Mercury in Biota and Surficial Sediments from Coatzacoalcos Estuary, Gulf of Mexico: Distribution and Seasonal Variation

Variation of mercury (Hg) in sediments and biota from Coatzacoalcos estuary during the dry, rainy and windy seasons was estimated. In sediments, Hg concentrations ranged from 0.07 μg g^?1 in site 13 (Ixhuatepec) located upstream, to 1.06 μg g^?1 in site 3 (Coatzacoalcos river), located in the industrialized area. Highest enrichment factor (EF) and index of geoaccumulation (I _geo) in surficial sediments were 53 and 5.1 respectively. From EF and I _geo, it is considered that Coatzacoalcos estuary is from moderately contaminated to contaminated. In most fish species from Coatzacoalcos estuary, the sequence of Hg concentration was liver>muscle>gills. Average Hg concentrations in soft tissue of bivalves ranged from 0.09 μg g^?1 in Corbicula fluminea to 0.18 μg g^?1 in Polymesoda caroliniana. Biota-sediment accumulation factor (BSAF) ranged from 0.9 in P. caroliniana during the rainy season (site 4) to 3.8 in P. caroliniana from the same site during the windy season.     

Environmental fate of mercury discharged into the upper Wisconsin river

We studied the distribution of Hg in sediments, fish, and crayfish in a 60 km reach of the Upper Wisconsin River that formerly received Hg in discharges from pulp and paper mills. The most heavily contaminated strata of sediments were deposited during the 1950s and early 1960s and buried under subsequent deposits; however, surficial sediments remained substantially enriched at certain sites in 1981. Median concentrations of Hg in surficial sediments, adjusted for grain size, were at least 10-fold greater at the main study area than at an upstream reference site. Total concentrations exceeded 1.0 μg g^?1 wet weight in axial muscle tissue in only 2 of 173 fish analyzed from the study area; however, historical comparisons revealed that Hg contamination of fish (common carp Cyprinus carpio and walleye Stizostedion vitreum vitreum) and crayfish (Orconectes) in the river had not decreased since the early 1970s. The availability of Hg to biota in this system may be enhanced by rapid methylation of the metal in surficial sediments, despite burial of the most heavily contaminated sediments. Management practices for this river should be designed to prevent conditions favoring mobilization and methylation of Hg in sediments.     

Trace metals concentrations in marine organisms from the coastal areas of Bahrain,Arabian Gulf

A total of 162 fish and shellfish samples representing important species have been collected from different coastal areas of Bahrain in the Arabian Gulf, and analyzed for lead, cadmium, mercury, and arsenic using electrothermal atomic absorption spectrophotometric method. The dverall mean levels for Pb, Cd, Hg and As in fish samples were 0.132, 0.032, 0.084 and 1.7 µg g^?1 wet weight, respectively, whereas for shellfish they were 0.149, 0.045, 0.042 and 3.61 µg g^?1 wet weight. These values indicate higher levels of metals in shellfish when compared with fish, except for mercury, and reveal that generally the levels of metals in these organisms are lower than existing guidelines, except for arsenic. The provisional tolerable weekly intake of Pb, Cd, Hg and As through fish was estimated to be 0.7, 0.17, 0.45 and 9 µg kg^?1 bodyweight per week, respectively. Our results did not reveal a clear pattern regarding variations of metals concentration between areas and species.     

Impact of anthropogenic activity on the Hg concentrations in the Piracicaba river basin (São Paulo State, Brazil)

A sampling and analysis program has been completed between 1995 and 1998 in order to determine mercury concentrations in water, sediments, soils and fish in the Piracicaba river basin, one of the most populated and industrialized regions in Brazil. In sediment, the average Hg concentrations varied between 33 ± 17 ng g^?1 and 106 ± 78 ng g^?1, in samples collected during the rainy and dry season, respectively. The same averages were also found for soil samples (35 ± 14 and 109 ± 61 ng g^?1). In water, the total Hg concentration varied between < 1.1 and 24.0 ng L^?1. In piscivore fish, up to 943 μ g Hg kg^?1 was found. Our results show that all compartments undergo Hg contamination, in view of the levels found in pristine environments. Water contamination seems to be due mainly to diffuse processes of soil erosion and suspension of river bed sediment during the rainy season. Also untreated wastewaters generated by industrial activities and from domestic sewage appear to be potential non-point sources in the most industrialized and populated part of the basin. On the other hand, atmospheric transport of mercury originating from the Campinas Metropolitan Region could be another source of mercury contamination, especially in the basin headwaters.     

