基于UNMIX模型的地质高背景地区土壤重金属源解析

采矿活动和高地质背景被认为是造成喀斯特地区土壤重金属污染的重要因素. 为了探究采矿活动和成土母质对喀斯特地区土壤重金属积累的影响，利用UNMIX模型和空间分析相结合的方法对广西北部典型金属工业区—刁江流域105个土壤样品中重金属(Cd、As、Pb、Cr、Ni)的分布特征与主要来源进行了研究，并将UNMIX模型源识别结果直接纳入GIS进行空间分析，对比采样点的主导源空间分布与污染源之间的关联性. 结果表明:①研究区土壤中w(Cd)、w(As)、w(Pb)、w(Cr)、w(Ni)的平均值为1.21、19.4、42.1、80.9、31.9 mg/kg；研究区土壤污染以Cd和As复合污染为主，个别采样点存在轻度的Pb污染. ②母质类型、土壤类型、土壤pH和工矿企业是影响重金属积累的重要因素. 对比分析可知，由碳酸盐岩母质发育而来的土壤和偏碱性土壤中重金属的平均含量较高；人为土中Cd、As和Pb的积累较明显，铁铝土中会出现Cr和Ni的共富集；污染影响区内w(Cd)、w(As)、w(Pb)偏高. ③源解析分析显示，研究区土壤重金属存在两类污染源，分别为土壤母质源(源1)、工农业混合源(源2)，占比分别为68.45%和31.55%；土壤母质源(源1)对Cr和Ni的贡献占主导作用；工农业混合源(源2)对As、Pb的贡献高于其他重金属；研究区Cd的积累由土壤母质源(源1)和工农业混合源(源2)共同主导. 研究显示，研究区土壤重金属污染水平整体较高，这既与碳酸盐岩中固有的高重金属浓度有关，也与碳酸盐岩风化过程中残留富集导致的浓度放大效应有关，并且研究区多年的工矿业活动与河水灌溉进一步加剧了研究区农田的重金属污染程度. 

Source Apportionment of Soil Heavy Metal(loid)s in High Geochemical Background Area Based on the UNMIX Model

Mining activities and high geological background are considered to be the key factors causing accumulation of heavy metal(loid)s in karst areas. To explore the influence of mining activities and soil parent material on the accumulation of soil heavy metal(loid)s in karst areas, this paper analyzed the distribution characteristics and main sources of Cd, As, Pb, Cr and Ni in 105 soil samples based on the UNMIX model and spatial analysis method. The source identification results of the UNMIX model were directly incorporated into GIS for spatial analysis, and the relationship between the dominant source spatial distribution of sampling sites and pollution sources was compared. The results showed that: (1) The average contamination of w(Cd), w(As), w(Pb), w(Cr) and w(Ni) in the study area were 1.21, 19.4, 42.1, 80.9, 31.9 mg/kg, respectively. Specifically, the pollutants in the study area were mainly Cd and As, and there was a slight Pb pollution at some sites. (2) Parent material type, soil type, soil pH, and industrial influence were important factors affecting the accumulation of heavy metal(loid)s in the study area. The soils developed from carbonate rocks showed higher average content of heavy metal(loid)s than other parent material, and alkaline soil also exhibited higher heavy metal(loid)s content. The anthrosol exhibited a significant accumulation of Cd, As, and Pb. The co-enrichment of Cr and Ni has been reported to occur in the ferrallitic soil. (3) Source analysis showed that there were two sources of heavy metal(loid)s in the study area, which was soil parent material source (source 1) and industrial and agricultural mixed source (source 2), accounting for 68.45% and 31.55%, respectively. Source 1 played a dominant role in the contribution of Cr and Ni in the soil. The contribution of source 2 to As and Pb was higher than that of others. The accumulation of Cd was jointly dominated by the soil parent material source (source 1) and industrial and agricultural mixed sources (source 2) in the study area. Our results indicated that the concentrations of heavy metal(loid)s in the surface soil of the study area are high, which is due to the inheritance of high concentration of heavy metal(loid)s in carbonate rocks, and the secondary enrichment of pedogenic processes was another dominant factor of the enrichments for heavy metal(loid)s. Furthermore, metallurgical activities and direct river irrigation have aggravated the contamination of the surrounding soil.