Mercury in air and plant specimens in herbaria: a pilot study at the MAF Herbarium in Madrid (Spain)

We present data from a study of mercury concentrations in air and plant specimens from the MAF Herbarium in Madrid (Spain). Hg (gas) emissions from old plant collections treated with mercuric chloride (HgCl(2)) in herbaria may pose a health risk for staff working in installations of this type. This is an issue not yet properly addressed. Plants that underwent insecticide treatment with HgCl(2) at the MAF Herbarium until the mid 1970s have persistent high concentrations of Hg in the range 1093-11,967 microg g(-1), whereas untreated specimens are in the range of 1.2-4.3 microg g(-1). The first group induces high concentrations of Hg (gas) in the main herbarium room, with seasonal variations of 404-727 ng m(-3) (late winter) and 748-7797 ng m(-3) (early summer) (baseline for Hg: 8 ng m(-3)). A test survey at another herbarium in Madrid showed even higher concentrations of Hg (gas) above 40,000 ng m(-3). The World Health Organization guidelines for chronic exposure to Hg (gas) are estimated at a maximum of 1000 ng m(-3). While staff was aware of the existence of HgCl(2) treated plants (the plant specimen sheets are labelled as 'poisoned'), they had no knowledge of the presence of high Hg (gas) concentrations in the buildings, a situation that may be relatively common in herbaria.     

Mercury speciation analyses in HgCl(2)-contaminated soils and groundwater--implications for risk assessment and remediation strategies

Since the 19th century, mercury(II)chloride (HgCl(2)) has been used on wood impregnation sites to prevent wooden poles from decay, leaving behind a legacy of highly contaminated soil/aquifer systems. Little is known about species transformation and mobility of HgCl(2) in contaminated soils and groundwater. At such a site the behaviour of HgCl(2) in soils and groundwater was investigated to assist in risk assessment and remediation. The soil is low in organic carbon and contains up to 11,000 mg Hg/kg. Mercury (Hg) concentrations in groundwater decrease from 230 to 0.5 microg/l within a distance of 1.3 km. Hg species transformations in soil and aqueous samples were analysed by means of solid-phase Hg pyrolysis and CV-AAS. In aqueous samples, Hg species were distinguished between ionic/reactive Hg and complex-bound Hg. Potential mobility of Hg in soils was studied through batch experiments. Most Hg in the soil is matrix-bound HgCl(2), whereas in the aquifer secondary formation to Hg(0) could be observed. Aqueous Hg speciation in groundwater and soil solutions shows that an average of 84% of soluble Hg exists as easily reducible, inorganic Hg species (mostly HgCl(2)). The proportion of complex-bound Hg increases with distance due to the transformation of inorganic HgCl(2). The frequent occurrence of Hg(0) in the aquifer suggests the formation and degassing of Hg(0), which is, in addition to dilution, an important process, lowering Hg concentrations in the groundwater. High percentage of mobile Hg (3-26%) and low seepage fluxes will result in continuous Hg release over centuries requiring long-term groundwater remediation. Results of soluble Hg speciation suggest that filtering materials should be adapted to ionic Hg species, e.g. specific resins or amalgamating metal alloys.     

Urinary mercury in adults in Poland living near a chloralkali plant

We conducted a study within the framework of the interdisciplinary European Mercury Emission from Chloralkali Plants (EMECAP) project to assess exposure to mercury (Hg) and the contribution of Hg emissions from a mercury cell chloralkali plant to urinary mercury (U-Hg) in adults living near the plant. We collected data from questionnaires and first morning urine samples from 75 subjects living near the Tarnow plant in Poland and 100 subjects living in a reference area. Median U-Hg was 0.32 mug/g creatinine (microg/gC) and 0.20 microg/gC, respectively. The median U-Hg was also higher in the amalgam-free subjects living near the plant (0.26 microg/gC) than in the reference group (0.18 microg/gC), but no such association was found in a multivariate analysis. There was a statistically significant positive association between U-Hg and number of teeth with amalgams, a negative association with age and a tendency towards higher U-Hg in female subjects. In the amalgam-free subjects there were statistically significant effects of female sex and fish consumption, and a negative association with age. The additional long-term average air Hg concentration from the plant, based on EMECAP environmental measurements and modelling, was estimated to be 1-3.5 ng/m(3) for the residential study area and should have a very small effect on U-Hg. The other Hg emission sources such as coal combustion facilities located nearby should be taken into account in assessing the overall impact of air Hg on U-Hg in this area.     

