Soil Hg Concentrations Research Articles

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.

Mercury in soils of intermountain depressions in the Western Baikal region

The article presents original data on the gross concentration of Hg in soils of various types in the territory of the southwestern Baikal region. Quantitative estimates of Hg distribution over the area of intermountain depressions and slopes of mountain ranges have been obtained. The features of the distribution of Hg concentrations in the surface component of soils depending on the type of soils, granulometric composition, hydrolytic acidity, the sum of exchangeable bases, the degree of saturation with bases, pH, humus, CO, N, and humic acids were revealed. The forms of Hg occurrence in soils of different types are determined: the largest proportion of Hg is in the forms associated with organic complexes and exchangeable bases. The calculated indicators indicate an increased natural geochemical background of mercury in soils, which is associated with the territorial belonging to the Baikal rift zone.

Concentration Characteristics of Heavy Metals in Farmland-Sphagnum System and Ecological Risk Assessment

In order to study the current status of heavy metal pollution, the accumulation capacity of farmland Sphagnum for heavy metals and the source of heavy metal pollution in the soil near Gaozhai Reservoir in Maojian Tea Town, Duyun City, Guizhou Province were assessed. Sphagnum and topsoil near this area were selected as the research object to measure the content of heavy metals. Spatial analysis and multivariate statistical analysis methods were used to conduct pollution evaluation and source analysis of heavy metals. The results showed that the heavy metal content in topsoil and farmland Sphagnum were V>Zn>Cr>Pb>Cu>Ni>As>Cd>Hg and Zn>Cr>Ni>Cu>Pb>V>As>Cd>Hg, respectively. The dominant species of Sphagnum in the study area were Sphagnum palustre L. ssp. palustre and Sphagnum ovatum Hamp.C.Muell, both of which had a strong ability to accumulate soil Cd, Ni, Cu, and Zn; however, the S. ovatum enrichment capacity of soil heavy metals was generally higher than that of the latter. Both the single pollution index (Cf) and the geo-accumulation index (Igeo) indicated that the Cd and Hg content in soil were at the highest levels, and the average comprehensive pollution index RI was 87.75, which indicates a slight ecological risk. The sources of heavy metals in soil and Sphagnum included transportation, domestic sewage, agricultural activities, and natural soil-forming processes.

Chemistry of surface water, precipitation, throughfall, leaves, sediment, soil, and air near a gold mining region in Peru.

Artisanal and small-scale gold mining (ASGM) is the primary global source of anthropogenic mercury (Hg) emissions and a large source of landscape change. ASGM occurs throughout the world, including in the Peruvian Amazon. This data set contains measurements of surface water, precipitation, throughfall, leaves, sediment, soil, and air samples from across the Madre de Dios region of Peru, in locations near and remote from ASGM. These data were collected to determine the fate and transport of Hg across the landscape. Samples were collected in 2018 and 2019. Data predominantly included total Hg and methyl Hg concentrations in surface water, precipitation, throughfall, leaves, sediment, soil, and air. Additional water and soil parameters were also measured to better characterize their chemistry. There are no copyright restrictions; please cite this data paper when the data are used in publication.

Distribution of mercury in foliage, litter and soil profiles in forests of the Qinling Mountains, China

