基于地理信息系统技术的新疆焉耆绿洲农田土壤重金属污染评价和潜在生态风险预警

GIS technology-based research on the heavy metal pollution evaluation and ecological risk warning assessment of farmland soils in Karashahar oasis,Xinjiang

在新疆焉耆绿洲采集农田土壤,测定As、Cd、Cr、Cu、Mn、Ni、Pb和Zn等8种重金属的含量。基于地理信息系统(GIS)技术,并采用污染负荷指数(I_(PL))、潜在生态风险指数(I_R)和生态风险预警指数(I_(ER))对焉耆绿洲农田土壤重金属污染状况进行评价。结果表明,焉耆绿洲农田土壤Cd是《土壤环境质量标准》(GB 15618—1995)二级标准限值(0.60mg/kg)的10.13倍。Cd、Cr、Ni、Pb和Zn分别是新疆灌耕土背景值的50.67、1.40、1.33、2.63、4.92倍。农田土壤Cd和Zn呈现重度污染,Pb为中度污染,Cr和Ni为轻度污染,Cu为轻微污染,As与Mn为无污染。重金属I_(PL)平均值为2.00,呈现轻度污染。重金属I_R平均值为318.38,属于较强风险。重金属I_(ER)平均值为4.83,属于中度预警。重金属I_(PL)、I_R与I_(ER)空间分布均呈现明显的地带性分布格局。Cd是污染水平与生态风险等级最高的重金属,表明焉耆绿洲农田土壤Cd污染风险必须给予关注。

Farmland soil samples were collected from Karashahar oasis, Xinjiang, and the contents of 8 heavy metal elements （As, Cd, Cr, Cu, Mn, Ni,Pb and Zn） were determined. The heavy metal of farmland soils in Karasha-har oasis were analyzed based on geographic information system （GIS） technology,pollution load index （7PL） ,poten- tial ecological risk index （I r） and ecological risk warning index （IER）. Results indicated that the average contents of Cd in farmland soils of Karashahar oasis was 10.13 times of the Grade II standard value （0.60 mg/kg） of“Environ-mental quality standard for soil”（GB 15618-1995）, whereas the average contents of Cd,Cr, Ni, Pb and Zn were 50.67, 1.40, 1.33, 2. 63 and 4.92 times of the background values for irrigation soil in Xinjiang, respectively. For farmland soils,Cd and Zn were in heavy pollution level, with Pb in moderate pollution level,Cr and Ni in light pollution level,Cu in slight pollution and As and Mn in no pollution level. The average value of IPL for heavy metals in farmland soil was 2.00, which showed a light pollution level. The average value of IR was 318.38, indicating a strong ecological risk situ-ation. The average value of I ER was 4.83 , implying a moderate warning situation. The spatial distribution of I pl,7r and I ER showed obvious zonal distribution patterns. Cd was a heavy metal element with the highest level of pollution and ecological risk. Therefore, the pollution risk of Cd should be a major concern during the process of agricultural production in Karashahar oasis.