Mercury and polychlorinated biphenyls in striped bass (Morons saxatilis) from two nova Scotia Rivers

Striped bass (Morone saxatilis) collected from the Annapolis and Shubenacadie Rivers in Nova Scotia, Canada, were analyzed for Hg in four tissues and for PCB's in two tissues. Average Hg concentrations in the muscle, liver, kidney, and gonad of 3.9 kg fish from Annapolis River were 0.77, 0.79, 0.26, and 0.07 μg g^?1, respectively, and the corresponding values for the much smaller, 1.5 kg, fish from the Shubenacadie River were 0.51, 0.27, 0.24, and 0.06 μg g^?1. The PCB concentrations in the muscle tissues of fish from Annapolis and Shubenacadie Rivers are 0.02 and 0.01 μg g^?1, respectively, while the concentrations in gonads are 1.4 and 0.04 μg g^?1 The observed lack of recruitment of striped bass in the Annapolis River may be related to high PCB concentrations in the gonad tissue.     

Accumulation of acridine from water,food, and sediment by the fathead minnow,Pimephales promelas

Azaarenes are one of several classes of organic compounds which contain mutagenic and carcinogenic substances that are found in synthetic fuels effluents. This study investigated the potential for a mutagenic azaarene, acridine, to accumulate in freshwater fish (Pimephales promelas) via four possible pathways: (1) direct uptake from water, (2) uptake via interaction with contaminated sediments, (3) uptake via ingestion of contaminated zooplankton (Daphnia pulex), and (4) uptake via ingestion of benthic invertebrates (Chironomus tentans) living in contaminated sediments. The results showed that acridine was rapidly accumulated from water by fathead minnows. Equilibrium concentration was attained within 24 h at a concentration factor ([acridine]_{fish, wet wt}/[acridine]_water) of 125±10. Depuration was rapid and appeared to occur in two stages, with a net elimination rate of 0.23 h^?1 [acridine]_fish at equilibrium. Equilibrium concentration factors of 51±5, 30±2, and 874±275 were observed forChironomus, Daphnia, and sediment, respectively. The calculated rates of uptake of acridine via ingestion of contaminated invertebrates (0.02 μg g^?1 h^?1) and ingestion of sediment (0.01 μg g^?1 h^?1) were negligible compared with direct uptake from water (1.40 μg g^?1 h^?1) in a hypothetical system with all compartments in equilibrium.     

Effect of pH on the bioaccumulation of low level,dissolved methylmercury by rainbow trout (Oncorhynchus mykiss)

An inverse relationship has been observed between pH and McHg concentration in freshwater fish. Many hypotheses exist regarding the mechanisms which lead to elevated levels of organic Hg in fish from low pH lakes. To determine if pH has a direct effect on the rate of McHg bioaccumulation in fish, rainbow trout fingerlings (Oncorhynchus mykiss) were exposed to a low concentration of aqueous methylmercuric chloride (1.38 ± 0.49 ng·L^?1) at four pH-levels (8.2, 7.0, 6.3, 5.8) for eight weeks. McHg and total Hg were specifically determined on whole fish homogenates and water samples. The pH was found to have a significant: inverse effect on the rate of McHg bioaccumulation in the fish only in the lowest exposure level. Fish held at pH 5.8 had an uptake rate of 1.11 ± 0.07 ng·g^?1·d^?1, while those at pH ≥ 6.3 had a MeHg tissue uptake rate of ≤ 0.64 ± 0.07 ng·g^?1·d^?1. Total body burden of MeHg in the fish held at pH 5.8 also showed an elevated level of MeHg when compared with fish held at higher pH-levels, but the difference was less dramatic. These results suggest that a portion of the Hg burden in fish from low pH systems may be due to the direct effects of low pH on bioaccumulation, but that a threshold may exist above which pH does not play a significant role.     

