Soil Mercury Concentrations Research Articles

Modelling mercury concentration in Ghanaian soil

Mercury usage in Artisanal Small Scale Gold Mining is a major anthropogenic source of mercury in the environment. In this study, mercury pools and fluxes have been established for Ghana, which has a large ASGM sector, based on estimated losses of mercury to the environment, deposition calculated with GLEMOS, a global long-range transport model for mercury in air, and mercury measured in soils and water in Ghana. A model for mercury in soils and water of Ghana with a resolution of 5 × 5 km2 and a monthly or yearly time step has been developed to assess the regional increase in soil and water concentrations that can be attributed to anthropogenic sources and to simulate scenarios into the future. The model has been calibrated to reproduce present-day mercury concentration in the soil (average 0.0193 mg kg−1) with current deposition calculated with the long-range transport model and past years’ deposition based on a scenario for the historic development of the mining activity. This calculation gives an average increase in soil concentrations from anthropogenic sources of 22%. The model gives a fair description of the regional differences in soil concentrations but underestimates concentrations in regions with intense mining activity and overestimates concentrations in regions with less mining when using deposition from the long-range model as input.

Monitoring soil mercury content based on hyperspectral data and machine learning methods

Mercury (Hg) is a heavy metal pollutant characterized by global migration, high bioaccumulation, and high biological toxicity. Soil Hg pollution seriously harms soil environmental quality and human health. The higher the content of Hg in the soil, the more serious the harm. Therefore, the acquisition of soil Hg content information is crucial for soil monitoring and restoration, and human health. The purpose of this study is to establish the best hyperspectral prediction model of soil Hg content in the study area. A total of 90 soil samples were collected from the mining areas and suburbs, and the Hg content was analyzed. Several preprocessing methods were applied to the hyperspectral data. Partial least-squares regression (PLSR), orthogonalized PLSR, random forest, and back propagation neural network (BPNN) were used to establish the relationship between soil hyperspectral data and soil Hg content to predict the soil Hg content. Specifically, the transferability of the best prediction model in yellow-brown and cinnamon soil data was discussed. The results showed that BPNN + standard normal variable + full-band (4 nm) is the optimum method to predict soil Hg content (Rtrain2=0.94, Rtest2=0.85). The transferability of the model is the best in yellow-brown soil. This research provides technical support for the rapid monitoring of soil Hg pollution information in central and eastern Shaanxi-Province, and the results enrich prediction models of soil Hg content in different soil types.

Total mercury content in soils and lake sediments of Vilkitsky Island (Kara Sea)

Mercury threatens Arctic ecosystems due to its well known deleterious effects. The development of energy resources in the Russian Arctic is currently being planned, which will inevitably be accompanied by emissions of heavy metals into the environment, but little is known about the distribution of mercury in soils of the permafrost regions. Total mercury (THg) concentrations were investigated in soils and lake sediments of Vilkitsky Island located in remote area of the Arctic. The concentration of mercury in soils varied from 1 to 36,6 ng g−1, in lake sediments – from 2.0 to 5.8 ng g−1. In sandy soils of the iseland the concentration of THg was minimal and was usually not higher than10 ng g−1, whereas in loamy soils it was 3.5 times higher. Correlation analysis has shown that THg concentration depended primarily on particle size distribution, in a lesser degree – on total carbon and total nitrogen concentrations. The soils of Viltisky Island have one of the lowest mercury concentration in comparison to soils of other Arctic territories, because of the predominance of sandy marine sediments and low soil organic matter content. Under influence of human activities, THg content has increased three-fold on average. The highest concentrations were observed in soils of an abandoned polar station. Calculation of CF and Igeo coefficients demonstrated the high level of mercury pollution on local sites. The maximum content of mercury (25.7-36.7 ng g-1) was observed in coastal sediments. It is assumed that the increased mercury content is a consequence of translocation. Thus, the coastal areas of the Arctic islands are at the greatest danger of pollution.

