Mean Total Mercury Concentration Research Articles

Assessment of mercury mobility and bioavailability by fractionation method in sediments from coastal zone inundated by the 26 December 2004 tsunami in Thailand

The 26 December 2004 tsunami covered significant portion of a coastal zone with a blanket of potentially contaminated sediments. In this report are presented results on mercury concentrations in sediments deposited by the tsunami in a coastal zone of Thailand. Since the total mercury concentrations are insufficient to assess mercury mobility and bioavailability in sediment, its fractionation was applied. Sediments were sampled within 50 days after the event and analyzed by sequential extraction method. The procedure of sequential extraction involved five subsequent stages performed with solutions of chloroform, deionized water, 0.5 M HCl, 0.2 M NaOH, and aqua regia. The mean concentration of total mercury in sediments was 119 ± 50 ng g−1 dry mass (range 66–230). The fractionation revealed that mercury is mainly bound to the least bioavailable sulphides 75 ± 6% (range 62–86), organomercury compounds 14 ± 7% (range 4–26), and humic matter 9 ± 7% (range 1–27). The lowest contributions bring fractions of water-soluble mercury 0.8 ± 1.0% (range 0.1–3.6) and acid soluble mercury 0.9 ± 0.5% (range 0.2–2.1). Although, the total mercury content is similar in a reference sample and in the tsunami sediments, the highly toxic organomercury fraction contribution is higher in the latter. The results were compared with chemical and sedimentological properties of the sediments but no significant correlations were obtained between them.

Mercury contamination in fish from gold mining areas in Indonesia and human health risk assessment

This study investigates the effects on fish and assesses human health hazards from mercury released in two gold mining areas in Indonesia: Tatelu (North Sulawesi Province) and Galangan (Katingan District, Central Kalimatan Province). In Tatelu, 154 fish specimens of 10 freshwater species were collected, as well as five marine species from the fish market. The mean concentration of total mercury in muscles of freshwater fish from this area was 0.58 ± 0.44 μg/g, with more than 45% of fish having Hg levels above the WHO guideline for human consumption of 0.5 μg/g. In Galangan, where 263 fish specimens of 25 species were collected, the total mercury in muscles averaged 0.25 ± 0.69 μg/g. Excluding data from flooded open pits in sub-area P4, mean Hg levels in fish from Galangan were 2 to 4 times lower than 0.5 μg/g, while fewer than 10% of fish from Galangan exceeded WHO guidelines. The Hazard Quotient (HQ) was applied to both areas to determine the threat of MeHg exposure for communities in both areas. The HQ is a risk assessment indicator which defines the ratio of exposure level to a single substance in relation to a reference dose. Samples from Tatelu (excluding marine species) had an HQ above one, while those from Galangan resulted in values of 2.4 for the whole area and 9.9 for sub-area P4, pointing to potentially harmful fish consumption for the local population. By using the single-compartment model to estimate mercury levels in blood and hair from daily intake dose, sub-area P4 showed the highest levels, higher than the upper limit guideline for pregnant women, but still lower than threshold levels associated with observed clinical effects.

Levels of non-essential elements in muscle from harp seal ( Phagophilus groenlandicus) and hooded seal ( Cystophora cristata) caught in the Greenland Sea area