Forest ecosystems have been confirmed to be a sink of the global mercury (Hg) in the biogeochemical cycle. However, few studies have investigated the distribution of Hg in forest ecosystems on a regional scale in China. This work aimed to investigate the concentrations, distribution and influential factors of Hg in the Qinling Mountains forests in central China. Foliage, litter and soil profile samples were collected at 24 sampling sites across the Qinling Mountains forests. The results of the present study showed that the concentrations of Hg in foliage, litter, organic soils and mineral soils were maintained at relatively low levels compared with those in subtropical forests of Southwest China. The average Hg concentrations followed the order litter (74 ± 34 ng g−1) > organic soil (71 ± 37 ng g−1) > mineral soil (34 ± 21 ng g−1) > foliage (31 ± 15 ng g−1). Mercury in foliage showed no obvious spatial pattern, likely due to differences in tree species and ages across the sampling sites. Higher concentrations of Hg in litter were observed on the southern slope (low altitude), while the distribution of Hg in organic soils was the opposite. Both the tree species and environmental parameters (altitude, temperature and precipitation) controlled the Hg concentrations in litter by regulating the decomposition rate of the litter. There were significantly positive correlations between the Hg concentrations and soil organic carbon, nitrogen and sulfur in all soil layers, indicating that organic matter has a high geochemical affinity for Hg in soils. Because of the lower turnover rate and the higher accumulation of organic matter in high altitude and low temperature areas, Hg loss from biogeochemical cycling processes was effectively reduced. The spatial distribution of Hg in forests soil can be shaped by the distribution of organic matter at the regional scale.

MERCURY ACCUMULATION IN WILD MUSHROOMS AT ABANDONED Hg-DEPOSIT MALACHOV (SLOVAKIA)

The aim of the presented article was to determine the Hg content in the fruiting bodies of 13 generally consumed mushroom species (Boletus reticulatus, Clitocybe nebularis, Lactarius deliciosus, Macrolepiota procera, Russula spp., Suillus grevillei, Tricholoma spp.) growing at the area of abandoned mercury deposit Malachov. The Hg concentrations were analyzed by thermal decomposition-gold amalgamation atomic absorption spectroscopy, using AMA-254 Advanced Mercury Analyzer. The Hg concentrations in soil varied widely (ranging from 0.01 to 2.44mg·kg-1), furthermore, they were particularly depended on the mushroom species. The fruiting bodies of Russula ochroleuca contained the highest concentrations of Hg (up to 16.69mg·kg-1). The lowest concentrations were detected in Russula aeruginea (from 0.04 to 0.06 in stipe stems and from 0.05 to 0.06mg·kg-1 in pileus) and in Russula vesca (0.05 in stipe stems; 0.09mg·kg-1 in pileus). Mercury is preferentially accumulated in the mushroom pileus (ranging from 0.05 in Russula vesca to 16.69mg·kg-1 in Russula ochroleuca). The bioconcentration factor was calculated for the rate of the Hg content in soil substrate vs. its concentration in the mushroom pileus (ranging from 0.03 to 29.22). The results indicate that some investigated mushroom species can be referred as Hg excluders (e.g. Russula vesca) whereas some other species as accumulators (e.g. Russula ochroleuca or Tricholoma portentosum). The obtained results were compared with the Government Decrees of Slovak Republic, showing that the substantial part of the studied mushroom species exceed the legal tolerance limit (0.25 mg kg-1) suggested for Hg in plant food and therefore they can be considered as inappropriate for human consumption.

The extensive mercury contamination in soil and legacy sediments of the Paglia River basin (Tuscany, Italy): interplay between Hg-mining waste discharge along rivers, 1960s economic boom, and ongoing climate change

PurposeThe extensive Hg contamination in soil and sediments occurring along the Paglia River (Central Italy) is the result of the interplay between the geomorphological changes of the river and anthropic activities, primarily associated to the exploitation of Hg-deposits in "The Monte Amiata mining district" (MAMD). The present study determines the implications of the morphological changes that occurred along the Paglia River in the last 200 years on the distribution of Hg along the floodplain and riverbed, which today represent one of the main Hg-reservoirs in the MAMD.Materials and methodsThe temporal changes of the Paglia riverbed and the extent of its alluvial deposits were reconstructed by a GIS-based analysis of the available maps and aerial photos. The Hg-concentration in soil and sediment samples, collected along five transects transverse to the Paglia River channel, was determined by ICP-MS.Results and discussionSamples along the investigated Paglia River segment typically show Hg-contents exceeding the Italian threshold for residential and public green soil use (1 mg kg−1). The distribution of Hg in the Paglia floodplain results from the combination of exceedance of sediment yield to the river during mining activities, that fed the floodplain with large amounts of Hg-contaminated sediments during its braided stage about 100 years ago, and the morphological changes of the river, that led to the evolution from a braided to the present-day single channel river. The magnitude of the extension of Hg-contamination, the river geomorphologic changes, and the processes of transport, deposition, and re-suspension did not allow a natural “clean up” of the river system, which shows a low resilience. Under high flow conditions, and especially in coincidence with intense rain events, large amounts of Hg stored in the overbank sediments are mobilized and redistributed, contributing to make the floodplain a secondary Hg-source. Extreme weather events, expected to intensify as a consequence of climate change, will contribute to the recurrent distribution of Hg-contaminated legacy sediments in the floodplain and along the Paglia river course.ConclusionFrom a water/land management perspective, the variability of the river flow, associated with an increase of extreme flood events driven by climate change, will affect the distribution of Hg-contaminated particles in the Paglia River, contributing to the Hg input into the Mediterranean Sea in the future.Graphical abstract

