Mercury In Biota Research Articles

Internal Dynamics and Metabolism of Mercury in Biota: A Review of Insights from Mercury Stable Isotopes.

Monitoring mercury (Hg) levels in biota is considered an important objective for the effectiveness evaluation of the Minamata Convention. While many studies have characterized Hg levels in organisms at multiple spatiotemporal scales, concentration analyses alone often cannot provide sufficient information on the Hg exposure sources and internal processes occurring within biota. Here, we review the decadal scientific progress of using Hg isotopes to understand internal processes that modify the speciation, transport, and fate of Hg within biota. Mercury stable isotopes have emerged as a powerful tool for assessing Hg sources and biogeochemical processes in natural environments. A better understanding of the tissue location and internal mechanisms leading to Hg isotope change is key to assessing its use for biomonitoring. We synthesize the current understanding and uncertainties of internal processes leading to Hg isotope fractionation in a variety of biota, in a sequence of better to less studied organisms (i.e., birds, marine mammals, humans, fish, plankton, and invertebrates). This review discusses the opportunities and challenges of using certain forms of biota for Hg source monitoring and the need to further elucidate the physiological mechanisms that control the accumulation, distribution, and toxicity of Hg in biota by coupling new techniques with Hg stable isotopes.

Mercury increase in Lake Champlain fish: links to fishery dynamics and extreme climatic events.

Mercury concentrations in Lake Champlain fish increased (2011-2017) for the first time in more than two decades. The increase, however, was not consistent among species or throughout the lake. Mercury concentrations in smallmouth bass and yellow perch from the three Main Lake segments increased significantly while concentrations in the eastern portions of the lake (Northeast Arm and Malletts Bay) remained unchanged or decreased; mercury concentrations in white perch remained unchanged. Factors examined to explain the increase included: atmospheric deposition, lake temperature, chlorophyll-a, fishery dynamics, lake flooding and loading of total suspended solids (TSS). This paper examines how each factor has changed between study periods and the spatial variability associated with the change. We hypothesize fishery dynamics, flooding and TSS loading may be partially responsible for the increase in fish mercury. Both growth efficiency and biomass of fish suggest mercury concentrations would increase in the Main Lake segments and decrease in the eastern portion of the lake. Additionally, two extreme climate events in 2011 resulted in extensive flooding and a four-fold increase in annual TSS loading, both potentially increasing biotic mercury with the impact varying spatially throughout the lake. Changes to the fishery and disturbance caused by extreme climatic events have increased biotic mercury and the processes responsible need further study to identify possible future scenarios in order to better protect human and wildlife health.

Cyanobacteria as regulators of methylmercury production in periphyton

Biotic mercury (Hg) methylation appears to depend on factors such as microbial activity and the concentration and bioavailability of Hg2+ to the Hg-methylating organisms. Recently, the presence of cyanobacteria has been linked with high methylmercury (MeHg) concentrations. The aim of this work was to test MeHg production in microcosms, in relation to the amount of periphytic cyanobacteria, dissolved organic matter (DOM) and phosphorus concentrations, as well as periphytic primary production rates. Water and periphyton samples were collected for cultivation and isolation of cyanobacteria from the Guaporé River floodplain, Brazil. We cultivated the periphyton in microcosms with different concentrations of cyanobacteria, total phosphorus and DOM. The highest net MeHg production (6.8 to 24.6% of added Hg d−1) occurred in the microcosm with added cyanobacteria, followed by microcosms with added phosphorus (6.1 to 11.4%) and added DOM (6.4 to 9.1%). Positive correlations were found between MeHg production, addition of cyanobacteria, phosphorus and DOM and periphytic primary productivity. Our results bring the first direct experimental evidence of the relevance of cyanobacteria and primary production as regulators of MeHg production in periphyton. These findings have numerous implications for the management of natural and engineered wetlands.