The non-essential elements, arsenic, cadmium, mercury and lead, inevitably accumulate in marine top predators such as seals. The concentration of these elements and the essential element selenium, due to its proposed protective properties against mercury toxicity in marine mammals, were measured in muscle, liver and kidney from reproductive active females of harp seal ( Phagophilus groenlandicus) and hooded seal ( Cystophora cristata) caught in the drift ice between Iceland and East Greenland. Arsenic levels were below 1 μg/g w.w. in all analysed samples, and were therefore low compared to other seafood products. The concentrations of arsenic found in the present study were comparable to the results reported in a similar study from 1985. Mean concentrations of total mercury in muscle from the present study were higher than levels in other seafood products. The levels of total mercury from the present study showed a tendency of lower levels in all tissue samples compared to the study from 1985. Methyl mercury displayed a trend of a lower ratio of methyl mercury to total mercury as the concentration of total mercury increased, indicating a demethylation of methyl mercury at high total mercury concentrations (e.g. mercury in liver of hooded seal). The concentration ratio of methyl mercury to total mercury in muscle samples was more than 75%, with total mercury concentration less than 0.5 μg/g w.w., whereas the ratio for liver was as low as 0.2% with a total mercury concentration of 128 μg/g w.w. The molar concentration ratios of selenium to mercury showed that selenium was present in a molar surplus to mercury in all tissues with low mercury concentration. However, there seemed to be a general mobilisation of selenium in liver and kidney tissues of harp seal and hooded seal, whereas an extraordinary mobilisation seemed to take place at hepatic mercury concentrations exceeding 50 μg/g w.w. The mean concentrations of lead in muscles in the present study were higher than in fish and other seafood products from the Barents Sea. The lead concentrations from the present study were lower than levels reported in the 1985 study. However, the levels of the non-essential elements analysed in muscle from the two seal species in the present study should not prevent the use of seal meat in human nutrition.

Mercury body burdens in Gambusia holbrooki and Erimyzon sucetta in a wetland mesocosm amended with sulfate

This study used an experimental model of a constructed wetland to evaluate the risk of mercury methylation when the soil is amended with sulfate. The model was planted with Schoenoplectus californicus and designed to reduce copper, mercury, and metal-related toxicity in a wastestream. The sediments of the model were varied during construction to provide a control and two levels of sulfate treatment, thus allowing characterization of sulfate’s effect on mercury methylation and bioaccumulation in periphyton and two species of fish––eastern mosquitofish ( Gambusia holbrooki) and lake chubsucker ( Erimyzon sucetta). After one year in the experimental model, mean dry-weight normalized total mercury concentrations in mosquitofish from the non-sulfate treated controls (374 ± 77 ng/g) and the reference location (233 ± 17 ng/g) were significantly lower than those from the low and high sulfate treatments (520 ± 73 and 613 ± 80 ng/g, respectively). For lake chubsucker, mean total mercury concentration in fish from the high sulfate treatment (276 ± 63 ng/g) was significantly elevated over that observed in the control (109 ± 47 ng/g), the low sulfate treatment (122 ± 42 ng/g), and the reference population (41 ± 2 ng/g). Mercury in periphyton was mostly inorganic as methylmercury ranged from 6.6 ng/g (dry weight) in the control to 9.8 ng/g in the high sulfate treatment, while total mercury concentrations ranged from 1147 ng/g in the control to a high of 1297 ng/g in the low sulfate treatment. Fish methylmercury bioaccumulation factors from sediment ranged from 52 to 390 and from 495 to 3059 for water. These results suggest that sulfate treatments add a factor of risk due to elevated production of methylmercury in sediment and porewater which biomagnified into small fish, and may potentially increase through the food web.

