Monitoring of Heavy Metal Contamination Using Tissues of Two Ardeids Chicks, Korea

This study presents concentrations of iron, zinc, manganese, lead and cadmium in livers and kidneys of Little Egret Egretta garzetta (n = 10) and Black-crowned Night-Heron Nycticorax nycticorax (n = 10) chicks from Pyeongtaek, Gyeonggi-do, Korea. Essential element concentrations such as iron, zinc and manganese did not differ between both species chicks in livers and kidneys, but lead and cadmium concentrations were significantly greater in both tissues of Little Egret chicks (lead 2.78 ± 4.06 μg/g wet weight, cadmium 10.3 ± 12.8 kg/g wet weight) than in those of Black-crowned Night-Heron chicks (lead 0.92 ± 0.73 μg/g wet weight, cadmium 1.00 ± 1.00 kg/g wet weight). Lead and cadmium concentrations in livers of Black-crowned Night-Heron chicks were highly related to sediment and/or prey concentrations of their foraging sites in Korean studies. It shows that lead and cadmium concentrations in livers of heron chicks can reflect those of surrounding environment of breeding sites. In this study, cadmium concentrations were higher in kidneys than in livers and it’s not recent high-level exposure but chronic background exposure to cadmium contamination around breeding site. Therefore, we suggest that cadmium concentrations in livers and kidneys can be used as a bioindicator of acute and/or chronic local contamination.     

Mercury Contamination in Idaho Bald Eagles, <Emphasis Type="Italic">Haliaeetus leucocephalus</Emphasis>

Because mercury contamination is potentially threatening to bald eagle (Haliaeetus leucocephalus) populations, we collected molted feathers at nests to determine the level of contamination in bald eagles in the state of Idaho, USA. Eagle feathers contained measurable amounts of cadmium (Cd), chromium (Cr), selenium (Se), lead (Pb), as well as mercury (Hg). Cadmium, Cr, Se, and Pb levels averaged 0.17, 4.68, 2.02, and 1.29 mg/kg dry weight, respectively, and were at or below concentrations indicated as causing reproductive failure in bald eagles. Mercury contamination was found to be the highest averaging 18.74 mg/kg dry weight. Although a concentration of only 7.5 mg/kg dry weight Hg in bird feathers can cause reduced productivity and even sterility, all of the eagles we sampled bred successfully and the population of bald eagles continues to grow annually throughout the state.     

Levels of Cadmium, Mercury, and Lead in Magellanic Penguins (Spheniscus magellanicus) Stranded on the Brazilian Coast

Cadmium (Cd), mercury (Hg), and lead (Pb) were determined in samples of liver and breast muscles of first-year Magellanic penguins (Spheniscus magellanicus), from two different areas on the Brazilian coast, 35 on the Rio de Janeiro coast and 12 on the Rio Grande do Sul coast. In both areas, Cd concentrations in muscle samples were <0.025 μg/g. However, the Cd and Hg concentrations found in liver and Hg concentrations found in muscle showed a significant difference between the two regions. The geometric mean of the concentrations was higher in the specimens from Rio de Janeiro (Cd—6.8 μg/g; Hg—liver, 1.6 μg/g, and muscle, 0.4 μg/g wet weight) than in those from Rio Grande do Sul (Cd—2.3 μg/g; Hg—liver, 0.9 μg/g, and muscle, 0.1 μg/g wet weight). The site differences could be related to differences in diet influenced by geographic factors. Brazil’s southeastern coast is highly urbanized, and its coastal waters are contaminated by the waste of agricultural and industrial activities. There is a lack of information on the levels of heavy metals in S. magellanicus, however, their wide distribution and top position in the trophic chain make the use of stranded specimens an attractive source of information for monitoring heavy metals in the South Atlantic coast.     