Subsurface seawater methylmercury maximum explains biotic mercury concentrations in the Canadian Arctic

Mercury (Hg) is a contaminant of major concern in Arctic marine ecosystems. Decades of Hg observations in marine biota from across the Canadian Arctic show generally higher concentrations in the west than in the east. Various hypotheses have attributed this longitudinal biotic Hg gradient to regional differences in atmospheric or terrestrial inputs of inorganic Hg, but it is methylmercury (MeHg) that accumulates and biomagnifies in marine biota. Here, we present high-resolution vertical profiles of total Hg and MeHg in seawater along a transect from the Canada Basin, across the Canadian Arctic Archipelago (CAA) and Baffin Bay, and into the Labrador Sea. Total Hg concentrations are lower in the western Arctic, opposing the biotic Hg distributions. In contrast, MeHg exhibits a distinctive subsurface maximum at shallow depths of 100–300 m, with its peak concentration decreasing eastwards. As this subsurface MeHg maximum lies within the habitat of zooplankton and other lower trophic-level biota, biological uptake of subsurface MeHg and subsequent biomagnification readily explains the biotic Hg concentration gradient. Understanding the risk of MeHg to the Arctic marine ecosystem and Indigenous Peoples will thus require an elucidation of the processes that generate and maintain this subsurface MeHg maximum.

Fifty years after its discharge, methylation of legacy mercury trapped in the Penobscot Estuary sustains high mercury in biota

Fifty years ago, the Penobscot Estuary was contaminated by mercury discharged from the chlor-alkali plant located in Orrington, Maine, USA. Almost all of the mercury was discharged from the plant during the late 1960s and early 1970s. Despite the much lower mercury discharges in recent decades, present-day concentrations in surface sediment remain high (averaging 350–1100 ng/g dw) and are still high in blood of marsh birds (up to 10.5 μg/g), black duck muscle (0.8 μg/g), and lobster muscle (0.4 μg/g). Methyl mercury (MeHg) concentrations in marsh birds exceed levels that impair reproduction. There are health advisories for duck hunters and closures of shellfish fisheries. These continuing high mercury concentrations are caused by the trapping of legacy mercury in a mobile pool of sediment that is retained in the upper estuary above a tidally forced salinity front, which travels up and down the estuary each tidal cycle - slowing the transport of particulate mercury to Penobscot Bay. The trapped legacy mercury continues to be available for methylation 50 years after it first entered the estuary. This is demonstrated by the fact that rates of MeHg production are positively related to the inorganic mercury concentration in parts of the estuary with elevated concentrations of legacy mercury. Thus, remediation measures that would lower the THg concentration in surface sediment would lower the MeHg in birds, fish and shellfish. All of this new information leads us to recommend two remediation options. Addition of mercury binding agents may lower mercury concentrations in birds in some wetland areas. System-wide, we also recommend Enhanced Natural Recovery (ENR), a novel approach that involves the partial removal of the contaminated mobile sediment pool followed by replacement with clean-clay particulates to dilute inorganic mercury concentrations, which would lower methylation rates and mercury concentrations in biota.

Mercury Toxicity: Ecological Features of Organic Phase of Mercury in Biota- Part I

Mercury is extensively used in industry with top usage in electrolytic chlorine. As a result of this elemental consumption in industry, different forms of inorganic and organic mercury get into the environment in great piles every day and many of these mercurial derivatives are converted to methylmercury by microorganisms. The study is assigned to inspect the ecological features of organic mercury species in biological and marine environments. In addition, the paper takes into account the uptake and the distribution of mercury in fish to investigate the conversion and mobilization of mercury from sediment deposits into the general environment. It has been confirmed that the biological half-life of methylmercury in human is about 70 days. In methodology, molecular identification of mercury has been defined. Monomethyl mercury in sediments was analyzed by gas chromatography (GC) hyphenated with electron capture detector (ECD) and the confirmation was measured by mass spectroscopy (MS). The conversion of mercury element to its organic species has been illustrated. In soil, it was found that lower pH favors monomethyl mercury and the higher pH, dimethylmercury formation, respectively. Dimethylmercury is the biological poisoning product and methylmercury is an artifact of isolation procedure. In next paper, we will turn to study the epidemiological features of organic phase of mercury and investigate in deep the distribution, metabolism, and toxicity of mercury and methylmercury in some essential raw food materials, domestic animal feedstock, and some other biological specimens using basically simple analytical methods of chromatography as paper (PC) and thin layer (TLC).