MERCURY IN FISH FROM CHRISTINA LAKE, ALBERTA, CANADA-RISK ASSESSMENT

Mercury is a concern in aquatic ecosystems due to its bioaccumulation and its developmental toxicity to the humans, especially young children. There is existing mercury-related fish consumption advisory on brook trout in Chrystina Lake issued in the early 1990s. In order to review the fish consumption advisory, a project of mercury levels in brook trout was carried out between 1999 and 2001. The field collection was carried out between August and September 1999 and in August 2001. Sixteen brook trout and white sucker were collected in 1999, and fifteen brook trout and white sucker were collected in 2001. Total mercury and methylmercury were analyzed in fillets of fish. The mean concentrations of total mercury in fillets of brook trout were 122 μg/kg (wet weight) in 1999 and 197 μg/kg (wet weight) in 2001. The mean concentrations of total mercury in fillets of white sucker was 188 μg/kg (wet weight) in 1999 and 2001. Health Canada proposed the guidelines and the total daily intake for consumption of mercury-contained fish. In the absence of the intake estimations, the guideline is 500 μg/kg (0.5 ppm) Hg for commercial fish. This guideline is used as a general screening tools. The guideline for subsistence fresh water fishing populations is 200 μg/kg (0.2 ppm) Hg. The concentrations of total mercury in brook trout and white sucker from Chrystina Lake were less than 200 μg/kg. Health Canada proposed that the total daily intake (TDI) of mercury for women of childbearing age and children is 0.2 μg Hg/Kg bw/d, and the 0.47 μg Hg/Kg bw/d for the general population. Estimated daily intake and exposure ratios based on TDIs from Health Canada are summarized in Table:Exposure ratios were greater than one for the high intake group of women of childbearing age and children. Hence, women of childbearing age and children should not consume a large quantity of brook trout caught from Chrystina Lake.

Bioaccumulation of mercury in a vestimentiferan worm living in Kagoshima Bay, Japan.

The present study reports on the mercury concentrations of the vestimentiferan worm, Lamellibrachia satsuma, (Annelida: Pogonophora) found near hydrothermal vents at a depth of 80-100 m in the northern parts of Kagoshima Bay. The vestimentiferan worms had total mercury concentrations of 238 ng/g in the anterior muscle of the body and 164 ng/g in the posterior trophosome. Methylmercury constituted only 7.6% of total mercury detected anteriorly and 16.3% posteriorly. The mean total mercury concentration in filtrated ambient seawater of the worm habitat was 1.1 ng/l. The worm should accumulate mercury in seawater by a one-step into the anterior and posterior parts as 2.2 x 10(%) and 1.5 x 10(5) times those of the filtered ambient seawater, respectively. The bioaccumulation factor of mercury by the worms with only their respiration would be actually larger than that by other marine animals through food webs. The high bioaccumulation factor of mercury in the worms suggest the following two possibilities: (i) the biological half-life of organomercury in the worm could be exceptionally long; or (ii) the lifetime of vestimentiferan worms examined in the present study could be extremely long. Various metals in one specimen of the worm were analyzed by using ICP-MS, and then gold as well as silver were detected in the worm. Gold was detected for the first time from marine animals.

Estimate of mercury emissions to the atmosphere from petroleum.

An estimate of the contribution of mercury to the atmospheric environment from petroleum processed in the United States is constructed from recent data. The estimate is based on a mass balance approach for mercury in crude oil, in refined products, and in waste streams (air, water, solid waste) from refineries. Although there are insufficient data at present to have a high degree of confidence in the mean amount and range of mercury concentrations in crude oil or in refined products, the framework of the estimate should assist direction for the acquisition of additional data. On the basis of selected data that put the estimated mean concentration of total mercury in crude oil close to 10 ppb, it is calculated that the total amount of mercury in U.S. petroleum processed yearly is slightly over 8000 kg/yr. Of this amount, approximately 6000 kg/yr is estimated to be emitted to the atmosphere from combustion of liquid hydrocarbon fuels, which represents about 10% of the U.S. yearly emission rate of atmospheric mercury from coal combustion. The material balance predicts that the amount of mercury in air emissions from all U.S. refineries is on the order of 1500 kg/yr based on the assumption that fugitive mercury emissions from refineries are negligible. Atmospheric emissions of mercury from fuel oil burned in the United States are estimated in the U.S. EPA Mercury Report to Congress to be approximately 10000 kg/yr, and this estimate may be in error on the high side by a factor of 3-10. If the mean amounts of mercury in U.S. distillate and residual fuel oils are in the range of 5-15 ppb, as suggested by more recent data, then U.S. fuel oil combustion should contribute no more that about 1000-3000 kg/yr (emission ratio = 1) of mercury to the atmospheric burden.

