Using Lichens as a Biomonitor to Examine Small Scale Gold Mines and its Implications on
Atmospheric Mercury Levels in the Brazilian Pantanal
K.N. Ma
Program in the Environment, University of Michigan, Ann Arbor, Michigan, USA
Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA
ABSTRACT
Due to its high binding affinity to gold, small scale gold mining operations use metallic mercury
(Hg) in large volumes to aggregate gold particles within a sediment matrix. Burning the goldmercury amalgam is one of the largest sources of Hg deposition in the Pantanal region. The
deposition of Hg into terrestrial environments and subsequent methylation of Hg by bacteria
transforms metallic Hg into toxic monomethylmercury (MMHg). The amount and concentration
of MMHg increases with every trophic order and can lead to toxic levels in higher trophic order
organisms, such as piscivorous fish. Direct inhalation during the burning process and
consumption of higher trophic order fish are the main pathways for human exposure. A
preliminary study of total mercury (THg) concentration for two species of tree lichens
(Parmotrema praesorediosum and Myelochroa lindmanii) was conducted in three study areas
within the Pantanal region to in attempt to estimate the amount of gaseous mercury (Hg (0)) in
the atmosphere. Tree lichens uptake nutrients directly from the atmosphere; therefore, measured
mercury concentrations in the plant tissue reflected average atmospheric mercury levels. The
THg concentration for the total 11 samples ranged 33 to 442 ng/g, with a mean value of 105 ±
100ng/g. The Poconé mining site showed higher overall THg concentrations than the Cangas
District mine. However, both mining sites displayed a possible spatial depositional trend.
Samples that were taken closer to the point source displayed higher THg than samples that were
retrieved from farther away. Due to the limited number of samples, I suggest that additional
samples must be collected in order to confirm the trend.
1
Introduction
Wetlands perform a wide variety of functions that help maintain fundamental ecosystem
interactions between living organisms and the environment. Recycling and storage of nutrients,
erosion control, and carbon sequestration are a few of the functions that wetlands help mediate.
This region, which is often times referred to as a biodiversity hotspot serves as a refuge for many
endangered species, such as jaguars, giant anteaters, and swamp deers. The Brazilian Pantanal is
a critically impacted ecosystem and the value of its ecosystem services for the country has been
estimated at over $15.5 billion USD (Seidle, 2000). In spite of this value, less than 2% of the
area is protected by the government (Seidle, 2000). One of the greatest threats to Pantanal is the
Hg (0) emissions from artisanal and small scale gold mines (ASGM).
ASGM release about 640 to 1350 Mg of mercury (Hg (0)) per annum globally into the
atmosphere, which averages to about 1000 Mg yr-1 of Hg (0) emissions from approximately 70
countries (Viega 2011). ASGM are responsible for some of the largest point source releases of
elemental mercury (Veiga 2011; Environmental Protection Agency, 2004). If given the right
conditions Hg (0) can transform into monomethylmercury (MMHg), a dangerous and toxic form
of mercury to humans. In Brazil alone, at least 200,000 people are employed by ASGM and
about 99% of all miners operate mines without government regulations and environmental
permits (Sousa 2011). Therefore, the possibility of mercury exposure is extremely high.
Small scale miners mix the ore with liquid mercury, which amalgamates the gold into the
mercury. Subsequently, the amalgam is heated up by using an open flame source, such as a blow
torch, which evaporates off the mercury, leaving the gold as residual particles. The open system
technique results in Hg (0) deposition into nearby environments. Metallic mercury, which can
become highly bioavailable upon environmental transformation to methlymercury, is of low cost
2
and also efficient at aggregating gold particles due to the high binding affinity between gold and
mercury (Veiga 2007).