Linking mercury, carbon, and nitrogen stable isotopes in Tibetan biota: Implications for using mercury stable isotopes as source tracers.

Tibetan Plateau is located at a mountain region isolated from direct anthropogenic sources. Mercury concentrations and stable isotopes of carbon, nitrogen, and mercury were analyzed in sediment and biota for Nam Co and Yamdrok Lake. Biotic mercury concentrations and high food web magnification factors suggested that Tibetan Plateau is no longer a pristine site. The primary source of methylmercury was microbial production in local sediment despite the lack of direct methylmercury input. Strong ultraviolet intensity led to extensive photochemical reactions and up to 65% of methylmercury in water was photo-demethylated before entering the food webs. Biota displayed very high Δ199Hg signatures, with some highest value (8.6%) ever in living organisms. The δ202Hg and Δ199Hg in sediment and biotic samples increased with trophic positions (δ15N) and %methylmercury. Fish total length closely correlated to δ13C and Δ199Hg values due to dissimilar carbon sources and methylmercury pools in different living waters. This is the first mercury isotope study on high altitude lake ecosystems that demonstrated specific isotope fractionations of mercury under extreme environmental conditions.

Mercury Emission by the Baltic Sea: A Consequence of Cyanobacterial Activity, Photochemistry, And Low-Light Mercury Transformation.

Marine mercury emission plays an important role in the atmospheric mercury budget. It is caused by the transformation of ionic mercury to volatile elemental mercury (Hg(0)) and the subsequent release of the latter from surface waters. In this study, we investigated mercury transformation using three approaches: incubation experiments, statistical analyses of phytoplankton and Hg(0) data, and microbiological determinations. The incubation experiments revealed that (1) biotic-light-dependent transformation accounted for an average of 30% of the total natural transformation, (2) photochemistry also contributed 30%, such that its contribution was less important than previously considered, and (3) low-light production accounted for 40%. Field experiments and the microbiological investigations suggested the cyanobacterial genera Synechococcus and Aphanizomenon as the main transformers of mercury. On the basis of the rough balance of biotic mercury transformation with mercury emission during summer, on average, only a small portion of a few percent of the mixed layer participates in active transformation.

Sediments and the EU-Water Framework Directive: revisiting the Elbe 2015 River Basin Management Plan