Modelling Mercury Concentration in Ghanaian Soil

Modelling Mercury Concentration in Ghanaian Soil

Inorganic and methylated mercury dynamics in estuarine water of a salt marsh in Massachusetts, USA

Salt marsh estuaries serve as sources and sinks for nutrients and elements to and from estuarine water, which enhances and alleviates watershed fluxes to the coastal ocean. We assessed sources and sinks of mercury in the intertidal Plum Island Sound estuary in Massachusetts, the largest salt marsh estuary of New England, using 25-km spatial water sampling transects. Across all seasons, dissolved (FHg) and total (THg) mercury concentrations in estuarine water were highest and strongly enhanced in upper marshes (1.31 ± 0.20 ng L−1 and 6.56 ± 3.70 ng L−1, respectively), compared to riverine Hg concentrations (0.86 ± 0.17 ng L−1 and 0.88 ± 0.34 ng L−1, respectively). Mercury concentrations declined from upper to lower marshes and were lowest in ocean water (0.38 ± 0.10 ng L−1 and 0.56 ± 0.25 ng L−1, respectively). Conservative mixing models using river and ocean water as endmembers indicated that internal estuarine Hg sources strongly enhanced estuarine water Hg concentrations. For FHg, internal estuarine Hg contributions were estimated at 26 g yr−1 which enhanced Hg loads from riverine sources to the ocean by 44%. For THg, internal sources amounted to 251 g yr−1 and exceeded riverine sources six-fold. Proposed sources for internal estuarine mercury contributions include atmospheric deposition to the large estuarine surface area and sediment re-mobilization, although sediment Hg concentrations were low (average 23 ± 2 μg kg−1) typical of uncontaminated sediments. Soil mercury concentrations under vegetation, however, were ten times higher (average 200 ± 225 μg kg−1) than in intertidal sediments suggesting that high soil Hg accumulation might drive lateral export of Hg to the ocean. Spatial transects of methylated Hg (MeHg) showed no concentration enhancements in estuarine water and no indication of internal MeHg sources or formation. Initial mass balance considerations suggest that atmospheric deposition may either be in similar magnitude, or possibly exceed lateral tidal export which would be consistent with strong Hg accumulation observed in salt marsh soils sequestering Hg from current and past atmospheric deposition.

Characteristics and Risk Assessments of Mercury Pollution Levels at Domestic Garbage Collection Points Distributed within the Main Urban Areas of Changchun City

The mercury that is released from the centralized treatment of municipal solid waste is an important source of atmospheric mercury. We chose the main urban area of Changchun as a representative area. Environmental factors such as total mercury content, temperature, wind speed, and other factors were measured in samples from the trash cans of two types of collection points (trash cans and garbage stations), the topsoil under the selected trash cans, and the ambient air above the selected trash cans. The potential ecological risks of mercury pollution were evaluated. The results showed that the mercury content levels of all sample types in the refuse transfer station were higher than the garbage cans and there were no significant differences observed between soil surface mercury and garbage cans. The mercury content levels in the atmosphere and the surface soil at the garbage collection points were found to increase along the cascade relationship of the garbage collection. However, there were no correlations observed between the atmospheric mercury content levels and the surface soil mercury content levels with the attachments and the sum of the former two. There were no correlations observed between surface soil and the attachments, or among the attachments, surface soil, and the atmospheric mercury content levels. The mercury content levels in the attachments, surface soil, and atmosphere of the garbage collection points in the study area were negatively correlated with the loop lines. Meanwhile, the potential ecological risk indexes of the garbage cans and garbage stations were found to be high. The chronic non-carcinogenic risks of mercury to children and adults were determined to be very low. The risks of mercury to children were higher when compared with adults. The highest non-carcinogenic risks of mercury pollution were determined to be within the central area of Changchun.

Characteristics of Mercury Pollution and Ecological Risk Assessment in Different Degraded Grasslands of the Songnen Plains, Northeastern China

Mercury (Hg) is a global and widely distributed heavy metal pollutant. Mercury can affect human health as well as the health of ecosystems and poses ecological risks. The subjects of this study are three types of grassland in the Beidianzi region, Songnen Plains, Northeastern China, characterized by different degrees of degradation. The mercury content levels in the atmosphere, soil, and forage grass on the different grasslands were determined. In addition, the relationships between the mercury pollution levels in the atmosphere and soil, and the mercury distribution correlations between the soil and plants, were examined in detail. The potential risk index (RI), single factor index (PI), and ground accumulation index (Igeo) were used to evaluate the ecological risks. The results showed that the mercury content in the soils of three types of grassland exceeded the China national standard (GB36600-2018), and the soil mercury content in the moderately degraded grassland was the highest. The single factor index method and land accumulation index method showed that the three types of grassland were slightly polluted, while the potential risk index showed that the three types of grassland were severely polluted, and the potential risk index of the moderately degraded grassland was the highest. The potential risk index decreased with the increase of soil depth. The variation trend of atmospheric mercury content was lower in the morning and evening and higher in the afternoon. The potential risk index of atmospheric mercury indicated that all types of grassland were at severe risk. There was a significant positive correlation between atmospheric mercury and soil mercury. The mercury content in herbage increased with the increase of degradation. The BP neural network prediction model constructed had good accuracy and had certain reference value.

