Environmental distribution of mercury and other trace elements in the geothermal area of Bagnore (Mt. Amiata, Italy).

The environmental distribution of mercury and other trace elements in the geothermal area of Bagnore (Mt. Amiata, central Italy) and its surroundings was evaluated by means of lichens used as bioaccumulators. Adopting a 'before-after' strategy, the impact of a recently built power plant was also evaluated. Four sites were sampled: (1) S. Fiora, a town 2 km SE of Bagnore; (2) Bagnore, a village where geothermal power is generated; (3) Aiole, a locality 1.5 km NW of Bagnore with an abandoned Hg smelting plant and a waste pile of roasted cinnabar; (4) Arcidosso, a town 3.5 km NW of Bagnore. At S. Fiora and Arcidosso, where most of the population is concentrated, mercury levels in lichens were within the background range (0.1-0.2 microg/g dw). On the contrary, at Aiole, Hg concentrations (0.63-0.67 microg/g dw) were much higher than background. After the new geothermal power plant went into operation at Bagnore, lichen concentrations of Hg showed a 50% increase from 0.22 to 0.32 microg/g dw. This value, however, is in line with those found in lichens from natural areas with hot springs and fumaroles.     

In vitro effect of agriculture pollutants and their joint action on Pseudokirchneriella subcapitata acid phosphatase

Acid phosphatase plays important roles in algae metabolism such as availability and recycling of inorganic phosphate, autophagic digestive processes and fertilization. Chemicals released into the environment from agriculture activities may impair algae phosphatase activity. The aim of this work was to evaluate the in vitro effect of twenty-four organic compounds and six metals used as pesticides, or present as contaminants in sewage sludge, on the acid phosphatase activity extracted from Pseudokirchneriella subcapitata. Results demonstrated that only the linear surfactant alkyl benzenesulphonate (LAS) and the heavy metals Hg(2+), Al(3+) and Cu(2+) markedly altered (50%) the enzyme activity. Join action inhibition studies indicated that Hg(2+) was more potent inhibitor than Al(3+) or LAS, and that the Hg(2+)+Al(3+) and Hg(2+)+LAS mixtures have, respectively, additive and slight antagonism effects. Copper, which demonstrated an activator effect when preincubated with the enzyme, behaved as a slight antagonist for the inhibitor effect of Hg(2+).     

Heavy metal contamination in sediments of an artificial reservoir impacted by long-term mining activity in the Almadén mercury district (Spain)

Sediments from the Castilseras reservoir, located downstream on the Valdeazogues River in the Almadén mercury district, were collected to assess the potential contamination status related to metals(oids) associated with river sediment inputs from several decommissioned mines. Metals(oids) concentrations in the reservoir sediments were investigated using different physical and chemical techniques. The results were analyzed by principal component analysis (PCA) to explain the correlations between the sets of variables. The degree of contamination was evaluated using the enrichment factor (EF) and the geoaccumulation index (Igeo). PCA revealed that the silty fraction is the main metals(oids) carrier in the sediments. Among the potentially harmful elements, there is a group (Al, Cr, Cu, Fe, Mn, Ni, and Zn) that cannot be strictly correlated to the mining activity since their concentrations depend on the lithological and edaphological characteristics of the materials. In contrast, As, Co, Hg, Pb, and S showed significant enrichment and contamination, thus suggesting relevant contributions from the decommissioned mines through fluvial sediment inputs. As far as Hg and S are concerned, the high enrichment levels pose a question concerning the potential environmental risk of transfer of the organic forms of Hg (mainly methylmercury) from the bottom sediments to the aquatic food chain.     

Mosses and lichens as biomonitors of trace metals. A comparison study on Hypnum cupressiforme and Parmelia caperata in a former mining district in Italy.