Many times, gold miners do not use protective gear and are directly exposed to Hg (0)
through inhalation (Viega, 2007). In addition, because of its highly volatile nature, metallic
mercury is released in its gaseous form where it can be transported to nearby environments. The
Hg (0) can deposit into the local environments or circulate into the atmosphere and undergo
deposition at a distant location. Hg (0) has a residence time up to one year in the atmosphere and
can travel globally and can be deposited into other pristine environments. Once deposited in its
oxidized form (Hg (II)), mercury can be microbially transformed to monomethylmercury
(MMHg) (Hintelmann, 2010), which is a dangerous neurotoxicant. In fact, methylmercury
(MeHg) can efficiently enter the food webs and can increase in concentration with increasing
trophic levels (Seixas 2012), often leading to unsafe levels in high trophic level organisms, such
as piscivorous fish and birds. The indirect pathway of mercury exposure in humans transforms
from elemental mercury Hg (0) to MMHg, which is a dangerous neurotoxicant. Side effects of
mercury exposure can start as dizziness, nausea, vomiting, but can escalate to more serious
health effects, such as autoimmune dysfunction, kidney dysfunction, miscarriages, and even
death (World Health Organization, 2013). Because of the low cost, highly effectiveness at
capturing gold, and accessibility, metallic mercury has become an ever increasing environmental
concern for the Pantanal, the world’s largest and arguably most pristine wetland.
Brazil is the largest gold-producing country in South America, and 90% of all the gold
comes from artisanal and small scale mining which emits approximately 100-200 metric tonnes
of mercury annually (Malm 1998). Since the 1980’s, at least 50 metric tonnes of mercury has
been released into the atmosphere by gold miners in Poconé, Brazil, a major city that borders the
3
Pantanal region (Oliveira, 2004) and there have been at least 130 registered small scale gold
mines, or garimpos that have employed about 5,000 people, almost 23% of the entire population
of Poconé (Oliveira, 2004). Many of the communities near or within the Pantanal rely on fish for
their primary diets, and mercury contaminated fish can therefore pose a serious risk to the locals,
especially for pregnant women and children (Malm 1998). Of the 256 fisherman that were
interviewed in the Oliveira (2000) study in Poconé, 92% indicated that they were fishing solely
for subsistence. Clearly, careful examination of the relation between the gold mining operations
and local mercury contamination is critical to better characterizing the impact posed by high
mercury levels on human health in local communities.
While there has been research showing that gold mining operations affect the
concentration levels of mercury in tropical aquatic systems (Ikingura, 2002), there has been little
information in the Pantanal as to whether small-scale gold mining operations affect atmospheric
concentration levels of mercury. It was estimated that about 55% of mercury used to aggregate
gold particles is released directly into the global atmosphere (Inkingura, 2002). Since mercury
may be locally released into the atmosphere at significantly higher amounts compared to areas of
low or non-existing mining activities, it can potentially become a major public health concern.
My thesis is a preliminary study aiming to examine whether small-scale gold mining operations
have a significant effect on the concentrations of gaseous elemental mercury in the atmosphere in
the Pantanal, using tree lichens as an atmospheric biomonitor for average levels of atmospheric
Hg (0). Instead of directly collecting atmospheric samples, two species of lichens were used as
biomonitor because their tissue mercury concentrations can be correlated to atmospheric mercury
levels (Lodenius, 2013). Furthermore, biomonitors offer an exceptional advantage because they
4
integrate atmospheric mercury over time, thus providing an estimate of average atmospheric
mercury levels among different seasons (Lodenius, 2013).
Climate and Geography
The Brazilian Pantanal is the world’s largest freshwater wetland, covering 210,000 km2
in the Brazilian states of Mato Grosso, Mato Grosso do Sul, eastern Bolivia, and northeastern
Paraguay (World Wildlife Fund). It is a United Nations Educational, Scientific, and Cultural
Organization (UNESCO) World Heritage Site and is home to over 4,700 plant and animal
species (WWF).
The Pantanal is located south of the equator in the tropical torrid zone, far enough south
that the area experiences pronounced seasonal changes in precipitation. During November to
April, the rainy season transforms the landscape into an enormous wetland with areas on average
of ½ to 2 meters deep with water. The wet summer climate is due to the moving equatorial
continental air masses originating from the northern Amazon. The dry season falls between midApril and mid-September and is characterized with clear skies, minimum precipitation, and high
temperatures. The dry winter regime is due to the tropical-Atlantic air mass coming from the
Chapada dos Guimarães highlands at an elevation between 600 and 700 meters above sea level
(Olivera, 2004).