Latitudinal gradient for mercury accumulation and isotopic evidence for post-depositional processes among three tropical forests in Southwest China

Tropical forest contributes to > 50% of global litterfall mercury (Hg) inputs and surface soil Hg storage, while with limited understanding of Hg biogeochemical processes. In this study, we displayed the 5−m resolution of Hg spatial distribution in three 1-ha tropical forest plots across the latitudinal gradient in Southwest China, and determined Hg isotopic signatures to understand factors driving Hg spatial distribution and sequestration processes. Our results show that tropical forest at the lowest latitude has the highest litterfall Hg input (74.95 versus 34.14−56.59 μg m-2 yr-1 at higher latitude plots), but the smallest surface soil Hg concentration (2−3 times smaller than at higher latitude sites). Hg isotopic evidence indicates that the decreasing climate mediated microbial Hg reduction in forest floor leads to the increasing Hg accumulation along the latitudinal gradient in three tropical forests. The terrain induced indirect effects by influencing litterfall Hg inputs, soil organic matters distribution and interplays between surface and deep soils drive the heterogeneity of surface soil Hg distribution within each sampling plot. Our results highlight though the elevated litterfall Hg inputs, the distinct post-depositional reductions induced Hg loss would remarkedly decrease atmospheric Hg net sink in tropical forest.

Heavy Metal Concentrations of Soil, Rock, and Coal Gangue in the Geological Profile of a Large Open-Pit Coal Mine in China

Risk assessment related to heavy metals in mining areas is crucial to ensuring the sustainable development of regional ecosystems and protecting human health. However, almost all research on the impact of mining activities on environmental quality entails field monitoring of surface soils or soil profiles. Here, to compare the variety of heavy metal concentrations in the geological profile, 39 samples (including soil, rock, and coal gangue) were collected and analyzed from hundreds of meters underground in the Pingshuo coal mine (Anjialing coal mine, Antaibao coal mine, and Donglutian coal mine), which is the largest open-pit coal mine in China. The mean heavy metal concentrations of Cd, Hg, As, Pb, Cr, Cu, Zn, and Ni in soils were 0.15 mg/kg, 0.02 mg/kg, 13.70 mg/kg, 27.12 mg/kg, 70.89 mg/kg, 26.10 mg/kg, 79.88 mg/kg, and 37.68 mg/kg, respectively; most of these metals were more concentrated in the soil samples than in the rock and coal gangue samples. A potential ecological risk assessment indicated that As, Pb, Cr, Cu, Zn, and Ni in all samples showed low risk, while the ecological risk degrees of Cd and Hg were higher and contributed most to the total risk index (RI). The highest E_r^i value (92.94) for Cd was found in rock samples, contributing to approximately 55.18% of the to tal RI. For Hg, four rock sampling sites had the highest E_r^i values (427.70, 270.78, 198.96, and 188.70), contributing approximately 68.36–88.07% of the total RI. Ranked after soil (0.15 mg/kg), limestone and shale showed high mean Cd concentrations (both 0.13 mg/kg). The highest mean concentration was found in coal gangue samples (0.1 mg/kg). Compared with the other types of samples, the mean concentrations of Cr, Cu, and Ni in soils, limestone, and mudstone were relatively higher. At different sites, heavy metal concentrations varied greatly at different depths, owing to diverse sample types and rock types. Correlations between heavy metals and soil nutrients indicated that N and P were closely correlated with heavy metals. Comparing the proportions of different heavy metals in various types of samples showed that heavy metals in soils were extremely similar to those in limestone, mudstone, and shale, implying that soils might indirectly inherit their features from their parent material.