Samples of the moss Hypnum cupressiforme and the epiphytic lichen Parmelia, caperata were collected during the summer of 1999 in an area (Colline Metallifere, central Italy) intensively exploited in the past for metals (Cu, Fe, Pb, Zn) and currently for geothermal resources. Lichens were more sensitive than mosses to emissions of S compounds near geothermal fields and abandoned sulphide ore smelting plants. Comparison of elemental compositions of the two cryptogamic species from the same sampling sites showed significantly higher concentrations of lithophile elements (Al, Cr, Fe, Mn, Ni, Ti) in the moss and atmophile elements (Hg, Cd. Pb, Cu, V, Zn) in the lichen. Patterns of bioaccumulation of elements throughout the study area were quite similar for widespread pollutants such as S, B, As, Zn, Cr and Ni, but the lichen and the moss showed different distribution patterns of Hg, Cd and other elements subject to long-range atmospheric transport. These results are due to differences in the morphology and ecophysiology of mosses and lichens and indicate that these organisms cannot be used interchangeably as biomonitors of metals in areas with mineral deposits.     

Effects of pollution on humic substances

To assess effects of industrial and environmental pollution on analytical characteristics of humic substances, we isolated humic acids (HA's) and fulvic acids (FA's) from unpolluted and polluted soils and sediments. Following purification, the HA's and FA's were characterized by elemental (C, H, O, N, S) and functional group (CO2H, phenolic OH, total acidity) analyses, infrared (IR) spectrophotometry, differential thermal analysis (DTA) and by metal (Fe, Al, Cu, Mn, Pb, Ni, Co, Zn, Cr, Cd, Hg, Ca and Mg) analyses. Si was also determined in all samples. Polluted HA's and FA's contained more N and S but less O and were richer in all metals and Si than were unpolluted ones. IR spectra showed that polluted humic materials were enriched in COO- groups, secondary non-cyclic amides and possible also in SO3H groups. DTA curves indicated that polluted HA's and FA's were more thermostable than unpolluted HA's and FA's. Unusually high N, S, Cu, Cr, Zn and Hg contents of humic materials appear to be useful indicators of soil and sediment pollution.     

Evaluation of vulnerability of Suillus variegatus and Suillus granulatus mushrooms to sequester mercury in fruiting bodies

This work determined the mercury (Hg) contents and bioconcentration potential of two Suillus mushrooms, and the probable dietary intake of this element from a mushroom meal. The determination of total Hg content of fungal and soil samples was performed using cold-vapour atomic absorption spectroscopy by a direct sample thermal decomposition coupled with gold wool trap of Hg and its further desorption and quantitative measurement at a wavelength of 253.7 nm. The median values of Hg contents (mg kg^?1 dry biomass) in 213 specimens of S. variegatus from 12 background areas varied widely from 0.087 to 0.51 for caps and from 0.041 to 0.24 for stipes. In 52 specimens of S. granulatus, the Hg contents ranged from 0.30 to 0.41 for caps and from 0.058 to 0.14 for stipes. Both species could be classified as moderate accumulators of Hg and the median bioconcentration factor values ranged from 7.0 to 14 (caps) and 2.1 to 13 (stipes) for S. variegatus and 9.5 (caps) and 1.3 (stipes) for S. granulatus. The estimated intake rates of Hg with the consumption of 300-g caps were from 0.0026 to 0.015 per capita or from 0.000037 to 0.00022 mg kg^?1 body mass and this do not indicate any cause for concern associated with eating a meal once or more in a week during the mushrooming season.     

Immunosuppression in the infaunal bivalve Scrobicularia plana environmentally exposed to mercury and association with its accumulation

This study aimed to test the hypothesis whether mercury (Hg) activates or suppresses inappropriately the immunity of the bivalve Scrobicularia plana inhabiting a Hg contaminated area (Laranjo basin, Ria de Aveiro, Portugal). Immunity endpoints, as well as lipid peroxidation (LPO) as a sign of damage, were evaluated in parallel with total Hg burden. Bivalves from both moderately (MO) and highly (HI) contaminated sites displayed higher haemolymph Hg load and reduced plasma agglutination. Increased haemocytes density and decreased phagocytosis were observed at HI, whereas increased oxidative burst activity (OBA) was observed at MO, pointing out that the immunotoxicity is a result of Hg direct contact involving no ROS intervention. OBA observed at MO was concomitantly associated to peroxidative damage as depicted by LPO increase in haemocytes and haemolymph plasma. Thus, S. plana can be suggested as a suitable bioindicator of metal pollution in coastal areas on the basis of Hg bioaccumulation and immunotoxicity responses.     