Mercury in soils,sediments, and clams from a North Carolina peatland

Mercury concentrations were measured in samples of peat soils, sediments and clams (Rangia cuneata) from a peatland region of the Albemarle-Panlico Peninsula of North Carolina. Total Hg concentrations in peat cores ranged from 40 to 193 ng g^?1 (dw); no depth-related trends were noted. Mercury concentrations in surface sediments from canals draining the peatlands and from the Pungo River that receives this drainage ranged from 8 to 20 ng g^?1 (dw). Selective extractions of these peat and sediment samples revealed that the bulk of the Hg was associated with organic matter-associated fractions (particularly humic/fulvic acid bound and organic-sulfide bound fractions). No Hg was detected in the relatively mobile and bioavailable water-soluble or ion-exchangeable fractions. Total Hg concentrations in the soft tissues of clams from the Pungo River ranged from 25 to 32 ng g^?1 (ww). No concentrations of methyl Hg above the detection limit of a 25 ng g^?1 were measured in soils, sediments, or clams. These data indicate that Hg concentrations in this region are at the low end of the distribution of levels reported for uncontaminated systems and that mining of these peatlands is unlikely to significantly elevate Hg concentrations in the receiving estuarine system.     

Concentrations and amounts of methylmercury in water and fish in the limed and acid basins of a small lake

Three months after neutralization concentrations of methylmercury (MeHg) were higher in the water of the limed than in the control basin of a small lake. After two years, the concentrations in the limed basin were somewhat lower than in the control (0.056–2.19 ng L^?1 and 0.129–2.65 ng L^?1, respectively). The highest concentrations were found in the anoxic hypolimnia. The total amount of MeHg in the water mass of the lake varied from 19 to 68 mg, showing a drop after spring and autumn overturns and a maximum during stratification periods. The total Hg concentrations of fish in L. Iso Valkjärvi varied from 0.06 to 0.14 μg g^?1 (ww) in whitefish to 0.1 to 0.7 μg g^?1 in perch and to 0.2 to 1.4 μg g^?1 in pike. The total amount of MeHg bound in the fish of the lake was quite similar to that in the water column, 43 to 59 mg in 1990–1993, 33 to 47 mg of which was in the perch population.     

Litterfall Mercury in Two Forested Watersheds at Acadia National Park, Maine, USA

Litterfall can be an important flux of mercury (Hg) to soils in forested landscapes, yet typically the only available data to evaluate Hg deposition is from precipitation Hg monitoring. Litterfall was collected at 39 sampling sites in two small research watersheds, in 2003 and 2004, and analyzed for total Hg. Four vegetation classes were designated in this study as hardwoods, softwoods, mixed and scrub. The mean litter Hg concentration in softwoods (58.8 ± 3.3 ng Hg g^?1 was significantly greater than in mixed (41.7 ± 2.8 ng Hg g^?1 and scrub (40.6 ± 2.7 ng Hg g^?1, and significantly lower than in hardwoods (31.6 ± 2.6 ng Hg g^?1. In contrast, the mean weighted litter Hg flux was not significantly different among vegetation classes. The lack of a significant difference in litter Hg flux between hardwoods and softwoods was attributable to the large autumnal hardwood litter Hg flux being balanced by the higher softwood litter Hg concentrations, along with the higher chronic litterfall flux throughout the winter and spring in softwoods. The estimated annual deposition of Hg via litterfall in Hadlock Brook watershed (10.1 μg m^?2 and Cadillac Brook watershed (10.0 μg m^?2 was greater than precipitation Hg deposition and similar to or greater than the magnitude of Hg deposition via throughfall. These results demonstrate that litterfall Hg flux to forested landscapes can be at least as important as precipitation Hg inputs.     

Lead contents of coal,coal ash and fly ash

Flameless atomic absorption spectrometry is applied for the determination of Pb in coal, coal ash and fly ash. Lead concentrations in coal and coal ash ranging from respectively 7 to 110 µg g^?1 and 120 to 450 µg g^?1 are found. A mean concentration of 1520 µg g^?1 in fly ash corresponding to a concentration of 117 µg m^?3 in the effluent gas suggests the importance of coal combustion as an atmospheric source of Ph. The contribution of coal combustion to the total Pb emissions is conservatively estimated at 6%.     