Bioconcentration and Biomagnification of Mercury and Methylmercury in North Sea and Scheldt Estuary Fish

Total Hg and MMHg concentrations were assessed in more than 350 fish and shellfish samples. Hg concentrations in Greater North Sea fish of prey range from 0.039 mg kg^–1 wet weight (ww; for ray) to 0.61 mg kg^–1 ww (for dogfish) and for all other fish species, from 0.045 mg kg^–1 ww (for plaice) to 0.33 mg kg^–1 ww (for sand sole), with 95 ± 2% of the Hg content in the MMHg form. In Belgian coastal zone, fish concentrations range from 0.063 mg kg^–1 ww for plaice to 0.13 mg kg^–1 ww for flounder, with 82–87% of the Hg content in the MMHg form. In fish of the Scheldt, which is a very polluted estuary, Hg levels, as well as the percent MMHg of the total Hg, were lower than in the two zones previously mentioned. The intraspecies variability is of the order of 50% in each of the three zones. In liver tissue, a much larger variability was observed than in muscle tissue, except for fish species of the Scheldt. In most cases, the MMHg fraction in a particular fish species is inversely related to the intraspecies variability. Bioconcentration and biomagnification factors (BCF and BMF, respectively) were assessed. MMHg-BMFs were a few orders of magnitude higher than Hg(inorganic)-BMFs, and for the same species were always highest in the Greater North Sea and lowest in the Scheldt. For each of the Belgian coastal zone four species, a weak positive correlation between Hg content and fish length was found; however, the larger the size-range, the better the correlation.Taking fish length into account, a statistically significant difference in contamination level was observed for species sampled from the different geographical zones.     

Mercury Status of the Amazon Continental Shelf: Guiana Dolphins (<Emphasis Type="Italic">Sotalia guianensis</Emphasis>, Van Benédén 1864) as a Bioindicator

Total mercury (Hg) was analyzed in muscle tissue of 27 accidentally captured Guiana dolphins (Sotalia guianensis) in order to evaluate Hg contamination levels present in the Amazon Continental Shelf, in Amapá state, North Brazil. The samples showed a mean concentration of 0.4 ± 0.16 μg/g wet weight (ww), ranging from 0.07 to 0.79 μg/g ww. As observed in several other cetacean species, Hg concentrations presented positive correlations to body length, related to the capacity to bioaccumulate this element throughout life. Hg concentrations were not significantly different between males (mean = 0.38 μg/g ww; n = 15) and females (mean = 0.42 μg/g ww; n = 12). Concentrations were low when compared to results of studies carried out with small cetaceans in the Northern Hemisphere, and with some previous studies in the south-eastern region of Brazil. In contrast with high Hg concentrations normally detected in river dolphin samples from Amazon River tributaries, our results suggest that the Amazon coast contains low levels of Hg in bioavailable form.     

Presence of Polycyclic Aromatic Hydrocarbons (PAHs) in Top Soils from Rural Terrains in Mexico City

A soil survey was carried out to determine the levels and sources and concentrations of 16 polycyclic aromatic hydrocarbons in 2 semi-rural terrains in Mexico City (Tlahuac and Milpa Alta) during 2008–2009. PAH determination was made by Soxhlet extraction and chromatographic clean-up with final analysis by gas chromatography with a flame ionization detector. The concentrations in Tlahuac were 9.13 mg/kg (dry season) and 11.22 mg/kg (wet season) and in Milpa Alta were 11.43 mg/kg (dry season) and 35.77 mg/kg (wet season). The variation of total PAH concentrations are due to environmental and anthropogenic conditions within Mexico City and also the addition of compost to the soils. According to Mexican regulations BaP, DaA, BbF and Ind were within the permissible limit (2 mg/kg) for agricultural and residential soils and BkF was close to the limit (8 mg/kg). The total PAH concentrations do however surpass the permissible European limit of 1,000 μg/kg and there is probably some risk to human health, in spite of measures aimed at decreasing contamination in Mexico City. Long term monitoring of soils will be necessary.     