According to Forstner (2002), p. 54 “The [EU] WFD aims at achieving a good ecological potential and good surface water chemical status in European river basins until the year 2015 by a combined approach using emission and pollutant standards. These consider priority pollutants from diffuse and point sources, but neglect the role of sediments as a longterm secondary source of contaminants. Such a lack of information may easily lead to unreliable risk analyses with respect to the – pretended – ‘good status’”. Now, with the Actualized River Basin Management Plan (RBMP) of the Elbe (RBC Elbe 2014), it is official that “without goaloriented measures for the reduction of primary and secondary pollution sources, the objectives of a good chemical and ecological quality in surface waters until the end of the second management period (of the WFD) and a good environmental state according to the [EU] Marine Strategy Framework Directive (MSFD) until 2020 will be strongly endangered”. Which raises the important question: why not point directly to the basic reasons for this failure? The River Basin Community (RBC) of the Elbe has exemplarily developed an understanding of “historical contaminated sediments” e.g. (RBC Elbe 2009). On the other hand, the typical Elbe issue of “dioxins” was neglected during the first WFD phase. In the period 2016–2021, dioxins/furans+dl-PCB will play a major role: (i) as new priority substances in the list of biotaenvironmental quality standards (EQS), (ii) as indicator substances at the land–sea interface (i.e. the interface between WFD and MSFD), and (iii) for solutions to advanced technical problems (Forstner 2015a). At first, the Actualized RBMP for the Elbe declared that none of the water bodies in the German part of the Elbe River basin will reach the level of a “good chemical state”—mainly due to the catchment-wide exceedance of the EQS of mercury in biota (RBC Elbe 2014). Directive 2013/39/EC (from August 24, 2013) reflects the latest development referring to newly identified priority substances such as dioxins and dioxin-like PCB compounds; here too, the relevance of the biota-EQS criterion for a target achievement is high, as has been proven from the study of environmental specimen bank organisms (e.g. fish, molluscs and crustaceans), where the EQS value of 0.0065 μg TEQ kg for dioxin was exceeded by >50 % of the tested specimens (Mohaupt et al. no date). The MSFD 2008/56/EC (from June 17, 2008) is similar to the WFD, in its stepwise implementation mode and with its main objective in the achievement of good environmental status (GES) in the marine environment by 2020. The MSFD also takes account of land-based and fluvial aspects and ensures comparable approaches and methodologies as in WFD. All of these should be indications for a mandate to the RBC Elbe; however, no activities at the land–sea interface are reported in the Actualized RBMP (RBC Elbe 2014). It seems that the situation has even worsened. For example, SaxonyAnhalt’s Agency for Contaminated Sites has banned the term “dioxin” from various documents (Forstner 2015b), and Hamburg together with the other German North Sea Laender (or States) renewed the exclusion of dioxin from the list of pollutants to be considered in the handling of dredged materials in coastal waters (Anon 2009/2013). * Ulrich Forstner u.foerstner@tu-harburg.de

Factors affecting biotic mercury concentrations and biomagnification through lake food webs in the Canadian high Arctic

In temperate regions of Canada, mercury (Hg) concentrations in biota and the magnitude of Hg biomagnification through food webs vary between neighboring lakes and are related to water chemistry variables and physical lake features. However, few studies have examined factors affecting the variable Hg concentrations in landlocked Arctic char (Salvelinus alpinus) or the biomagnification of Hg through their food webs. We estimated the food web structure of six high Arctic lakes near Resolute Bay, Nunavut, Canada, using stable carbon (δ13C) and nitrogen (δ15N) isotopes and measured Hg (total Hg (THg) in char, the only fish species, and methylmercury (MeHg) in chironomids and zooplankton) concentrations in biota collected in 2010 and 2011. Across lakes, δ13C showed that benthic carbon (chironomids) was the dominant food source for char. Regression models of log Hg versus δ15N (of char and benthic invertebrates) showed positive and significant slopes, indicting Hg biomagnification in all lakes, and higher slopes in some lakes than others. However, no principal components (PC) generated using all water chemistry data and physical characteristics of the lakes predicted the different slopes. The PC dominated by aqueous ions was a negative predictor of MeHg concentrations in chironomids, suggesting that water chemistry affects Hg bioavailability and MeHg concentrations in these lower-trophic-level organisms. Furthermore, regression intercepts were predicted by the PCs dominated by catchment area, aqueous ions, and MeHg. Weaker relationships were also found between THg in small char or MeHg in pelagic invertebrates and the PCs dominated by catchment area, and aqueous nitrate and MeHg. Results from these high Arctic lakes suggest that Hg biomagnification differs between systems and that their physical and chemical characteristics affect Hg concentrations in lower-trophic-level biota.

