Mercury In Soils Research Articles

Mercury in soils impacted by alluvial gold mining in the Peruvian Amazon

Gold mining is the largest source of mercury (Hg) pollution worldwide. The discharge of mercury in the environment bears direct human health risks and is likely to increase cascading effects throughout local food chains. In the Peruvian Amazon the mining process consists of slashing and burning trees, followed by extraction of gold-bearing sediment, amalgamation with Hg and gold recovery, leading each year to the degradation of 6,000-10,000 ha and the release of 180 metric tons of Hg per year to the enviroment. The purpose of this study was to determine soil Hg levels in soils of abandoned alluvial gold mine spoils and undisturbed forest in the Madre de Dios region, the epicenter of alluvial gold mining in Peru. We selected gold mine spoils of the two most important technologies locally applied for gold extraction, i.e., Minimally Mechanized Mining (MMM) and Highly Mechanized Mining (HMM), in the native communities of Laberinto and Kotzimba, respectively. We collected 127 and 35 soil samples (0-20cm depth) from potentially contaminated sites and undisturbed forest, respectively. Physicochemical analysis and determination of Hg levels were determined for all soil samples. None of the samples had Hg concentrations above Peruvian, Canadian and British Environmental Quality Standards for Agricultural Soil (6.6mg/kg). Hg levels in MMM and HMM were not significantly different between the two areas. The main variables explaining variation of soil Hg concentrations were the vegetation cover, soil organic matter, soil pH and clay particle content, which explained up to 80% of data set variation. Surprisingly, highest Hg concentrations were found in untouched old-growth forest bordering the mine spoils, but there was also a trend of increasing Hg concentrations with the regenerating vegetation. Our findings suggest that Hg concentrations in old mine spoils are low and shouldn’t stand in the way of efforts to restore soil conditions and develop sustainable land uses. However, it is urgent to end the use of Hg in mining operation to decrease human and environmental risks.

Distribution and pools of mercury in forest soils near recent and historical mercury emission sources in the central Czech Republic

The fate of atmospherically deposited mercury (Hg) was studied in forest soils situated near various Hg anthropogenic emission sources, including chlor-alkali plants, cement production, and pig iron and steel factories in the Czech Republic. Some of these emission sources were more active in the past, while others continue operation with lowered dust and Hg emissions up to the present day. The impact of Hg emission sources on forest soil was assessed with respect to other soil parameters, including organic carbon, soil nitrogen, soil sulfur, and soil oxalate-extractable aluminum and iron concentrations. The site-specific mean Hg concentrations in organic horizons (174–479 μg kg−1) were greater than mean Hg concentrations in mineral soil (15–88 μg kg−1). Site specific mean Hg/C ratios in organic horizons at four study sites ranged from 0.8 to 2.4 μg g−1, while mean mineral soil Hg/C varied from 2.0 to 3.4 μg g−1. Near cement plants, an 8- to 30-cm thick layer composed of dust particles was identified below or mixed with current O and A horizon material (Hg concentrations 122 to 401 μg kg−1). Mean mineral soil pools of Hg (13–24 mg m−2) dominated over the mean organic horizon Hg pools (2–11 mg m−2). Near cement plants and steel works, Hg concentrations and pools in organic horizons and mineral soils were within the range reported from pristine Czech forest soils. Elevated Hg concentrations in organic horizons were found near a chlor-alkali plant. Thermal decomposition analysis indicated that Hg in A horizons at all sites and dust horizons near cement plants was bound similarly to Hg in foliage.

Atmospheric mercury in the Latrobe Valley, Australia: Case study June 2013

Gaseous elemental mercury observations were conducted at Churchill, Victoria, in Australia from April to July, 2013, using a Tekran 2537 analyzer. A strong diurnal variation with daytime average values of 1.2–1.3 ng m–3 and nighttime average values of 1.6–1.8 ng m–3 was observed. These values are significantly higher than the Southern Hemisphere average of 0.85–1.05 ng m–3. Churchill is in the Latrobe Valley, approximately 150 km East of Melbourne, where approximately 80% of Victoria’s electricity is generated from low-rank brown coal from four major power stations: Loy Yang A, Loy Yang B, Hazelwood, and Yallourn. These aging generators do not have any sulfur, nitrogen oxide, or mercury air pollution controls. Mercury emitted in the 2015–2016 year in the Latrobe Valley is estimated to have had an externalized health cost of $AUD88 million. Air pollution mercury simulations were conducted using the Weather Research and Forecast model with Chemistry at 3 × 3 km resolution. Electrical power generation emissions were added using mercury emissions created from the National Energy Market’s 5-min energy distribution data. The strong diurnal cycle in the observed mercury was well simulated (R2 = .49 and P value = 0.00) when soil mercury emissions arising from several years of wet and dry deposition in a radius around the power generators was included in the model, as has been observed around aging lignite coal power generators elsewhere. These results indicate that long-term air and soil sampling in power generation regions, even after the closure of coal fired power stations, will have important implications to understanding the airborne mercury emissions sources.