High Mercury Concentrations Reflect Trophic Ecology of Three Deep-Water Chondrichthyans

The relative contributions of proximity to mercury sources and trophic ecology to realized axial muscle mercury concentrations were explored for three deep-water chondrichthyans (Etmopterus princeps, Centroscymnus coelolepis, and Hydrolagus affinis), two species of which are harvested for human consumption. Samples were taken at three North Atlantic Ocean locations: the Azores, the Charlie Gibbs Fracture Zone, and the Bear Seamount. Despite the long distances between anthropogenic sources and the sampling locations, all species from all locations had muscle mercury concentrations exceeding the United States human health screening value of 0.3 mg/kg wet weight. Proximity to anthropogenic sources was not an obvious determinant of these elevated concentrations. Generally, mercury concentrations appeared to increase with increased dependence on benthic versus pelagic food sources (as indicated by interspecies differences in δ¹³C), and with higher position in the trophic web (as indicated by differences in δ¹⁵N).     

Ontogenetic patterns in bluefish (Pomatomus saltatrix) feeding ecology and the effect on mercury biomagnification

In this study, bluefish (Pomatomus saltatrix; age 0-7, n?=?632) and their prey (forage fish, macroinvertebrates, zooplankton; n?=?2,005) were collected from the Narragansett Bay estuary (RI, USA), and total Hg concentration was measured in white muscle and whole-body tissues, respectively. Bluefish Hg concentrations were analyzed relative to fish length, prey Hg content, and ontogenetic shifts in habitat use and foraging ecology, the latter assessed using stomach content analysis (n?=?711) and stable nitrogen (δ(15)N) and carbon (δ(13)C) isotope measurements (n?=?360). Diet and δ(13)C analysis showed that age 0 bluefish consumed both benthic and pelagic prey (silversides, sand shrimp, planktonic crustaceans; δ(13)C?=?-?16.52‰), whereas age 1?+ bluefish fed almost exclusively on pelagic forage fish (Atlantic menhaden, herring; δ(13)C?=?-?17.33‰). Bluefish total Hg concentrations were significantly correlated with length (mean Hg?=?0.041 and 0.254?ppm wet wt for age 0 and age 1?+ bluefish, respectively). Furthermore, Hg biomagnification rates were maximal during bluefish early life stages and decelerated over time, resulting in relatively high Hg concentrations in age 0 fish. Rapid Hg accumulation in age 0 bluefish is attributed to these individuals occupying a comparable trophic level to age 1?+ bluefish (δ(15)N?=?15.58 and 16.09‰; trophic level?=?3.55 and 3.71 for age 0 and age 1?+ bluefish, respectively), as well as juveniles having greater standardized consumption rates of Hg-contaminated prey. Finally, bluefish larger than 30?cm total length consistently had Hg levels above the U.S. Environmental Protection Agency criterion of 0.3?ppm. As such, frequent consumption of bluefish could pose a human health risk, and preferentially consuming smaller bluefish may be an inadequate strategy for minimizing human dietary exposure to Hg.     

Tissue Concentrations of Pesticides,PCBs and Metals Among Ospreys, <Emphasis Type="Italic">Pandion haliaetus</Emphasis>, Collected in France

In this study, osprey (Pandion haliaetus) tissues collected in France were used for contaminants analyses by a non-invasive approach. 53 pesticides (organochlorine, organophosphate, carbamate, pyrethroids, herbicides, anticoagulant rodenticides), 13 PCBs, and 5 metals (mercury, lead, cadmium, copper and arsenic) were quantified in liver of 14 individual samples. PCBs and mercury were frequent (mean 0.5 mg/kg, range < d.l.−2.6 mg/kg and mean 3.4 mg/kg, range < d.l.−16.3 mg/kg wet weight, respectively). Inter-individual variations in contaminant diversity and amounts were noticed. Immediate conservation of the species in the country does not seem to be threatened by global contamination.     