Acidification, metals and macrophytes

Plant-specific and metal-specific uptake of Al, Cd, Pb and Hg are reviewed, using examples from bryophytes, lichens, wetland plants, woody plants and crop plants. Ranges of plant metal concentration, toxic thresholds and effects, and effects of metal on biomass are derived from the literature. Relationships of metal in plants to metals in sediment, soil water and air are discussed. Plant Al is negatively correlated with pH of water in lakes and with soil pH. Cadmium in crop plants is negatively related to soil pH. Lead in submergents is related negatively to sediment pH at 4.5 to 6. Little information on plant Hg was available. Factors affecting plant uptake include soil or sediment organic content, carbon exchange capacity, oxide and carbonate content, and Eh as well as total metal content.     

The effects of acidification on the geochemistry of Al, Cd, Pb and Hg in freshwater environments: a literature review

Acidification of freshwater environments (terrestrial, surface water, and freshwater sediment) can significantly affect the geochemistry of Al, Cd, Pb and Hg; for example, metal mobility within soils (Al, Cd), the relative distribution of dissolved metal species (Al, Cd, Pb, Hg), and the sedimentation rate of metals in standing water bodies (Cd, Pb) can be altered by acidification. In this critical review of the literature over the last decade concerned with the interaction of acidification with these four metals, we have attempted both to provide an assessment of the current state of knowledge in this field and to emphasize those areas where significant progress has been made since the possible implications of environmental acidification on metal geochemistry became widely appreciated in the late 1970s. We have also indicated those areas which we feel are most in need of further research.     

Dry deposition and foliar leaching of mercury and selected trace elements in deciduous forest throughfall

The estimated annual throughfall deposition flux of Hg in a northern mixed-hardwood forest in the Lake Huron Watershed was 10.5±1.0 μg m⁻² compared to an annual precipitation Hg flux of 8.7±0.5 μg m⁻² (June 1996–June 1997). The source of this additional Hg in throughfall is often attributed to wash-off of dry deposition, but foliar leaching of Hg may also be important. To determine the influence of both dry deposition and foliar leaching of Hg and other elements in throughfall, we measured a suite of trace elements (Hg, Al, Mg, V, Mn, Cu, Zn, As, Rb, Sr, Cd, Ba, La, Ce, and Pb) in throughfall, precipitation, and ambient air samples from a northern mixed-hardwood forest. Based on a multiple linear regression model, dry deposition had the most important influence on Hg, Al, La, Ce, V, As, Cu, Zn, Cd, and Pb fluxes while foliar leaching strongly influenced Mg, Mn, Rb, Sr, and Ba fluxes in net throughfall. The Hg dry deposition flux was estimated using gaseous and aerosol Hg measurements and modeled deposition velocities. The calculated dry deposition flux (∼12–14 μg m⁻²) of Hg to the canopy indicated that atmospheric deposition of Hg could easily account for all of the Hg deposited in net throughfall (1.9±0.1 μg m⁻²). Although there is a large uncertainty associated with these techniques, the modeling estimates indicate that atmospheric Hg may account for all of the Hg deposited in litterfall (11.4±2.8 μg m⁻²).     

Variation of heavy metals within and among feathers of birds of prey: effects of molt and external contamination

In this study we examined the effect of external contamination on the heavy metal (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn) concentration in feathers. We compared the heavy metal content among the 10 primary wing feathers of sparrowhawks (Accipiter nisus), little owls (Athene nocta) and barn owls (Tyto alba) and the variation within the outermost tail feather of sparrowhawks and tawny owls (Strix aluco). The concentration of Hg was significantly higher in feathers molted first, suggesting that levels in feathers reflect levels in the blood during formation. For some other elements (Al, Co, Ni, Pb, Zn) on the other hand, there are strong indications that external contamination may have an important impact on the levels detected in the feathers. This should be taken into account in future monitoring studies.     

