations
Reeve, R.N. (2002)
Monitoring:
A Systematic Investigation of the Environment
•
Specific investigation of the environment requires:
– monitoring by repeated measurements made over time and space
– sufficient sample density to make a realistic assessment of variations
and trends
Monitoring:
A Systematic Investigation of the Environment
•
Important to define the reasons for monitoring before starting any
investigation
Generalization:
Monitoring is done in order to gain information about the present levels of
harmful or potentially harmful pollutants in discharges to the environment
itself, or in living creatures that may be affected by these pollutants
Monitoring:
A Systematic Investigation of the Environment
•
Specifics - Monitoring may be carried out to:
(a) assess pollution affects on man and his environment, and to identify any possible
cause and effect relationships between pollutant concentrations and, for example,
health effects, or environmental change
(b) assess the need for legislative controls on emissions and to ensure compliance
with standards
(c) activate emergency procedures in areas prone to pollution episodes
(d) obtain a historical record of environmental quality (useful, for example in
epidemiological studies)
(e) to ensure the suitability of water supplies or land for domestic or industrial use
Monitoring:
A Systematic Investigation of the Environment
Designing a Monitoring Program
• Number and location of sampling sites, measured parameters, duration of
the survey, time resolution of sampling all vary according to what the
collected data are to be used for
•
Starting with a clearly defined purpose and objectives is key
•
Continual appraisal of the data generated can be used to adjust the
organization or execution of the survey if necessary
Monitoring:
A Systematic Investigation of the Environment
•
Systematic steps in a
monitoring program
Types of Monitoring
May have any combination of:
Phases of pollutants
• Solid
• Liquid
• Gas
In compartments:
• Atmosphere
• Hydrosphere
• Biosphere
• Lithosphere
Types of Monitoring
•
Specific phase in a particular compartment
e.g. sulfur dioxide in air
•
Two or more phases in a particular compartment
e.g. dissolved and particulate phase metals in water
Types of Monitoring
•
Two distinct approaches to monitoring:
Source monitoring – samples taken before discharge and dispersion to
the environment (point source)
Ambient monitoring – samples taken after discharge from multiple
sources (non-point sources)
Types of Monitoring
Source Monitoring
General Objectives
• Source monitoring may be carried out to:
– Determine emission rates, and assess how these are affected by
process variations
– Evaluate pollution control devices
– Evaluate emission compliance
Types of Monitoring
Source Monitoring
Stationary Source Sampling (Gases)
• Industrial processes are cyclical
• Must be representative of the entire plant
• EPA has standard test methods for emissions monitoring
Types of Monitoring
Source Monitoring
Mobile Source Sampling (Gases)
• Vehicle emissions are heavily dependent on operating conditions
• May be done when idling or under specific conditions
e.g. using a dynamometer of ‘rolling road’
Types of Monitoring
Source Monitoring
Source Monitoring (Liquids)
• Liquid wastes (effluents)tend to be heterogeneous
• Care is required when selecting sampling locations, region should be well
mixed
• If homogeneous regions are not available, samples may need to be taken at
several locations
• If composition varies with time, grab samples will need to be taken and
integrated over the time span
Types of Monitoring
Source Monitoring
Source Monitoring (Solids)
• From wastewater/sewage treatment (sludge), ash from incinerators,
gypsum from desulfurization plants in power stations
• Less homogeneous than liquid or gas effluents
• Must ensure sample is representative of the whole waste
•
e.g. EPA sets sewage sludge application levels for heavy metals
– Sludge is regularly monitored for heavy metals
– 80-100% of Pb in a sewage treatment plant ends up in sludge
– Pb levels 100-3000 μg/g (ppm)
– Used in many countries as a fertilizer
Types of Monitoring
Source Monitoring
Source Monitoring (Solids)
• Pollution loading: Analysis of samples gives total elemental concentration
• Total metal concentration is not very useful
• Physical, chemical and biological responses to pollution varies according to
its speciation:
– Determines behavior under varying conditions of pH and pe
– Determines solubility
– Determines association with particles and organic matter
•
•
Information on physiochemical speciation is required
Complicated and time consuming compared with total metal determination
Speciation
Organic
Inorganic
Volatile
Reactive
Elemental Mercury
Mercury Ion Hg2+
Methyl Mercury
Hg0
AKA ‘reactive gaseous’
mercury’ (RGM) e.g. HgCl2(g)
CH3Hg+
Particulate bound
Dimethyl Mercury
Hg-P
CH3HgCH3
Regional
?