Heavy Metals in Archaeological Soils

AbstractPortable X-ray fluorescence (pXRF) spectroscopy is commonly used for testing toxic levels of heavy metals in modern industrial waste sites, and it has seen growing applicability in the context of archaeological survey and soils. In this study, we present the results of our pXRF analysis of surface soils at a historic silver refinery located near Puno, Peru, in the western Lake Titicaca Basin. The results of our analysis identified hazardous levels of antimony (Sb), arsenic (As), mercury (Hg), and lead (Pb) in excavation soils, necessitating the relocation of planned excavation units and the use of personal protective equipment. This study highlights the advantages of rapid, in situ pXRF analysis of surface soils in contaminated industrial archaeology sites to assess potential harm to human health.

Risk Assessment of Mercury in Soil and Surface Water in Brgy. Santa Lourdes, Puerto Princesa City, Palawan

Mercury sources influence human health, especially in urban areas with high population density and intensive anthropogenic activities. Barangay Sta. Lourdes, Puerto Princesa, Palawan in South-Eastern Philippines, was one of the mercury hotspots with cinnabar as a primary mineral. The mines had to close because of economic downtrends during the 1970s. Several samples were taken from the area, and concentration distribution was determined to identify potential hazard exposure. Doses contacted through ingestion, inhalation, and dermal absorption were calculated using US EPA exposure parameters. The soil was found to be enriched in Hg with the highest Total Hg (THg) recorded at 977.70 ppm. The correlation of soil pH and Hg shows a 0.64 decrease in THg for every unit increase in pH. High THg was noted during the rainy season and tended to erode mercury-laden soil into the river. The highest risk is associated with ingestion and dermal absorption, with negligible risk through air inhalation. The samples near the abandoned quicksilver mines recorded the highest THg concentrations with a hazard index (HI) greater than 1, signifying possible adverse health risks for the nearby residents. Mercury soil contamination maps indicated sources of the contamination, which can help future studies for remediation.

Understanding the effects of long-term different fertilizer applications on methylmercury accumulation in rice (Oryza sativa L.) plants

The effects of long-term applications of fertilizer form and rate on methylmercury concentration in rice grain have been previously reported. However, there remains a large gap in understanding fertilizer treatments affect the transformation of mercury (Hg) in paddy soils and the translocation of Methylmercury (MeHg) in rice plants. Thus, we investigated the effects of four fertilizer treatments (NK, nitrogen and potassium; NPK, nitrogen, phosphorus and potassium; NPKM, nitrogen, phosphorus, potassium and swine manure; and NPKS, nitrogen, phosphorus, potassium and rice straw) on mercury (Hg) methylation in paddy soils and on MeHg translocation in rice plants after a 24-year period; specifically, we investigated differences in MeHg production in paddy soils and MeHg mass flow in rice plants. The results showed that Geobacteracea and Methanosarcinacea were the major Hg-methylating microorganisms and their relative abundances were significantly promoted by rice straw return, which led to the significantly higher MeHg concentration both in paddy soils and in the rice grain of NPKS treatment compared with control. In addition, the phosphate and organic fertilizers increased MeHg translocation from the roots to the leaves and grain more than the nitrogen and potassium fertilizers did. In detail, compared with the control, NK increased MeHg concentrations in the rice grain by approximately 1-fold; NPK and NPKM, by approximately 3-fold; and NPKS, by approximately 8-fold. Last, we suggest that policy-makers worldwide should comprehensively assess the high potential risk of MeHg in rice grain in large production areas where rice straw is returned.

Polycyclic Aromatic Hydrocarbons, Mercury and Arsenic Content in Soils of Larsemann Hills, Pravda Coast and Fulmar Island, Eastern Antarctica.

