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.
Highlights
With the rapid development of the urbanization and industrialization process in China, high-intensity development and utilization of mineral resources and improper use of chemical fertilizers and pesticides, heavy metals containing pollutants cannot be degraded by microorganisms after entering the soil, water and other environments [1,2,3], and they are characterized by long action times, wide ranges of pollution, high concealment and difficulty in being reversed, as a result of which, the heavy metal pollution in soil becomes increasingly severe [4,5]
Province and are 4.53, 1.23 and 1.05 times those of the background values, respectively, and there is a certain degree of accumulation; the average contents of As, Cu, Mn, Ni and Zn do not exceed the background values of the soil in Qinghai Province, but a few samples are found to have excessive heavy metals by 31, 21, 43, 7 and 18 times, respectively; it indicates that these five heavy metals have an accumulation to varying degrees and will have a certain impact on the local farm and pasture products, but excessive Cr is not found in the samples
The results of the soil heavy metal harmfulness risk assessment imply that the study area on the whole is deemed to have a strong pollution risk, and individual sampling points are subject to severe–extreme pollution, so that they should be paid special attention to during environmental pollution control
Summary
With the rapid development of the urbanization and industrialization process in China, high-intensity development and utilization of mineral resources and improper use of chemical fertilizers and pesticides, heavy metals containing pollutants cannot be degraded by microorganisms after entering the soil, water and other environments [1,2,3], and they are characterized by long action times, wide ranges of pollution, high concealment and difficulty in being reversed, as a result of which, the heavy metal pollution in soil becomes increasingly severe [4,5]. Lake make the content of heavy metals lower than that in other areas of China, with the development and utilization of natural resources and the continuous development of tourism, as well as the industrial development and large population of adjacent areas, the soil ecosystem in the region around Qinghai. With the development of traffic, transportation has become one of the artificial factors affecting the content of heavy metals in the roadside soil of Qinghai Lake [9,10]. The study of heavy metals in soil is mainly concentrated in farmland and cultivated land, mining areas and areas around power plants, different urban function areas and both sides of roads, while it is less carried out in the region around Qinghai. It can be preliminarily judged that Cd and Cu in the soil of the study area may be subject to point source pollution and are obviously affected by some local pollution sources in the area and human interference
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