Effects of methylmercury on reproduction in American kestrels

Sixty breeding pairs of captive American kestrels (Falco sparverius) were exposed to a range of sublethal dietary concentrations of mercury (Hg), in the form of methylmercuric chloride, and their subsequent reproduction was measured. Egg production, incubation performance, and the number and percent of eggs hatched decreased markedly between 3.3 and 4.6 mg/kg dry weight of Hg (1.2 and 1.7 mg/kg wet wt), in the diet. The number of fledglings and the percent of nestlings fledged were reduced markedly at 0.7 mg/kg dry weight (0.3 mg/kg wet wt) and declined further between 2 and 3.3 mg/kg dry weight (0.7 and 1.2 mg/kg wet wt). Dietary concentrations of >or=4.6 mg/kg dry weight (1.7 mg/kg wet wt) were associated with total fledging failure. The estimated decline in fledged young per pair (24%, Bayesian regression) for kestrels consuming 0.7 mg/kg dry weight (0.3 mg/ kg wet wt) raises concerns about population maintenance in areas subject to high inputs of anthropogenic Hg. Mercury concentrations in 20 second-laid eggs collected from all groups were related to dietary concentrations of Hg, and the Hg concentrations in 19 of these eggs were related to eggs laid and young fledged. Concentrations of Hg in eggs from the highest diet group (5.9 mg/kg dry wt; 2.2 mg/kg wet wt) were higher than egg concentrations reported for either wild birds or for captive birds (nonraptors) fed dry commercial food containing 5 mg/kg methylmercury. Accumulation ratios of Hg from diets to eggs were higher than those reported for feeding studies with other species.     

Mercury in Tadpoles Collected from Remote Alpine Sites in the Southern Sierra Nevada Mountains,California, USA

Amphibians in alpine wetlands of the Sierra Nevada mountains comprise key components of an aquatic–terrestrial food chain, and mercury contamination is a concern because concentrations in fish from this region exceed thresholds of risk to piscivorous wildlife. Total mercury concentrations were measured in whole tadpoles of the Sierra chorus frog, Pseudacris sierra, two times at 27 sites from high elevations (2786–3375 m) in the southern Sierra Nevada. Median mercury concentrations were 14 ng/g wet weight (154 ng/g dry weight), which were generally low in comparison to tadpoles of 15 other species/location combinations from studies that represented both highly contaminated and minimally contaminated sites. Mercury concentrations in P. sierra were below concentrations known to be harmful in premetamorphic tadpoles of another species and below threshold concentrations for risk to predaceous wildlife. Concentrations in tadpoles were also lower than those observed in predaceous fish in the study region presumably because tadpoles in the present study were much younger (1–2 months) than fish in the other study (3–10 years), and tadpoles represent a lower trophic level than these fish. Mercury concentrations were not related to distance from the adjacent San Joaquin Valley, a source of agricultural and industrial pollutants.     

Presence of Polycyclic Aromatic Hydrocarbons (PAHs) in Apple in Rural Terrains from Mexico City

This paper describes PAH concentrations in apple crops that are growing in rural terrains in Mexico City. The concentrations of individual PAHs showed great variability, there being low and high molecular weight compounds in dry (high molecular weight for Tlahuac 7.06 μg/g and Milpa Alta 3.96 μg/g) and wet months (high molecular weight for Tlahuac 11.25 μg/g and Milpa Alta 12.05 μg/g). Some PAHs indicators and cross plot ratios Ant/(Ant + Phe) and Flu/(Flu + Pyr) define fossil fuels and vegetation combustion as the source of contamination over the cuticle of the apples. It is likely that deposition (dry and wet) is the principal source o f contamination over the apple surface. This study reveals the presence of PAHs in apples due to the high air contamination of Mexico City.     