Mercury uptake by Paspalum distichum L. in relation to the mercury distribution pattern in rhizosphere soil.

Paspalum distichum L. was tested to evaluate their phytoremediation capacity for Hg contaminated soil through analyzing the dissipation of Hg in soil through a greenhouse study by using self-made rhizos box. Original soil samples were collected at Hg mining site with serious Hg contamination and a control site, respectively. Planting of P. distichum. L last for 60 days. Soil and plant samples were collected from four periods (0 d, 20 d, 40 d, and 60 d) and soil samples were collected from five different rhizosphere distance in horizontal direction (0-2 cm, 2-4cm, 4-6cm, 6-8cm, 8-10cm). The results showed that the presence of P. distichum. L significantly accelerated the Hg dissipation in soil compared with control. Hg concentration in the rhizospheric soil was affected by the plant growth period and the distance to the plant roots. The closer of soil to the root of P. distichum. L, the lower mercury concentration in soil. During the 60-day growing period, the concentrations of total Hg (THg) and methylmercury (MeHg) reduced by 45% and 64%, respectively, in the rhizosphere (0-2cm) of Hg contaminated soil. However, MeHg concentration was increased near the roots (0-4 cm) during the initial growing period (0-20 d), which may be attributed to the influence of root exudates. Root is the major part for Hg accumulation in P. distichum. L. The low ratio between Hg concentrations in underground and aboveground tissues indicated that it seemed difficult for Hg translocation from root to shoot. The highest THg (9.71 ± 3.09 μg·g-1) and MeHg (26.97 ± 0.98 ng·g-1) value in root of P. distichum. L were observed at the 20th day when P. distichum. L grown in Hg contaminated soil. The results of chemical fractions analyses showed that elemental Hg and residual Hg were the two major speciations followed by organic bound Hg in the Hg contaminated soil, which indicated the high bioavailability and ecological potential risk of Hg in Hg contaminated soil.

Vertical distribution characteristics of soil mercury and its formation mechanism in permafrost regions: A case study of the Qinghai-Tibetan Plateau

Continuing permafrost degradation is increasing the risk of mercury (Hg) exposure in the permafrost regions on the Qinghai-Tibetan Plateau (QTP), but related studies are still limited, especially the ones on the detailed Hg migration processes in permafrost. The vertical distribution characteristics of soil Hg were investigated in three ecosystems in the Beiluhe area on the QTP, and its influencing factors and formation mechanism were investigated. The results indicate that the total soil mercury (THg) concentration in the Beiluhe area remains at an extremely low level (6.33 ± 2.45 ng/g). In the vertical profile, the THg concentration of the shallow soil layer (0–50 cm) (5.96 ± 2.22 ng/g) is significantly lower than that of the deep layer (50–400 cm) (7.44 ± 2.71 ng/g) (p < 0.05). Within the upper 50 cm, the THg concentration decreases with soil depth, and the peak THg concentration occurs at 100–300 cm on the entire profile. Although the THg concentration is slightly affected by the organic matter in the shallow soil layer, in general, the soil parent material is the dominant factor affecting the THg concentration. Intense weathering results in a low THg concentration in the shallow soil layer because the soil Hg is carried downward with the soil moisture. To a certain depth, the impermeable frozen soil layer intercepts the flow of the soil Hg, and it forms a Hg enrichment layer. This paper presents the distinctive pattern of the soil Hg distribution in the permafrost regions of the QTP.

Mercury Content in Three Edible Wild-Growing Mushroom Species from Different Environmentally Loaded Areas in Slovakia: An Ecological and Human Health Risk Assessment.