Global
Types of Monitoring
Source Monitoring
Source Monitoring (Solids)
• e.g. mercury case study – previously assumed only inorganic Hg
(metallic mercury) released in landfill gas
Types of Monitoring
Source Monitoring
Atmospheric Environment, Vol. 39, pp. 249-258.
Types of Monitoring
Ambient Monitoring
General Objectives
• Samples should be representative of prevailing conditions at the time and
place of collection
• Careful choice of sampling location and position at the chosen location
• Selection of site requires consideration of 4 steps:
– Identification of the purpose of monitoring
– Identification of the type of site that will best serve this purpose
– Identification of the general location of sites
– Identification of specific monitoring sites
Types of Monitoring
Ambient Monitoring
Ambient Air Monitoring
(a) Source-orientated sites for monitoring individual or small groups of
emitters
(b) Large-scale surveys of expected high pollutant concentrations
(c) Baseline stations to obtain background concentrations, usually remote or
rural sites
Types of Monitoring
Ambient Monitoring
Ambient Air Monitoring
• (a) Source Oriented
– Sited at point of anticipated
maximum ground level concentration
and at a background location
– e.g. using Gaussian dispersion
models
Types of Monitoring
Ambient Monitoring
Ambient Air Monitoring
• (b) Large-scale Surveys
– Geographical extent of air pollution
– Can provide real-time data to public
– Historical archived information
– e.g. Local (Health Dept.) and regional (EPA) monitoring networks
http://www.pittsburghtoday.org/web/chart.jsp?id=5_3_2&type=graph&gr=mcya_cr_n
http://www.epa.gov/air/data/repsst.html?st~PA~Pennsylvania
Types of Monitoring
Ambient Monitoring
Ambient Air Monitoring
• (c) Baseline stations to obtain background concentrations, usually remote or
rural sites Geographical extent of air pollution
– Principal siting requirement is that background levels need to be
measured over a long time period without interference from local
sources
e.g. 1) long-term measurement of CO2 at Manua Loa since 1956, and
e.g. 2.) national radon studies
Tellus, Vol. 28, No. 6, pp. 538-551.
Source: Turco (2002)
Health Effects
Radon Gas
Progenies (‘daughters’) build up
in confined space –are breathed
in, stick to surface of airways
and emit α-particles
Types of Monitoring
Ambient Monitoring
Ambient Air Monitoring
• e.g. Radon surveys
Types of Monitoring
Ambient Monitoring
Environmental Water Monitoring
• Enter from air (dry or wet deposition), land (runoff), direct discharge
(domestic, agricultural, industrial)
• Undesirable effects:
– Stimulation of plant growth – eutrophication – deoxygenation and loss of
biodiversity
– Direct or indirect toxic effects on biota
– Loss of amenity and practical value of water body
Types of Monitoring
Ambient Monitoring
Environmental Water Monitoring
• Sampling may be carried out:
(a) in rivers, lakes estuaries and the sea – overall water quality
(b) for rainwater, ground water and runoff – to assess influence of pollutant
sources
(c) at points where water is taken for domestic supplies
(d) using sediments and biota in order to assess accumulation of pollutants
and as indicators of pollution
Types of Monitoring
Ambient Monitoring
Environmental Water Monitoring
• Biomonitors or ‘biomarkers’ are organisms collected from contaminated
sites, or placed at a contaminated site for a period of time after the event
has occurred
• Analyzed in the lab chemically for toxins
e.g. collection of mussels and subsequent analysis for heavy metals
Types of Monitoring
Ambient Monitoring
Environmental Water Monitoring
• Location of Sampling Sites
– Sampling should be done at points
representative of he bulk of the water
body
– Studies of some pollutants require
sampling at considerable distances
downstream of effluent inputs
e.g. Dissolved oxygen
– Variable discharges with time require
close proximity to point of input
Types of Monitoring
Ambient Monitoring
Environmental Water Monitoring
• Location of Sampling Sites
– Temporally variable discharges
require sampling in close proximity
to point of input
– Dilution
– Contaminant levels no longer
show variation with time
Types of Monitoring
Ambient Monitoring
Environmental Water Monitoring
• Sampling in Lakes
– e.g. enrichment or eutrophication of lakes - excessive ‘blooms’ of
cyanobacteria (blue-green algae)
Types of Monitoring
Ambient Monitoring
Once this increased biomass dies and settles to the bottom of the water body where
decomposition occurs, oxygen levels may become depleted thus killing off fish and
other animals, releasing phosphorus from the sediments (i.e. internal loading), and a
suite of other problems.
