Occurrence, Source and Dietary Exposure of Toxic and Essential Elements in the Indian Food Basket.

In this study, representative urban and peri-urban Indian food baskets have been studied for the presence of toxic and essential elements. The concentration of target toxic and essential elements was used to estimate dietary intakes (EDIs) and health risks. Across all food matrices, toxic elements like Cd and Pb were dominant. The highest concentrations of the target elements were found in vegetables, with Cd, Pb, and Ni being beyond permissible limits of the Food and Agriculture Organization of the United Nations and the World Health organization (0.05 mg/kg, 0.1 mg/kg, and 1.5 mg/kg, respectively) in okra, spinach, and cauliflower. The sum of concentrations of the toxic elements (As, Ni, Hg, Cr, Cd, Pb) in vegetables had a range of 0.54-12.08 mg/kg, the highest sum was found in spinach (median 12.08 mg/kg), followed by okra (median 1.68 mg/kg). The EDI was observed for vegetables with a contribution as high as 92% for Cd. Dairy products were found with the highest loading for Ni with a dietary intake of 3.1 mg/kg/day for adults and twice as much for children. Carcinogenic risk for Ni was the highest and found above the threshold for all food categories, as was the case with As. Cumulative carcinogenic and non-carcinogenic risks were mostly contributed by milk and vegetables, in particular, spinach.

Effects of the soil microbial community on mobile proportions and speciation of mercury (Hg) in contaminated soil.

The precise characterization of the behavior of individual microorganisms in the presence of increased mercury contents in soil is necessary for better elucidation of the fate of mercury in the soil environment. In our investigation, resistant bacterial strains isolated from two mercury contaminated soils, represented by Paenibacillus alginolyticus, Burkholderia glathei, Burkholderia sp., and Pseudomonas sp., were used. Two differently contaminated soils (0.5 and 7 mg kg(-1) total mercury) were chosen. Preliminary soil analysis showed the presence of methylmercury and phenylmercury with the higher soil mercury level. Modified rhizobox experiments were performed to assess the ability of mercury accumulating strains to deplete the mobile and mobilizable mercury portions in the soil by modification; microbial agar cultures were used rather than the plant root zone. A sequential extraction procedure was performed to release the following mercury fractions: water soluble, extracted in acidic conditions, bound to humic substances, elemental, and bound to complexes, HgS and residual. Inductively coupled plasma mass spectrometry (ICP-MS) and a single-purpose atomic absorption spectrometer (AMA-254) were applied for mercury determination in the samples and extracts. Gas chromatography coupled to atomic fluorescence spectrometry (GC-AFS) was used for the determination of organomercury compounds. The analysis of the microbial community at the end of the experiment showed a 42% abundance of Paenibacillus sp. followed by Acetivibrio sp., Brevibacillus sp., Cohnella sp., Lysinibacillus sp., and Clostridium sp. not exceeding 2% abundance. The results suggest importance of Paenibacillus sp. in Hg transformation processes. This genus should be tested for potential bioremediation use in further research.

Analysis of mercury and other heavy metals accumulated in lichen Usnea antarctica from James Ross Island, Antarctica.

The study was designed to investigate the content and distribution of selected heavy metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Fe, Pb and Zn) in samples of fruticose macrolichen Usnea antarctica from James Ross Island. A special emphasis was devoted to mercury and its species (elemental mercury and methylmercury). It was found that mercury contents were relatively high (up to 2.73 mg kg(-1) dry weight) compared to other parts of the Antarctic Peninsula region, while the concentrations of most other elements were within reported ranges. Mercury contents in lichens originating from the interior were higher than those from the coast, which is probably the result of local microclimate conditions. Similar trends were observed for Hg(0) and MeHg(+), whose contents were up to 0.14 and 0.098 mg kg(-1) dry weight, respectively. While mercury did not show a significant correlation with any other element, the mutual correlation of some litophile elements probably refers to the influence on thalli of resuspended weathered material. The influence of habitat and environmental conditions could play an essential role in the bioaccumulation of contaminants rather than just the simple presence of sources. Thus, the study of the thalli of this species can bring a new perspective on the interpretation of contaminant accumulation in lichens of the polar region.

Stabilizing agents for calibration in the determination of mercury using solid sampling electrothermal atomic absorption spectrometry.

Tetramethylene dithiocarbamate (TMDTC), diethyldithiocarbamate (DEDTC), and thiourea were investigated as stabilizing agents for calibration purposes in the determination of mercury using solid sampling electrothermal atomic absorption spectrometry (SS-ETAAS). These agents were used for complexation of mercury in calibration solutions and its thermal stabilization in a solid sampling platform. The calibration solutions had the form of methyl isobutyl ketone (MIBK) extracts or MIBK-methanol solutions with the TMDTC and DEDTC chelates and aqueous solutions with thiourea complexes. The best results were obtained for MIBK-methanol solutions in the presence of 2.5 g L(-1) TMDTC. The surface of graphite platforms for solid sampling was modified with palladium or rhenium by using electrodeposition from a drop of solutions. The Re modifier is preferable due to a higher lifetime of platform coating. A new SS-ETAAS procedure using the direct sampling of solid samples into a platform with an Re modified graphite surface and the calibration against MIBK-methanol solutions in the presence of TMDTC is proposed for the determination of mercury content in solid environmental samples, such as soil and plants.

Concentrations of Thirteen Trace Metals in Scales of Three Nototheniid Fishes from Antarctica (James Ross Island, Antarctic Peninsula).