Three edible mushroom species (Imlera badia, Boletus subtomentosus, Xerocomellus chrysenteron) sampled in 60 different localities of Slovakia were evaluated to determine health risks (associated with mercury content) arising from their consumption. Total content of mercury in soil and mushroom samples was determined by an AMA-254 analyzer. Soil pollution by mercury was evaluated by contamination factor (Cf), pollution load index (PLI), and geoaccumulation index (Igeo). Bioaccumulation factor (BAF), translocation factor (Qc/s), provisional tolerably weekly intake (%PTWI), estimated daily intake (EDI), and target hazard quotient (THQ) were used to describe and compare uptake and transition abilities of mushrooms, and the health risk arising from mushroom consumption. Mercury content in soil significantly influences the content of mercury in mushroom fruiting body parts. Caps and stipes of Boletus subtomentosus were found to be the best mercury accumulator. According to the EDI, consumption of the evaluated mushroom species represents a serious threat for adults and children. The lowest values of THQ were found for Xerocomellus chysenteron.

Mercury Content in the Soil-Vegetation Cover of Russky and Shkot Islands (Peter the Great Bay, Primorsky Territory)

The ecological situation on Shkot Island and the adjacent part of Russky Island in terms of mercury content in soils and leaves of tree and shrubbery vegetation has been analyzed. The main sources of mercury input into geosystems have been revealed. To determine its content in soils and vegetation, 3 and 16 plots have been sampled on Russky and Shkot islands, respectively. It is shown that the soil cover of Russky and Shkot islands is represented by typical and dark brown burozems (brown forest soils) and their pyrogenic analogues. Mercury distribution depends on soil properties in a soil cover and on plant species in vegetation. The results of laboratory research of mercury content in geosystems are presented. Using interpolation method, maps of mercury content in the soil cover and oak leaves (Quercus mongolica) have been compiled for Shkot Island. The average mercury content in the soil cover of Shkot Island and the adjacent part of Russky Island is 81.2 ng/g. The average contents in various plant species are as follows: 26.3 ng/g for Carpinus cordata, 24.5 ng/g for Quercus mongolica, 9.1 ng/g for Artemisia gmelinii. Such variations are caused by different mercury accumulation ability of the plant species. It is assumed that the high mercury content in the soil and vegetation in the eastern part of Shkot Island is due to tectonic features. The maximum soil mercury content on Shkot Island is confined to the Dotovaya Bay coast, which is the island’s main recreation area in summer. Numerous campfires and wood and household waste (first of all, polyethylene) combustion lead to mercury redistribution in the adjoining territories. In terms of mercury content, the ecological setting in the soil-vegetation cover of Russky and Shkot islands is viewed as favorable. The mercury content in soil is much below maximum permissible concentration. Since maximum permissible concentration of mercury in plants is not available, the comparison has been carried out for Clarke values. The mercury content exceeds Clarke values for Carpinus cordata and Quercus mongolica, which can be attributed to natural regional specifics. The obtained data can be used as background indicators.

Plant Morphofunctional Response to Environmental Changes in Active Fault Zones of the Kurai Ridge (Gorny Altai)

Integrated geological, geophysical, geochemical, and botanical studies in the Kuraika River Valley (Kurai Ridge, Gorny Altai) have revealed sharp changes in the growth environment of blue honeysuckle (Lonicera caerulea) at the conjunction zone of the regional Kubadra and local active faults. A high-gradient magnetic field is accompanied by the increased variability of the concentrations of radionuclides and macro- and micro-elements in soil, an increased mercury content in soil and surface air, and an increased γ-radiation exposure rate. Depending on combinations of geoenvironmental factors, the micropopulations of blue honeysuckle have produced increased or decreased fruit size and seed productivity. The observed tripling of accumulated biologically active phenol compounds in fruits, the simultaneous decrease in their concentration in leaves, and the reduction in the ratio between the content of some polyphenol classes in leaves and fruits are considered a response to the stressing impact of environmental factors associated with active tectonic processes in this area of Altai.