Inorganic elemental concentrations in birch bolete mushroom (Leccinum scabrum) and top soil: contamination profiles,bioconcentation and annual variations

Abstract

Analysis of inorganic and organic contaminants in foodstuffs aids in understanding the human exposure to these compounds via consumption. In this study, an edible mushroom species (Leccinum scabrum) and top soil samples were analysed for essential and toxic substances including phosphorus and inorganic elements over a period of three fruiting seasons. Analysis of silver (Ag), aluminium (Al), barium (Ba), calcium (Ca), cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), mercury (Hg), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), phosphorus (P), lead (Pb), rubidium (Rb), strontium (Sr) and zinc (Zn) in mushrooms and topsoil were performed using inductively coupled plasma optical emission spectroscopy (ICP-OES) with ultrasonic cross flow nebulizer. Total mercury was determined by cold-vapour atomic absorption spectroscopy (CV-AAS). The results exhibited wide variation in concentrations of metals between soil and mushroom (cap and stipes) during three fruiting seasons. Positive bioconcentration factors (BFCs) indicate on bioaccumulation of several metals including, Cd, Cu, Hg, K, Mg, Na, P, Rb and Zn in caps and stipes of fruitbodies of this mushroom, while other metals such as Al, Ba, Ca, Co, Fe, Mn, Ni, Pb and Sr were not exhibiting significant positive BFCs. Over a period studied, the caps were characterised by different (p?<?0.05) concentrations of Al, Co, Cu, Hg, Mn, Ni, P, Pb and Sr. Contamination profiles, temporal fluctuations, BCFs should be taken into consideration when assessing the nutritional value of this mushroom.     

Correlates of mercury in fish from lakes near Clyde Forks, Ontario, Canada

Subsurface soils near Clyde Forks, Ontario, Canada, can have naturally high concentrations of mercury (Hg) from local geological sources. To investigate Hg in local aquatic food webs, Hg was measured in fish dorsal muscle (mainly yellow perch [YP] and pumpkinseed sunfish [PS]) and surface sediments from 10 regional lakes. Water chemistry, along with fork length, weight, and stable isotopes (delta15N, delta13C, delta34S) in fish were also measured. No lake sediments had elevated (>0.3microg/g dw) Hg, and average Hg concentrations in fish were not sufficiently high (<1microg/g dw) to be of concern for fish-eating wildlife. Variance in fish Hg was best explained by dietary carbon source (delta13C), and certain lake variables (e.g., pH for YP). PS with more pelagic feeding habits had higher delta34S and Hg than those with more littoral feeding habits. Potential biological linkages between fish Hg and delta34S, a parameter that may be related to the lake sulphate-reducing bacteria activity, requires further investigation.     

Surface compositions of carbon sorbents exposed to simulated low-rank coal flue gases

Bench-scale testing of elemental mercury (Hg0) sorption on selected activated carbon sorbents was conducted to develop a better understanding of the interaction among the sorbent, flue gas constituents, and Hg0. The results of the fixed-bed testing under simulated lignite combustion flue gas composition for activated carbons showed some initial breakthrough followed by increased mercury (Hg) capture for up to approximately 4.8 hr. After breakthrough, the Hg in the effluent stream was primarily in an oxidized form (>90%). Aliquots of selected activated carbons were exposed to simulated flue gas containing Hg0 vapor for varying time intervals to explore surface chemistry changes as the initial breakthrough, Hg capture, and oxidation occurred. The samples were analyzed by X-ray photoelectron spectroscopy to determine changes in the abundance and forms of sulfur, chlorine, oxygen, and nitrogen moieties as a result of interactions of flue gas components on the activated carbon surface during the sorption process. The data are best explained by a competition between the bound hydrogen chloride (HCl) and increasing sulfur [S(VI)] for a basic carbon binding site. Because loss of HCl is also coincident with Hg breakthrough or loss of the divalent Hg ion (Hg2+), the competition of Hg2+ with S(VI) on the basic carbon site is also implied. Thus, the role of the acid gases in Hg capture and release can be explained.     