In this study, we assessed concentrations of 13 trace metals in the scales of Notothenia coriiceps, Trematomus bernacchii and Gobionotothen gibberifrons caught off the coast of James Ross Island (Antarctic Peninsula). Overall, our results for scales broadly match those of previous studies using different fish and different organs, with most metals found at trace levels and manganese, aluminium, iron and zinc occurring at high levels in all species. This suggests that scales can serve as a useful, non-invasive bioindicator of long-term contamination in Antarctic fishes. High accumulation of manganese, aluminium, iron and zinc is largely due to high levels in sediments associated with nearby active volcanic sites. Manganese, vanadium and aluminium showed significant positive bioaccumulation in T. bernacchii (along with non-significant positive accumulation of iron, zinc, cobalt and chromium), most likely due to greater dietary specialisation on sediment feeding benthic prey and higher trophic species. Levels of significance in bioaccumulation regressions were strongly affected by large-scale variation in the data, driven largely by individual differences in diet and/or changes in habitat use and sex differences associated with life stage and reproductive status. Increased levels of both airborne deposition and precipitation and meltwater runoff associated with climate change may be further adding to the already high levels of manganese, aluminium, iron and zinc in Antarctic Peninsula sediments. Further long-term studies are encouraged to elucidate mechanisms of uptake (especially for aluminium and iron) and possible intra- and interspecific impacts of climate change on the delicate Antarctic food web.

Leaching of mercury from seal carcasses into Antarctic soils.

More than 400 seal mummies and skeletons are now mapped in the northern part of James Ross Island, Antarctica. Decomposing carcasses represent a rare source of both organic matter and associated elements for the soil. Owing to their high trophic position, seals are known to carry a significant mercury body burden. This work focuses on the extent of the mercury input from seal carcasses and shows that such carcasses represent locally significant sources of mercury and methylmercury for the environment. Mercury contents in soil samples from the surrounding areas were determined using a single-purpose AAS mercury analyzer. For the determination of methylmercury, an ultra-sensitive isotopic dilution HPLC-ICP-MS technique was used. In the soils lying directly under seal carcasses, mercury contents were higher, with levels reaching almost 40 µg/kg dry weight of which methylmercury formed up to 2.8 % of the total. The spatial distribution implies rather slow vertical transport to the lower soil layers instead of a horizontal spread. For comparison, the background level of mercury in soils of the investigated area was found to be 8 µg/kg dry weight, with methylmercury accounting for less than 0.1 %. Apart from the direct mercury input, an enhanced level of nutrients in the vicinity of carcasses enables the growth of lichens and mosses with accumulative ability with respect to metals. The enhanced capacity of soil to retain mercury is also anticipated due to the high content of total organic carbon (from 1.6 to 7.5 %). According to the results, seal remains represent a clear source of mercury in the observed area.

Mercury species in formerly contaminated soils and released soil gases.

Total mercury (T-Hg), elemental mercury (Hg0), methylmercury (MeHg+), phenylmercury (PhHg+), and gaseous elemental mercury (GEM) species were determined in soils formerly contaminated by different processes from two sites in the Czech Republic. Analytical methods involved atomic absorption spectrometry (AAS) using a single-purpose Advanced Mercury Analyser AMA-254 and radiochemical neutron activation analysis (RNAA) for T-Hg determination, a thermal desorption method was used for Hg0 determination, gas chromatography coupled with atomic fluorescence spectrometry (GC-AFS) was employed for assay of MeHg+ and PhHg+, while GEM measurement was carried out using a portable Zeeman-AAS device Lumex RA-915+. The first sampling site was in the surroundings of a former PhHgCl-based fungicide processing plant next to Príbram (central Bohemia). Although the use of Hg-based fungicides as seed mordant have been banned, and their production stopped at the end of 1980's, highly elevated Hg contents in soil are still observed in the vicinity of the former plant, reaching T-Hg values >13mgkg-1. The second sampling site was an abandoned mining area named Jedová hora Hill near Horovice (central Bohemia), where cinnabar (HgS) was occasionally mined as by-product of Fe ores hematite and siderite. Mining activities have been stopped here in 1857. Very high contents of T-Hg are still found at this site, up to 144mgkg-1. In most cases we found a statistically significant correlation between T-Hg and Hg0 values regardless of the pollution source. On the contrary, insignificant correlation was observed neither between T-Hg and GEM values, nor between GEM and Hg0. Concentrations of the investigated organomercury species were above a limit of detection (LOD) only in the most contaminated samples, where their levels were about two to three orders of magnitude lower compared to those of T-Hg.

Electrochemical modification of a graphite platform for a solid sampling electrothermal atomic absorption spectrometry of mercury.

An electrodeposited palladium and iridium/gold mixture has been investigated as a chemical modifier for mercury determination in environmental samples by solid sampling electrothermal atomic absorption spectrometry. Electrochemical procedures of platform surface modification performed in a cell with 20 ml of solution, and in a drop of modifier solution have been optimized. Simple electrolysis in a drop was found to be the most consistent, taking the reproducibility as the major criterion. A total mass of 250 µg of electrodeposited palladium or an iridium/gold mixture was used. The lifetime of 60 - 70 firings for a deposited iridium/gold mixture was smaller than that for palladium with a lifetime of 100 - 120 firings. The detection limit was 120 pg Hg. Different sample masses of between 0.1 and 10 mg were weighed into modified platforms according to the mercury content. The results obtained for mercury in environmental samples as soils, sediments and plant, using solid sampling and calibration against aqueous standards stabilized by potassium permanganate, were in good agreement with those achieved by using the thermal deposition of modifiers and with measurements by pyrolysis atomic absorption spectrometry with gold amalgamation.