Токсико-екологічний аналіз поводження з ртутьвмісними відходами в Україні

Relevance. The multifaceted intersectoral problem of human security in contact with mercury has gained global significance in the twentieth century, it is relevant today. Considerable attention is paid to the environmental and hygienic aspects of mercury hazards in the field related to the production and disposal of waste containing Hg. The Aim of the Research. Analyze the data of own research on mercury content in the environment in connection with the management of mercury-containing waste and justify a set of preventive environmental and hygienic, technological and organizational measures to improve safety, public health and improve the environment in the region and the country in general. Materials and Methods. Sampling, sample preparation and determination of mercury content in environmental facilities and bioassays were performed according to MI “Methodical instructions for the determination of mercury in biological material, air, drinking water, food products and the environment.” The concentration of mercury was measured by the method of AAS “cold steam” on the upgraded device “Yulia-2M”. The mercury content in soil and air at the spontaneous dump of mercury lamps in Odessa region, on the border of the sanitary protection zone and in the air of the working zone of the enterprise for utilization of mercury lamps was studied. For sample preparation, chemically pure nitric acid (56%) was used, to reduce mercury during the analysis of chemically pure tin (II) chloride. Results and Conclusions. Mercury lamps have been shown to be hazardous to the environment and human health without proper disposal. Mercury lamps should be collected and disposed of as hazardous waste not only in industrial facilities but also in the general public. The formation of spontaneous unauthorized landfills of mercury lamps is unacceptable. The problem of environmental monitoring needs to be addressed at the state level with the mandatory involvement of specialists in the field of hygiene, toxicology and analytical chemistry of heavy metals in cases of violations to assess the level of danger and make informed decisions on approaches to elimination of mercury sources. Key Words: mercury, mercury lamps, ecology.

Effects of mercury stress on methylmercury production in rice rhizosphere, methylmercury uptake in rice and physiological changes of leaves

Methylmercury (MeHg) in rice is presumed to be derived from MeHg formed in the soil, although it is still controversial. Moderate soil mercury (Hg) concentration can affect the diversity of soil microorganisms and may also impact the physiological changes and MeHg absorption of rice. In this study, the pot experiment was conducted to explore the effects of Hg concentration gradients (0, 0.3, 3, and 30 mg kg−1) stress on Hg transformation in the rhizosphere, Hg translocation in rice, and physiological changes in rice leaves during the whole rice growing season. Moderate soil Hg concentration (3 mg kg−1) greatly increased the MeHg/THg (1.69%) of rhizosphere, while 30 mg kg−1 soil Hg concentration sharply reduced the MeHg/THg (0.29%) of rhizosphere. Highest MeHg/THg of the four groups all appeared at the blooming or filling stage. There was a significant positive correlation between Fe2+ in rhizosphere and MeHg/THg, but no significant correlation between SO42− and MeHg/THg was observed. Although the 3 mg kg−1 soil Hg concentration significantly enhanced MeHg concentrations in seeds, it considerably reduced the bioaccumulation factors of MeHg in roots, stalks, old leaves and young leaves. Soil Hg concentration of 30 mg kg−1, to a certain extent, curtailed MeHg concentrations in seeds, while MeHg concentrations in the husk were significantly increased. Consistent with the result that there was no significant difference for THg concentrations in old and young leaves among the four Hg treatment groups, the content of chlorophyll, H2O2, malondialdehyde and antioxidant substances, and the activities of antioxidant enzyme in old and young leaves varied indistinctly among groups. Main findingModerate soil mercury concentration (3 mg kg−1) could extremely enhance MeHg production in the rhizosphere soil and its accumulation in rice; MeHg production in the rhizosphere soil increased greatly at the blooming or filling stage, whereas little effect on antioxidant systems in leaves was observed.

Ecological and geological soil assessment of the Loshamye Lake catchment area (national park “Smolensk Lakeland”)

The authors conducted the ecological and geochemical study of Lake Loshamye and adjacent territories (national park “Smolensk Lakeland”) to identify the distribution patterns of heavy metals and their associations (Hg, Cr, Mn, Fe, Co, Cu, Zn, As, Cd, Pb, Sr, etc.) in soils of the lake’s catchment area. In 2008, the annual monitoring by the national park revealed abnormally high concentrations of mercury in the water of Lake Loshamye (20 MPC). In subsequent years, the mercury concentration decreased to the minimum natural level. A set of studies in the catchment area and in the lake itself established a probable technogenic source and determined the qualitative and quantitative characteristics of the impact. Scientists studied the soil of the catchment area of the lake to verify the version of the pollutant intake from outside. The article presents the results of the study, a set of mathematical methods of information processing. Authors conducted a correlation, factor and cluster analysis to identify patterns of distribution of heavy metals in soils. Peculiarities of the distribution of most elements in the soil today indicate the presence of a low technogenic impact on the soils of the Lake Loshamye basin regarding the formation of low-contrast anomalies Cu, As, Mn, Pb and Cr, Hg. Patterns of the distribution of heavy metals including mercury in soils and their concentration have natural character. The gross mercury content in soils is significantly lower than the MPC (2100 μg/kg), the median of the sample is 42 μg/kg, which practically corresponds to the world Clark of mercury in soils (40 μg/kg). The research results show that the soils of the lake’s catchment area do not bear traces of anthropogenic impact. This suggests that there are no sources of contamination with mercury and other heavy metals in the study area, and this area is not a transit hub for the movement of the pollutant from the outside, and in 2008 there was probably salvo-type pollution directly into the lake’s water.