Risk assessment of trace elements accumulation in soil-herbage systems at varied elevation in subalpine grassland of northern Tibet Plateau.

Ecological environment of remote grassland has become a problem in many countries due to mining, tourism, grazing, and other human activities. In this study, a total of 15 pairs of soil-herbage samples were collected in the northeast of the Tibet Plateau to study the relationship between physicochemical properties and content of trace elements in soils at different elevation, and to examine the accumulation and fractionation of heavy metals in soil-herbage systems. In addition, the ecological risk of the subalpine grassland was also assessed. The average concentrations of Hg, As, Cu, Zn, Pb, Cd, Cr, and Mn in soil were higher than their background values of Gansu soil, but the average concentrations of these heavy metals in herbage satisfied Hygienical Standard for Feeds. The speciation analysis of heavy metals in soil indicated that the exchangeable content of heavy metal was very low, except Pb, Cd, and Mn. There was a linear relationship between pH, CaCO3, total phosphorus (TP), organic matter (OM), concentrations of Hg, As, Zn, Pb, Cr, and Mn in soils, dry weight of herbage, and elevation, while there was a quadratic curve trend between Cu, Cd in soils, and elevation. The results of risk assessment showed that there was no obvious ecological risk in the study area.

Impacts of Extreme Weather on Mercury Uptake and Storage in Subtropical Forest Ecosystems

AbstractAs climate change accelerates, extreme weather events become more severe and frequent. We analyzed the datasets of decade‐long observation (2005–2020) of mercury (Hg) stored in two subtropical evergreen forests to understand the impacts of extreme weather on the sequestration of atmospheric Hg in forest ecosystems. Results show a weak correlation between litterfall Hg and atmospheric Hg0 concentration. Droughts and snowstorms significantly disturb Hg accumulation in litterfall and soils. Litterfall Hg concentration and deposition both display an increasing trend during the period of extended droughts in 2011–2014, but a decreasing trend after droughts. This is caused by the water stress that influences the change of tree physiology and processes of foliage Hg0 uptake. Snowstorm damages large areas of canopy, which leads to substantial canopy epiphyte cover mixed into the forest floor, thus considerably increasing soil Hg concentrations. Over a decadal timescale, soil Hg variabilities are shaped by the combined effects of atmospheric Hg inputs and processes of organic soil mineralization mediated climatic factors. Our study highlights that the accelerated climate change increases the unpredictability of Hg accumulation in terrestrial ecosystems. Future studies are needed for better understanding the response of Hg biogeochemical cycling to climate change among different terrestrial biomes.

Adsorption and desorption characteristics of metal(oid)s in the yellow soils of a typical karst area, southwest China