This study is aimed at investigation of various potential contaminants (arsenic, mercury and polycyclic aromatic hydrocarbons) content in soils of different landscapes of Eastern Antarctica ice-free areas. Our data not only showed that intensive human impact might result in significant direct contamination of surrounding landforms, but also revealed a specific role of ornithogenic transport in distribution of contaminants. Analysis revealed that the contents of investigated elements were 0.100-8.055mgkg-1 (arsenic), 0.025-0.027mgkg-1 (mercury) in Larsemann Hills and 0.100-1.213mgkg-1 (arsenic), 0.023-0.593mgkg-1 (mercury) in vicinities of Mirny station and Fulmar Island. Accumulation of some elements in guano-derived and moss materials lead to higher values of other soil pollution indices at natural sites. Results of our study revealed the predominance of light molecular weight PAHs (fluorene and acenaphthylene) in studied soils. Results of our study are not completely in agreement with the idea of an practically uncontaminated Antarctic ecosystem which was previously reported for Eastern Antarctica ice-free areas. Various human activities carried out at local scale have been found to be responsible for increase of metal levels in studied Antarctic environments.

Characteristics and evaluation of mercury pollution in paddy soil of a watershed in Zhanjiang

[Objective] The potential risk of mercury in paddy soil of a watershed in Zhanjiang were investigated to provide reference for reasonable planting of farmland and ensuring the safety production of agricultural products. [Method] The mercury content in 42 soil samples of paddyfield in the upper, middle and lower reaches of the study area was determined, mainly through using the single-factor index, geo-accumulation index and potential ecological risk index. Also, the spatial distribution characteristics of mercurypollution probability were analyzed by Indicator Kriging method. [Result] The mercury content of paddy soil of a watershed in Zhanjiang ranged from 0.040 to 0.504 mg/kg, and the coefficient of variation was 68.42%, which belonged to the middle degree of variation. The average value of mercury content in the study was 0.193 mg/kg, which was generally shown as middle reaches>upper reaches>lower reaches. The average value of middle reaches was 0.343 mg/kg, which was the highest in the whole watershed. Although it did not exceed the national screening value of 0.5 mg/kg of agricultural soil pollution risk, it was as 4.3 times as the mercury content of the background value of Zhanjiang soil (0.045 mg/kg), and far higher than the background value of soil in Zhanjiang. The mercury pollution in the paddy soil of the whole watershed was obvious. The results of single factor index evaluation based on the background value of soil in Zhanjiang showed that the site of heavy accumulation of mercury in paddy soil is as high as 52.38%. The results of land accumulation index analysis showed that 33.33% of the samples belonged to medium to strong pollution. The average value of the potential ecological risk index of mercury in the whole basin was 160–320, and the risk level was IV, which was a very strong potential ecological risk. The results of Indicator Kriging method showed that, there was a high probability of mercury pollution in paddy soil of the watershed, especially in the middle reaches. [Conclusion] The content of mercury in paddy soil in this study area of Zhanjiang belongs to the safe range, but there arepotential serious ecological risks. Attention should be paid to mercury pollution in paddy soil, which is caused by the extensive use of pesticides and chemical fertilizers and automobile exhaust. 摘要: 【目的】 开展湛江某流域水稻田土壤汞污染调査, 为流域农田合理种植及农产品安全生产提供参考依据。 【方法】 测定研究区上、中、下游水稻田共42份土壤的汞元素含量, 综合采用单因子指数法、地累积指数法及潜在生态 风险指数法进行污染评价, 并结合指示克里格法分析汞污染概率的空间分布特征。 【结果】湛江某流域水稻田土壤汞 元素含量范围为0.040~0.504 mg/kg, 变异系数为68.42%, 属中等变异程度; 土壤汞含量平均值为0.193 mg/kg, 总体上 表现为中游>上游>下游, 其中中游平均值为0.343 mg/kg, 为全流域最高。总体上虽未超过国家农用地土壤污染风险 筛选值(0.5 mg/kg)但远高于湛江土壤背景值(0.045 mg/kg), 汞含量平均值是湛江土壤背景值的4.3倍。整个流域 水稻田土壤中汞污染较明显, 基于湛江土壤背景值的单因子指数评价结果表明, 水稻田土壤中汞出现重度累积的样 点高达52.38%; 地累积指数分析结果显示33.33%的样点为中污染至强污染; 整个流域水稻田土壤的汞元素潜在生态 风险指数平均值在160~320范围内, 风险等级为IV级, 属于很强潜在生态风险。指示克里格法分析结果显示该流域 水稻田土壤中具有较高汞污染概率, 尤其是中游流域污染情况较突出。 【结论】湛江该流域水稻田土壤汞含量属于安 全范围, 但存在很强的潜在生态风险。农药化肥的大量使用及汽车尾气排放可能导致水稻田土壤汞污染的问题应引 起重视。