The tropical alluvial basin wetland is divided into three regions; Alto (high), Médio
(medium), and Baixo (low) Pantanal. Annual rain fall and inundations are most extreme in the
Baixo Pantanal, where there is little relief for drainage and rainfall can be up to three to four
meters of rain annually. The Médio Pantanal is the transition zone between the Baixo and Alto
Pantanal. This area receives about three to four months of heavy rain. The Alto Pantanal, which
5
is located at higher a higher elevation receives 30-40 centimeters of rain for two to three months
during the rainy season. Average daily temperatures in the wet summer (October- April) are well
over 35˚C. During the cooler months, the average daily temperatures during the months of May
and September are approximately 20˚C (Oliveira 2004). The prevailing winds dominate from
west and north east during the months of October to April due to the heated air masses from the
from the western Amazon rainforest (Oliveira, 2004). From May to September, the polar air can
cause dramatic decreases in temperature resulting in south and southeast winds (Oliveira, 2004).
Gold Mining and Societal Implications
Poconé, which is an artisanal and small scale gold mining based economy located in the
state of Mato Grosso, is impacting the local environment due to unregulated mercury emissions
from amalgamation burning. In 1777, the first gold rush occurred in Cuiabá and expanded 104
km southeast to Poconé and eventually into the Cangas District, which restricted gold mining to
only soil surface excavation (Callil, 2010). After this technique exhausted the superficial gold, an
unfortunate smallpox outbreak killed 50% of the population in Poconé during the years of 18641870 (Callil, 2010).
The second gold rush of 1976 in Poconé was purposefully stimulated by the Special
Program for the Development of the Pantanal (PRODEPAN), which officially declared that
mining was a fundamental and essential asset to the economy of Mato Grosso. In 1982, the
garimpeiros, (or miners) had established a culture of small scale gold mining in Poconé, which
dramatically changed the socio-economic and cultural dynamics among the people in the area
(Callil, 2010). Before the gold mining sector dominated the local economy, small populations of
cattle ranchers served as community leaders instead of traditional political figureheads (Callil,
6
2010). By establishing paternalistic and hierarchical relationships among the other families,
people were dependent on informal and verbal agreements with other cattle ranchers. In addition,
due to the isolated and remote populations, inaccessible roads, and long distances between each
community, children of the cattle ranchers had limited opportunities to attend school. This
restricted the career opportunities for children other than farm work. Around 1985, the small
community structure was drastically altered when 10,000 garimpeiros migrated to Poconé during
the peak of the gold rush, which offered an alternative to farm work, created incentive to develop
efficient gold-separating technology, and introduced a large cash flow into a traditionally
structured community (Callil, 2010). Participating in the gold rush offered a higher monetary
incentive and social influence, which encouraged the local people to abandon their traditional
cattle ranching responsibilities and enter the small scale gold mining industry. Because of the
lack of authority, planning, and regulations by the local government, the small scale gold mining
industry has caused severe environmental destruction (Callil, 2010). Due to the fact the city lies
directly on gold-containing land, anyone can start a microfinance business by simply panning for
gold. It has been observed there has been prospecting for gold even in personal gardens (Callil,
2010).
Currently, the Pantanal faces threats of industrial development and environmental
degradation, which has led to national organization, such as Pantanal Private National Heritage
Reserve (SESC) and the UNESCO World Heritage Site-Pantanal Conservation dedicated to
combating degradation and restoring natural resources to enable local communities to stay within
the Pantanal (Callil, 2010). However, interventions from these organizations still do not address
the issues of mercury released from small scale gold mines. Around 1995, FEMA (Fundaco
Estadual do Meio Ambiente de Mato Grosso), the environmental agency of Mato Grosso issued
7
an implementation plan to decrease Hg emissions to the air (Oliveira, 2004). Since then, gold
mining companies have modified their operations, favoring heavy machinery specialized for
digging and more advanced technology for decreasing Hg (0) release (Callil, 2010).
Advantages of using biomonitors
A biomonitor is any type of living organism that can be used to quantify the quality of the
environment (Nui 2013). By directly incorporating nutrients from the atmosphere through
extracellular ion exchange or intracellular uptake, lichens can reflect an integrated estimate of Hg
(0) concentrations, averaging seasonal changes, wind pattern contrasts, and changing
temperatures (Sensen 2001). Most commonly, lichens are used to analyze adjacent to point
sources of pollution. High levels of Hg (0) are typically found near the point source, with nearexponential decrease in Hg (0) levels occurring with distance (Sensen 2001).