ABSTRACT Yellow soil is a type of soil rich in hydrated iron oxide that is extensively distributed in the typical karst areas of Guizhou Province, southwest China. Concomitantly, the higher contents of metal(oid)s are observed in the soil of karst areas in Guizhou Province, and there are few reports to study the inner relationship between local soil and metal(oid)s in the here. Hence, the present study mainly aimed to understand the adsorption and desorption characteristics of metal(oid)s in yellow soils of a typical karst area using kinetics and adsorption isotherms. The effects of temperature, pH and electrolytes on adsorption were also examined. The risk of metal(oid)s in soil was also evaluated by geoaccumulation and tomlinson pollution load indexes. The results showed that the pH value of yellow soil collected from Guizhou Province was 6.41, making it a weakly acidic soil, and the average concentrations of organic matter and CaCO3 were approximately 1.12% and 0.88%, respectively. The adsorption of metal(oid)s did not significantly vary with an increase in the CaCO3 concentration in the yellow soil. The metal(oid)s adsorption of the yellow soil improved with an increasing clay content. The Hg content in the yellow soil far exceeded the standard value (GB 15618–2018), with a corresponding cumulative evaluation of grade 1 according to the geoaccumulation index. Tomlinson pollution load indexes exhibited that the comprehensive score of the selected metal(oid)s in the yellow soil was 0.60, corresponding to no pollution. The adsorption behavior of As onto the yellow soil can be interpreted through pseudo-second-order kinetics and the Langmuir model, where the maximum adsorption was observed at 1318 mg/kg. The adsorption of most metal(oid)s increased with increasing temperature. The adsorption of Pb, Cr, Cu, Zn and As did not obviously fluctuate with an increasing NaNO3 concentration. Notably, local related departments should take measures to decrease the Hg content in this soil.

Ant colonization increased total mercury but reduced methylmercury contents in boreal mires, Northeast China

Soil macroinvertebrates as ecosystem engineers play significant, but largely ignored, roles in affecting mercury (Hg) cycle by altering soil physical-chemical properties. Ant is likely expanded into boreal mires with climate warming, however, its impacts on Hg cycle remained poorly understood. We compared total Hg (THg) and methylmercury (MeHg) contents in soils from antmounds (Lasius flavus) and the nearby ambient in a boreal mire in Northeast China. The present work seeks to unravel factors that controlling MeHg levels in case of ant appearance or absence. The average THg was 179 µg/kg in the ant mound and was 106.1 µg/kg in nearby soils, respectively. The average MeHg was 10.9 µg/kg in the ant mound and was 12.9 µg/kg in nearby soils, respectively. The ratios of MeHg to THg (%MeHg) were 7.61% in ant mounds and 16.75% in nearby soils, respectively. Ant colonization caused THg enrichment and MeHg depletion, and this change was obvious in the 10-20 cm depth soil layer where ants mainly inhabited. Spectrometry characteristics of soil dissolved organic matter (DOM) exert a stronger control than microorganisms on MeHg variation in soils. A structural equation model revealed that the molecular weight of DOM inhibited MeHg irrespective of ant presence or absence, while humification conducive to MeHg significantly in ant mound soils. Microorganisms mainly affected Hg methylation by altering the molecular weight and humification of DOM. We propose that the effects of ant colonization on MeHg rested on DOM feature variations caused by microorganisms in boreal mires.

Mercury spatiality and mobilization in roadside soils adjacent to a savannah ecological reserve

Mercury (Hg) is a persistent environmental pollutant of global concern. Recognized anthropic contributions to environmental Hg pollution include fuel fossil emissions, soil erosion, and industrial and mining activities. Environmental Hg that enters water bodies can be methylated before entering the food chain and contaminating man and wildlife. We used a kriging approach for sampling and X-ray crystallography to study the pressure of road-traffic Hg emissions on soil Hg concentrations in an ecological reserve (ESECAE) in Central Brazil’ savannah. We took samples of organic (n = 144) and mineral (n = 144) layers from the road-side and from the undisturbed soils at 0.1, 1, and 2 km from traffic, inside the ESECAE. Overall, total mercury (THg) concentrations determined by atomic absorption spectrophotometry were significantly higher in the organic layer than in the mineral layer. The mean soil THg in the organic and mineral layers was highest at the roadside (respectively 19.77 ± 12.01 and 16.18 ± 11.54 μg g−1), gradually decreasing with the distance from the road. At 2 km, the mean soil THg was 0.09 ± 0.30 and 0.029 ± 0.03 μg g−1, respectively, for the organic and mineral layers. X-ray crystallography showed mineralogical similarity of the sampled soils, indicating Hg externality, i.e, it did not originate from existing soil minerals. Co-kriging analysis (n = 288) confirmed Hg hotspots on the roadsides and a faster mobilization occurring up to a distance of 1 km for both layers. The soil reception and retention of traffic Hg emissions are mainly in the organic layer and can impact subsoil and adjacent areas. Thus, traffic soil-Hg pollution is limited to the road proximities; THg concentrations are high up to 100 m with an inflection point at 1 km.