Mercury in sediment and fish from North Mississippi Lakes

Sediments and/or fish were collected from Sardis, Enid and Grenada Lakes, which are located in three different watersheds in North Mississippi, in order to assess mercury contamination. The mean total mercury concentration in sediments from Enid Lake in 1997 was 0.154 mg Hg/kg, while 1998 sediment concentrations in Sardis, Enid and Grenada Lakes were 0.112, 0.088 and 0.133 mg Hg/kg, respectively. Sediment mercury concentrations in 1999 were similar in all three lakes but, generally lower than 1998. Mean total mercury concentrations in edible fillets of fish collected from Enid Lake in 1998 were above the human health FDA action level (>1.0 mg Hg/kg) for bass (1.40), crappie (1.69) and gar (1.89); however, tissue concentrations were less than 1.0 mg Hg/kg in carp (0.63) and catfish (0.82). Human hazard indexes for each species was ⩾1 for both adults and children, indicating that there is a potential for toxic effects to occur. In addition, calculated consumption limits indicate that adults may consume 4–12 oz. of fish per month, depending on the species consumed. For children, 2 oz. per month may be consumed. Further studies are needed to determine the exact environmental consequences and human health impacts associated with mercury contamination in North Mississippi and the Southeastern United States.

Mercury Concentrations in Spotted Seatrout (Cynoscion nebulosus) from Northwest Florida

We determined total mercury concentrations in dorsal muscle tissue of 112 spotted seatrout (Cynoscion nebulosus) collected between 1993 and 1996 from Pensacola Bay and Choctawhatchee Bay, FL. We describe the relationships of length, weight, age, and sex to total mercury concentrations in this species. Fish ranged in size from 235 to 613 mm total length (TL), with a mean of 463 mm TL. The majority (84%) of the fish collected were female. The mean total mercury concentration detected in all fish combined was 0.40 ± 0.15 ppm, and in individual fish, total mercury concentration ranged from 0.11 to 0.88 ppm. We detected no significant differences in mercury concentrations between sexes. Total mercury concentration was positively correlated with fish TL and weight. However, no relationship was evident between total mercury concentration and age. Mercury concentrations detected in the majority of spotted seatrout examined from northwest Florida were below the State of Florida's limited-consumption advisory of 0.5 ppm.

Atmospheric mercury concentrations in the basin of the amazon, Brazil.

A wide regional mercury pollution in Amazon, Brazil is closely associated with goldmining that has been carried out in the basin of tributaries of the Amazon since the eighteenth century. Possible involvement has been discussed on atmospheric circulation in distributing the volatile pollutant. We developed a portable air sampler for the collection of mercury compounds and determined atmospheric mercury concentrations at several sites in Brazil including the basin of the Amazon tributaries. The mean concentration of total mercury was between 9.1 and 14.0 ng/m(3) in the basin of the Uatumã River located in the tropical rain forest far from goldmining sites and from urbanized area. These mercury levels exceeded the background level previously reported in rural area and, furthermore, were higher than concentrations observed in Rio de Janeiro and in Manaus that were compatible with the reference values for urban area. Mercury concentrations were also determined in gold refineries in the basin of the Tapajos River, and detected at a significant but not a health deteriorating level. Although only preliminary data were available, the present observations were in favor of the hypothesis that mercury is distributed widely by long distant transport by the atmospheric circulation after released at gold mining sites.

Total mercury intake from fish and shellfish by Japanese people

Elevated mercury concentrations have been reported in fish in recent years. Japanese people eat a great deal of raw fishes and shellfishes as “Sashimi” and “Sushi”. The action level of large predatory fish such as tuna with total mercury levels exceeding the Japanese maximum permitted limit of 0.4 ppm is exempted from regulation in Japan. Therefore, current total mercury intake from fish and shellfish of Japanese people is unknown. The purpose of this investigation was to estimate the total mercury intake from fish and shellfish. It was found that the mean total mercury concentration of 1.11 ppm in tuna of eatable base as Sashimi or Sushi was clearly higher than the normal level. The mean total mercury intake from fish and shellfish was 0.17mg per capita per week . According to the hypothesis that 75% of total mercury in fish and shellfish is methylmercury, the weekly intake of 0.13 mg as methylmercury was corresponding amount to about 74% of provisional tolerable weekly intake 0.17 mg of methylmercury set by the Welfare Ministry of Japan.

