Mapping the probability of exceeding environmental quality standards for Cd and Pb concentrations in soil of northern Tarim Basin using Bayesian geostatistical model

Abstract

Cadmium and Pb are important hazardous trace metals in the biosphere, and they are considered to pose a great threat to environmental health. The probability map exceeding the environmental quality standard (EQS) can be used to measure the uncertainty of the spatial distribution of soil Cd and Pb and provides useful information for decision-making for environmental management. Many researchers have focused on Cd and Pb environmental problems in agricultural soils, and there are few studies that have investigated the Cd and Pb contents exceeding EQS in natural soils of the arid desert areas of northwest China. We collected 150 samples at 0-0.05 m and 0.05-0.1 m depths in the natural solonchak soil of northern Tarim Basin, Xinjiang Province. The average concentrations of Cd and Pb were 0.45 mg/kg and 42.13 mg/kg at 0-0.05 m, and 0.29 mg/kg and 16.88 mg/kg at 0.05-0.1 m, respectively. The soil Cd and Pb concentrations were increased in comparison with the environmental background values. In addition, the soil Cd and Pb concentrations at 0-0.05 m were significantly higher than those at 0.05-0.1 m. We used the Bayesian geostatistical model to predict the spatial distribution of Cd and Pb concentrations and to map the probability of soil Cd and Pb exceeding the EQS. These probability maps are expected to be helpful for soil environmental protection of northern Tarim Basin.