Because of the wide distribution of tree lichens,easy accessibility, and low cost of
collection, there have been many applications of lichens as biomonitors. In particular, there
have been many studies that have used with lichens (and in some cases mosses) that serve as
biomonitors for Hg (0) in air (Fernandéz et al., 2000; Sensen et al., 2002; Krishna et al., 2003;
Harmens et al., 2008; Grangeon et al., 2011; Blum 2012 et al.,; Nui et al., 2013; and Lodenius
et al., 2013). For this study, lichens growing on deciduous trees were sample in order to monitor
Hg (0) emissions from the nearby small scale gold mines. Tree lichens were sampled near and
far from the point source in order to assess the impact of Hg (0) emissions from the area and
investigate spatial depositional trends.
8
Methods
Site Description
During the summer of 2013, tree lichen samples were collected from Poconé, the Cangas
District, and at the 114 km marker along the Transpantaniera (MT-060) in the Pantanal region
(Fig. 1 and Fig. 2).
Tree lichen samples were collected along transects away from the mines. Two transects
were chosen; one in the municipality of Poconé in a global northeastern direction (Fig. 2); and
one in the Cangas District in a global north northwest direction from their respective gold mines
(Fig. 3).
Both transects were situated along the northeastern boundary of the Pantanal region of
Mato Grosso, Brazil (16°15'16.89"S, 56°40'18.08"W) (Table 1). As a control sample, tree lichen
were collected from the heart of the Pantanal about 116 km from the nearest known gold mining
activity, which is located along the Transpantaneira (MT-060) 114 km southwest from Poconé
(17°06'00.3"S 56°56'31.1"W). The first two sites were located in areas the small scale gold
mining activity, while the third site was 114 km from any urban areas and small scale gold
mining activity (Fig.4).
The prevailing wind directions are south and southeast during the months of May and
September, which was during the sample month (Oliveira, 2002.) The prevailing wind directions
during the months of October and April are from the west and northwest (Oliveira, 2002).
9
Sampling
The tree lichen species Parmotrema praesorediosum and Myelochroa lindmanii were
collected in three locations between June 10 and 23, 2013 on days with fair weather (ambient
temperatures between 32-35 ˚C), however one week prior to sampling the all three study sites
experienced light rain. Five samples were collected at the Poconé mining area, four samples were
collected at the Cangas District mining area, and two samples were taken on the Transpantaniera
with the Pantanal. At each site, samples of P. praesorediosum and M. lindmannii were collected
while wearing latex gloves and using stainless steel forceps. The forceps were cleaned with
isopropanol in between each sample. Due to the scarcity of available lichen material, samples
were taken from both the trunks and branches of deciduous trees. Samples were collected from a
height of approximately two to three meters above the ground. The samples were stored in
polyester (Ziploc) sample bags and stored in a freezer in Poconé, Brazil. Once the samples
arrived to the Biogeochemistry & Environmental Isotope Geochemistry Laboratory at the
University of Michigan, the samples were immediately placed in a freezer. Three weeks later, the
samples were transferred into acid-washed clean glass vials, rinsed with de-ionized water, and
placed into an oven at 50˚C for 12 hours. The samples were then cleaned by removing bark,
leaves, and any other foreign matter using acid washed Teflon-coated tweezers and they were
subsequently freeze-dried. Afterwards, the samples were homogenized using an agate mortar and
pestle that was cleaned with isopropanol in between each sample. All concentrations were
recorded based on the dry weight.
10
Hg Concentration Analysis
The samples were combusted at approximately 800˚C and were analyzed for total
mercury concentration (THg) using a Nippon Instruments MA-2000 AAS Hg analyzer. The
calibration curve was established a using a series of dilutions of the standard solution NIST SRM
standard solution and was checked between every five samples with a secondary standard
solution (average measured THg= 58± 0.4%, n=4). Lichen reference material BCR-482 (average
measured THg= 456 ± 18 μg/g, n =4) was combusted alongside the 11 samples. Each reference
material analysis was within 10% of the certified values. When lichen material was in excess,
duplicates were combusted with the corresponding sample. The replicate samples were within
±1.5% RSD. The minimum detection limit was 1.66 ng/g.