Environmental impact on the natural resources of an area affected by mining activity in Bolivia: a geochemical evaluation of soils and sediments

The current methods used in Bolivia to extract gold using the amalgamation process with mercury result in environmental contamination and a risk to human health. The objective of this study was to determine Hg, As, Cu, Cd, Pb and Zn concentrations in soils and sediments from three mining districts. Results showed As and Hg concentrations were higher in the topsoil than in the sub-surface soils in the Sunchullí-Viscachani area, indicating active As/Hg atmospheric deposition, where concentrations exceeded the threshold levels. In addition, concentrations of Cd and Zn largely exceeded the threshold levels in the Katantica and Sural mining districts. In addition, the Sunchullí and Viscachani lagoon sediments were contaminated by Hg, As, Cd, Zn and Cu, whilst Katantica lagoon showed high concentrations of Zn, Cd and Hg, and high levels of As, Zn and Cu were reported in the Sural lagoon. Our results showed that the Cu, Pb, As and Hg concentrations in sediments in the Sunchullí river; As, Hg and Cu in the Pelechuco river, and As and Hg in the Rayo Rojo river all come from direct mine discharges into the rivers. These high concentrations of metals and metalloids must cause an impact on the aquatic ecosystems and human health. Therefore, there is a need to study the availability and speciation of metals and metalloids in soils and sediments to better understand the cycling of these elements and their transfer to the food chain.

Greenhouse Characterization of Inorganic Mercury, Methyl Mercury and Ethyl Mercury Migration and Transformation in Indian Mustard and Chinese Pakchoi

Soil mercury (Hg) contamination has long been a problem that threatens the environment and organisms. Thus, exploring the migration and transformation of Hg from soil to vegetable is vital. In this study, different Hg solutions were employed in greenhouse experiments. The Hg contents in soil and vegetable samples were determined by inductively coupled plasma – mass spectrometry. The results showed that the Hg accumulation depended on its concentration and form. A greater accumulation of inorganic Hg was observed in the roots (2.2–27.4 mg/kg) than in the aerial parts (0.6–6.0 mg/kg). A similar trend was also found in the methyl mercury (MeHg) and ethyl mercury (EtHg) irrigated groups. The MeHg contents were 0.7–8.0 μg/kg in roots and 0.1–3.7 μg/kg in aerial parts. The EtHg concentrations were 0.5–3.3 μg/kg in roots and 0.3–1.1 μg/kg in aerial parts. The translocation factors of inorganic Hg and organic Hg for both vegetables in most treatments were less than 0.5, which suggested that Hg primarily accumulated in the roots. The biological concentration factors of inorganic Hg were less than 0.4, and those for MeHg and EtHg were between 0.4 and 0.95, which indicated that the vegetables were more likely to absorb organic Hg from the soil. The methylation of inorganic Hg occurred in the roots. The potential hazards of Hg on food safety and human health must be considered in regions with serious Hg pollution.

Distribution Characteristics and Ecological Risk Assessment of Soil Heavy Metals in the Eastern Mountainous Area of the Nanyang Basin

The spatial distribution, pollution degree, and ecological risk of heavy metals in the soil were studied by analyzing the contents of As, Hg, Cd, Cr, Pb, Zn, Ni, and Cu and pH values in surface soil samples of the eastern mountainous area of the Nanyang basin. The results showed that the contents of Cd, Cu, Cr, Ni, Pb, Zn, and As in the soil exceeded the screening value of soil pollution risk. The spatial distribution of soil heavy metals displayed regional-and island-shaped. The highest concentration of heavy metals was found in the south of the study area, where a mining area is located. Most of the samples had no pollution levels except some samples with high contents of Cd. For As, Cr, Pb, Zn, Ni, and Cu, the potential ecological risk of most samples were low, while Cd and Hg posed medium risk in most areas. The areas with high and relatively high ecological risk index accounted for 58.93% and 37.66%, respectively. Soil Hg, Cd, and Pb contents were related to anthropogenic activities such mineral mining. As derives from geological processes, while Zn, Ni, Cr, and Cu are both controlled by anthropogenic activities and geological processes. The mining of mineral resources is the main driving factor of soil heavy metal pollution and ecological risk in the study area.