A survey of total mercury and methylmercury in edible fish and invertebrates from Azorean waters

Levels of total mercury and methylmercury were determined in invertebrates and edible fish collected during 1993–1994 in Sao Miguel Island in the Azores. Among the invertebrates, the highest mean concentrations of total mercury (0.864 and 1.265 μg g −1 dry weight, respectively) were found in the gills and midgut gland of the edible crab ( Cancer pagurus). The proportion of total mercury present as the methylated form in invertebrates varied widely between species, and with trophic position. Apart from white seabream ( Diplodus sargus cadenati) the mean total mercury concentrations found in muscle tissues of the fish studied were generally low, ranging between 0.043 and 0.371 μg g −1 wet wt. Extreme inter-individual variability in mercury concentrations was found in white seabream of intermediate size, levels ranging between 0.132 and 24.61 μg g −1 wet wt. The particularly elevated mercury concentrations found in certain individuals of white seabream may be derived from local hot spot area(s) with raised environmental mercury levels. Methylmercury was the major form of the element accumulated in fish, comprising on average more than 80% of the total mercury. The selenium concentration in white seabream was significantly correlated to the total mercury concentration, although molar ratios of the two elements varied markedly between individual fish.

Accumulation of total mercury and methyl mercury in insect larvae of hydroelectric reservoirs

Mean total mercury (Hg) and methyl mercury (MeHg) concentrations in insect larvae from hydrolelectric reservoirs were 3-5 times (up to 10 times) higher than in their counterparts from natural lakes. Taxonomic differences, which may be related to feeding behavior, and substrate type (lake sediment or flooded soils) together explained a large part of the total variability of total Hg (r2 = 0.64) and MeHg (r2 = 0.79) concentrations in insects. MeHg concentrations in flooded soils increased from 0.3-2 ng Hg cdot g dry weight-1 after 1-2 years of flooding to 15-2 ng Hg cdot g dry weight-1 after 16 years of impoundment. Total Hg and MeHg concentrations in insect larvae followed a similar pattern, but only weak correlations of both total Hg and MeHg concentrations were found between flooded soils and insect larvae, suggesting that factors other than MeHg content of flooded soils also affect the accumulation of these compounds in insects. Our results indicate that suspended particulate matter eroded from flooded soils by wave and ice action and bacterial activity enhanced by the release of labile carbon and nutrients from the flooded soils may indirectly transfer MeHg from flooded soils to insect larvae.

Concentration of mercuryin hair of Japanese people

This investigation was made to estimate current normal concentrations of total mercury in the hair of Japanese people. Hair samples were collected from 365 healthy volunteers in Tokyo and the surrounding areas from June 1992 to June 1993. Mercury contents in the samples were analyzed by gold amalgam flameless atomic absorption spectrophotometry. The mean of the concentrations of total mercury in the hairs of the males(2.98 ppm,81 volunteers with an average age of 34.7, age 11 to 73) was higher than that of the females(2.02 ppm, 284 volunteers with an average age of 26.5, age 12 to 82). In both the male and female, the mean of the concentrations of total mercury in hair increased with age up to their thirties,then gradually decreased. The concentrations of total mercury in the hair of females at age 18 to 40 showed greater fluctuation, as compared to those of males in the same age groups. In both males and females, the concentration of total mercury in the hair was higher in volunteers who have a preference to fish in their diet than in those who prefer other foods. In both males and females, there was no positive correlation between the total hair mercury and the place of residence of the volunteer although the total hair mercury (2.30 ppm) of male volunteers who inhabit Ibaragi and Chiba, in eastern part of Tokyo, facing the Pacific Ocean or both the Pacific Ocean and Tokyo Bay, was lower than those(3.30 and 3.25 ppm) of male volunteers of other two areas. The mean concentration of total mercury in the hair obtained from all the volunteers was 2.23 ppm, which is considerably lower than that (6.02 ppm) from 73 healthy inhabitants of the same areas in the early 1960's. It is speculated from these results that a major current route for mercury exposure in the Japan is fish consumption.