Mercury Concentrations in Water and Hybrid Striped Bass (<Emphasis Type="Italic">Morone saxatilis</Emphasis> × <Emphasis Type="Italic">M. chrysops</Emphasis>) Muscle Tissue Samples Collected from the Ohio River,USA

We report on long-term aqueous mercury (Hg) measurements collected at fixed locations along the Ohio River, offer insights into patterns of water and fish tissue Hg levels, and calculate site-specific bioaccumulation factors (BAFs) along an extensive longitudinal basis. We examined the relationship between total recoverable Hg concentrations in water and fish samples collected from 12 locations on the mainstem Ohio River. Water samples were collected on a bimonthly basis from each location over a 6-year period preceding the collection of fish tissue samples. This abundance of data enabled us to calculate the long-term average aqueous Hg concentrations and approximate the lifetime aqueous Hg exposure experienced by fish, enabling the calculation of appropriate BAFs. Hybrid striped bass (HSB; Morone saxatilis × M. chrysops) were collected from the Ohio River, composited (three fish), and analyzed for Hg in muscle tissue from each location. Concentrations ranged from 0.2 to 0.4 mg/kg and 41.7% of all samples collected were higher than the US Environmental Protection Agency regulatory threshold of 0.3 mg Hg/kg wet weight. Hg levels generally increased with fish weight, length, and age. However, Hg concentration in the water was the strongest predictor of tissue concentrations. We found that both water and tissue concentrations increased with drainage area, albeit at different rates. This discrepancy in spatial patterns revealed that the bioaccumulation rate of methylmercury might not be consistent throughout the Ohio River mainstem. BAFs calculated at each location supported this finding, as values decreased with increasing drainage area. Our study serves to fill critical, previously identified data gaps and provides decision-makers with the information necessary to develop more appropriate BAF development and risk-management strategies.     

Heavy Metals in the Farming Environment and in some Selected Aquaculture Species in the Van Phong Bay and Nha Trang Bay of the Khanh Hoa Province in Vietnam

Aquaculture is currently one of the most rapidly growing production sectors in Vietnam. This publication describes the concentrations of heavy metals in the farming environment and some aquaculture species in the Khanh Hoa Province in Vietnam. The concentration of total As in the sediments ranged from 0.07 to 0.64 mg/kg, whereas the concentration of Hg varied from <0.0005 to 0.56 mg/kg. The corresponding concentration span for Cd and Pb, were 0.001–0.069 and 0.016–0.078 mg/kg, respectively. The concentrations of As in the aquaculture organisms spanned from 0.14 to 1.03 mg/kg. For Hg the concentrations varied from 0.1 to 0.45 mg/kg, for Cd from 0.02 to 0.10 mg/kg and for Pb from 0.07 to 0.37 mg/kg.     

A multispecies-monitoring study about bioaccumulation of mercury in Iranian birds (Khuzestan to Persian Gulf): Effect of taxonomic affiliation and trophic level

In the present study, the first baseline concentration of mercury (Hg) in different species of Iranian birds was investigated. From April to October 2005, the tail feathers of 100 birds belonging to 27 species (14 families) from different places in southwest Iran (Khuzestan to Persian Gulf) were collected. The Hg levels were evaluated in relation to taxonomic affiliation and trophic level (type of food). The results showed that the Hg levels in the feathers were between 0.07 and 4.71 mg/kg dry weight (dw), and there was a significant effect of taxonomic groups in relation to Hg concentration (p<0.001). The highest mercury concentrations were in Laridae and Ciconidae. Alcedinidae had intermediate values, whereas Upupidae, Glareolidae, Scolopacidae, Turdidae, Ardeidae, Anatidae were in subsequent orders; and the lowest concentrations of Hg were in Rallidae, Cuculidae, Pycnonotidae, Corvidae and Columbidae. The results indicated a significant difference between the trophic levels (p<0.001). Fish predators had the highest level of Hg (3.07 mg/kg). Invertebrate predators and herbivorous birds had the lowest concentration of Hg (0.84 and 0.64 mg/kg, respectively), whereas crab and fish predators and omnivorous birds had moderate values (1.73 and 1.70 mg/kg, respectively). In the present study, the concentration of Hg was significantly higher in tail feathers than in primary and secondary (p<0.001). A significant positive correlation among Hg concentration of feather types was observed (r>0.96). The results obtained in this study indicated that among 100 birds tested, 6% of them had Hg concentrations greater than 5 mg/kg in feather (adverse level).     