Types of Monitoring
Ambient Monitoring
Certain cyanobacteria can produce nerve toxins
that render water unsafe (Carmichael, 1994; 1997)
Killed 16 cows on a farm near Baldur,
Manitoba (Canada) in 1996.
Hydrobiologia, Vol. 495, pp. 79-91.
Types of Monitoring
Ambient Monitoring
Environmental Water Monitoring
• Sampling of Natural Waters
– e.g. Arsenic
Source: http://water.usgs.gov/nawqa/trace/arsenic
Types of Monitoring
Ambient Monitoring
Sediments and Soil Monitoring
• May become polluted in a number of ways:
(a) Substances may get into soil/plants and then into the food supply
(b) Substances may wash from the land and pollute water supplies
(c) Contaminants may be resuspended and subsequently inhaled
(d) Substances polluting the land may make it unsuitable for future use
(e) Ecological systems may be damaged
Types of Monitoring
Ambient Monitoring
Sediments and Soil Monitoring
• Many contaminants are also naturally occurring (background levels)
• Some contaminants are solely anthropogenic (e.g. pesticides and artificial
radionuclides)
• Many studies on heavy metal contamination have established sources and
relative contributions to total intake of humans
e.g. Pre-Incan Metallurgy and the New World
Metals and the Environment
Intensive Pre-Incan Metallurgy and the New World
•
•
15-16th century well known use of Ag by Incans
“mountain of silver” in Bolivian Andes
– AD 1130-1150 peak in Pb and others
(used in smelting silver)
– Coincides with Tiwanaku Empire
and decline due to drought
– Ag exhausted in 16th century,
start of Sn mining in 19th century
Shaded zones identify distinct metallurgical zones:
-Tiwanaku (AD 1000 to 1250),
- Inca - early Colonial (AD 1400 to 1650),
- rise and crash of tin mining (AD 1850 – 1950)
(Abbott and Wolfe, 2003)
Types of Monitoring
Ambient Monitoring
Sediments and Soil Monitoring
• e.g. application of sewage sludge to land
– Samples of surface water, groundwater, soil, vegetation and sludge
would be tested for fecal coliform, nutrients, metals and pH
– Results would be compared to predicted levels
Types of Monitoring
Ambient Monitoring
Sediments and Soil Monitoring
• Background levels may be derived from measurements in plants or
organisms that soils and sediments support
e.g. lichens and shellfish act as bioconcentrators of heavy metals
Types of Monitoring
Ambient Monitoring
Sediments and Soil Monitoring
• e.g. Dioxins and furans in soils around an incinerator
– Incinerators are a major source of chlorine containing toxic organics
– Columbus incinerator estimated to have produced nearly 1 kg/yr of
dioxin TEQ
– 1/10th of total US output
– Unit was closed due to this massive output
– Since no air data was available, had to study soil
Types of Monitoring
Ambient Monitoring
Lorder et al., 1998
Sediments and Soil Monitoring
• e.g. Dioxins in soils around an incinerator
– Soil showed characteristic ‘fingerprint’ of toxic organics released
– Clear decrease in concentration with distance from source
– 15,747 pg/g total dioxin on-site, 235 pg/g for background samples
Types of Monitoring
Ambient Monitoring
Biological Monitoring
• Well-recognized relationships exist between the abundance and diversity of
a species and the degree of pollution
e.g. frogs and fish are frequently used in water treatment facilities
•
Number and types of species or taxonomic families at a particular location
and comparing this data to a reference background one
•
Macroinvertebrates (e.g. insects, mollusks, nematotodes etc.) are often
used in assessing the biological quality of rivers
Sampling Methods
Sampling Methods
• Monitoring of pollutants involves:
(i) collection of air, water, and soil/sediment samples for laboratory analysis
(ii) instantaneous instrumental monitoring of air and water
•
In this section we will look at sample collection methods.
