Source apportionment of soil heavy metals in abandoned mining areas in Dafan Mountain of Anhui Province based on the UNMIX model

Abstract: This study aims to find out the content and source of heavy metals in the soil of the abandoned alum mining area in Lujiang County of Anhui Province, in China. A smart grid distribution was used to divide the research area into the 50 typical feature points with the center of Dafan Mountain. Five typical heavy metal elements (As, Cd, Cu, Mn, and Ni) were determined in the local soil. An UNMIX model was selected to apportion the potential sources and their contributions to soil heavy metals. A Kriging interpolation in the ArcGIS geo-statistical module was also utilized to determine the spatial distribution of soil heavy metals, further verifying the accuracy of the source analysis. The results showed that: 1) The average contents of As, Cd, Cu, Mn, and Ni were 47.38, 2.03, 30.89, 77.76, and 4.08 mg/kg in the 0-10 cm soil layer, and 50.62, 2.24, 30.82, 71.39, and 3.62 mg/kg in the 10-20 cm soil layer. The average contents of As, Cd, and Cu were all higher than the local background values. Specifically, the median contents of As and Cd were 1.28 and 7.17 times the risk screening value of soil pollution. 2) There were three major pollution sources of heavy metals in the 0-10 cm soil layer in the study area. Source 1 played a dominant role in Cu, indicating a traffic source with a contribution rate of 5.75%. There were higher contributions of Mn and Ni in Source 2, indicating the coal-burning source with a contribution rate of 49.86%. The contribution of Source 3 to As and Cd was higher than other metals. Source 3 was presented the weathering of rocks effects with a contribution rate of 44.39%. 3) There were two sources of heavy metals in the 10-20 cm soil, including the mixed sources of soil parent material and garbage (Source 1), as well as leaching, ore mining, and transportation (Source 2), where the contribution rates were 47.46% and 52.54%, respectively. 4) According to the land use types and human activities in the study area, the combination of receptor model and spatial analysis was used to comprehensively analyze the sources of heavy metals in the soil.