基于PMF模型的兰州耕地土壤重金属来源解析

为了分析Pb、Cd、Cr、Hg、As、Cu、Zn、Ni等8种重金属的污染状况、空间分布及污染来源.2019年9月共采集382个兰州耕地表层土壤样品，并测定其重金属含量.结果表明：①兰州市耕地土壤重金属Pb、Cd、Cr、Hg、As、Cu、Zn、Ni的平均含量分别为20.96，0.24，0.05，6.40，8.36，48.57，101.92，34.34mg/kg，其中Hg的均值超过国家土壤污染风险筛选值，Cd、Hg、Cu、Zn、Ni的均值超过兰州市土壤背景值.内罗梅综合指数表明研究区耕地52.62%样点呈现轻度污染，37.70%样点呈现中度污染，3.66%样点呈现重度污染，无重金属污染的样点占6.02%.潜在生态风险指数表明13.09%的样点属于轻微生态风险，68.85%的样点属于中等生态风险，17.54%的样点属于强生态风险，0.52%的样点属于很强生态风险.②基于PMF模型可知8种重金属有4种主要来源，其中Pb、Cd、Zn、Ni以交通运输源为主，贡献率分别为52.4%、50.7%、56.7%和50.2%；Hg以农业活动和医疗设备源为主，贡献率为83.7%；Cr、Cu和Ni以自然源为主，贡献率分别为81.2%和61.3%和49.8%；As以工业活动源为主，贡献率为68.3%.③从空间分布来看，研究区内除Cr外，Pb、Cd、As、Cu、Zn、Ni在城关区和七里河区都有高值区出现，其中Zn和Ni的高值范围较广，可能与人为影响有关；Hg在城关区、安宁区、七里河区以外的研究区内均有高值出现.

Sources appointment of heavy metals in cultivated soils of Lanzhou based on PMF models

In order to analyze the pollution status, spatial distribution and sources of heavy metals (Pb, Cd, Cr, Hg, As, Cu, Zn, Ni), 382 cultivated land surface soil samples were collected from Lanzhou in September 2019 and their heavy metal content was determined. The results showed that the mean concentrations of heavy metals Pb, Cd, Cr, Hg, As, Cu, Zn, and Ni in the samples were 20.96, 0.24, 0.05, 6.40, 8.36, 48.57, 101.92, and 34.34mg/kg, respectively. Among them, the mean concentrations of Hg exceeded the national soil pollution risk screening value, mean concentrations of Cd, Hg, Cu, Zn, and Ni exceeded the local soil background values. The comprehensive index revealed that 52.62% of sample points in the study area showed low pollution, 37.70% of the samples showed moderate pollution, 3.66% of the samples showed severe pollution, and only 6.02% of the samples were free of heavy metal pollution. The potential ecological risk index analysis indicated that 13.09% of the samples were with low ecological risks, 68.85% of the samples were with moderate ecological risks, 17.54% of the samples were with high ecological risks, and 0.52% of the samples were with extreme ecological risks. The source analysis based on the PMF model revealed that there were four main sources of these eight heavy metals. Transportation sources were the main source of Pb, Cd, Zn, and Ni with contribution rates of 52.4%, 50.7%, 56.7%, and 50.2%, respectively. Agricultural activities and medical equipment were the main source of Hg with contribution rates was 83.7%. Natural sources were the main source of Cr, Cu, and Ni with contribution rates of 81.2%, 61.3%, and 49.8%, respectively. Industrial activity was the main source of As with contribution rates of 68.3%. In terms of spatial distribution, except Cr, the concentration of Pb, Cd, As, Cu, Zn, and Ni were higher in Chengguan District and Qilihe District, particularly, the concentrations of Zn and Ni had relatively wide high-value due to possible human impacts. Hg had high concentration values in research areas outside of Chengguan District, Anning District, and Qilihe District.