Different factors related to mercury concentration in sediments and zooplankton of 73 Canadian Lakes

Surficial sediments were sampled with a light-weight gravity corer at 175 sites in 73 Ontario and Québec lakes and Zooplankton was collected with a 225 μm mesh size net in 24 lakes. Hg concentrations in surficial sediments (0–2 cm) ranged from 3 to 267 ng g^?1 dry weight with a mean of 80 ng g^?1 dry weight for all sites. A regression model including organic content of sediments and the ratio of the catchment area/lake surface explained 60% of the variation in sediments Hg concentrations. Hg in Zooplankton ranged from about 25 to 377 ng g^?1 dw with a mean of 108 ng g^?1 dw and was weakly correlated with catchment area, primary productivity and TOC. Our data indicate that an important fraction of Hg originates from the catchments, but do not show a clear west-east regional gradient for Hg concentrations in surficial sediments or in zooplankton.     

Sediment trace metal contamination in the Ivory Coast,West Africa

To help expand our global perspective on trace metal contamination, concentrations of Cu, Fe, Hg, Mn, Ni, Pb, and Zn were determined for sediments from the Ebrie Lagoon in the Ivory Coast, a developing West African nation. Excess loading of several metals, especially Hg, Pb, and Zn was found at several sites. The maximum concentration of Hg measured in sediments from the Ebrie Lagoon (2250 ng g^?1) is about 30 times greater than natural levels. Similarly, Pb and Zn concentrations for the Ivorian lagoonal sediments are as high as 250 and 560 μg g^?1, respectively, showing sizeable anthropogenic inputs. Trace metal sources to the Ebrie Lagoon include untreated sewage and industrial wastes.     

Polluted precipitation and the geochronology of mercury deposition in lake sediment of northern Minnesota

Elevated Hg levels in game fish from wilderness lakes in northern Minnesota led to the present study of sediment cores from two lakes to ascertain the source and history of Hg deposition. Natural background levels of Hg were found to range from 0.03 to 0.06 μg g^?1, with cultural levels as high as 0.16 μg g^?1. Reconstructed geochronologies reveal a dramatic two-fold increase in Hg flux, from 0.008 to 0.017 μg cm^?2 yr^?1, occuring after the year 1880, suggesting an anthropogenic influence. No industrial or geologic source of Hg is found in the study watersheds. The entire historical increase in Hg flux can be accounted for by atmospheric loading provided that 1/5 of all the Hg presently supplied to the watershed via precipitation is ultimately deposited in lake sediment. Hg levels in fish are not correlated with Hg levels in lake sediment, although there is a link to acid-sensitivity of lake water, amount of acid-neutralizing geologic material exposed in the watershed, and watershed area/lake volume ratio. Thermal stratification of lake water and a complexation-adsorption mechanism are proposed to account for variations in Hg levels observed in sediment collected from different sites.     

Mercury dispersal in water,sediments and aquatic biota of a gold mining tailing deposit drainage in pocone,Brazil

In the Pocone district, Brazil, Hg distribution was studied in a small watershed which drains tailings from a 10 yr old gold mining operation. Heavy regional rains are responsible for continuous weathering, thereby making it possible to transport Hg into the ecologically important Pantanal area. Mercury concentrations in creek sediments range from < 0.02 to 0.18 mg. kg^?1. The highest concentrations occur close to the tailings deposit. Mercury concentrations in the water were always below the detection limit of the analytical method used (<0.04 µg. L^?1). Suspended matter samples collected before, during and after a storm, showed a Hg peak value of 0.61 mg kg^?1. about 30 min after the event. Dissolved Hg concentration still fell below the detection limit. Among the biota, molluscs accumulated moderately high concentrations of Hg, while macrophytes and fish did not. Mercury concentrations in molluscs were dependent on size, with larger animals presenting higher Hg concentration. We conclude that Hg present in the tailings shows low mobility and that its eventual transport into the drainage system is dependent on the erosion of fine material from the wastes during rains, resulting in a restricted contamination of the area and low Hg concentration in the biota.     