Results and Discussions
Background THg Concentrations
The two lichen controls samples had THg concentrations of 34 and 60 ng/g (n=2). The
average THg concentrations was 47 ± 15 ng/g. Sample PCER-J and its duplicate displayed
consistent concentrations of 59.9 ng/g and 60.3 ng/g, respectively. The second control sample
PCER-P however, had a lower concentration of 34 ng/g (Fig. 7). Based on the precision from the
PCER-J sample and the duplicate, these two samples may better reflect the area’s estimate Hg
(0) atmospheric levels.
THg concentrations for samples close to the mine and along the transect
Mercury concentrations for the Poconé and Cangas District transect displayed generally
decreasing THg concentration values as distance from the point source increased. Samples T-0
11
and C-2, which were located closest to the amalgam burning site showed the highest THg
concentrations. Sample T-0 was over 8 times the average background THg values. Samples (T-1,
T-2, T-3, T-4, C-1, 2C-1, C-3, and C-4) that were collected further from the point source
revealed lower THg concentrations. The THg concentrations for the 11 samples ranged from 34
to 442 ng/g with a mean value of 105± 100 ng/g (table 2). The five samples collected at the
Poconé mine had THg concentrations ranging from 74 to 442 ng/g. The average THg
concentration was 96 ± 15 ng/g (Fig. 5). The highest THg concentration in lichens was found in
the Poconé transect, approximately 30 meters away from the amalgam burning site. About 270 m
northwest from T-0 the THg concentration drop drastically to 74 ng/g. The remaining samples
vary in THg concentrations but all remain under120 ng/g.
Four lichen samples from the Cangas District had THg concentrations ranging from 33
to 109 ng/g with an average THg concentration of 75 ±32 ng/g (Fig. 6). The highest THg
concentration, sample C-2, had a Hg (0) concentration of 109 ng/g, and was 0.33 km away from
the amalgam burning site. Sample C-3, located only 0.36 km away from the amalgam burning
site was drastically lowers at 33 ng/g. A similar trend was observed in Steinnes and Kroger
(1977), where high levels Hg (0) were found close to the point source (or amalgam burning site)
and levels drastically decreases within a short distance.
Samples that were collected at the Poconé site revealed higher THg concentrations on
average compared to the two other sites. However due to the limited number of samples
collected there is not enough data to conclude definitively whether the atmospheric Hg (0) was
sourced from the Poconé mine. In addition, there are six other known ASGM within a 2 km
radius that could be responsible for the elevated THg concentration levels. Furthermore, with
only two known surrounding ASGM within a 3 km radius, the likelihood of atmospheric Hg (0)
12
coming from the surrounding ASGM is much less. Therefore, the Cangas District mine samples
had an expected overall lower average THg concentration.
Conclusions
Two species of tree lichens (P. praesorediosum and M. lindmannii) were collected in two
areas with different levels of predicted atmospheric Hg (0), just outside of the Pantanal. The tree
lichen analysis although very limited in scope gave a general estimation of the levels of
atmospheric Hg (0) in the municipality of Poconé and narrowed the possible point sources. Total
Hg concentrations of tree lichens have been used as a biomonitor in many previous studies in
order to outline the atmospheric Hg (0) depositional pattern.
The results from this preliminary study reveal that tree lichens closest to the mining areas
have the highest Hg concentrations, confirming that workers at these sites are exposed to
elevated atmospheric Hg (0) levels. The results also suggest that the elevated Hg (0) is rather
local to mines and that the communities located approximately at least 3 to 4 km from the mining
areas are most likely not exposed to elevated Hg (0) levels. However, the sample size and spatial
distribution of the samples analyzed in this study were not adequate to give detailed information
on the spatial variability of Hg (0)
With a larger sample size, the biomonitoring could better identify atmospheric mercury
pathways and locate communities and villages who are at higher risk of mercury exposure.
Further exploratory analyses could be conducted to determine the total Hg (0) levels in P.
praesorediosum and M. lindmannii and in turn extrapolate people’s average Hg (0) exposure.