Geochemistry Signatures of Mercury in Soils of the Amazon Rainforest Biome

Geochemistry Signatures of Mercury in Soils of the Amazon Rainforest Biome

Heavy metal pollution characteristics and health evaluation of farmland soil in a gold mine slag area of Luoyang in China

The characteristics of eight heavy metals (lead, zinc, copper, nickel, chromium, cadmium, mercury and arsenic) in the surface soil of the historical slag area of the Au ore dressing plant in the South-West of Luoyang City were investigated and evaluated in terms of a pollution index, potential ecological hazards and health risks. The results showed that the average amounts of the heavy metals Pb, Zn and As in the soils of plots S3, S5, S7, S12 and S18 exceeded the soil pollution risk screening values. The Mero comprehensive pollution index in plots S7, S12 and S18 was greater than 3, indicating severe pollution. The severe pollution plot integrated the potential ecological risk index (RI) of each sampling point, which was in the order of RIS12 > RIS18 > RIS7 > RIS5 > RIS3. Among the heavy metals, Cd poses the greatest threat to ecological and human health. The effects of heavy metals in soil on the single non-carcinogenic health risk index (HQ) and the non-carcinogenic total risk index through three exposure pathways were in the order of HQHg < HQCu < HQNi < HQZn < HQCd < HQCr < HQPb < HQAs < 1, which meant that the adult and child total carcinogenic risk (TCR) and individual carcinogenic health risk indices were above the maximum acceptable human health level recommended by the USEPA (10-6). TCRAs and TCRCd accounted for 75.65% and 23.94% of the adult TCR, respectively. TCRAs and TCRCd accounted for 75.93% and 23.97% of the child TCR, respectively. Overall, the TCR of children was greater than that of adults. In summary, the soil in the historical slag area of the Au ore dressing plant constitutes a serious threat to the surrounding ecological environment and to residents. Keywords: historical slag area, heavy metals, pollution assessment, health assessment, farmland soil, ecological hazard DOI: 10.25165/j.ijabe.20211405.6536 Citation: Wang H, Zhang H, Xu R K. Heavy metal pollution characteristics and health evaluation of farmland soil in a gold mine slag area of Luoyang in China. Int J Agric & Biol Eng, 2021; 14(5): 213–221.

Soil Bioavailability and Native Plant Uptake of Mercury in the Contaminated Sites at Kodaikanal, India

This paper presents the evaluation of soil contamination with bioaccumulation and bioavailability of mercury in the surroundings of a former thermometer factory at Kodaikanal in connection with several other soil chemical characteristics. Mercury (Hg), a rare earth element, evolves to be the global concern because of its solubility and its persistence in nature. It is also widely known as a potential neurotoxin since it has the ability to bind with the thiol functional groups in the living system because of the accumulation in food chain and its biomagnifications. The Study was carried out at Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore, India during 2018-2020. Geo-coded soil and plant samples were collected in and around the former thermometer factory in different possible direction. The total mercury content in the soil ranged from 0.19 to 4.7 mg kg-1 and the water soluble mercury fraction ranged from 0.01 to 0.07 mg kg-1 in various sampling sites. The total mercury of the samples ranged from 0.24 to 3.80, 0.84 to 1.55, 0.45 to 1.67 and 0.19 to 4.97 mg kg-1 in east, north, south and west directions, respectively whereas the water soluble mercury fraction ranged from 0.01 to 0.07 and 0.01 to 0.04 mg kg-1 in east and west direction, respectively corresponding to 0.5 to 5.36 % of the total. Despite this analysis, other chemical parameters were also studied to determine their extent of influence on mercury accumulation and availability. Among those parameters, pH was found to be having significant correlation with total mercury and water soluble mercury. The concentration of total mercury and water soluble mercury recorded were less than the permissible limit set by International standards (Canadian Soil Quality Guidelines). Among different plant species, Roots of Sterculia sp. was found to accumulate 1.19 mg kg-1 whereas mercury content was found to be below detectable limits in other plants. Based on the results obtained from Potential Ecological Risk Index, it was concluded that risk associated with soil mercury contamination is low in the study area at Kodaikanal.