Distribution of Mercury and Monomethylmercury in Sediments of Vigo Ria, NW Iberian Peninsula

Fifty four samples of surface sediments (1-cm of thickness) and a gravity core of 154-cm long were collected in the Vigo Ria, NW of Iberian Peninsula. In the laboratory the sediments were oven dried at 40°C, desegregated, homogenised and analyzed for total Hg, monomethylmercury (MMHg), Al, and particulate organic carbon (POC). Mercury in sediments varied within a broad range: 0.09 to 8.9 nmol g^?1 the higher concentrations being found in the shipyards and docks areas of Vigo port (southern–middle Ria zone). No correlation was found between Hg and POC. The good exponential correlation between total Hg and Al levels suggests that Hg is closely associated with the fine fraction of sediments. Monomethylmercury concentrations in surface sediments ranged between <1.4 (DL) and 8.5 pmol g^?1 being the spatial distribution similar to that observed for total Hg. The lack of correlations MMHg–Al and MMHg–POC suggests that in situ processes of methylation/demethylation are responsible for MMHg distribution rather than the sediment characteristics. Additionally, these processes appear mercury-dependent only for Hg concentrations above 2.5 nmol g^?1. On the basis of these results it was estimated that 155 kg of Hg (0.1% MMHg) are present in the surface sediments of Vigo Ria, being 61% of anthropogenic origin.     

Concentrations of trace elements in yellow perch (Perca flavescens) from six acidic lakes

Yellow perch (Perca flavescens) were collected from six small acidic lakes in northwestern New Jersey. Analyses of muscle tissue identified a pattern of increased concentrations of Hg in fish from the most acidic lakes; levels of Cd and Pb were greatly elevated in livers of specimens from two of the most acidic lakes. At one site, Sunfish Pond, positive correlations between fish size and Hg levels in muscle and Cd concentrations in livers were detected. In only one case did Hg concentrations in muscle tissue exceed the U.S. FDA action level of 1 μg g^?1 (wet wt).     

Biogeochemical Cycle of Mercury and Methylmercury in Two Highly Contaminated Areas of Tagus Estuary (Portugal)

Mercury (Hg) dynamics was evaluated in contaminated sediments and overlying waters from Tagus estuary, in two sites with different Hg anthropogenic sources: Cala Norte (CNOR) and Barreiro (BRR). Environmental factors affecting methylmercury (MMHg) production and Hg and MMHg fluxes across sediment/water interface were reported. [THg] and [MMHg] in solids (0.31–125 μg g^?1 and 0.76–201 ng g^?1, respectively) showed high variability with higher values in BRR. Porewater [MMHg] (0.1–63 ng L^?1, 0.5–86% of THg) varied local and seasonally; higher contents were observed in the summer campaign, thus increasing sediment toxicity affecting the sediment/water Hg (and MMHg) fluxes. In CNOR and BRR sediments, Hg availability and organic carbon were the main factors controlling MMHg production. Noteworthy, an upward MMHg diffusive flux was observed in winter that was inverted in summer. Although MMHg production increases in warmer month, the MMHg concentrations in overlying water increase in a higher proportion compared to the levels in porewaters. This opposite trend could be explained by different extension of MMHg demethylation in the water column. The high concentrations of Hg and MMHg and their dynamics in sediments are of major concern since they can cause an exportation of Hg from the contaminated areas up to ca. 14,600 mg year^?1 and an MMHg deposition of up to ca. 6000 mg year^?1. The results suggest that sediments from contaminated areas of Tagus estuary should be considered as a primary source of Hg for the water column and a sink of MMHg to the sedimentary column.     

The effects of mercury,copper, and zinc on calcium uptake by larvae of the clam,mulinia lateralis

A sensitive and rapid bioassay system using Ca-45 uptake by larvae of Mulinia lateralis as indicator is described. The values of Ca uptake per larva^?1 versus elapsed time were linear and some of the Ca uptake rates, expressed as pg Ca larva^?1 h^?1, were 148.2 (no added heavy metal), 114.4 (20 µg kg^?1 of added Hg), 89.7 (200 gg kg^?1 of added Zn) and 20.5 (40 µg kg^?1 of added Cu). Linearities were also obtained by plotting log of Ca uptake per larva^?1 against heavy metal concentrations. A new terminology, ^xCa _inf50 ^supt , was proposed which expressed the concentration of heavy metal, x, causing 50% depression of Ca uptake over the exposure time, t. For Cu, Hg, and Zn, the values of ^x Ca _inf50 ^sup72h were 18.5, 26.5 and 176.0 µg kg^?1 respectively, which were comparable to the published values of LC₅₀. The effectiveness of Ca uptake depression on a weight basis was Cu > Hg > Zn, and the same sequence was also observed for larval mortalities.