No Indication of in Vivo Methylation of Inorganic Mercury in Chloralkali Workers

It has been shown in vitro that human oral and intestinal bacteria are able to methylate inorganic mercury (Hg) to methylmercury (MeHg). In vivo methylation has been reported for guinea pigs, and several studies have found higher levels of organic Hg in blood of workers exposed to inorganic Hg. In search for indications of in vivo methylation of Hg, we determined total Hg in urine (U), plasma (P), and erythrocytes (Ery), and MeHg in erythrocytes, in 22 chloralkali workers exposed to inorganic Hg, and in 22 age-matched referents. The subjects in both groups ate fish not more than once a week. MeHg was determined using ion exchange separation and cold vapor atomic absorption spectrometry. The mean concentrations of total mercury in chloralkali workers and referents were 26 vs 2.3 μg/g creatinine (U-Hg), 9.7 vs 1.8 ng/g (P-Hg), and 11.4 vs 5.6 ng/g (Ery-Hg). The mean Ery-MeHg concentrations were 3.0 vs 3.7 ng/g, and there were no correlations between Ery-MeHg on the one hand and U-Hg or P-Hg on the other. Our results indicate no significant in vivo methylation of inorganic Hg in man. Contradictory results from previous studies may be due either to bias owing to fish consumption or to analytical shortcomings.

Background levels of total mercury concentrations in blood and urine.

We investigated the background levels of total mercury in blood and urine samples from Japanese subjects without occupational exposure to mercury vapor. Blood and urine specimens were decomposed in sealed Teflon containers, and total mercury concentration was measured by reductive vaporization-gold amalgam capture-atomic absorption spectrophotometry. The mean total mercury concentration in the blood of 56 women aged 34-65 was 18.2 +/- 9.9 ng/ml (range 3.9-56.8 ng/ml). The mean total mercury concentration in the urine of 130 men aged 22-39 was 2.33 +/- 1.50 micrograms/l (range 0.27-10.26 micrograms/l). The mean total mercury concentration in urine adjusted by specific gravity was 2.19 +/- 1.15 micrograms/l (range 0.68-7.68 micrograms/l), and that adjusted by creatinine was 1.51 +/- 0.68 micrograms/g creatinine (range 0.39-4.21 micrograms/g creatinine). These concentrations did not differ greatly from those reported from Europe and Japan. In expressing the total mercury concentration in urine, the creatinine-adjusted range between the minimum and maximum values was smaller than the range adjusted by specific gravity.

Mercury Contamination in the Newark Bay Estuary

As a result of several decades of industrialization, heavy metals, including mercury, have become the focus of ecological and human health concerns in Newark Bay, New Jersey. In this study, concentrations of mercury were determined in 18 surficial sediment samples collected from throughout the estuary. Measured concentrations ranged from nondetectable (0.1 mg/kg) to 9.8 mg/kg (dry weight). These results were compared to data from previous investigations of sediment and biota in the estuary in an effort to characterize the extent of mercury contamination and the potential for toxic effects in humans and biota. Mean concentrations of total mercury were elevated above estimated background levels throughout the estuary. Areas with the highest sediment concentrations included the lower Passaic River and the Arthur Kill. Comparisons to various state and federal sediment quality criteria and guidelines suggest that the presence of mercury poses a toxic hazard to aquatic biota. These data suggest that further investigation of sources is needed to reduce or eliminate this contamination.