Potential Effects of Mercury on Threatened California Black Rails

San Francisco Bay (SFB) estuary sediments contain high levels of mercury (Hg), and tidal marsh resident species may be vulnerable to Hg contamination. We examined Hg concentrations in California black rails, a threatened waterbird species that inhabits SFB tidal salt marshes. We captured 127 black rails during the prebreeding and postbreeding seasons and examined the influence of site, sex, and year on Hg, methylmercury (MeHg), and also selenium (Se) concentrations in feathers and blood. Feather Hg concentrations averaged 6.94 μg/g dry weight (dw) and MeHg and Se concentrations in blood averaged 0.38 and 0.42 μg/g wet weight (ww). We used Akaike’s information criterion model selection process to evaluate the importance of year, site, sex, and age on patterns of MeHg concentrations; sex and year were the most important of these factors. Feather Hg concentrations (dw) were higher in males (8.22 μg/g) than females (6.63 μg/g) and higher in adult birds (7.36 μg/g) than in hatch-year birds (4.61 μg/g). A substantial portion of SFB black rail populations may be at risk of reproductive effects due to MeHg contamination, as 32–78% of feathers and <10% of blood samples exceeded no observed adverse effect levels. Sea level rise and other anthropogenic threats to endemic tidal marsh species such as black rails may be exacerbated by the presence of MeHg. Further study of population demographics and toxicological effects would further elucidate the effects of MeHg contamination on black rail populations in SFB.     

Metal Concentrations of Common Freshwater and Marine Fish from the Pearl River Delta,South China

Sediments and fish, including tilapia (Oreochromis mossambicus), bighead carp (Aristichthys nobilis), grass carp (Ctenopharyngodon idellus), and mandarin fish (Siniperca chuatsi) were collected from different fish ponds in the Pearl River Delta (Tanzhou, Sanjiao, Guangzhou, Shipai, Changan, and Mai Po) for the analysis of metalloids and heavy metals [arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), and lead (Pb)]. The pollution of As in pond sediments was great; however, As in the edible parts of pond fish were within the international permissible safety levels for human consumption. Axial muscles from 10 species each of freshwater and marine fish purchased from markets in Hong Kong were also analyzed for As, Cd, Cr, Cu, Hg, Ni, Pb and Zn. Freshwater fish contained 0.24 to 2.13 mg/kg As, 0.10 to 0.17 mg/kg Cd, 0.09 to 0.36 mg/kg Cr, 0.06 to 0.35 mg/kg Cu, 0.07 to 0.34 mg/kg Hg, 0.04 to 0.36 mg/kg Ni, 0.11 to 0.52 mg/kg Pb, and 2.67 to 19.1 mg/kg Zn (wet weight). Marine fish had higher Hg and lower Pb concentrations than freshwater fish. A few fish species had average concentrations greater than the international standards for Cd and Pb established by the European Union and the China National Standard Management Department. Total Hg concentrations in 10 of 20 market fish species were generally greater than those of the World Health Organization’s recommended limit of 0.2 mg/kg for at-risk groups, such as children and pregnant women. Daily intake through fish consumption of these metals were compared with the Provisional Tolerable Weekly Intake proposed by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives. There appears to be potential threat to local people from Hg contamination because of the high marine fish consumption rate (142 g/d/person).     

