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Purpose: Beichuan River is a primary tributary of Huangshui River and a secondary tributary of Yellow River. However, the soil in the watershed has been polluted due to decades of agricultural and urbanization development. Effective pollution investigation and source control of the Beichuan River basin is the key to soil conservation. In this study, the spatial distribution and physical and chemical properties of potentially toxic metals (PTMs) in soil of Beichuan River basin were studied for the potential ecological risks and source apportionment. The results can provide guidance for the environmental protection of Beichuan River and can also provide technical support for the contamination of similar river basins. Materials and methods: The contents and ecological risk of nine PTMs (Cr, Hg, As, Pb, Ni, Cd, Co, Cu, and Zn) in 37 surface soil samples were investigated with several evaluation methods (geo-accumulation index, potential ecological risk index, and toxic risk index). The fraction species of soil samples were treated by Tessier sequential extraction. The potential sources of the nine PTMs were explored with a combination of Pearson's correlation coefficient, geostatistics, and source analysis method. Results and discussion: Four potential contamination source were identified in the study area: (1) industrial source of chemical industry and smelting industry related to coal combustion; (2) traffic emission and atmosphere deposition; (3) agricultural activities, which included fertilizers, pesticides and livestock manure; and (4) the natural source. The source apportionment indicated that the non-point source contamination in agriculture has an obvious influence on the PTMs in the Basin. The risk assessment demonstrated that the Cd and Cr were the heavy metal with serious pollution. The fingerprinting of the PTMs and physicochemical property in soil can be analyzed to two cluster, with the different physical and chemical properties and the contamination. Conclusions: The risk assessment results and the source apportionment indicated that PTM contamination occurred in the southeast and northwest of the study region. The results can help distinguish the sources of the contamination, which will achieve the regional contamination control and ecological protection of soil in extreme weather areas of the plateau. Meanwhile, this study has a guiding significance for the high-quality development of the Yellow River. [ABSTRACT FROM AUTHOR]

This study analyzed the contents of Cd, Co, Cr, Cu, Ni, Pb, Zn, Hg and As in 39 surface soil samples in the lower reaches of Huangshui River basin. The results showed that the proportions of Cd, Co and Cr exceeding the standard values in all samples were 17.95%, 17.95% and 12.82%, respectively. The geo-accumulation index analysis showed that 58.33% of Cd was above moderate pollution level. 64.10% of Cr was at the level of moderate pollution and above. Improved Nemerow index evaluation showed that all soil samples had ecological risk of heavy metal pollution, and 64.10% of the samples were in moderate or above pollution level. The results of potential ecological risk index showed that Cd posed a higher ecological risk than other heavy metals. There were 2.6% of the samples with high risk, and the proportions of considerable, moderate and low ecological risks were 12.8%, 2.6% and 82%, respectively. Correlation analysis and PMF analysis showed that the heavy metals in soil were mainly from atmospheric deposition, agricultural and traffic activities, industrial emissions and natural sources. The health risk of soil heavy metals is low, and the health risk caused by any exposure pathway is acceptable. In contrast, Cr, As and Pb were the most important factors contributing to non-carcinogenic risk, and As, Cd and Cr were the main carcinogenic risk factors. Children have higher health risks than adults, and the main route of exposure is ingestion. [ABSTRACT FROM AUTHOR]

Huangshui River, a tributary of the upper Yellow River, is one of the most important water resources conservation and recharge area of the Yellow River. In recent decades, agricultural cultivation and urbanization in Huangshui River Basin led to soil contamination. The Huangshui River were also seriously polluted, all at Grade V for many years before. Quantitative assessment model of heavy metal contamination in environment can provide guidance for regional policy making. In the present study, the distribution characteristics of potentially toxic metals in soil of Huangshui River plateau region were studied, and the contamination risk of heavy metals was evaluated. 113 top-soil samples were collected and surveyed for toxic element concentrations. The high coefficient of variation (CV) of Cd (274.5), Co (225.1), Pb (115.9), Hg (139.3) showed the high dispersion of heavy metal. The study built the distribution model of species sensitivity in the study area and calculated the environmental non-effect concentration (NOEC). Meanwhile, the ecological risk based on the environmental non-effect concentration and the background value (BC) was compared to explore the difference. The RI result based on the background value showed a maximum value of 1491, which is much higher than the ecological risk 520 based on the SSD result. The results indicated that there are some limitations in the risk evaluation of selecting the standard value or background value as the evaluation factor, which may exaggerate the risk. At the same time, the method was also suitable for the soil in other regions under the premise that the sensitivity distribution model could be constructed. Health risks of adults and children were made with the health risk assessment model for the two land use types. The hazard index (HI) of element Cr for children was 1.06, which was potential non-carcinogenicity to human health. The CR of Cd, Cr and As were above 10E-6 for children and adults, which was viewed as a risk range. This study established a credible risk assessment system, which can provide guidance for soil and ecological health development and policy making. [ABSTRACT FROM AUTHOR]