Foliar exchange of mercury as a function of soil and air mercury concentrations

Previous research has indicated that foliar mercury (Hg) flux is bi-directional, with influence from both atmospheric and soil Hg. This work investigated the role of soil and air Hg concentrations on foliar Hg exchange using a single-plant gas-exchange system. The exchange of Hg vapor with aspen seedlings grown in soil Hg concentrations of 0.03+/-0.01, 5.8+/-0.5, and 12.3+/-1.3 microg g(-1) and exposed to atmospheric Hg concentrations of 2.4+/-0.5, 11.0+/-0.9, and 30.4+/-2.2 ng m(-3) was measured. At background atmospheric Hg concentrations of 2.4 ng m(-3), foliage released Hg at all three soil Hg concentrations and fluxes ranged from 1.6 to 5.5 ng/m(2)/h. At higher atmospheric Hg concentrations (>11 ng m(-3)), net deposition to foliage ranged from -9 to -47 ng/m(2)/h, exhibiting increase uptake with higher air Hg concentrations. Fluxes associated with aspen showed an immediate response to changes in atmospheric Hg concentrations. Compensation points, the air concentration where no net flux of Hg vapor occurred, were 3-4 ng m(-3) in the light and 2-3 ng m(-3) in the dark for trees grown in soils of 0.03 and 6 microg g(-1) Hg content, and 5-6 ng m(-3) in the light and 2.5-3.5 ng m(-3) in the dark for trees grown in 12 microg g(-1) Hg soils.     

Concentrations of selected essential and non-essential elements in arctic fox (Alopex lagopus) and wolverines (Gulo gulo) from the Canadian Arctic

Arctic fox (Alopex lagopus) and wolverine (Gulo gulo) tissues were collected in the Canadian Arctic from 1998 to 2001 and analyzed for various essential and non-essential elements. Several elements (Ag, Al, As, B, Ba, Be, Co, Cr, Mo, Ni, Sb, Sn, Sr, Tl, U and V) were near or below the detection limits in >95% arctic fox and wolverine samples. Concentrations of Cd, Cu, Fe, total Hg (THg), Mn, Pb, Se and Zn were quantifiable in >50% of the samples analyzed and reported herein. Hepatic elemental concentrations were not significantly different among arctic foxes collected at Ulukhaqtuuq (Holman), NT (n=13) and Arviat, NU (n=50), but were significantly greater than concentrations found in wolverine liver from Kugluktuk (Coppermine), NU (n=12). The mean (+/-1 S.E.) concentrations of Cd in kidney were also significantly greater in arctic fox (1.08+/-0.19 microg g(-1) wet wt.) than wolverine (0.67+/-0.18 microg g(-1) wet wt.). However, mean hepatic Cu concentrations (Ulukhaqtuuq: 5.5+/-0.64; Arviat: 7.1+/-0.49 microg g(-1) wet wt.) in arctic foxes were significantly lower than in wolverines (32+/-3.3 microg g(-1) wet wt.). Hepatic total Hg (THg) concentrations in arctic fox from this study were not significantly different from specimens collected in 1973, suggesting that THg concentrations have not changed dramatically over the past 30 years. The mono-methylmercury (MeHg) concentrations in selected (n=10) arctic fox liver samples from Arviat (0.14+/-0.07 microg g(-1) wet wt.) comprised 14% of THg. While the molar concentrations of THg were correlated with Se in arctic foxes and wolverines, the hepatic Hg/Se molar ratios were consistently lower than unity; suggesting that Se-mediated detoxification pathways of Hg are not overwhelmed at current exposure.     