Mercury and selenium in axial white muscle of yellowtail kingfish from Sydney, Australia

Altogether, 123 specimens of yellowtail kingfish were collected in ocean waters offshore from Sydney, N.S.W. and analysed for total and methyl mercury. Only 111 of these were analysed for selenium. The mean total mercury concentration of muscle tissue was 0.15 mg kg −1, the maximum was 1.13 mg kg −1 and the integrated average mercury content was calculated as 0.20 mg kg −1 (based on length frequency distribution of the catch) and 0.34 mg kg −1 as determined from the gutted weight distribution of the catch. The methyl mercury concentration averaged 87.9% of total mercury. The correlation between the logarithm of total mercury content and length of fish was significant (r=0.838). The mean selenium concentration was 0.33 mg kg −1 with a maximum of 0.72 mg kg −1. The correlation between the mercury and selenium concentrations in the muscle tissue of yellowtail kingfish was not significant (r=0.316).

Effects of oxygen concentrations on release of mercury from sediments and accumulation byCeratophyllum demersum andAnodonta grandis

The effects of different oxygen concentrations on the release of mercury from sediments and its subsequent accumulation by the plant,Ceratophyllum demersum, and the clam,Anodonta grandis, were investigated. Clams and plants were subjected to three treatments which were designated as control, treatment 1 and treatment 2. Two of the control replicates had normal oxygen concentrations (x=6.4–6.6 mg.L−1) while the third had reduced concentration (x=1.8 mg.L−1)- Oxygen concentrations in treatment 1 were reduced (¯x 1.3–2.0 mg.L−1) for all three replicates. The three replicates in treatment 2 had normal oxygen concentrations (x=6.7–7.2 mg.L−1). Mercury was added to the sediments in treatments 1 and 2. The resulting measured mean total mercury concentrations ((μg.g−1 dry weight) in the sediments of the replicates were 0.05–0.09 (controls), 4.42–7.28 (treatment 1) and 3.92–5.90 (treatment 2). The mercury concentration in water ranged between 0.10 μg.L−1 to 0.20 μg.L−1 for the six week period that the clams and plants were exposed to one of the three treatments. The total mercury concentrations in water were significantly lower in controls than in treatment 2. In plants, the mercury concentration was significantly higher in deoxygenated treatment 1 as compared to oxygenated treatment 2 and in controls. No significant difference in mercury concentration occurred between control and treatment 2 plants. Clams in treatments 1 and 2 contained significantly more mercury compared to the controls. Mercury concentrations in treatment 1 clams were also significantly higher than in treatment 2 clams. The mercury concentration in water, plants and clams was not significantly different in oxygenated and deoxygenated controls.

Mercury concentrations in edible tissues of Elasmobranchs, teleosts, crustaceans and molluscs from south-eastern Australian waters

Mean concentrations of total mercury in the axial muscle tissues from 4 species of elasmobranchs (1.33-3.15 �g g-1) and 14 species of teleosts (0.14-0.73�g g-1) from waters deeper than 75 m were generally higher than the mean concentrations in 23 different species of elasmobranchs (0.13- 1.70 �g g-1) and 30 different species of teleosts (0.01-0.29�g g-1) from shallower waters outside Port Phillip Bay. In 5 of the 11 species of teleosts from Port Phillip Bay, which is shallow, almost landlocked and drains a largely urbanized catchment, mean concentrations were 0.39-0.63�g g-; in the remaining 6 species, they were 0.04-0.27�g g-1. Differences in the diets and the longevity of the species are discussed as possible explanations of the variations in the mercury concentrations. Most of the results were similar to those from other studies undertaken on the same species collected from waters off Tasmania and New South Wales, but tended to be higher than the results for the same species collected from New Zealand waters. Mean concentrations of mercury in various soft tissues from eight species of molluscs were 0.01-0.11�g g-1 and in abdominal and thoracic muscle tissues from three species of crustaceans were 0.03-0.13�g g-1..