Analysis of Several Heavy Metals in Wild Edible Mushrooms from Regions of China

The metal (Cu, Ni, Cd, Hg, As, Pb) contents in wild edible mushrooms collected from three different sites in China were determined by atomic absorption spectrometry and atomic fluorescence spectrometry. All element concentrations were determined on a dry weight basis. A total of 11 species was studied, five being from the urban area and six from rural areas in China. The As content ranged from 0.44 to 1.48 mg/kg. The highest As content was seen in Macrolepiota crustosa from the urban area, and the lowest in Russula virescens from rural areas. A high Ni concentration (1.35 mg/kg) was found in Calvatia craniiformis from the urban area. The lowest Ni level was 0.11 mg/kg, for the species R. virescens and Cantharellus cibarius. The Cu content ranged from 39.0 to 181.5 mg/kg. The highest Cu content was seen in Agaricus silvaticus and the lowest in C. cibarius. The Pb content ranged from 1.9 to 10.8 mg/kg. The highest Pb value was found in C. craniiformis. The Cd content ranged from 0.4 to 91.8 mg/kg. The highest Cd value was found in M. crustosa. The Hg content ranged from 0.28 to 3.92 mg/kg. The highest Hg level was found in Agaricus species. The levels of the heavy metals Cd, Pb, and Hg in the studied mushroom species from urban area can be considered high. The metal-to-metal correlation analysis supported they were the same source of contamination. High automobile traffic was identified as the most likely source of the contamination. Based upon the present safety standards, consumption of those mushrooms that grow in the polluted urban area should be avoided.     

Seasonal Variations in the Concentrations of Metals in Crassostrea corteziensis from Sonora, México

This study examines seasonal variations in the concentrations of Cd, Cu, Pb, and Hg in experimentally cultured Crassostrea corteziensis, an oyster species known to have high resistance to physical and chemical stressors. The highest levels of Cd (4.92 mg/kg), Cu (3.45 mg/kg), and Pb (0.67 mg/kg) were detected in oyster samples collected during the summer, while Hg concentrations were similar (0.03 to 0.04 mg/kg) throughout all seasons. Results indicate that except for Cd, Crassostrea corteziensis accumulates metals to levels below those recommended by the US. FDA and the Mexican government. For Cd, its concentration correlates more strongly with the temperature of the oyster’s environment rather than to the oyster growth cycle.     

Distribution of Mercury in Several Environmental Compartments in an Aquatic Ecosystem Impacted by Gold Mining in Northern Colombia

Mercury (Hg) used in gold amalgamation is a major source of contamination in developing countries. Water, sediments, plankton, fish, and human samples from Grande Marsh, a Hg-polluted marsh located in the south of Bolívar, municipality of Montecristo, Colombia, were collected during both the rainy and the dry seasons (2003–2006), at three different sampling sites, and analyzed for total Hg (T-Hg) content. Water, sediment, seston, phytoplankton, and zooplankton T-Hg concentrations were 0.33 ± 0.03 μg/L, 0.71 ± 0.03, 1.20 ± 0.06, 0.52 ± 0.03, and 0.94 ± 0.05 μg/g dry weight (wt), respectively. T-Hg levels in these compartments were highly pair-correlated (p < 0.05), and for all of them, except sediments, greater values were found during the dry season. Significant differences were observed for T-Hg concentrations in fish according to their trophic position. Average highest T-Hg values were found in carnivorous species such as Caquetaia kraussi (1.09 ± 0.17 μg/g fresh wt), Hoplias malabaricus (0.58 ± 0.05 μg/g fresh wt), and Plagioscion surinamensis (0.53 ± 0.07 μg/g fresh wt), whereas the lowest were detected in noncarnivorous species such as Prochilodus magdalenae (0.157 ± 0.01 μg/g fresh wt). In those fish species where seasonal comparisons were possible, specimens captured during the dry season had greater T-Hg levels in muscle. Although the T-Hg mean level for all fish samples (0.407 ± 0.360 μg/g fresh wt) did not exceed the recommended limit ingestion level, risk assessment based on the hazard index suggested that a fish intake of 0.12 kg per day (a small carnivorous specimen) could increase the potential health effects related to Hg exposure in the local human population, whose hair T-Hg median value was 4.7 μg/g, and presented a low but significant correlation with fish consumption (r = 0.250, p = 0.016). In short, Hg pollution from gold mining around Grande Marsh has permeated the food web, and currently levels in fish represent a serious concern for human health.