Effect of dietary methylmercury and seleno-methionine on Sacramento splittail larvae

The effects of methylmercury (MeHg) and selenium (Se) contamination on food webs in the San Francisco Estuary have received considerable attention during the past decade. However, knowledge of their effects on native fishes of California is lacking. This study investigated the interactive effects of dietary MeHg and seleno-methionine (SeMet) on Sacramento splittail (Pogonichthys macrolepidotus) larvae. Twelve diets containing increasing levels of SeMet (0.64, 8.2 and 35.0 microg Se g(-1) diet) and MeHg (0.01, 0.13, 4.7 and 11.7 microg Hg g(-1) diet) were fed to 21-day post-hatch larvae for 4 weeks in 2-L beakers at 25 degrees C. Fish were fed twice a day at a feeding rate of 40, 30, 25 and 20% of body weight during the 1st, 2nd, 3rd and 4th week, respectively. At the end of week 4, no significant difference (P>0.05) was observed among treatments for mortality, body length or weight, and condition factor. Bioaccumulation of Hg and Se responded positively and significantly (P<0.05) to their dietary concentrations. The molar ratio of Se/Hg in diets was linearly correlated to the ratio of Se/Hg in fish. Dietary Se inhibited Hg accumulation, which was negatively correlated to the dietary Se/Hg ratio. Histopathological examination revealed severe gill anomaly and liver glycogen depletion in fish fed the 11.7 microg Hg g(-1) diet. Liver glycogen depletion and kidney tubular dilation were found in larvae fed the 11.7 microg Hg and 11.7 microg Hg+35 microg Se g(-1) diets. In conclusion, dietary Hg enhanced Se accumulation but dietary Se inhibited Hg accumulation in splittail. Dietary Se showed a protective effect in fish fed the high MeHg diet. This protection was related to the dietary Se/Hg ratio, which is a more reliable criterion for evaluating the interactive effect between Se and Hg in splittail.     

Mercury speciation in the French seasonal snow cover

Snow samples have been collected in the French Alps in 1998, 1999 and 2000 in order to measure both total Hg (HgT) and reactive Hg (HgR). Concentrations of HgT were between 13 and 130 pg g(-1) and HgR concentrations were below the detection limit (approximately 0.8 pg g(-1)). Hg speciation in snow was evaluated on the basis of ionic complexation equilibrium with chloride, hydroxide, oxalate. The pH of the snow was found to be an important parameter for Hg speciation. For pH values near 3, HgC2O4 is predominant in snow samples except for snow strongly influenced by anthropogenic sources (in which case HgCl2 predominates). When pH > 4, Hg(OH)2 and HgOHCl are predominant. These latter pH values are observed for precipitation not influenced by anthropogenic sources but more by soil erosion, e.g. Saharan dusts. The knowledge of Hgr speciation in snow is a key question for understanding the mechanisms of transformation of these complexes in snow after precipitation.     

The Almadén district (Spain): anatomy of one of the world's largest Hg-contaminated sites

We present data from an early reconnaissance survey (stream sediments, soil, and water Hg chemistry; plants and water crustaceans Hg intake) of the Almadén district (central Spain), that was carried out to establish the potential environmental hazards derived from the anomalous mercury concentrations measured in this realm. The Almadén mercury district (approximately 300 km2) can be regarded as the largest geochemical anomaly of mercury on Earth. The district includes a series of mercury mineral deposits, having in common a simple mineralogy (dominant cinnabar: HgS, and minor pyrite: FeS2). The ore deposits have been mined for more than 2000 years, and the main mine of the district (Almadén), has been active from Roman times to present day with almost no interruptions. The mercury distribution in soils of the district reveals the existence of high, and extremely high mercury values (up to 8889 microg g(-1)), whereas concentrations in stream sediments and waters reach exceptional values of up to 16,000 microg g(-1) and 11,200 ng l(-1) respectively. On the other hand, very high concentrations of methylmercury (MeHg) have been detected in calcines (up to 3100 ng g(-1)), sediments (0.32-82 ng g(-1)), and waters (0.040-30 ng l(-1)). Mercury gets incorporated to edible river crustaceans and plants. The red swamp crayfish Procambarus clarkii, has Hg concentrations of up to 9060 ng g(-1) (muscle) and 26,150 ng g(-1) (hepatopancreas). Regarding plants, the local wild asparagus (Asparagus acutifolius) yields values of up to 298 microg g(-1) Hg. Mercury also escapes to the atmosphere, and mineral deposits, together with metallurgical activities, generate strong anomalies of atmospheric Hg. The most important concentrations relate to the emissions from the Almadén metallurgical roaster, in the order of 14,000 ng Hg m(-3). Additionally, large open pit operations also contribute to the district atmospheric pool of mercury, with high concentrations above 1000 ng Hg m(-3). Thus, no system (rocks, soils, sediments, waters, atmosphere, biota) in the Almadén district is free from strong Hg contamination.     