Sampling Methods
Air
Air Sampling Methods
• Sampling systems for airborne pollutants may be active or passive
• Usually consist of 4 component parts:
– Intake component
– Collection (or sensing) component
– Flow measuring component
– Air moving device (pump)
•
Note: All must be chemically and physically inert to the sampled air (other
than the collector or sensor itself)
Sampling Methods
Air
Air Sampling Methods
• Intake Design
– Dependent on analyte
– e.g. vertical opening for
dustfall deposit gauge
Horizontal dust deposit
gauge (Deposition)
Dustfall gauge:
- Deposits via gravitational settling
- Used to calculate depositional flux
(mg m-2 d-1)
- Bulk sampling device
Directional dust
gauge (flux)
Sampling Methods
Air
Air Sampling Methods
• Intake Design
– Sampling aerosols is particularly difficult, inlet is usually a tube
– Flow rate of sample at the inlet should be equal to the flow of the gas
being sampled [case (b)]
Too few particles
Disturbance at the
intake can lead to
under or over
sampling…
Too many particles
Sampling Methods
Air
Air Sampling Methods
• Sample Collection
Methods most commonly used for atmospheric particulate samples:
– Filtration;
– Impingement;
– Sedimentation;
And for gaseous samples:
– Adsorption;
– Absorption;
– Condensation;
– Grab samples
Sampling Methods
Air
Air Sampling Methods
• Sample Collection
– Filtration
Pros
Cons
Glass
FIber
- Low water uptake
- High efficiency for particles > 0.3 μm
- Resistant to high T
Cellulose
- Low head loss
- Low metallic contamination level
- Easily ashed
- Hydrophillic
Membrane
- Flat for microscopic analysis
- Hydrophobic
- Chemically resistant
- Large head loss
- Brittle
- Not resistant high T
Use
Organics
Metals +
inorganic ions
Chose correct filter for analyses:
Retain correct size
Absence of impurities
Compatible with analytical procedure
Sampling Methods
Air
Air Sampling Methods
• Sample Collection
– Impingement – cascade impactors
(i) small jets through which an air
stream is forced, velocity and
momentum of suspended
particles is increased
(ii) particles collect on impaction
surfaces
- Uses adhesion of PM rather than filtration
- Flow is constricted, velocity increases
- Successively smaller particles adhere to each successive surface
- Fractionated according to mass (2.5 – 10 μm / < 2.5 μm)
Sampling Methods
Air
Air Sampling Methods
• Sample Collection
– Sedimentation
e.g. frisbee-type deposit gauge –
during wet weather dust is washed into
collection bottle
Sampling Methods
Air
Air Sampling Methods
• Sample Collection
– Adsorption – gas molecules bound by intermolecular attraction to a
surface
– Used for low-concentration VOC’s
e.g. activated charcoal, silica gel, alumina, polymers (Tenax Resin,
PUF)
Sampling Methods
Air
Air Sampling Methods
• Sample Collection
– Absorption – gases may be collected by dissolving in liquid phase or by
chemical reaction
e.g. NO2 via Palmes diffusion tubes
Sampling Methods
Air
Air Sampling Methods
• Sample Collection
– Grab sampling – gas samples collected in an impermeable container
and analyzed in the lab
e.g. determination of organics via GC-MS
– collection in Teflon bag or SS canister
Sampling Methods
Air
‘Hi-Vol’ sampler
• Determines total suspended
particulates (TSP) mg/m3
• Pump up to 90 cfm (~150 m3 h-1)
• Draws large volume of air over 24
hr period
– Glass fiber or membrane filter
– Weighed before and after
– 0.3 to ~100 μm particle size
• Impaction inlet may be used for PM10, PM-2.5
• May analyze filter for chemicals
Reeve, 2002
Question
Calculate the PM-10 concentration for the following conditions:
Filter mass gain = 0.000670 mg
Sample time = 1446 min
Initial sampler flow rate = 1.875 cm3 min-1
Final sampler flow rate = 1.807 cm3 min-1
Average flow rate = 1.841 cm/min
Volume of air = 1.841 cm3/min x 1446 min = 2662 cm3 = 2.662 x10-3 m3
