The spatial distribution pattern and influencing factors of Chromium (Cr) in topsoil of eastern and central China

Abstract

Chromium (Cr) is a potentially hazardous heavy metal, and identifying its spatial driving factors is essential for effective soil management. However, China has a vast territory, and the spatial distribution of soil Cr is influenced by differences in geological background and environmental conditions, as well as the superposition of anthropogenic activities. This poses significant challenges in accurately identifying the factors that influence Cr distribution and their interactions. This study utilized large-scale geochemical data comprising 376,743 samples to investigate the spatial distribution pattern of Cr in topsoil on a regional scale, particularly in eastern and central China. Furthermore, the contributions of various factors to Cr distribution were quantified, and their interrelationships were clarified through the method that combines Geodetector and interpretable machine learning model. The results indicate that TFe₂O₃ concentration and parent rocks are the main factors controlling Cr distribution. In the topsoil developed from mafic rocks, the contributions of soil properties, climate, anthropogenic activities, and topography to the distribution of Cr concentration are 41.9%, 31.6%, 13.5%, and 13.0%, respectively. The partial least squares path model reveals that whether the impacts are direct or indirect, climatic and topographical factors consistently influence soil Cr concentration in the same direction. Industrial and agricultural activities directly increase soil Cr levels, while soil properties indirectly reduce Cr concentration through migration or dilution. Our findings provide crucial insights into the regional spatial variability of soil Cr and offer scientific evidence for formulating effective soil remediation and management strategies.