Geochemical fractions and risk assessment of trace elements in soils around Jiaojia gold mine in Shandong Province, China

Cadmium and zinc isotope compositions indicate metal sources and retention mechanisms in different soil particle size fractions

Soil particle size may significantly affect metal distribution and stable isotopic behavior. Here, two soils were separated into four particle size fractions, namely fine sand, silt, fine silt, and colloidal particles and used to determine cadmium (Cd) and zinc (Zn) concentrations and isotope compositions. Concentrations of Cd and Zn were generally enriched in the finer particles and positively correlated with the iron (Fe) and manganese (Mn) oxide contents. However, Cd concentration in the fine sand was higher than in the silt fraction due to the higher soil organic matter contents in the former particle fraction. The maximum δ114/110Cd value was found in the colloidal particles (-0.02 and 0.01‰) of both soils while the minimum was in the silt particles (-0.12 and 0.06‰). Incorporation into the mineral lattice of Fe and Mn oxides is suggested to explain the slight enrichment of heavy Cd isotopes in the colloidal fraction. The similar δ66Zn values of the four particle fractions (0.20-0.29‰ with a mean of 0.25‰) indicate similar Zn sources in different particle sizes. Metal isotopic fingerprint of different soil particle size fractions provides further insight into the underlying metal retention mechanisms within soil micro-zones and helps in tracing metal sources and biogeochemical processes.

Environmental contamination and health risk assessment of potentially toxic trace metal elements in soils near gold mines - A global meta-analysis

Gold mining is the most important anthropogenic source of heavy metal emissions into the environment. Researchers have been aware of the environmental impacts of gold mining activities and have conducted studies in recent years, but they have only selected one gold mining site and collected soil samples in its vicinity for analysis, which does not reflect the combined impact of all gold mining activities on the concentration of potentially toxic trace elements (PTES) in nearby soils at a global scale. In this study, 77 research papers from 24 countries were collected from 2001 to 2022, and a new dataset was developed to provide a comprehensive study of the distribution characteristics, contamination characteristics, and risk assessment of 10 PTEs (As, Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, and Zn) in soils near the deposits. The results show that the average levels of all 10 elements are higher than the global background values and are at different levels of contamination, with As, Cd, and Hg at strong contamination levels and serious ecological risks. As and Hg contribute to a greater non-carcinogenic risk to both children and adults in the vicinity of the gold mine, and the carcinogenic risks of As, Cd, and Cu are beyond the acceptable range. Gold mining on a global scale has already caused serious impacts on nearby soils and should be given adequate attention. Timely heavy metal treatment and landscape restoration of extracted gold mines and environmentally friendly approaches such as bio-mining of unexplored gold mines where adequate protection is available are of great significance.

Comprehensive evaluation of environmental availability, pollution level and leaching heavy metals behavior in non-ferrous metal tailings

Amounts of abandoned non-ferrous metal tailings(NMT) piled in the open air are released under geochemistry and migrated to the surrounding environment, causing severe harm to the environment and human health. It is essential to evaluate the heavy metal pollution of NMT. In this study, RAC, I_geo, EF, and RI were used to evaluate the heavy metal pollution risk of NMT. To uniformly simplify the four evaluation results into a comprehensive evaluation result that can reflect the degree of heavy metal pollution risk. Assuming heavy metals' concentration, occurrence, and mobility make the same contribution to the degree of heavy metal pollution. Score the above four evaluation results according to the pollution level, and then weigh the scores to obtain a complete integral result: CRS_Mo (17) > CRS_Cd (13) > CRS_Pb (11) > CRS_Sr(8) > CRS_Mn(7) > CRS_Cu(5) > CRS_Ni(4) > CRS_Cr(3) = CRS_Zn(3). Five higher risk heavy metal elements Mo, Cd, Pb, Sr, and Mn, were found. Cu, Ni, Cr, and Zn are at lower risk. The results showed that Mo, Mn, and Sr's evaluation is more accurate. Pb and Cd have not reached the detection limit for the time being, indicating that the release of heavy metal elements in tailings is not only related to the total concentration, occurrence state, and mobility of heavy metals but also affected by the pH of the tailings. This study's most significant finding is to propose a comprehensive integration result of pollution risk levels based on RAC, I_geo, EF, and RI as the comprehensive evaluation result of heavy metal pollution risk. Simultaneously, this research is also a valuable supplement to the existing risk assessment of heavy metal pollution.