Investigating effects of soil chemicals on density of small mammal bioindicators using spatial capture-recapture models.

Monitoring the ecological impacts of environmental pollution and the effectiveness of remediation efforts requires identifying relationships between contaminants and the disruption of biological processes in populations, communities, or ecosystems. Wildlife are useful bioindicators, but traditional comparative experimental approaches rely on a staunch and typically unverifiable assumption that, in the absence of contaminants, reference and contaminated sites would support the same densities of bioindicators, thereby inferring direct causation from indirect data. We demonstrate the utility of spatial capture-recapture (SCR) models for overcoming these issues, testing if community density of common small mammal bioindicators was directly influenced by soil chemical concentrations. By modeling density as an inhomogeneous Poisson point process, we found evidence for an inverse spatial relationship between Peromyscus density and soil mercury concentrations, but not other chemicals, such as polychlorinated biphenyls, at a site formerly occupied by a nuclear reactor. Although the coefficient point estimate supported Peromyscus density being lower where mercury concentrations were higher (β = –0.44), the 95% confidence interval overlapped zero, suggesting no effect was also compatible with our data. Estimated density from the most parsimonious model (2.88 mice/ha; 95% CI = 1.63–5.08), which did not support a density-chemical relationship, was within the range of reported densities for Peromyscus that did not inhabit contaminated sites elsewhere. Environmental pollution remains a global threat to biodiversity and ecosystem and human health, and our study provides an illustrative example of the utility of SCR models for investigating the effects that chemicals may have on wildlife bioindicator populations and communities.

A scoping review of sources of mercury and its health effects among Pakistan's most vulnerable population.

Mercury and methyl mercury are poisonous to human body. In the recent times, exposure to mercury has been anthropogenic in nature. Within the past several decades, many incidences of mercury poisoning have been documented in several countries including Pakistan. Mercury has been ingested where it has been used to preserve crops, through the point and non-point source discharge into the surface water, and consequently entering the food chain. We conducted this scoping review of mercury and its health effects in Pakistan in order to raise the flag to a silent ongoing Minamata disease in the country. We conducted a systematic search of the available literature in Google Scholar, PubMed, and grey literature of unpublished theses and reports of various universities across the country. We found that in the northern Pakistan, suspended sediments were the major pathway of the riverine mercury transport. Sediments of Hunza and Gilgit River were found high in mercury concentrations. Gold mining leads to an increase in mercury concentration in soil and river waters flowing in this region. High concentrations up to 108ng/L were found in Shimsal River. It is suspected that that high level of mercury transport may be leading to accumulation of mercury in major water bodies and lakes downstream. Occupational exposure to mercury and other heavy metals is common in an unregulated private sector of the country. Goldsmiths burn the amalgamated gold without personal protective measures. Direct exposure to the fumes of mercury leads to respiratory, dermatological, systemic and neurological ailments specific to mercury poisoning. We found good evidence of bioaccumulation of mercury in fish and fish products in Pakistan. The untreated waste water discharge is responsible to not only afflicted the fish but also the birds which feed on this fish. Further, the same untreated waste water from factories and agriculture runoffs affect vegetables grown in it. Studies looking at the biomarkers for mercury in humans have shown increased and even toxic levels of mercury among the most vulnerable populations of the country. Other sources of mercury exposure included mercury in traditional medicines and cigarette products. Though no evidence was found for its presence in drinking water, its existence in the food chain and occupational exposure pose great threat to the humans as well as animals.