Soil mercury pollution caused by typical anthropogenic sources in China: Evidence from stable mercury isotope measurement and receptor model analysis

Abstract Human activities have caused serious soil mercury (Hg) pollution in industrial areas worldwide. Abatement of soil Hg pollution requires knowledge of Hg sources and transport pathways across various environmental media. In this study, four areas containing typical anthropogenic Hg emissions in China were selected to evaluate soil Hg pollution. Results showed that soil Hg contents were significantly elevated in areas of Hg mining, gold mining, and zinc smelting, but only slightly elevated in an area of coal-fired power plant, with averages of 44.0, 1.17, 0.73, and 0.14 μg g−1 (dry weight) in these four areas, respectively. The average percentage contributions from these anthropogenic sources to soil Hg in surrounding areas were estimated to be 92.2 ± 9.70% from Hg mining (among which 77.6 ± 12.0% from unroasted Hg ore and 14.6 ± 7.50% from Hg calcine), 63.5 ± 0.83% from the zinc smelting, 41.6 ± 1.90% from gold mining, and 21.1 ± 3.58% from coal-fired power plant. Atmospheric deposition was speculated to be the main pathway for soil Hg contamination, but mercury mining area contained significant runoff accumulation. Speciation and concentration of Hg in emission gas are crucial factors for Hg pollution in surrounding soils, because of short residence time of Hg2+/Hgp in the atmosphere. The results obtained in this study can provide scientific advices for risk assessment and soil remediation of Hg in China and other regions with similar industries.

Evaluation of the bioaccumulation of mercury (Hg) and fluorine (F) in garden produce in south Benin

Objectives: The richness of the soils in metallic trace elements (MTEs) and Fluorine, which are potentially toxic elements, makes it necessary to pay attention to the risks of transfer of these elements to the food chain. The aim of this study is to evaluate the content of mercury and fluorine in soils, irrigation water and market garden products in South Benin. Methodology and Results: A total of 21 composite soil samples (0-20cm), 21 samples of irrigation water per growing area and 87 plant samples were collected. After sampling under aseptic conditions, they were sent for analysis in laboratories. The Excel spreadsheet calculated the contents and the GraphPad Prism 8.0 calculated the averages and tests of two ways. Before determining the bioaccumulation, the contents were compared to the minimum concentration referenced by international standards. All matrices were contaminated with mercury and fluorine. The minimum reference concentration (0.55mg/Kg) was higher than the average levels of the study soils in Mercury (0.11±0.1. 10-2 to 0.164±0.345 .10-3 mg/Kg) and in Fluorine (8.123±1.772 to 23.5±1.126mg/Kg). Mercury and Fluorine levels in site irrigation water were below the standards. The levels of mercury (0.46 .10-3 ±0.13 .10-4 to 0.001±0.38. 10-4 mg/L) and fluorine (0.15±0.07 to 2.17±0.41mg/L) in the irrigation water of the sites are lower than the standards, except for the Houéyiho borehole. In leaves such as amaranth, there was a very significant difference (0.001 &lt; p &lt; 0.01) at Sèmekpodji and Grand-popo. Amaranth is a leaf that is in direct contact with the chemicals used in the environment and could absorb mercury. Fluorine levels exceed the maximum recommended concentration (0.05 mg/Kg) so the vegetables are polluted with fluorine. Conclusion and application of results: In Houéyiho, a medium bioaccumulation in amaranths and carrots was observed while in chili peppers bioaccumulation was low. On the other hand, in Sèmè-kpodji and Grandpopo, a low bioaccumulation of mercury in all the vegetables was observed. Fluorine bioaccumulation is medium in amaranth and carrot at Houéyiho and Sèmè-kpodji and low in chilli peppers at both sites. While bioaccumulation is low in vegetables produced at the Grand-popo site. Key words: bioaccumulation, soil contamination, vegetable contamination, mercury, fluorine, MRC, Benin

Interpretations of Hg anomalous sources in drainage sediments and soils in China

China Geochemical Baselines project provides mercury dataset of drainage catchment sediments and soils during 2008–2012 in China. Fifty-seven mercury anomalous regions exceeding the risk limits of the China National Environmental Standards for Heavy Metals in Soil (GB 15618-1995) are delineated in China. The sources of Hg risk anomalies of the top and deep samples are variously interpreted with respect to geology/mineralisation and human activities. Nearly 72% anomalies (41 among the totaling 57 anomalous locations) are due to natural geological mineralisation belts and mining of Hg, As, Sb, Au, Ag, Pb, Zn, coal etc. The mining activities cause superimposed contents of Hg on the natural mineralisation belts. The influence of large-scale mining of Hg, non-ferrous metals and gold are significantly reflected in the geochemical maps. The anthropogenic sources of urbanisation emission, agriculture, coal combustion, and smelting industry cause the much more degree of mercury pollution in the eastern China where is highly populated and industrial density areas. Agriculture is an important Hg-emission source in the eastern China and Chengdu Plains where agricultural base for more than 2500 years in China. It is critical to carry out the follow-up detailed source investigation and monitor the temporal changes of Mercury in soils.