Albatross as Sentinels of Heavy Metal Pollution: Local and Global Factors

Heavy metal pollution in the Pacific Ocean has garnered significant attention in recent years, especially with regard to rising mercury emissions from Asia. Uncertainty exists over the extent to which mercury in biota may have resulted from increases in anthropogenic emissions over time. Albatrosses, including those inhabiting the North Pacific, are wide-ranging, long-lived, keystone, avian predators. Consequently, they serve as ideal sentinel species for investigating the effects of historical and contemporary pollution as well as local and global factors related to heavy metal exposure, bioaccumulation, and ecotoxicological risk. To date, high levels of mercury and lead have been documented in albatross species throughout the Pacific. To address biotic exposure to these multiple stressors, here we synthesize and conduct meta-analyses of total mercury, methylmercury, and lead exposure data in Black-footed albatross (Phoebastria nigripes) and Laysan albatross (Phoebastria immutabilis). Our approach includes data from the field and literature, and for total mercury and methyl mercury, we use measurements from museum feathers spanning the past 130 years for Black-Footed albatross. We discuss the use and application of stable isotopes (δ15N and δ13C) as a way to control for temporal changes in trophic structure and diet and we demonstrate the importance of conducting speciation analyses for mercury to account for historical, curator-mediated, inorganic mercury contamination of specimens. Our data showed higher levels of inorganic mercury in older specimens of Black-Footed albatross as well as two non-pelagic species (control samples) lacking historical sources of bioavailable mercury exposure, which suggests that studies on bioaccumulation should measure methylmercury rather than total mercury when utilizing museum collections. Changes in methylmercury levels in Black-Footed albatross were consistent with historical global and recent regional increases observed among published estimates and proxies of anthropogenic mercury emissions. At the local scale, previous research has also reported that lead paint exposure from buildings was also an important environmental stressor for Laysan albatross. Thus, albatross species face heavy metal exposure threats at both local (lead) and global scales (mercury, and potentially heavy metals in plastics). Specific types of plastic pollution entering marine environments have been documented to contain heavy metals at levels, which if bio-available, may present a non-localized source of lead exposure in albatross species known to ingest (and regurgitate to their young) large amounts of marine plastic. Heavy metal toxicity along with other stressors may undermine current and future reproductive outcomes in these seabird species, although unraveling effects from specific metals in the context of a complex metal mixture presents some challenges. Collectively, our findings and review of the literature suggest that albatrosses in this region may be an effective marine flagship species and raising the profile of these organisms likely would successfully support broader biodiversity conservation efforts in the North Pacific.

Mercury contamination in aquatic ecosystems under a changing environment: Implications for the Three Gorges Reservoir

Mercury is one of the primary contaminants of global concern. As anthropogenic emissions of mercury are gradually placed under control, evidence is emerging that biotic mercury levels in many aquatic ecosystems are increasingly driven by internal biogeochemical processes, especially in ecosystems that have been undergoing dramatic environmental changes. Here we review the unique properties of mercury that are responsible for the exceptional sensitivity of its biogeochemical cycles to changes in climatic, geochemical, biological and ecological processes. We show that, due to rapid climate warming, a shift from sources-driven to processes-driven mercury bioaccumulation is already happening in the Arctic marine ecosystem. We further suggest that such a shift might also be operating in the Three Gorges Reservoir due to changes in these biogeochemical processes induced by the damming. As a result, the effectiveness of mercury emission control is expected to be followed by long delays before ensuing reduction is seen in food-web levels, making it all the more pressing to control and reduce mercury emissions to the reservoir. Long-term monitoring and targeted studies are urgently needed to understand how biotic mercury levels in the reservoir are responding to changes in mercury emissions and in biogeochemical processes.