Methylmercury, fish consumption, and the precautionary principle

This paper considers several broad issues in the context of probabilistic assessment of the benefits of curtailing mercury (Hg) emissions from U.S. coal-fired power plants, based on information developed from recent literature and epidemiology studies of health effects of methylmercury. Exposure of the U.S. population is considered on the national scale, in large part because of recent questions arising from survey and experimental data about the relative importance of local deposition of airborne Hg. Although epidemiological studies have provided useful information, safe levels of Hg exposure remain uncertain, in part because of other dietary considerations in the populations that were studied. For example, much of the seafood consumed in one of the major studies was also contaminated with polychlorinated biphenyls, as are fish taken from some U.S. fresh waters. The primary epidemiological approach involves cross-study comparisons in relation to mean exposures, rather than detailed critiques of individual effects reported in each study. U.S. exposures are seen to be well below the levels at which adverse health effects are reported. This analysis supports the conclusion that unilateral reduction of Hg emissions from U.S. coal-fired power plants alone is unlikely to realize significant public health benefits.     

Modeling interactions of Hg(II) and bauxitic soils

The adsorptive interactions of Hg(II) with gibbsite-rich soils (hereafter SOIL-g) were modeled by 1-pK surface complexation theory using charge distribution multi-site ion competition model (CD MUSIC) incorporating basic Stern layer model (BSM) to account for electrostatic effects. The model calibrations were performed for the experimental data of synthetic gibbsite-Hg(II) adsorption. When [NaNO(3)] > or = 0.01M, the Hg(II) adsorption density values, of gibbsite, Gamma(Hg(II)), showed a negligible variation with ionic strength. However, Gamma(Hg(II)) values show a marked variation with the [Cl(-)]. When [Cl(-)] > or = 0.01M, the Gamma(Hg(II)) values showed a significant reduction with the pH. The Hg(II) adsorption behavior in NaNO(3) was modeled assuming homogeneous solid surface. The introduction of high affinity sites, i.e., >Al(s)OH at a low concentration (typically about 0.045 sites nm(-2)) is required to model Hg(II) adsorption in NaCl. According to IR spectroscopic data, the bauxitic soil (SOIL-g) is characterized by gibbsite and bayerite. These mineral phases were not treated discretely in modeling of Hg(II) and soil interactions. The CD MUSIC/BSM model combination can be used to model Hg(II) adsorption on bauxitic soil. The role of organic matter seems to play a role on Hg(II) binding when pH>8. The Hg(II) adsorption in the presence of excess Cl(-) ions required the selection of high affinity sites in modeling.     

Accumulation, distribution and cellular partitioning of mercury in several halophytes of a contaminated salt marsh

This work evaluates the role of a plant community in mercury (Hg) stabilization and mobility in a contaminated Portuguese salt marsh. With this aim, the distribution of Hg in below and aboveground tissues, as well as the metal partitioning between cellular fractions (soluble and insoluble) in four different species (Triglochin maritima L., Juncus maritimus Lam, Sarcocornia perennis (Miller) A.J. Scott, and Halimione portulacoides (L.) Aellen) was assessed. Mercury accumulation, translocation and compartmentation between organs and cellular fractions were related to the plant species.Results showed that the degree of Hg absorption and retention was influenced both by environmental parameters and metal translocation/partitioning strategies. Different plant species presented different allocation patterns, with marked differences between monocots (T. maritima and J. maritimus) and dicots (S. perennis, H. portulacoides). Overall, the two monocots, in particular T. maritima showed higher Hg retention in the belowground organs whereas the dicots, particularly S. perennis presented a more pronounced translocation to the aboveground tissues. Considering cellular Hg partitioning, all species showed a higher Hg binding to cell walls and membranes rather than in the soluble fractions. This strategy can be related to the high degree of tolerance observed in the studied species. These results indicate that the composition of salt marsh plant communities can be very important in dictating the Hg mobility within the marsh ecosystem and in the rest of the aquatic system as well as providing important insights to future phytoremediation approaches in Hg contaminated salt marshes.     

