典型锰矿区周边农田土壤重金属污染风险评价及其来源分析

为探究典型锰矿区周边农田土壤重金属污染状况及主要来源，以重庆市秀山县溶溪锰矿区周边农用地的土壤为研究对象，测定了土壤中镉、砷、铅、铬、镍、铜、锌和锰的含量，采用了多种分析方法（包括多元统计分析、单因子污染指数法、内梅罗指数法和地质累积指数法）研究土壤重金属污染水平、分布特征，并结合皮尔逊相关性分析、PCA和APCS-MLR分析，解析研究区土壤重金属的主要来源和贡献率。结果表明，锰矿区周边水稻田土壤Mn均值含量显著低于其它农作物土壤（p＜0.05），其他7种重金属均值含量在各农田土壤中均无显著差异（p＞0.05）。内梅罗综合污染指数表现为红薯地（13.34）＞大豆地（2.73）＞玉米地（2.19）＞水稻田（1.80），重金属污染程度由大到小表现为：Mn＞Cd＞As＞Ni、Zn＞Pb、Cr、Cu。地累积指数由大到小表现为：Mn＞As＞Pb＞Zn＞Ni＞Cd＞Cu＞Cr。污染源解析表明，研究区土壤中Cd、Pb、Ni、Cu、Zn和Mn之间存在显著正相关关系（r=0.5~0.8、p＜0.01），主要受到矿业开采等活动影响，贡献率分别为80.0%、55.3%、57.9%、61.4%、73.3%和98.4%。As和Cr存在显著正相关关系（r=0.548、p＜0.01），主要受到土壤母质等自然因素的影响，贡献率分别高达88.5%和76.3%。因此，应重点加强对Mn和Cd的来源管控和污染防治。此外，红薯地8种重金属污染累积程度均高于其他农作物土地，应开展相应整治，防止持续对红薯地土壤造成污染。

Pollution Evaluation and Source Analysis of Heavy Metals in Farmland Soils around the Typical Manganese Mining Area

In order to explore the pollution status and main sources of heavy metals in farmland soils around the Rongxi manganese mining area in Xiushan county, Chongqing. The contents of Cd, As, Pb, Cr, Ni, Cu, Zn and Mn in soils were determined, and the single factor pollution index, Nemerow pollution index and Muller index were used to evaluate the pollution level and distribution characteristics of heavy metals. Meanwhile, correlation analysis, PCA and APCS-MLR were employed to investigate the sources and contribution rate of heavy metals in soils. The results show that Mn average concentration in paddy soil is significantly lower than that in other farmland soils (p<0.05), and the average concentrations of other 7 heavy metals have no significant difference among different farmland soils (p>0.05). The comprehensive Nemerow pollution index is sweet potato field (13.34) > soybean field (2.73) > corn field (2.19) > paddy field (1.80), the sequence of heavy metal pollution is Mn > Cd > As > Ni, Zn > Pb, Cr and Cu. The accumulation degree of heavy metals in soil is Mn > As > Pb > Zn > Ni > Cd > Cu > Cr. The analysis of pollution sources shows that there is a significant positive correlation between Cd, Pb, Ni, Cu, Zn and Mn (r =0.5~0.8, p<0.01), which are mainly affected by mining activities, with contribution rates of 80.0%, 55.3%, 57.9%, 61.4%, 73.3% and 98.4%, respectively. Meanwhile, there is a significant positive correlation between As and Cr (r=0.548, p<0.01), which is mainly affected by natural factors such as soil parent material, with contribution rates of 88.5% and 76.3%, respectively. Therefore, it is necessary to strengthen the source control and pollution prevention of Mn and Cd. In addition, the accumulation degree of eight heavy metals pollution in sweet potato land is higher than that in other crop land, thus corresponding remediation should be carried out to prevent continuous pollution of sweet potato soil.