PM concentration = 6.70 x 10-1 μg / 2.662 x 10-3 m3 = 251.7 μg m-3
Sampling Methods
Water
•
500 mL to 2.0 L typical volume
Objective:
Collect a portion of material small
enough in volume to be transported
and large enough for analysis while
still accurately representing the
material being sampled
Sampling Methods
Water
Grab - bottle, bag, messenger (Niskin, Kemmerer
or Van Dorn type), peristaltic pump
Depth Integrating – vertical water column
Automatic – remove samples at fixed intervals
Sampling Methods
Water
•
Adsorption of filtration media may be used to concentrate the species of
interest in situ
e.g. trace metals, organics, radionuclides
•
Peristaltic pumps have been used to sample water at various depths in
lakes
Sampling Methods
Water
Container and Preservation Choices
• Plastic is typically used
• Glass – hard glass (Pyrex) recommended for all organics
• Amber Glass – recommended for light-sensitive compounds
• 1 L sample necessary for most analyses
• Some determinations require preservation prior to analysis
See p1-33 of Standard
Methods Book
1-33
Standard Methods (1998)
Sampling Methods
Water
Contamination issues
• Care must be taken to ensure that sample container and collecting
equipment do not contaminate the samples
• Occurs via:
– Leaching of contaminants from surface of containers
– Leaching of organic substances from plastics or glass
– Adsorption of trace metals onto surfaces of containers
– Reaction of the sample with container material
– Change in equilibrium between pollutants in particulate and
solution phases
• If sample is to be subjected to an extraction technique then
extraction reagents must be sufficiently clean
Sampling Methods
Soil and Sediments
•
•
•
Typically inhomogenous – large variations
Surface samples are possible – truer representation obtained with cores
Usually plastic core tubes – extruded in field or lab
Sampling Methods
Soil and Sediments
Sampling Methods
Soil and Sediments
•
•
•
Stored in plastic bags
Usually soils and sediments are air dried, disaggregated (mortar and
pestle), sub-sampled and stored prior to analysis
Important to avoid contamination at each step
Sampling Methods
Sediments
Coring platform
• Cores are taken through the water column
• From a boat, platform or ice cover
• Coring equipment
Collecting surface lake sediments using a
small diameter Glew (1991) gravity corer from
the pontoons of a helicopter in Arctic Canada.
Smol, 2008
Sampling Methods
Sediments
Coring equipment
• Last 100 years contained in 50 cm (N. America) (cf. fast accumulation)
• More ancient histories contained in cores 2 m or longer
• Recent sediments are ‘unconsolidated’ > 90 % water
Short Cores (Surface Sediments)
• Open-barrel gravity corers
(plastic tubes)
– Close-on-contact type
(line tension)
– Messenger-operated
Sampling Methods
Sediments
Surface sediments
• Freeze-crust samplers
• Designed to preserve chemistry of the sediment-water interface
Figure 4.3. General operation of a freezecrust sampler.
Inset: Corer chamber is filled with dry ice and
a coolant, such as alcohol. The corer top is
secured.
A: Corer is lowered through the water column
B: Corer is lowered into the sediment,
sediment freezes to the corer
C: Sediment-encrusted corer brought to the
surface.
Sampling Methods
Sediments
Long Cores
• Livingstone corer
– Rod driven piston corer
Simplified diagram showing the basic principles used in piston coring.
A) To recover an undisturbed core sample, the corer is positioned at the sediment surface
B) The piston held stationary, while the core tube is pushed past it into the sediment using the coring rod.
C) The core section is recovered to the surface, with the core tube and piston locked together. The sealing of the piston in
the core tube prevents any tendency for the sample to slide out or for the core material to be deformed.