Elevated CO2 and soil mercury stress affect photosynthetic characteristics and mercury accumulation of rice

This is a novel study about responses of leaf photosynthetic traits and plant mercury (Hg) accumulation of rice grown in Hg polluted soils to elevated CO2 (ECO2). The aim of this study was to provide basic information on the acclimation capacity of photosynthesis and Hg accumulation in rice grown in Hg polluted soil under ECO2 at day, night, and full day. For this purpose, we analyzed leaf photosynthetic traits of rice at flowering and grain filling. In addition, chlorophyll content, soluble sugar and Malondialdehyde (MDA) of rice leaves were measured at flowering. Seed yield, ear number, grain number per ear, 1000-grain weight, total mercury (THg) and methylmercury (MeHg) contents were determined after harvest. Our results showed that Hg polluted soil and ECO2 had no significant effect on leaf chlorophyll content and leaf mass per area (LMA) in rice. The contents of soluble sugar and MDA in leaves increased significantly under ECO2. Mercury polluted soil treatment significantly reduced the light saturated CO2 assimilation rate (Asat) of rice leaves only at flowering, but not at grain filling. Night ECO2 greatly improved rice leaf water use efficiency (WUE). ECO2 greatly increased seed yield and ear number. In addition, ECO2 did not affect THg accumulation in rice organs, but ECO2 and Hg treatment had a significant interaction on MeHg in seeds, husks and roots.

Survival and early growth of 51 tropical tree species in areas degraded by artisanal gold mining in the Peruvian Amazon

Artisanal gold mining in Amazon forests and rivers has been reported in all Amazonian countries. Amazon mining has a wide range of negative effects and severe environmental and social consequences. Given that the activity in the region is mostly illegal, there are few studies published in the scientific literature on recovery of areas degraded by gold mining. This study conducts an experimental reforestation project aimed to evaluate soil degradation and explore the seedling survivorship and early growth of 51 tropical tree species in gold mined areas at 5 study sites distributed across the Madre de Dios region, in the Peruvian Amazon. The study evaluates the effect of biochar amendments on the survivorship and growth of 51 tropical species. The study also analyzes the influence of species wood density on seedling performance one year after planting. In order to inform further restoration plantation strategies, species were chosen with the end goals of timber production, biodiversity enhancement, and soil restoration. Site degradation, soil properties and mercury levels were analyzed in degraded areas and paired reference forest patches. Soils after gold mining are found to be highly degraded, with soil C being nearly absent, cation content greatly decreased, and loss of fine sediment. Soil mercury levels were found below national and international environmental quality standards. A positive correlation and a statistically significant relationship were found between survivorship and wood density. This reveals that the higher the wood density of the species, the higher the survival percentage. Growth and overall performance of mid, and especially low wood density species were significantly increased by biochar additions, while no effect was recorded on high wood density species growth. The study provides guidance on the post-ASGM restoration potential for 51 common and useful tree species and gives practitioners recommendations for combinations of species and fertilization treatments to optimize restoration designs.

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.

A gas reporting whole-cell microbial biosensor system for rapid on-site detection of mercury contamination in soils

As optical reporting elements, fluorescent proteins are extensively used in whole-cell microbial biosensors. However, the use of these optical reporters is limited in opaque media such as soil. This study described a method utilizing gas as a reporting signal that could be used for the rapid on-site detection of mercury in soil. In this biosensor, the MerR protein could capture mercury ions and then bind the promoter of the efe gene to initiate the synthesis of the ethylene (C2H4)-forming enzyme that produced the gas. The research showed that the mercury ion concentrations could be converted into C2H4 gas signals, which were quantified using a handheld C2H4 sensor. By optimizing the biosensor to improve its anti-interference ability in the system, it could detect mercury ion concentrations in the soil ranging from 0.2 to 20 mg/kg within 45 min, effectively reflecting whether the mercury pollution in the soil exceeded the limit standard. This study provides a simple, inexpensive, and portable method for the on-site detection of soil pollutants.

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.