13
Acknowledgments
This project would not be possible without the funding from the Scott Turner Grant,
LS&A Honors Grant, Barger Leadership Institute Fellowship Grant, and the Biogeochemistry
& Environmental Isotope Geochemistry Laboratory. A special thanks to the Pantanal
Partnership, the Pantanal Center for Education and Research (PCER), Ethan Shirely, and the
Martins/Campos Family.
14
Figures and Tables
Figure 1: Location of the two study sites, Poconé and the Cangas District of Mato Grosso, Brazil. Map by
Marcos Figuieredo
15
Figure 2: Aerial view of the Poconé Mine Transect, labelled with the corresponding THg
concentrations. Image from Google Earth
Figure 2: Aerial view of the Cangas District Mine Transect, labelled with the corresponding THg
concentrations (ng/g). Image from Google Earth
16
Figure 4: Aerial view of Mato Grosso, Brazil, showing all three study sites. Image from Google Earth
Sample No.
T-4
T-1
T-3
T-2
T-0 (Poconé Mine)
C-1
2C-1
C-3
C-2
PCER-J
PCER-P
Location
Poconé
Poconé
Poconé
Poconé
Poconé
Cangas District
Cangas District
Cangas District
Cangas District
Pantanal
Pantanal
Latitude
16°15'46.37"S
16°15'46.48"S
16°15'20.45"S
16°15'19.08"S
16°15'16.89"S
16° 3'28.48"S
16° 3'3.85"S
16° 3'6.66"S
16° 3'7.49"S
16°58'47.30"S
16°58'48.53"S
Longitude
56°39'23.76"W
56°39'23.36"W
56°40'7.36"W
56°40'9.37"W
56°40'18.08"W
56°32'38.44"W
56°32'47.83"W
56°32'45.20"W
56°32'44.45"W
56°56'45.46"W
56°56'49.44"W
Table 1: Latitude and longitude coordinates of the 11 samples
17
Sample No.
Location
Distance (m) from mine
T-Hg (ng/g)
Poconé
1.91
119.90
T-4
Poconé
1.87
95.33
T-1
Poconé
1.87
99.26
T-1*
Poconé
0.35
94.03
T-3
Poconé
0.35
96.26
T-3*
Poconé
0.27
73.99
T-2
Poconé
0
441.97
T-0
Cangas District
0.49
70.89
C-1
Cangas District
0.42
88.49
2C-1
Cangas District
0.36
33.25
C-3
Cangas District
0.33
109.30
C-2
Pantanal
85.41
from
T-0
59.88
PCER-J
Pantanal
85.41 from T-0
60.31
PCER-J*
Pantanal
86.1
33.92
PCER-P
Table 2: Mercury concentrations for lichens from the Pantanal area, Brazil
(*) Duplicate samples
Concentration of Hg (ppb)
Hg Concentrations in Poconé, Brazil
450
400
350
300
250
200
150
100
50
0
Pocone
0
0.5
1
1.5
2
Distance from the Poconé Mine (km)
Figure 5: Plot of distance (km) and concentrations of Hg (ppb) for the five lichen samples in Pocone,
Brazil. The five sample THg concentrations ranged from 74 to 442 ng/g, with an average THg
concentration of 96 ± 15 ng/g.
18
Concentration of Hg (ppb)
Hg Concentrations in the Cangas District, Brazil
120
110
100
90
80
70
60
50
40
30
Cangas
0
0.1
0.2
0.3
0.4
0.5
0.6
Distance from the Cangas District Mine (km)
Figure 6: Plot of distance (km) and concentrations of Hg (ppb) for the four lichen samples in the Cangas
District of Poconé, Brazil. The four sample THg concentrations ranged from 33 to 109 ng/g, with an
average THg concentration was 75 ±32 ng/g.
Figure 7: Plot of distance (km) and concentrations of Hg (ppb) for the two control lichen samples in
relation to the Poconé transect. The THg concentrations ranged from 34 to 60 ng/g. The average THg
concentrations were 51 ± 15 ng/g.