Mercury levels in lichens from different host trees around a chlor-alkali plant in New Brunswick,Canada

Mercury concentrations were determined in the epiphytic lichen Hypogymnia physodes along five transects starting from a chlor-alkali plant located at Dalhousie, New Brunswick, a landfill site and a nearby electricity generating station. Lichen samples were collected from white birch (Betula papyrifera) and spruce (Picea sp.) or balsam fir (Abies balsamea). Average lichen background mercury values were 0.088+/-0.005 microg/g from white birch and 0.148+/-0.046 microg/g from spruce trees, with a detection limit of 0.05 microg/g. The chlor-alkali plant and a power plant were identified, respectively, as a major source and a minor source of elevated mercury levels in lichens. At 125 m north-west of the New Brunswick Power plant, 0.28 microg/g Hg were found in Hypogymnia physodes from spruce trees, while at 250 m west (downwind) of the chlor-alkali plant, 3.66 microg/g of mercury were determined. High values, 0.98 microg/g in lichens from spruce trees and 0.79 microg/g in lichen samples from white birch were also measured at 125 m south of the chlor-alkali plant and decreased exponentially with distance. The sphere of influence of the chlor-alkali plant with respect to mercury deposition was estimated to extend 2.4-3.4 km from the plant. The mercury concentrations in Hypogymnia physodes collected from white birch were significantly lower than the concentrations in the same lichen from spruce trees in areas with elevated levels of mercury, but not in areas with low mercury levels. The magnitude of this difference dropped with distance from the source.     

Distribution of trace elements in the tissues of benthic and pelagic fish from the Kerguelen Islands

New information on the concentrations of Cd, Cu, Hg and Zn in the liver, kidney and muscles of eight marine benthic and pelagic sub-Antarctic fish species are presented to determine the importance of these metals in the marine systems of the Kerguelen Islands. Compared to the reported metal concentrations in other Antarctic fish species, the present results are globally within the same range of concentrations, although Cd displayed a very high interspecific variability in liver and kidney. Indeed, the highest Cd concentrations in liver, ranging from 10.0 to 52.1 microg x g(-1) dry wt. but also the lowest Cd concentrations in muscles (<0.030 microg x g(-1) dry wt.) have been displayed by the pelagic Myctophidae Gymnoscopelus piabilis. Metal concentrations differences might be related to diet and feeding habits of benthic and pelagic fish species. However, Cd and Hg concentrations in the edible muscle are lower than the French limit values (相似文献   

Distribution of some trace metals in Lochnagar, a Scottish mountain lake ecosystem and its catchment

Anthropogenic trace metals enter the entire ecosystem of Lochnagar solely through atmospheric deposition. Trace metals, including Hg, have been monitored in atmospheric deposition and lake water, and measured in catchment vegetation, aquatic plants and zooplankton, revealing contamination levels in the ecosystem. Furthermore, 17 sediment cores were taken from different areas of the lake. Hg, Pb, Cd, Zn and Cu were analysed in all the cores, which show that the sediments have been heavily contaminated by these trace metals since the 1860s. The distribution of trace metals in the lake sediments was found to be heterogeneous, with concentrations in the surface sediments varying significantly: 110-250 ng/g, 100-360 microg/g, 39-180 microg/g, 0.3-1.9 microg/g and 8-25 microg/g for Hg, Pb, Zn, Cd and Cu, respectively. Trends in the concentration profiles for different trace metals in the same core are different, as are the trends of the profiles for the same metal in different cores. Hence, a single sediment core cannot represent the pollution history of the whole lake. As the soils and sediments contain a high proportion of plant debris and the debris has a high affinity for Hg, resulting in Hg enrichment. Hg was measured in plant debris (> 63 microm) separated from catchment soils and lake sediments. Plant debris may play an important role in storing and transferring Hg in this ecosystem.     

