Geodetector based identification of influencing factors on spatial distribution patterns of heavy metals in soil: A case in the upper reaches of the Yangtze River, China

With the acceleration of urbanization and industrialization, soil heavy metal pollution has become a serious problem threatening ecological security. Identification of influencing factors on the variations and distribution of heavy metals in soils becomes a critical problem to be solved. Here, the geographical detector (geodetector) method was applied to study the influencing factors on the spatial distribution pattern of heavy metals (As, Cd, Cr and Hg) in soils in the upper reaches of the Yangtze River, China. Based on the geodetector model, eight influencing factors were selected, including 5 natural factors of pH, precipitation, soil type, rock type and landform, 2 anthropogenic factors of land use and road density, and 1 comprehensive factor of deposit density). The influence of each factor on the spatial distribution of 4 heavy metals shows that 1) for As, the dominant influencing factors were pH and deposit density, and the secondary influencing factors were precipitation and rock type, 2) for Cd, precipitation had the greatest explanatory power, while pH, land uses, road density and deposit density also had significant effects, 3) for Cr, the main influencing factors were rock type and soil type, and the secondary factors were pH and deposit density, 4) for Hg, the deposit density and rock type dominated its distribution. Compared with single factors, the interaction between factors significantly improved the explanatory power of heavy metals. Taking Cd as an example, the single factor contributions of road density and precipitation are 12.4% and 13.2%, respectively, while the explanatory power of their interaction was as high as 49.8%. This finding indicated that the geodetector can be a helpful method for us to understand the factors affecting the distribution patterns of heavy metals in soil, and it can further service for land management and pollution remediation.