Sampling Methods
Sediments
Long Cores
• Mackereth compressed air piston corer (Mackereth, 1958; 1969)
Sampling Methods
Sediments
Sediment Sectioning
• Should be sectioned
lake-side / ASAP
Modeling of Environmental Dispersion
•
•
Substances can be found over large ranges of concentrations
Analytical techniques must be very flexible
Ariola et al, 2004
Ions Found in Natural Waters
Conc. Range
Cations
(mg L-1)
0-100
Ca2+, Na+
Anions
Cl-, SO42-, HCO3-
0-25
Mg2+, K+
NO3-
0-1
Fe2+, Mn2+, Zn2+
PO43-
0-0.1
Other metal ions
NO2-
Reeve, 2002
Modeling of Environmental Dispersion
•
In order to appreciate the variability of pollutant levels, and hence the
complexity of designing an adequate monitoring porogram it is necessary:
(i) to have some understanding of environmental dispersal, mixing and sink
processes
(ii) to have some understandingd of the time scales over which these
processes act
•
Modeling of dispersal is complex, uses computer models
Modeling of Environmental Dispersion
Modeling of Environmental Dispersion
Atmospheric Dispersal
•
•
•
Advection (wind) and turbulent diffusion (mixing) are the primary dispersion
routes
Vertically limited to the boundary layer (layer closest to earth’s surface)
Important factors:
– Wind direction and speed
– Solar radiation, cloud cover
– Release height of plume and buoyancy
– Topography
– Surface obstructions, buildings etc.
– Loss mechanisms (deposition at ground, chemical reactions)
Modeling of Environmental Dispersion
Atmospheric Dispersal
•
Simplest model is Guassian plume model (chp. 2)
– Good short-term estimates (within factor of 3), longer-term estimates
require newer models (AERMOD, ADMS)
•
Modeling produces good estimates of the real situation
– Must understand limitations of the model
– Avoid treating output as definite answers
– We may have good wind speed data but turbulence characteristics
poorly understood
Modeling of Environmental Dispersion
Aquatic Mixing
•
•
•
Advection (movement of water) and mixing/diffusion are the primary
dispersion routes (same as air!)
Vertical mixing is constrained by water depth or thermal stratification
Large number of models to describe movement of water pollutants
e.g. river model – estimate of long-term average concentrations at point of
discharge from a continuous release:
C=
q
v(1 + KdS)
Where q = rate of input of a substance to the river (kg s-1), v = flow rate (m3
s-1), Kd = partition coefficient (m3 kg-1) and S = suspended solid load (kg m-3)
Modeling of Environmental Dispersion
Aquatic Mixing
•
e.g. exponential decay model to predict (i) the change in water quality downstream
from a discharge into a river,
Cx = C0e-kt
Where Cx = concentration at point x, Co = initial concentration at point of discharge, k
= decay constant, t = time taken for flow from point of discahrge to x
•
or (ii) decline in organic pollution levels in a lake
Ct = C0e-kt
Where Ct = concentration at time t, Co = initial concentration, k = decay constant, t =
time
•
More recent models account for sorption, volatilization, hydrolysis, photolysis,
oxidation, etc. (see for example MINEQL, FATE etc.)
Question
The PCB concentration in Lake Michigan is declining according to a first-order
rate constant of 0.078 yr-1. If the PCB concentration averaged 0.047 ppt in 1994,
what will it be in 2010? In what year will the concentration fall to 0.010 ppt?
What is t1/2?