Mobility of heavy metals from polluted sediments of a semi-enclosed basin: in situ benthic chamber experiments in Taranto’s Mar Piccolo (Ionian Sea,Southern Italy)

In situ benthic flux experiments were conducted at two stations in the Mar Piccolo of Taranto (Italy), one of the most industrialised and contaminated coastal areas of the Mediterranean. Sediments of the two stations are notably different in their trace metal content, with a station closer to a Navy harbour showing higher mean concentrations of almost all investigated metals (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn). Conversely, both stations are characterised by significant Hg contamination, compared to the local baseline. Results of a sequential extraction scheme on surface sediments suggest a relatively scarce mobility of the examined metals (Zn > Ni > Cr > As > Cu > Pb). A Hg-specific extraction procedure showed that most of the element (93.1 %) occurs in a fraction comprising Hg bound to Fe/Mn oxi-hydroxides. Reduction of these oxides may affect Hg remobilisation and redistribution. Porewater profiles of dissolved trace metals were quite similar in the two sites, although significant differences could be observed for Al, Cu, Fe and Hg. The highest diffusive fluxes were observed for As, Fe and Mn. Mobility rates of several trace elements (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn) were directly measured at the sediment–water interface. Results from benthic in situ incubation experiments showed increasing dissolved metal concentrations with time, resulting in higher fluxes for Cu, Fe, Hg, V and Zn in the most contaminated site. Conversely, fluxes of Mn, Ni and Pb were comparable between the two stations. The estimated flux of Hg (97 μg m^?2 day^?1) was the highest observed among similar experiments conducted in other highly contaminated Mediterranean coastal environments. Benthic fluxes could be partially explained by considering rates of organic matter remineralisation, dissolution of Fe/Mn oxy-hydroxides and metal speciation in sediments. Seasonal and spatial variation of biogeochemical parameters can influence metal remobilisation in the Mar Piccolo area. In particular, metals could be promptly remobilised as a consequence of oxygen depletion, posing a serious concern for the widespread fishing and mussel farming activities in the area.     

Linking Cellulose Fiber Sediment Methyl Mercury Levels to Organic Matter Decay and Major Element Composition

Methylation of mercury (Hg) to highly toxic methyl Hg (MeHg), a process known to occur when organic matter (OM) decomposition leads to anoxia, is considered a worldwide threat to aquatic ecosystems and human health. We measured temporal and spatial variations in sediment MeHg, total Hg (THg), and major elements in a freshwater lagoon in Sweden polluted with Hg-laden cellulose fibers. Fiber decomposition, confined to a narrow surface layer, resulted in loss of carbon (C), uptake of nitrogen (N), phosphorus (P), and sulfur (S), and increased MeHg levels. Notably, fiber decomposition and subsequent erosion of fiber residues will cause buried contaminants to gradually come closer to the sediment–water interface. At an adjacent site where decomposed fiber accumulated, there was a gain in C and a loss of S when MeHg increased. As evidenced by correlation patterns and vertical chemical profiles, reduced S may have fueled C-fixation and Hg methylation at this site.     

A theory on the mechanisms regulating the bioavailability of mercury in natural waters

A number of quantifiable properties of natural waters have been used by various scientists to 'explain' the Hg content in fish (e.g. pH, level of bioproduction, humosity, conductivity, calcium content, oxygen conditions, zinc and selenium content). This work presents a theory aimed at providing an explanation of the chemical mechanisms behind many established statistical relationships. The theory focuses on some equilibrium reactions and the causal relationships behind these reactions. The basic concept of the theory is that the activity of Hg(2+) in natural waters is essentially regulated by the activity of S(2-), which, in turn, is strongly affected by pH and redox conditions. Due to protonisation reactions, the S(2-) activity is very low at natural pH levels. The equilibrium between Hg(2+) and HgS(s) is given by the solubility constant Ks = 10(-52). This is an extremely low constant, which indicates that, in the presence of sulphide, essentially all Hg will appear as HgS(s). The Hg(2+) activity, and the Hg content in fish, can be increased if the S(2-) activity is decreased by lowering the pH and/or increasing the redox potential. Besides sulphide there are two other elements with a similar relationship towards Hg; namely, Se and Te (Ks = 10(-58) and Ks = 10(-70), respectively). The Hg(2+) concentration in natural waters varies quite widely, but is often about 5 ng litre(-1). This is a high concentration in these contexts. Such as high concentration can prevail only if the S(2-) (and/or the Se(2-)) activity is very small. In waters where the S(2-) and/or the Se(2-)) activity is high, e.g. from sulphide rocks in the drainage area, or if S(2-) and/or Se(2-) are added to the water, the Hg(2+) activity, and the Hg content in fish, will be effectively reduced.