Distribution of total and organic mercury in soils around an artisanal and small-scale gold mining area in West Java, Indonesia

This study was conducted to understand the environmental behavior of mercury released by artisanal and small-scale gold mining (ASGM) activities. For this purpose, we attempted to assess the effect of diffused mercury on mercury concentrations in soil, demonstrate the presence of methylmercury in soil affected by the deposited mercury and determine the reactions associated with methylmercury production. The vertical profiles of mercury were obtained from two sites in the forest of the ASGM village in Pongkor (West Java, Indonesia) and from two sites in Mount Halimun-Salak National Park, which is approximately 12 km from the ASGM village. The highest total mercury concentration, 8.9 mg kg−1, was observed for soil samples collected at the ASGM village. The mercury was concentrated at the surface or in the subsurface layers, and the concentrations were several times to more than ten times higher than the lowest values observed in the deeper layers at each site. Even in the national park, the highest concentration of 1.9 mg kg−1 was observed in the upper soil layer. These results suggest that the primary source of mercury in the forest soil is atmospheric deposition; fallen plant leaves also deliver accumulated mercury to the soil surface. The organic mercury percentages of the total mercury were 0.2 ± 0.1% for the national park and 0.3 ± 0.2% for ASGM sites. The vertical variation in organic mercury concentration did not always match that in total mercury concentration, which suggested that the formation of methylmercury in soil was closely related to the decomposition of organic matter near the surface. The soil surface is an important reaction field for methylmercury production in forested areas.

Total mercury and methylmercury in the soil and vegetation of a riparian zone along a mercury-impacted reservoir

The Baihua Reservoir (Guizhou Province, Southwest China) has a history of mercury contamination associated with past acetic acid production activities at the Guizhou Organic Chemical Plant (GOCP). Soil and plant samples collected from riparian zones were analyzed for total Hg (THg) and methylmercury (MeHg) using cold vapor atomic fluorescence spectroscopy. The concentrations of THg and MeHg in soil samples were in the range of 109–371 ng g−1 and 0.32–1.80 ng g−1, respectively. Soils in the riparian zones close to the pollution source (the GOCP) presented higher Hg contamination, with relatively light Hg contamination in remote areas. This suggests a decreasing trend of THg concentrations along the riparian zones, with higher concentrations closer to the pollution source. Significant correlations were found between MeHg and soil organic matter (n = 24, p = 0.01). THg concentrations varied 11.3–161 ng g−1 in aboveground areas and 11.3–193 ng g−1 in underground areas. MeHg concentrations ranged from 0.23 to 1.06 ng g−1 in aboveground areas to 0.13–1.51 ng g−1 in the below ground areas. The vegetation studied showed different concentrations of THg and MeHg and can be considered to be impacted by Hg contamination. Different concentrations of total and methyl mercury were found among the different plant species. The high Hg concentrations in soils and vegetation suggests that the ability of Hg to bioaccumulate in riparian plants is affected by plant physiological characteristics and soil mercury concentrations. Although the bioaccumulation factors (BCFs) of the studied plants were low, their transfer factors (TFs) were >1. Our findings suggest that vegetation exhibiting TFs for THg >1 have the potential for phytoextraction in Hg-impacted riparian zones.

Atmospheric mercury pollution deciphered through archaeological bones

Mercury is a major environmental pollutant extensively used by humans, whose pollution dates back at least to c. 3250 BCE (South Iberian Peninsula). As it happens today, past populations were mostly affected by low dose chronic mercury exposure, with levels that varied with the intensity of some anthropogenic activities (mining and metallurgy in particular). Despite its toxic nature, mercury impact in humans themselves has been hardly addressed by Archaeology. The aim of this research is to increase our knowledge on mercury levels in past populations by 1) analysing human (cortical) bone from skeletons recovered in a necropolis from NW Iberia covering contrasting periods of atmospheric pollution: Roman, AD 1st to 4th centuries, and post-Roman, AD 5th to 7th centuries; 2) considering bone type variability; 3) contextualizing our findings with previous works. Samples from 3 types of bone (n = 143) as well as soils/sediments associated to the burials (n = 34) were analysed. Mercury concentrations in soil were below 5 ng g−1, while the average in bone was 36 ± 52 ng g−1, making post-depositional incorporation unlikely. We found significant differences between the two periods (Romans: 54 ± 60 ng g−1, post-Romans: 21 ± 23 ng g−1), but no effect of type of bone, sex, age, social status or diet of the individuals. Our results agree with the chronology of mercury pollution reconstructed from a local peatland, which suggests a predominant atmospheric source. This fact contrasts with previous research in which high mercury concentrations were mainly related to post-mortem burial customs and pre-mortem medical treatment and poisoning. Thus, mercury distribution in past communities was possibly more complex than previously thought, with different pre- and post-mortem sources interacting. Furthermore, our research also supports the use of archaeological bone as environmental archive of metal pollution, when metal cultural exposure is low.