C = C0e-kt
Let 1994 be equivalent to t = 0
2010 will be t = 16 y
C = 0.047e-0.078 x 16 = 0.047e-1.248 = 0.013 ppt
Find t when C = 0.010 ppt
0.010/0.047 = e-0.078t
t = 19.8, concentration declines to 0.010 ppt by the year 2014
t1/2 = ln2 / k = 8.9 y
Modeling of Environmental Dispersion
Variability in Soil and Sediment Pollutant Levels
•
•
•
•
Physical mixing by agricultural practices, dredging, bioturbation by
burrowing organisms
Level of contamination depends mainly on deposition rate and
vertical/horizontal migration
Rate of movement is dictated by the degree of adsorption, leaching from
particles and flux rate of pore waters
Physiochemical properties influence rate of adsorption or leaching
e.g. Pb favored by low rainfall and high clay content,
Hg favored by high SOM
Modeling of Environmental Dispersion
Variability in Soil and Sediment Pollutant Levels
•
Contaminant concentrations are
usually higher in soils or sediments
with finer grain size
(increased surface area for
adsorption)
Trace metal concentrations in
sewage sludge
Cu associated with SOM
Zn associated with small
particles and SOM
Duration and Extent
Duration of Survey and Frequency of Sampling
•
•
•
•
•
Dependent on purpose of study
Pollutant levels fluctuate – long-term mean data not as useful as short-term
(may miss pollutant maximums)
More variability requires more samples to assess trends
Fast response continuous monitors can be used for the more common air
pollutants and basic water parameters
Require calibration and periodic checks
Duration and Extent
Duration of Survey and Frequency of Sampling
•
D
Carnegie Sci. Center EPA Monitor
Duration and Extent
Duration of Survey and Frequency of Sampling
•
Methods for water analysis:
Duration and Extent
Methods of Reducing Sampling Frequency
•
•
Sampling frequency may be impractical with resources on hand
Can be reduced by:
– Reducing the number of sampling locations
– Reducing the sampling frequency
– Reducing the number of determinants
•
•
Also possible to use composite samples to reduce sample numbers
Mix two individual samples to give indication of average quality over a given
area
Duration and Extent
Number of Sites
•
Dependent on objectives of the study
•
Proability of a fixed number of stations dtecting a release is a function of the
quantity released, number of samplers, distance of sampler from source,
plume dimensions, height of release, and duration
•
GPS systems are now often used to accurately determine sampling
locations
Prerequisites for Monitoring
•
Prior to monitoring:
(i) Information, techniques and methodologies must be available
(ii) Objectives must be set
•
Also:
– Definition of monitoring protocol
– Availability of meteorological and hydrological data
– Availability of emissions data
– Likely pollutant concentrations to be expected
– Availability of equipment
– Availability of analytical techniques
– Definition of suitable environmental quality standards
Prerequisites for Monitoring
Monitoring Protocol
•
Carefully planned and documented procedures are necessary to ensure
reliable and comparable results
•
Main components of monitoring protocol?
Prerequisites for Monitoring
Monitoring Protocol
(a) Reference methods (sampling and analysis)
– may be standard or non-standard
(b) Methodology
– location,
– frequency, duration,
– determinants,
– accuracy required,
– detection limit,
– principles of sampling,
– meteorological and hydrological conditions,
– health and safety,
– access power and security arrangements,
– procedures adopted when standard
procedures fail
(c) Quality control procedures which define
requirements for:
– calibration of measurement devices,
– maintenance of instruments,
– sample storage and transport,
– data handling and reporting
(d) Quality assurance program to ensure:
– measurements are made in accordance
with standard methods
– quality control procedures are in place
– quality control procedures are being
adhered to
– sample ID and routing procedure is well
documented
– that the correct reporting procedure is
being used
Prerequisites for Monitoring
Meteorological and Hydrological Data
•
•
•
•
•
Care must be taken to ensure data are representative of the area of study
Wind in particular is susceptible to local interferences
Portable weather stations and hand-held anemometers may be used
Lapse rate and inversion height may be obtained with weather balloons
Turbulence measurements at low-level can be obtained using a bivane and
anemometer on a 10 m mast
Prerequisites for Monitoring
Meteorological and Hydrological Data
•
Reasons for requiring Met Data:
– When fast response measurements are unavailable, may construct
time-weighted pollution roses that show how pollutant levels vary with
wind direction
