Spatial distribution, source identification, and risk assessment of heavy metals in the cultivated soil of the Qinghai–Tibet Plateau region: Case study on Huzhu County

Abstract

Assessing the risk and sources of heavy metals in cultivated soil is important for the agricultural development of the Qinghai–Tibet Plateau. A survey was conducted in this study to determine the spatial distribution and possible sources of heavy metals in the agricultural soils in Huzhu county, a representative agricultural suburb in Qinghai-Tibet Plateau. A total of 120 surface soil samples were collected, soil pH and concentrations of chromium(Cr), cadmium(Cd), plumbum(Pb), arsenic(As), and hydrargyrum(Hg) were analyzed. The pollution risk degree of heavy metal pollution was also evaluated. The mean concentrations of the heavy metals were 70.8, 0.24, 23.7, 12.2, and 0.08 mg/kg for Cr, Cd, Pb, As, and Hg, respectively, higher than the soil background values of Qinghai Province with the exception of As, but lower than the guideline values of Chinese standard for soil contamination of agricultural land. The sampling point contamination risk of the heavy metals showed a site feature, and most sampling points of Cd and Hg was exhibit polluted. The potential ecological risk index indicated that most of the cultivated soils have low and moderate ecological risks. Multivariate and geostatistical analysis suggested that Cr, As, and Pb were due mainly to soil parent materials, Cd contamination was caused by agricultural and transportation activities, and Hg contamination was caused by coal combustion and industrial activities. The results of this study is a basis for undertaking more effective and accurate heavy metal control strategies to protect the safety of agricultural ecosystems. • Concentrations of heavy metals were measured in cultivated soils of Huzhu County in the Qinghai-Tibet Plateau. • The cultivated soils were mainly polluted by Cd and Hg. • Spatial heterogeneity of heavy metals was closely related with human activities.