Use of native and transplanted mosses as complementary techniques for biomonitoring mercury around an industrial facility

Terrestrial mosses were used simultaneously in passive (native species, Scleropodium purum and Hypnum cupressiforme) and active (S. purum transplants in moss bags) biomonitoring techniques in a study that aimed to demonstrate the compatibility of the two methods by detailed investigation of the spatial distribution of mercury in the surroundings of a chlor-alkali plant. Native mosses were sampled and transplants exposed (for periods of 30 days) at two different times of the year in order to take into account different environmental conditions (precipitation, temperature, prevailing winds, etc.). The concentrations of Hg in the native mosses ranged between 0.04 and 11.78 microg g(-1) in February and 0.26 and 12.7 microg g(-1) in September; in the transplants the concentrations ranged between 0.39 and 1.9 microg g(-1) in June and 0.036 and 2.75 microg g(-1) in November. These values are all within the ranges reported in the literature. The total concentrations were transformed into either contamination factors (CF) (by taking into account the background levels of Hg in the native mosses) or enrichment factors (EF) (by taking into account the initial concentrations in the transplants). In both cases, there was a clear relationship with the distance from the source of emission, irrespective of the time of year. Within the range of distances for which data were available for natives and transplants, the CF and EF were highly correlated. This implies that transplants sited in the area immediately surrounding the plant, where the density of native mosses was very low, can be used to determine the degree of contamination in this area. The study also illustrated that the native moss appeared to adapt to the surrounding environment because at an equal distance (> 500 m) from the source of emission the value of the CF for native mosses fell to 1, but the EF for transplanted mosses remained still high (5.2).     

Mercury speciation in the hair of pre-school children living near a chlor-alkali plant

Exposure to mercury species was assessed in the hair of 130 Spanish children (age 4) from the general population in two areas. Both areas are exposed to different sources of mercury: a point source in Ribera d'Ebre (northeastern Spain) and a diffuse source on the island of Menorca (northwestern Mediterranean). The median MeHg values in the hair of children from Ribera d'Ebre (RE) were nearly twice (0.631 microg/g vs. 0.370 microg/g) those of children from Menorca (MC) (p < 0.05). Total Hg showed a similar trend (REmedian: 0.720 microg/g vs. MCmedian: 0.476 microg/g). Nevertheless, inorganic mercury levels were similar in the two groups of children (REmedian: 0.186 microg/g vs. MCmedian: 0.210 microg/g). Two subgroups of the Ribera d'Ebre group were defined: children living in Flix (a village near a chlor-alkali plant) (RE1) and children living on the outskirts of Flix with no clear, direct influence of the plant (RE2). The mercury concentrations in RE1 were also significantly higher than those in Menorca, but no significant differences were found between Menorca and the RE2 subgroup. We evaluated the fish consumption of RE1, RE2 and MC and found that the Menorcan children consumed significantly less fish (p < 0.05) than the other two subgroups. Children who consumed fish more than three times a week had higher MeHg concentrations (beta (SE) = 0.991 (0.279) than those who ate it less than once a week. Nevertheless, the differences in MeHg levels between children from Ribera d'Ebre and Menorca remained statistically significant after adjustment for fish intake and other variables (beta (SE) = 0.779 (0.203) for children from RE1). In conclusion, local sources other than seafood contribute significantly to MeHg content in hair in the two Ribera d'Ebre subgroups.     

Human exposure to mercury due to small scale gold mining in northern Tanzania

In northern Tanzania large numbers of small scale miners use mercury in the gold extraction process causing contamination of the environment and risks to human health. Human exposure to Hg was assessed in populations in and around small scale gold mining camps by means of human hair and urine surveys. We also determined Hg concentration in fish in aquatic bodies close to these camps. Urinary Hg testing in three communities showed that 36% of the gold miners working with amalgam exceeded the WHO guideline concentration of 50 microg Hg/g creatinine. Data from a hair survey of fishermen and farmers confirm that at present, the fish-eating population close to the southern tip of Lake Victoria is at low risk with regard to Hg exposure. Concentrations in fish were low and > 90% of the hair samples from the fish-eating population were below 2 microg/g T-Hg. Highest Hg concentrations in fish caught along the southern shores of Lake Victoria and in rivers draining from gold processing sites were detected in lungfish species (Protopterus aethiopicus), and lowest Hg concentrations in tilapia (Oreochromis niloticus and Tilapia zilii).     

