Environmental geochemistry baseline and pollution assessment of soil heavy metals in typical river source area of northeastern Hunan Province

A total of 87 surface soil samples were collected from typical river source areas in northeast Hunan Province, and the distribution characteristics of soil heavy metals (Cd, Pb, Cr, Hg and As) were analyzed. The environmental geochemical baselines of five heavy metals were determined by the standardized method of reference elements and the cumulative frequency curve method, and the environmental pollution status was evaluated with the environmental geochemical baselines and environmental background values, respectively. The mean values of soil Cd, Pb, Cr, Hg and As were 0.197, 41.065, 130.512, 0.294, 11.633mg/kg, respectively. The environmental geochemical baseline values of soil Cd, Pb, Cr, Hg and As were 0.196, 41.065, 126.301, 0.283, 9.931. The pollution evaluation results based on the environmental geochemical baseline values show that 79.31% of the points in the typical river source area of northeast Hunan have a comprehensive pollution index ranging from 1.0 to 2.0, which is in the mild pollution level, and the pollution indexes of the five heavy metals are all less than 1, which is in the non-pollution level. The environmental geochemical baseline determines the evaluation benchmark for small-scale spatial areas, which can compensate for the pollution caused by the lack of baseline values. The environmental geochemical baseline determines the spatial small-scale regional evaluation benchmark, which can make up for the ambiguity of its assessment results due to the lack of benchmark values. © 2023 Chinese Society for Environmental Sciences. All rights reserved.