标题：SOURCE TRACING OF SOIL HEAVY METALS BASED ON SPATIAL STRUCTURE CHARACTERISTICS: A CASE STUDY OF SEWAGE IRRIGATION AREA IN SOUTHEAST SUBURB OF BEIJING
摘要：Spatial distribution of soil heavy metals is controlled by different factors, and a single structure is insufficient to characterize the real spatial structure influenced by different factors. On this basis, 376 surface (0-20 cm) soil samples were collected in a typical sewage irrigation area (southeast of Beijing) and analyzed for total As, Cd, Cu, and Pb concentrations to study the spatial structure characteristics and the influence of multi-scale factors of soil heavy metals. The results showed that the spatial structures of soil all As, Cd, Cu, and Pb concentrations appeared as nested structures. The spatial distributions of Cd, Cu, and Pb concentrations were closely related to river flow trend and indicated strong spatial correlations in the northwest-southeast direction. High-value areas were mainly distributed in the middle north region of the study area (Liangshui River basin), west of the study area (Yongding River basin), and northeast of Tongzhou District. Activities of sewage irrigation and soil parent materials were the main sources of soil heavy metals in the study area; the two scale factors co-existed and made spatial structures of Cd, Cu, and Pb concentrations nested ones. The spatial autocorrelation distances of Cd, Cu, and Pb concentrations dominated by small-scale factor such as sewage irrigation were 7.60, 11.35, and 9.49 km. However, spatial autocorrelation distances dominated by large-scale factor such as soil parent material were 23.18, 26.65, and 31.70 km. The sources of As contamination should be further studied. By analyzing the different influencing scale factors of the spatial distribution of soil heavy metal content in the area studied, the sources of soil heavy metal pollution can be clearly traced.