Changes of mercury and methylmercury content and mercury methylation in Suaeda salsa soil under different salinity.

In this paper, we studied the changes of Hg and MeHg contents in Liaohe estuarine Suaeda salsa soils under anaerobic conditions by simulated indoor incubation at constant temperature and whether the changes of salinity (CK, 0.5%, 1.0%, 1.5%, 2.0%) affected SRB and dominated the formation of MeHg. The lowest Hg content is found in the subsurface Suaeda salsa soils at 2.0% salinity. The MeHg content in the soil also showed a general trend of increasing and then decreasing with increasing flooding salinity, and the MeHg content was higher at 0.5-1.0% flooding salinity. SRB was present in the soil under all salinity conditions and reached the maximum value at 15days of incubation. The SRB content was higher under CK, S1 and S2 conditions, and the soil MeHg content showed a significant positive correlation with the number of SRB bacteria, indicating that the formation of MeHg was related to SRB which is of great significance to the study of estuarine wetlands.

Pollution Characteristics, Spatial Patterns, and Sources of Toxic Elements in Soils from a Typical Industrial City of Eastern China

Soil pollution due to toxic elements (TEs) has been a core environmental concern globally, particularly in areas with developed industries. In this study, we sampled 300 surface (0–0.2 m) soil samples from Yuyao City in eastern China. Initially, the geo-accumulation index, potential ecological risk index, single pollution index, and Nemerow composite pollution index were used to evaluate the soil contamination status in Yuyao City. Ordinary kriging was then deployed to map the distribution of the soil TEs. Subsequently, indicator kriging was utilized to identify regions with high risk of TE pollution. Finally, the positive matrix factorization model was used to apportion the sources of the different TEs. Our results indicated that the mean content of different TEs kept the order: Zn > Cr > Pb > Cu > Ni > As > Hg ≈ Cd. Soil pollution was mainly caused by Cd and Hg in the soil of Yuyao City, while the content of other TEs was maintained at a safe level. Regions with high TE content and high pollution risk of TEs are mainly located in the central part of Yuyao City. Four sources of soil TEs were apportioned in Yuyao City. The Pb, Hg, and Zn contents in soil were mainly derived from traffic activities, coal combustion, and smelting. Meanwhile, Cu was mainly sourced from industrial emissions and atmospheric deposition, Cr and Ni mainly originated from soil parental materials, and Cd and As were produced by industrial and agricultural activities. Our study provides important implications for improving the soil environment and contributes to the development of efficient strategies for TE pollution control and remediation.

Biomonitoring of Mercury Contamination in Poland Based on Its Concentration in Scots Pine (Pinus sylvestris L.) Foliage.

This work evaluates current mercury (Hg) contamination in Poland, represented by the Hg concentrations in Scots pine foliage. Samples were collected over 295 investigation plots in monitoring grids throughout Poland, from pines aged between 12 and 147 years. Analyses were conducted with consideration of bioclimatic factors and soil properties. Concentrations in the pine foliage did not exceed the values characteristic of an ecosystem unaffected by industrial pollution, ranging from 0.0032 to 0.0252 mg kg−1 dry mass. However, pine stands located in western and central Poland, and in the northwest near the Baltic Sea, exhibited higher Hg concentrations in foliage than in eastern regions. Hg content in foliage depends on the mean temperature of the driest quarter, as well as on Hg content in soils. This indicates that the periods of drought observed in recent years in Poland may affect Hg concentrations in pine foliage.