Assessment of mercury and methylmercury pollution with zebra mussel (Dreissena polymorpha) in the Ebro River (NE Spain) impacted by industrial hazardous dumps

Large amounts of industrial waste containing high concentrations of mercury (up to 436 microg/g) are dumped in a reservoir adjacent to a chlor-alkali plant in Flix (Catalonia, Spain), on the lower Ebro River. In order to assess the spatial redistribution of mercury from the point source and its bioavailability to the aquatic food web, zebra mussels (Dreissena polymorpha) were collected at several sites. The highest total Hg (THg) and methylmercury (MeHg) concentrations ever reported for zebra mussels were found (THg: 0.02 to 0.81 microg/g ww; MeHg: 0.22 to 0.60 microg/g ww). At the most polluted site, close to the waste dump, the mean values were 20 times greater than the local background level. Concentrations decreased with increasing mussel size at all sites. The MeHg/THg ratio was ca. 60% (range: 50-80%). A comparison of similar size classes clearly indicated the hot spots of Hg bioavailability to the aquatic food web and downstream transport.     

Mercury contamination in the vicinity of a derelict chlor-alkali plant. Part I: sediment and water contamination of Lake Balkyldak and the River Irtysh

A mercury-cell chlor-alkali plant operated in Pavlodar, Northern Kazakhstan, for 18 years and caused widespread contamination of the surrounding environment. Untreated wastewater from the plant was discharged to Lake Balkyldak, a shallow impounded lake without an outlet. The nearby River Irtysh was also suspected to be impacted by mercury (Hg) via the transport of contaminated groundwater. We took sediment and water samples from both aquatic systems, and also sampled soils along the shoreline of the lake and in the Irtysh flood plain. Sediments from Lake Balkyldak were found to be very heavily contaminated, with Hg concentrations in the surface layer reaching up to approximately 1500 mg kg(-1) near the wastewater outfall pipe. The contaminated lake sediments are prone to wind-driven resuspension and are acting as a strong source of Hg to the water column. Unfiltered lake water samples taken in shallow areas within 10-15 m from the shoreline contained from 0.11 microg Hg L(-1) in the less contaminated northern part of the lake to 1.39 microg L(-1) near the pollutant outfall in the south (up to 7.3 microg L(-1) on windy days). Sediments from the River Irtysh were only slightly impacted, with maximum Hg concentrations of 0.046 mg kg(-1) in the old river channel and 0.36 mg kg(-1) in floodplain oxbow lakes. In water samples from the River Irtysh, Hg was generally not detected, although trace concentrations (3 to 9 ng L(-1)) were found in some samples taken from oxbow lakes. We conclude that the river is not significantly impacted by Hg, but the highly contaminated Lake Balkyldak poses a threat and is in need of remediation. Potential remediation options for the lake are reviewed and are discussed in the context of experiences made at other Hg-contaminated sites.     

Maximum likelihood mixture estimation to determine metal background values in estuarine and coastal sediments within the European Water Framework Directive

Some of the recently derived European Directives, such as the Water Framework and Marine Strategy, have, as ultimate aims, to achieve concentrations of hazardous substances in the marine environment near background values. Hence, the determination of natural background levels, in marine sediments, is highly relevant. The present study proposes the use of the maximum likelihood mixture estimation (MLME) to determine regional background levels and upper threshold of metal concentration, with the Basque Country as a case study (with a data set of 575 samples, from estuarine and littoral areas, including both intertidal and subtidal sediments). The heuristic procedure is applied with unimodal data distributions (Cd, Cr, Fe and Ni) and the mixture density estimations, based upon maximum likelihood, are carried out with polypopulational data distributions (As, Cu, Mn, Hg, Pb and Zn). The upper limits of the distribution are proposed, as the limits between 'High Status' and 'Good Status' (according to the Water Framework Directive terminology). The regional upper limits were 0.45 microg g(-1) for Cd, 71 microg g(-1) for Cr, 53,542 microg g(-1) for Fe, 57 microg g(-1) for Ni, 24 microg g(-1) for As, 64 microg g(-1) for Cu, 447 microg g(-1) for Mn, 0.27 microg g(-1) for Hg, 66 microg g(-1) for Pb, and 248 microg g(-1) for Zn. The results from this study can assist further in the determination of sediment reference conditions, to assess chemical status, within the above-mentioned directives; likewise, it will be studied as a useful methodology in determining regional metal backgrounds in other European countries.     