Indicators of sediment and biotic mercury contamination in a southern New England estuary

Total mercury (Hg) and methylmercury (MeHg) were analyzed in near surface sediments (0–2cm) and biota (zooplankton, macro-invertebrates, finfish) collected from Narragansett Bay (Rhode Island/Massachusetts, USA) and adjacent embayments and tidal rivers. Spatial patterns in sediment contamination were governed by the high affinity of Hg for total organic carbon (TOC). Sediment MeHg and percent MeHg were also inversely related to summer bottom water dissolved oxygen (DO) concentrations, presumably due to the increased activity of methylating bacteria. For biota, Hg accumulation was influenced by inter-specific habitat preferences and trophic structure, and sediments with high TOC and percent silt–clay composition limited mercury bioavailability. Moreover, hypoxic bottom water limited Hg bioaccumulation, which is possibly mediated by a reduction in biotic foraging, and thus, dietary uptake of mercury. Finally, most biota demonstrated a significant positive relationship between tissue and TOC-normalized sediment Hg, but relationships were much weaker or absent for sediment MeHg. These results have important implications for the utility of estuarine biota as subjects for mercury monitoring programs.

Mercury levels and trends (1993–2009) in bream ( Abramis brama L.) and zebra mussels ( Dreissena polymorpha) from German surface waters

Mercury concentrations have been analysed in bream ( Abramis brama L.) and zebra mussels ( Dreissena polymorpha) collected at 17 freshwater sites in Germany from 1993–2009 and 1994–2009, respectively, within the German Environmental Specimen programme. Mercury concentrations in bream ranged from 21 to 881 ng g −1 wet weight with lowest concentrations found at the reference site Lake Belau and highest in fish from the river Elbe and its tributaries. Statistical analysis revealed site-specific differences and significant decreasing temporal trends in mercury concentrations at most of the sampling sites. The decrease in mercury levels in bream was most pronounced in fish from the river Elbe and its tributary Mulde, while in fish from the river Saale mercury levels increased. Temporal trends seem to level off in recent years. Mercury concentrations in zebra mussels were much lower than those in bream according to their lower trophic position and varied by one order of magnitude from 4.1 to 42 ng g −1 wet weight (33–336 ng g −1 dry weight). For zebra mussels, trend analyses were performed for seven sampling sites at the rivers Saar and Elbe of which three showed significant downward trends. There was a significant correlation of the geometric mean concentrations in bream and zebra mussel over the entire study period at each sampling site (Pearson’s correlation coefficient = 0.892, p = 0.00002). A comparison of the concentrations in bream with the environmental quality standard (EQS) of 20 ng g −1 wet weight set for mercury in biota by the EU showed that not a single result was in compliance with this limit value, not even those from the reference site. Current mercury levels in bream from German rivers exceed the EQS by a factor 4.5–20. Thus, piscivorous top predators are still at risk of secondary poisoning by mercury exposure via the food chain. It was suggested focusing monitoring of mercury in forage fish (trophic level 3 or 4) for compliance checking with the EQS for biota and considering the age dependency of mercury concentrations in fish in the monitoring strategy.

Spatial patterns of mercury in biota of Adirondack, New York lakes

We studied the spatial distribution patterns of mercury (Hg) in lake water, littoral sediments, zooplankton, crayfish, fish, and common loons in 44 lakes of the Adirondacks of New York State, USA, a region that has been characterized as a “biological Hg hotspot”. Our study confirmed this pattern, finding that a substantial fraction of the lakes studied had fish and loon samples exceeding established criteria for human and wildlife health. Factors accounting for the spatial variability of Hg in lake water and biota were lake chemistry (pH, acid neutralizing capacity (ANC), percent carbon in sediments), biology (taxa presence, trophic status) and landscape characteristics (land cover class, lake elevation). Hg concentrations in zooplankton, fish and common loons were negatively associated with the lake water acid-base status (pH, ANC). Bioaccumulation factors (BAF) for methyl Hg (MeHg) increased from crayfish (mean log10 BAF = 5.7), to zooplankton (5.9), to prey fish (6.2), to larger fish (6.3), to common loons (7.2). MeHg BAF values in zooplankton, crayfish, and fish (yellow perch equivalent) all increased with increasing lake elevation. Our findings support the hypothesis that bioaccumulation of MeHg at the base of the food chain is an important controller of Hg concentrations in taxa at higher trophic levels. The characteristics of Adirondack lake-watersheds (sensitivity to acidic deposition; significant forest and wetland land cover; and low nutrient inputs) contribute to elevated Hg concentrations in aquatic biota.Electronic supplementary materialThe online version of this article (doi:10.1007/s10646-011-0717-y) contains supplementary material, which is available to authorized users.