– Trajectory of an air parcel over the synoptic-scale may be required for
source appointment or dispersion studies (surface pressure field)
•
Reasons for requiring hydrological data:
– Tidal range needed for dispersion studies at sea
– Flow and volume data for rivers and lakes (retention times)
Prerequisites for Monitoring
Source Inventory
•
•
•
Cost-effective method of identifying likely pollutants is to look at emissions
Identify likely pollutants prior to monitoring using emissions data
Emissions inventory should contain information on:
– Types of source
– Composition of emissions
– Rates of discharge of individual pollutants
•
Supplementary information on raw materials, processes and control
techniques
•
Emissions inventory should be considered a tool and not an alternative to
monitoring
Prerequisites for Monitoring
Suitability of Analytical Technique
•
Pollutants found in environmental compartments over very wide
concentration ranges…
Ariola et al, 2004
Ions Found in Natural Waters
Conc. Range
Cations
(mg L-1)
0-100
Ca2+, Na+
Anions
Cl-, SO42-, HCO3-
0-25
Mg2+, K+
NO3-
0-1
Fe2+, Mn2+, Zn2+
PO43-
0-0.1
Other metal ions
NO2-
Reeve, 2002
Prerequisites for Monitoring
Suitability of Analytical Technique
•
•
Several procedures for instrumental analysis are often available
Considerations affecting choice of method:
– Sensitivity
– Specificity
– Response time
– Response range
– Ease of use
– Ease of calibration
– Cost and reliability
– Precision and accuracy
Hewitt, C.N., 1991
Prerequisites for Monitoring
Suitability of Analytical Technique
•
•
Precision – reproducibility of analyses
– Measured using separate representative sub-samples
– Measured at intervals during the analysis
Accuracy – measure of the determinant present
– Measured using international standard reference materials
Prerequisites for Monitoring
Environmental Quality Standards
•
•
Devised and adopted for many air and water pollutants
Required for most monitoring programs (not required for source
apportionment, historical or fate and transport studies)
Prerequisites for Monitoring
Environmental Quality Standards
Prerequisites for Monitoring
Environmental Quality Standards
Prerequisites for Monitoring
Environmental Quality Standards
•
With any standard for environmental quality there may be difficulty in
ensuring compliance
e.g. removing contaminants down to EPA safe levels requires new
technological developments in water purification
Remote Sensing
•
•
•
Sophisticated techniques for sensing air and water pollutants
Use is almost entirely restricted to specialized monitoring exercises
Aerial photography is an example of a less expensive RS technique
– Conventional color film photography for site surveys
– Monitoring of liquid effluent dispersal using tracer dyes
– Monitoring of oil spills
– Airborne heat-sensing IR equipment used to measure thermal pollution
of water
•
RS techniques measure light absorption through a section of the
atmosphere
Long pathlengths compensate for low concentrations
•
Remote Sensing
•
Tunable lasers allow long-path
absorption measurements of:
SO2, NO2, CO, O3
and OH radical
Remote Sensing
•
•
•
•
Light Detection and Ranging (LIDAR) – measurement of backscatter from a pulsed
laser – compare backscatter intensity between strong absorption band and weak
absorption band
Similar to RADAR - uses pulsed laser instead of radio waves
Light is scattered by particles providing different absorption paths
– Amount of light returned from each height is proportional to the atmospheric
density
– Knowing the speed of light, the time is converted into distance/height
– Concentration profile is built over entire range
DIAL (Differential Absorption LIDAR)
uses two wavelengths
– One max (absorbed)
– One min (removes background)
Remote Sensing
•
Differential Optical Absorption Spectrometry (DOAS) – relates quantity of
light absorbed to number of gas moleucles in light beam path – measures
many different species in same light beam
Analysis and Presentation of Data
•
•
•
•
Organization and summarization of most
essential characteristics
Changes, trends and patterns must be
made apparent
Descriptive and inferential statistics used
Use of GIS for mapping
Monitoring
Summary
•
G
References
•
•
•
•
•
•
Artiola, J.F., Pepper, I.L., and Brusseau, M. (2004) Environmental
Monitoring and Characterization. Elsevier, Amsterdam.
Harrison, R.M. (2006) Introduction to Pollution Science. The Royal
Society of Chemistry, London.
Hewitt, C.N. (ed.) (1991) Instrumental Analysis of Pollutants. Elsevier,
London.
Kegley, S.E. and Andrews, J. (1998) The Chemistry of Water.
University Science Books.
Reeve, R.N. (2002) Introduction to Environmental Analysis. Wiley.
Smol, J.P. (2008) Pollution of Lakes and Rivers: A
Paleoenvironmental Perspective. Wiley-Blackwell.