19
References
Blum, J.D., Johnson, M.W., Gleason, J.D., Demers, J.D., Landis, M.S., Krupa,S. 2012. Mercury
Concentration and Isotopic Composition of Epiphytic Tree Lichens in the Athabasca Oil Sands
Region. Environmental Science. 3, 373-390
Callil, C.T., Junk, J,W. (Gold-mining near Pocone: Environmental, social and economic impact)…The
Pantanal: Ecology, biodiversity and sustainable management of a large neotropical seasonal wetland
Fuga, A., Saiki, M., Marcelli, M. P., & Saldiva, P. H. N. 2008. Atmospheric pollutants monitoring by
analysis of epiphytic lichens. Environmental Pollution,151(2), 334-340.
Grangeon, S., Guedron, S., Asta, J., Sarret, G., Charlet, L., 2012. Lichen and soil as indicators of an
atmospheric mercury contamination in the vicinity of a chlor-alkali plant (Grenoble, France). Ecol.
Indic. 13 (1), 178–183.
Hintelmann H. 2010. Organomercurials. Their formation and pathways in the environment. Met Ions Life
Sci. 7:365-401.
Ikingura, J.R., Akagi, H.2002. Lichens as a Good Bioindicator of Air Pollution by Mercury in SmallScale Gold Mining Areas, Tanzania. Bulletin of Environmental Contamination and Toxicology. 68.
699-704.
Käffer, M.I., de Azevedo Martins, S.M., Alves,C., Pereira, V.C., Fachel, J., Ferrão Vargas, V.M., 2011.
Corticolous lichens as environmental indicators in urban areas in southern Brazil. Ecological
Indicators. 11(5), 1319-1332.
Käffer, M.I., Lemos, A.T., Apel, M.A., Vaz Rocha, J., de Azevedo, S., Ferrão Vargas, V.M., 2012. Use of
bioindicators to evaluate air quality and genotoxic compounds in an urban environment in Southern
Brazil. Environmental Pollution. 163, 124-131.
Lodenius, M. 2013. Use of plants for biomonitoring of airborne mercury in contaminated areas. Environ
Res. (in press)
Niu, Z., Zhang, X., Wang, S., Ci, Z., Kong, X., Wang, Z., 2013. The linear accumulation of atmospheric
mercury by vegetable and grass leaves: Potential biomonitors for atmospheric mercury pollution.
Environmental Science and Pollution Research. 20:6337–634.
Oliveira, L.J., Hylander, L.D., de Castro e Silva, E. 2004. Mercury Behavior in a Tropical Environment:
The Case of Small-Scale Gold Mining in Poconé, Brazil. Environmental Practice. 6(2) 121-134.
Seixas, T.G., Moreira, I., Malm, O., Kehrig, H. 2012. Ecological and biological determinants of
methylmercury accumulation in tropical coastal fish. Environmental Science and Pollution Research
International. 20 (2) 1142-1150.
Sensen, M., Richardson D.H., 2002. Mercury levels in lichens from different host trees around a
chloralkali plant in New Brunswick, Canada. Science of the Total Environment. 293(1-3):31-45.
Sousa, R. N., Veiga, M. M., Klein, B., Telmer, K., Gunson, A. J., & Bernaudat, L. 2010. Strategies for
reducing the environmental impact of reprocessing mercury-contaminated tailings in the artisanal and
small-scale gold mining sector: Insights from tapajos river basin, brazil. Journal of Cleaner
Production,18 (16–17), 1757-1766.
20
Steinnes E, Krog H. 1977. Mercury, arsenic and selenium fall-outbfrom an industrial complex studied by
means of lichen transplants. Oikos. 28:160 –164.
United Nations Environment Programme (UNEP). A Practical Guide: Reducing Mercury Use in Artisanal
and Small-Scale Gold Mining, 2011. (Accessed on February 15, 2014 at
http://www.unep.org/chemicalsandwaste/Portals/9/Mercury/Documents/ASGM/Techdoc/UNEP%20
Tech%20Doc%20APRIL%202012_120608b_web.pdf)
World Health Organization. 2013. Mercury Exposure and Health Impacts among Individuals in the
Artisanal and Small-Scale Gold Mining (ASGM) Community. (Assessed on February 2, 2014 at
http://www.who.int/ipcs/assessment/public_health/mercury_asgm.pdf)
Veiga, M.M., et al. (2005). Pilot Project for the Reduction of Mercury Contamination Resulting
From Artisanal Gold Mining Fields in the Manica District of Mozambique.
21