Carbonate bedrock control of soil Cd background in Southwestern China: Its extent and influencing factors based on spatial analysis

• Published in: Chemosphere (Oxford) Vol. 290; p. 133390
• Main Authors: Xia, Xueqi, Ji, Junfeng, Zhang, Chaosheng, Yang, Zhongfang, Shi, Huading
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2022
• Subjects: Background; Cadmium; Cadmium - analysis; Carbonate; Carbonates - analysis; China; Environmental Monitoring; Humans; Metals, Heavy - analysis; Soil; Soil Pollutants - analysis; Spatial Analysis; China; Soil; Spatial analysis; Cadmium; Carbonate; Background
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.133390

Previous studies have found that Cadmium (Cd) may be condensed during the processes of the weathering and soil formation over carbonate bedrock, which is a typical phenomenon in the southwest region of China. However, the extent of the high value background and the geographical factors influencing its spatial distribution are still unknown. This study collected data from the Multi-Purpose Regional Geochemical Survey (MPRGS) and the Regional Geochemistry-National Reconnaissance Program (RGNR) to investigate the extent and its controlling factors based on spatial analysis. It was found that the RGNR is an ideal data source for regional Cd background studies. Spatially, the high Cd area (Cd > 1.5 m/kg with reference of the GB15618-2018 soil environmental quality in China, 68.9 × 103 km2) coincide well with the carbonate distribution. In the total area (68.9 × 103 km2) with high Cd concentration, 89.8% is related to carbonates. The composition of parent rock, climate conditions, and landuse are controlling factors of the enrichment. The high Cd background effect of limestone is higher than that of dolomite and their effects decease with increasing detritus component they contain. Warm and humid climate in forest land helps to enrich Cd during weathering. Soil Cd concentration related to carbonate background can be predicted by major element concentrations, which is useful for differentiating Cd background from human pollution in the future soil pollution monitoring. Modelling by artificial neural network (ANN) is recommended rather than tradition multiple linear methods (LM) as the latter may have the effect of collinearity. [Display omitted] •∼90% of soil high Cd (>1.5 mg/kg) is related to carbonate bedrock.•Proportion of calcite, dolomite, and detritus influences the degree of enrichment.•Dolostone tends to have relatively low effect of Cd enrichment than limestone.•Climate and landuse type also influence the enrichment.•Cd background value can be predicted by major elements.