Mercury and selenium concentrations in hair samples of women in fertile age from Amazon riverside communities

The aim of the present study was to evaluate mercury and selenium concentrations in hair samples of reproductive age women from riverside communities of the Tapajós River basin. We studied 19 pregnant and 21 non-pregnant women, 13 to 45 years old, living in the region for at least 2 years, and having a diet rich in fish. The analysis of Se and total Hg were performed in the Instituto de Pesquisas Energéticas e Nucleares (IPEN, S?o Paulo, Brazil) by using a Varian AA220-FS atomic absorption spectrometer with a flow injection system. There were no differences between the two groups - pregnant and non-pregnant -- concerning age (23.80 +/- 6.92 and 26.60 +/- 9.60 years old, respectively) and residential time (20.21 +/- 8.30 and 22.20 +/- 10.90 years, respectively). The geometric means and ranges for total Hg concentration were similar (p > 0.05): 8.25 microg/g (1.51-19.43) in pregnant and 9.39 microg/g (5.25-21.00) in non-pregnant women, respectively. Total Hg concentrations were also similar in different gestational stages. However, there was a significant difference between the two groups (p < 0.05, Student t test) in relation to Se concentration: 0.61 microg/g (0.40-2.33) in pregnant and 2.46 microg/g (0.92-5.74) in non-pregnant women, respectively. We concluded that Hg exposure levels in reproductive age women were only slightly higher than a provisional tolerable weekly intake of MeHg would provide, that Hg concentration in maternal hair samples was independent of gestational age, and that low Se concentration in pregnant women indicates high mineral consumption by fetal organism to satisfy their metabolic requirements raised during pregnancy, including as a protective mechanism for Hg cytotoxic effects.     

Hydrochemistry and mercury cycling in a High Arctic watershed

Mass budgets for total mercury, major ions and nutrients were calculated for Amituk Lake, located on Cornwallis Island, Nunavut, Canada. Total mercury in two distinct snowpacks averaged 1.25 and 4.21 ng L(-1); the discharge-weighted concentration of influent streams averaged 0.76 ng L(-1). The recent and pre-industrial Hg(T) fluxes in atmospheric deposition to the catchment were estimated to be 0.57 and 0.23 microg m(-2) but through retention within the catchment and/or re-volatilization from the melting snowpack, these decreased by 69% in the lake inflow. The spring freshet was the prime conduit for transporting Hg(T) into Amituk Lake. Because of limited mixing of surface runoff with the lake water column during snowmelt, 59% of the Hg(T) input was directly discharged through the outflow, 16% entered the lake water column where concentrations increased from 0.23 to 0.33 ng L(-1) from June to August and 25% was deposited to the bottom sediments producing a sediment Hg(T) flux of 3.1 microg m(-2).     

Levels of selenium and antioxidative enzymes following occupational exposure to inorganic mercury

Levels of selenium and mercury in blood and urine were analysed in 37 male workers exposed to elemental mercury vapour in a chloralkali plant and in 39 unexposed controls of the same age. Mean urinary Hg was 223 nmol l-1 (15 nmol/mmol creatinine) in the exposed group and 26 nmol l-1 (2.0 nmol/mmol creatinine) in the controls. Mean blood and plasma Hg levels were 46 and 36 nmol l-1, respectively, in the exposed group, as compared with 17 and 7 nmol l-1 in the controls. The concentrations of Se in plasma and erythrocytes did not differ between the two groups. Urinary Se levels were, however, slightly but significantly lower in the exposed group (median values 23 vs 29 nmol/mmol creatinine), and there was a negative correlation between urinary Se and plasma Hg in the exposed group. This may be due to a retention of Se in the kidneys. In a subgroup of exposed workers and controls, glutathione peroxidase, superoxide dismutase and catalase were also analysed. No differences were found between the groups with respect to these antioxidative enzymes. The effect on Se status of moderate Hg exposure seems to be of minor clinical importance.