High levels of mercury in biota of a new Prairie irrigation reservoir with a simplified food web in Southern Alberta, Canada

This study examined mercury levels in northern pike (Esox lucius) from the Twin Valley Reservoir in southern Alberta, 2 years after construction in 2003. The hypothesis was tested that mercury concentrations in pike from the reservoir are significantly higher than in pike from the nearby Oldman River. Mercury concentrations in muscle tissue (0.37–1.54 ppm) generally exceeded the consumption guideline of 0.5 ppm total mercury (THg), and were significantly higher (3.5-fold) than northern pike mercury concentrations in the Oldman River. In addition, these levels exceeded (up to 2-fold) previously published data from other reservoirs of the northern hemisphere. Gill-netting followed by stomach contents and stable isotope analysis revealed a very simple food web. No zooplanktivorous fish species were present, and the benthic fish community contained only few white sucker (Catostomus commersoni). Thus, the reservoir almost completely lacked forage fish, and the pike fed primarily on amphipods (Gammarus lacustris and Hyalella azteca), whose average mercury concentrations were 0.21 ppm. An observed low growth trajectory of northern pike in this reservoir may reflect low growth efficiency as a result of their invertebrate diet.

Sensing mercury for biomedical and environmental monitoring.

Mercury is a very toxic element that is widely spread in the atmosphere, lithosphere, and surface water. Concentrated mercury poses serious problems to human health, as bioaccumulation of mercury within the brain and kidneys ultimately leads to neurological diseases. To control mercury pollution and reduce mercury damage to human health, sensitive determination of mercury is important. This article summarizes some current sensors for the determination of both abiotic and biotic mercury. A wide array of sensors for monitoring mercury is described, including biosensors and chemical sensors, while piezoelectric and microcantilever sensors are also described. Additionally, newly developed nanomaterials offer great potential for fabricating novel mercury sensors. Some of the functional fluorescent nanosensors for the determination of mercury are covered. Afterwards, the in vivo determination of mercury and the characterization of different forms of mercury are discussed. Finally, the future direction for mercury detection is outlined, suggesting that nanomaterials may provide revolutionary tools in biomedical and environmental monitoring of mercury.

The molecular form of mercury in biota: identification of novel mercury peptide complexes in plants

The molecular structure of a variety of novel mercury-phytochelatin complexes was evidenced in rice plants exposed to inorganic mercury (Hg2+) using RP-HPLC with simultaneous detection via ICP-MS and ES-MS.

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

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

Determination of Organic Mercury in Biota, Plants and Contaminated Sediments Using a Thermal Atomic Absorption Spectrometry Technique

A simple, rapid procedure for the determination of organic mercury in sediments, plants and fish tissues has been developed and validated. Extraction and separation of organic mercury compounds from the sample matrix was achieved by an established procedure based on an acid leaching of the sample (H2SO4/KBr/CuSO4), followed by extraction of the organic mercury halide with toluene and back-extraction with an aqueous solution of thiosulphate. Detection and quantification of mercury, in the liquid extracts, was made by atomic absorption spectrometry (AAS), following thermal decomposition of the sample. The method was evaluated using Certified Reference Material (CRM) BCR 463 (tuna fish), BCR 580 (estuarine sediment), IAEA-140TM (sea plant homogenate) and NRCC TORT-2 (lobster hepathopancreas). The recovery factors for organic mercury in all tested CRM were between 81–107%. The precision of the method has relative standard deviations of less than 10% for sediments and fish tissues and of less than 16% for plant material. The method was successfully applied to natural samples of sediments, plants, macroalgae and fish tissues collected from an estuarine ecosystem and could, therefore, be used for routine analyses.