Distribution Characteristics of Heavy Metals and Pb Isotope in Profile Soils from a Mining and Smelting Area in Northwestern China

The distribution characteristics of typical heavy metals (HMs) and Pb isotopic compositions in profile soils from different areas were investigated in Baiyin district, northwest China. The soil samples from the ore district and the sewage irrigation area showed an obvious enrichment of HMs in different depths, and the difference in the longitudinal migration depth of Pb, Cu, Zn, and Cd was insignificant, which might be due to the migration behavior of HMs mainly controlled by carbonate in alkaline soil. With the sewage irrigation activities, the content of soil organic matter was no longer the main controlling factor for the migration behavior of HMs. In ore district and sewage irrigation area, the HMs contents of nonresidual fractions in topsoil were much higher than that in the corresponding deep soil, which indicated that HMs activities in topsoil were significantly high. The Pb isotopic compositions of profile soils indicated that the long-term mining and smelting activities remained the main source of vertical enrichment of HMs in Baiyin district. Moreover, the Pb isotope ratios 206Pb/207Pb of nonresidual fractions (1.1359-1.1916) were all lower than that in the corresponding residual fractions (1.1641-1.2010), showing the characteristics that HMs input from anthropogenic source were in different degrees. The Pb isotopic compositions of residual fractions in the topsoil of ore district and sewage irrigation area (1.1641 and 1.1703) were between the two end-members composed of background soil and local mineral samples, which suggested that some anthropogenic HMs might enter into the residual components in the soil that was greatly affected by the input of HMs.

To the question of raw material sources of mining and smelting centers of the Paleometal Epoch in Central Kazakhstan

The subject of this research is the copper deposits, copper-ore resource, and sources of alloying raw materials for mining and smelting production of the Paleometal Epoch in Central Kazakhstan, namely within the Kazakhstan mining and smelting region and Zhezkazgan-Ulytau mining and smelting center. The article provides the interim results of comprehensive research of geoarchaeological production facilities in the territory of copper deposits within the Zhezkazgan-Ulytau mining and smelting center, which allow determining the peculiarities of metallogenic complexes that used to be potential objects of the development of copper-ore reserves during the establishment of copper metallurgy, as well as making a predictive assessment of mineral raw materials potential of the region. The initial premise of this research lies in the authors' pursuit to integrate natural scientific methods of research into the field of humanities to the maximum effect via studying smelting slags and ore relics from the ancient settlements of the region for the purpose of reconstructing the mining and smelting process of the Bronze Age in Central Kazakhstan. The authors offer the variants of localization of the mineral raw materials complex of Zhezkazgan-Ulytau mining and smelting center within the Kazakhstan mining and smelting region. Based on examination of the ores and smelting slags of Bronze Age settlements in Central Kazakhstan, the authors believe that the main copper raw materials in the Zhezkazgan-Ulytau region were the oxidized malachite-azurite and rich sulfide ores, as well as the zones of secondary sulfide enrichment of copper sandstones of the Zhezkazgan ore region. The conducted research allow to get closer to establishing patterns of localization of various types of copper deposits and development of copper-ore resources for mining and smelting production of Zhezkazgan-Ulytau region during the Paleometal Epoch.

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.

Contamination Features and Source Apportionment of Heavy Metals in the River Sediments around a Lead-Zinc Mine: A Case Study in Danzhai, Guizhou, China

The spatial patterns, ecological risks, and sources of heavy metals (HMs), including Pb, Zn, Mn, Cu, Cd, Hg, and As in river sediments, were identified around a lead-zinc mine of Danzhai, Guizhou, China. The concentrations of selected HMs and their coefficient variations indicated that the river sediments around this typical lead-zinc mine were obviously contaminated with HMs. Anthropogenic activities had further enhanced the accumulation of HMs. The higher contents of the most common selected HMs were mainly distributed in the area close to the lead-zinc mine. Based on the combined evaluations of the single factor pollution index, geo-accumulation index, and potential ecological risk index, it indicated that the ecological risks of Hg, Cd, Zn, and Pb were high or extremely high, and of Mn, Cu, and As were slight or none in the sediments around this lead-zinc mine. It was found that lead-zinc mining and smelting activities, coal mining activities, and agricultural activities (livestock and poultry breeding) are the primary sources of selected HMs, based on the results of correlation analysis together with principal component analysis (PCA) and positive matrix factorization (PMF) model. The pollution of HMs in the river sediments around a lead-zinc mine was predominantly caused by lead-zinc mining and smelting activities. Therefore, for environmental persistence, lead-zinc mining and smelting activities should be given careful consideration and under close surveillance.