Spatial distribution, risk assessment, and source identification of pollutants around gold tailings ponds: a case study in Pinggu District, Beijing, China

This work investigated heavy metal and cyanide pollution in surface soils and edible plants around Yanzhuang gold tailings ponds in the region of Yanzhuang Village in Pinggu District, Beijing. Surface soil samples were collected from 33 sites around gold tailings ponds, and concentrations of seven heavy metals (i.e., Sb, As, Cd, Cu, Pb, Zn, and Hg) and cyanide were analyzed to determine their spatial distributions, pollution degrees, and sources. The potential ecological risks of As, Cd, Cu, Pb, Zn, and Hg were preliminarily assessed. The results showed that the mean cyanide, Sb, As, Cd, Cu, and Pb concentrations were higher than the standard values. The pollutant concentrations around the tailings ponds were high and decreased with increasing distance from the ponds. The single pollution index indicated that cyanide, As, and Cd were the main pollutants. The Nemerow pollution index revealed a large region and serious degree of heavy metal pollution in soils. The potential ecological risk level of the study area was moderate, with Cd and As posing the main risks. Multivariate statistical analysis suggested that the heavy metal and cyanide pollution present mainly derived from gold tailings, with agricultural pollution also had a certain effect. However, the 12 edible plants sampled were basically not polluted.

Pollution Assessment of Potentially Toxic Elements (PTEs) in Soils around the Yanzhuang Gold Mine Tailings Pond, Pinggu County, Beijing, China

The accumulation of tailings from gold mining and smelting may result in PTE pollution. We investigated PTE contamination from a large amalgamated gold mine tailings pond in Pinggu County, Beijing. In November 2017, 30 soil samples were collected around the tailings pond. The concentrations and pollution degree of PTEs in the samples and the sources of Sb, As, Cd, Cu, Pb, Zn and Hg were analyzed. The average concentration of these elements in soil samples near the tailings pond (16.24, 28.29, 0.99, 171.04, 263.25, 99.73, 0.72 mg/kg, respectively) were higher than their corresponding standard values and background values of the study area. The geoaccumulation index showed that the pollution degree of As, Pb and Hg was moderate, while Sb and Cu present non-pollution to moderate pollution. The average EF values of the elements were Sb (38.31), As (4.23), Cd (0.71), Cu (3.68), Pb (21.24), Zn (0.82) and Hg (5.29), respectively. The environmental risk assessment developed throughout the PERI method indicated that Sb, As, Hg and Pb were the main pollutants in the study area. The three quantitative risk indicators (RI, Igeo and EF) were positively correlated, and all of them indicated that PTEs had significant pollution to the local area. Thus, Sb, As, Pb, Cu, and Hg pollution should be highly concerning. Multivariate statistical analysis shows that the pollution of PTEs was mainly caused by the accumulation of tailings ponds after gold mining and smelting. The research result is of great significance for the prevention and control of soil pollution of PTEs near the tailings pond.

Distribution characteristics of heavy metals in surface soils from the western area of Nansi Lake, China

Surface soil samples collected from the western area of Nansi Lake, China, were analyzed for selected heavy metals including As, Cd, Pb, and Zn, to determine their spatial distributions and environmental effects. The average concentrations of As, Cd, Pb, and Zn in soil were 13.21 mg/kg, 0.20 mg/kg, 23.94 mg/kg, and 79.95 mg/kg, respectively. The concentration of As, Cd, and Zn was approximately 1.44-, 2.33-, and 1.25-fold higher than its background values in study area, respectively. Meanwhile, the concentrations of heavy metals progressively decreased from east to west within the study area, in a step-function distribution. The differences in the heavy metal distribution characteristics might be caused by the lake water irrigation and agricultural activities such as fertilizer and pesticide use. There were significant positive correlations between the values of OrgC, Al₂O₃, and Fe₂O₃ and concentrations of heavy metals. According to the Geo-accumulation index (I_geo) and the potential ecological risk index (PERI), Cd posed higher potential ecological risk in surface soil when compared with As, Pb, and Zn. These results could provide the scientific basis on which to evaluate the distribution of heavy metals under natural and anthropogenic influences in the surface soil near Nansi Lake, China.

Assessment of the mobility, bioaccessibility, and ecological risk of Pb and Zn on a dirt road located in a former mining area-Ribeira Valley-Brazil

The inadequate transportation of foundry slags during the construction of a mining waste landfill accounted for the presence of slags in the dirt road that connects the working district of Vila Mota to the city of Adrianópolis. The objectives of this work were to assess the lead (Pb) and zinc (Zn) contamination of the dirt. Three samples separated by 2 km were collected along a dirt road (samples: Adrianópolis, Deposit, and Plant). The conducted assays were physico-chemical parameters, pseudototal concentration, three sequential extraction procedures, and bioaccessibility assay. The laboratory data was used as input in the calculation of contamination indices risk assessment code (RAC) and potential ecological risk (Erⁱ). The dirt road presented high concentrations of Pb (mean 1426.5 mg kg^-1) and Zn (mean 4964.8 mg kg^-1). The BCR SEP (Bureau Community of Reference Sequential Extraction Procedure) method was more adequate in extracting the soluble-exchangeable fraction, and this fraction was correlated with the gastric phase. The bioaccessible fraction is mainly present in the stomach fraction and is transported to the intestinal phase. Using BCR SEP method to calculate the contamination indices, sample Deposit yielded very high risk when calculating RAC and Erⁱ for Pb (72.9% and 639.5, respectively). For Zn, high risk was obtained with RAC and very high risk for Erⁱ (42.5% and 344.2, respectively). The high content of Pb and Zn on the dirt road presents a risk to the population that uses this road, since the soil particles are easily transported, deposited on the dermis, and inhaled.

