A Study on Heavy Metals in the Surface Soil of the Region around the Qinghai Lake in Tibet Plateau: Pollution Risk Evaluation and Pollution Source Analysis

Abstract

In order to reveal the pollution characteristics and sources of heavy metals in surface soil of the region around the Qinghai Lake in Tibet Plateau, improve the prevention awareness and measures of local residents and urge the local government to implement necessary prevention and control measures, nine heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) in the surface soil samples of the region around the Qinghai Lake have been collected and analyzed. The methods such as statistic method, geo-accumulation index method, Nemerow index method, potential ecological risk index method, human health risk evaluation method and positive matrix factor analysis model (PMF) have been used to evaluate pollution characteristics and potential risks and analyze the sources of heavy metals. The results are shown below. First, the average contents of heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) in soil are 11.73 ± 3.78, 0.62 ± 1.40, 12.38 ± 3.68, 41.35 ± 13.01, 19.33 ± 8.92, 546.96 ± 159.28, 21.18 ± 7.04, 21.86 ± 6.61 and 63.51 ± 19.71 mg·kg−1, respectively. Compared with the background values of the soil environment in Qinghai Province, it can be seen that there is an accumulation of these heavy metals to varying degrees, which is the most serious in Cd, Co and Pb. Second, the analysis of the geo-accumulation index and Nemerow index indicates that the heavy metals in the surface soil of the region around the Qinghai Lake have reached the level of heavy pollution, mainly polluted by Cd, and the accumulation of heavy metal pollution in the north, south, southwest and southeast of the study area is more serious. Third, the results of potential ecological risk evaluation show that the study area as a whole is classified as an area with high ecological risk, and Cd contributes the most to the overall risk. In fact, the heavy metals in the soil of the study area produce no noncarcinogenic and carcinogenic health risks to human health, and children and adults may be exposed to these risks by the mouth. Finally, the PMF results reveal that the sources of heavy metals in the study area include the sources of agricultural production, the nature, coal burning and transportation, with a contribution rate of 43.10%, 25.34%, 19.67% and 11.89%, respectively.

Assessment of Contents and Health Impacts of Four Metals in Chongming Asparagus—Geographical and Seasonal Aspects

“…The formula for calculating the carcinogenic health risk index is as follows: where CR refers to the carcinogenic health risk index of metals in the exposure pathway, and SF is the carcinogenic slope factor (Cd: 6.1, As: 1.5) [ 38 ]. When CR < 1.0 × 10 −6 , it means that the metal has no carcinogenic risk; when 1.0 × 10 −6 < CR < 1.0 × 10 −4 , it means that the carcinogenic risk is acceptable; when CR > 1.0 × 10 −4 , it means the metal has carcinogenic risk.…”

Distribution Pattern and Enrichment Mechanism of Selenium in Topsoil in Handan Se-Enriched Belt, North China

“…In addition, the burning of coal may also be a source of Cu, Ni, and Zn in soils around coal-fired power plants. Cr and As in soil are less contaminated by external sources and are most likely induced by natural processes such as weathering and erosion of sedimentary rocks [77]. Therefore, the first group is part of a mixed natural and anthropogenic source.…”

“…was identified as a major source of PTEs contamination in soil [78]. Specifically, Pb is a critical component of gasoline and diesel, and Pb from vehicle exhaust can infiltrate the soil following atmospheric deposition [77]. Furthermore, Cd is a common component of agricultural products such as herbicides and fertilizers [79].…”

Potential Sources, Pollution, and Ecological Risk Assessment of Potentially Toxic Elements in Surface Soils on the North-Eastern Margin of the Tibetan Plateau

“…Therefore, soil PTE pollution on the Qinghai–Tibet Plateau should not be ignored. Existing studies have mainly focused on investigating PTEs in Qingha-Tibet soils [ 4 , 23 , 24 ], glacial soils [ 25 ], railways [ 22 ], highways [ 15 ] and the litter catchment [ 26 ]. And found that the cryosphere (glaciers, permafrost, ice, and snow) was the essential source of PTEs during climate warming [ 27 ].…”