Heavy metal pollution in soil associated with a large-scale cyanidation gold mining region in southeast of Jilin, China

Different gold mining and smelting processes can lead to distinctive heavy metal contamination patterns and results. This work examined heavy metal pollution from a large-scale cyanidation gold mining operation, which is distinguished from artisanal and small-scale amalgamation gold mining, in Jilin Province, China. A total of 20 samples including one background sample were collected from the surface of the mining area and the tailings pond in June 2013. These samples were analyzed for heavy metal concentrations and degree of pollution as well as sources of Cr, Cu, Zn, Pb, Ni, Cd, As, and Hg. The mean concentrations of Pb, Hg, and Cu (819.67, 0.12, and 46.92 mg kg^-1, respectively) in soil samples from the gold mine area exceeded local background values. The mean Hg content was less than the first-class standard of the Environmental Quality for Soils, which suggested that the cyanidation method is helpful for reducing Hg pollution. The geochemical accumulation index and enrichment factor results indicated clear signs that enrichment was present for Pb, Cu, and Hg, with the presence of serious Pb pollution and moderate presence to none of Hg and Cu pollution. Multivariate statistical analysis showed that there were three metal sources: (1) Pb, Cd, Cu, and As came from anthropogenic sources; (2) Cr and Zn were naturally occurring; whereas (3) Hg and Ni had a mix of anthropogenic and natural sources. Moreover, the tailings dam plays an important role in intercepting the tailings. Furthermore, the potential ecological risk assessment results showed that the study area poses a potentially strong risk to the ecological health. Furthermore, Pb and Hg (due to high concentration and high toxicity, respectively) are major pollutants on the risk index, and both Pb and Hg pollution should be of great concern at the Haigou gold mines in Jilin, China.

International variability in diet and requirements of manganese: Causes and consequences

Manganese (Mn) is an essential trace element that is critical for human health and development. At the turn of the century when diets were based on whole grains, cereals and other traditional foods, Mn intakes (8-9mg/d) were much greater than that prevalent today (2mg/d). As societies have developed, diets have shifted as part of a nutrition transition, to those that are high in processed foods, fat, and sugar. These foods are virtually devoid of Mn. Thus, dietary Mn has declined substantially throughout the world, as confirmed by several wide-scale, total diet studies. International variability in dietary Mn is considerable, due to tremendous diversity in food and culture. In countries where fruit and vegetable intake may be limited, i.e. the United Kingdom, populations may ingest much lower levels of Mn (1.4mg/d) as compared to Asian cultures (4mg/d) which have an abundance of plant foods in their food supply and cuisine. The bioavailability of Mn must be considered, including chemical form, oxidation state, mineral-mineral interactions, presence of dietary components and traditional food processing techniques (milling, germination, malting, fermentation). Manganese toxicity is a public health problem that results from exposure to a naturally high water source or contaminated environment of the soil and/or drinking water. In contrast, inadequate intake is associated with adverse health effects such as diabetes, metabolic syndrome, poor birth outcomes and possibly, cancer. Future studies are recommended to set dietary standards for this mineral in countries that lack recommendations to help achieve optimal health.

Ecological risk, source and preliminary assessment of metals in the surface sediments of Chabahar Bay, Oman Sea

In this study, concentrations of Aluminum (Al), Iron (Fe), Chromium (Cr), Copper (Cu), Nickel (Ni), Vanadium (V), Zinc (Zn), Arsenic (As), Cobalt (Co) and lead (Pb) in the surface sediments from Chabahar Bay were studied to assess the degree of heavy metal pollution as a consequence of natural and anthropogenic sources. Metal contents in the sediments were observed in the order of: Al>Fe>Cr>V>Ni>Zn>Cu>>As>Pb>Co. According to enrichment factor (EF), Arsenic was higher than 1.5 at some sites, indicating anthropogenic inputs. Contents of Ni, As and Cr in the some sampling sites were higher than sediment quality guideline implying adverse impacts of these metals. Based on potential ecological risk (PER), the Chabahar Bay had low ecological risk.