龙口市污水灌溉区农田重金属来源、空间分布及污染评价

Source Analysis,Spatial Distribution and Pollution Assessment of Heavy Metals in Sewage Irrigation Area Farmland Soils of Longkou City

采集龙口市污水灌溉区农田土壤,分析测定土壤pH和重金属含量,以采集的70个土壤样点为研究对象,根据多元统计中的相关分析和主成分分析探究研究区重金属的来源;采用地统计理论与GIS空间插值相结合的方法研究重金属元素的空间结构和分布特征;最后利用内梅罗指数法和改进的模糊综合评判法做重金属污染评价.结果表明,研究区内9种重金属元素在土壤中均有一定程度的富集,其中重金属Cd的均值是当地背景值的3.06倍,富集情况最为明显;指数法进行的污染评价显示Cu、Cd和Pb的综合污染指数分别为7.06、6.10和5.54,三者均属重度污染;相关分析和主成分分析结果显示,Cu、Zn和Pb、Cd主要受人为因素影响,污水灌溉是它们的共同污染因素,前两者为农业生产中化肥农药的过量使用与长时间的累积作用,而北部煤矿开采和煤矸石的堆积产生的污染以及电镀、机械制造等工业污染是后两者的污染来源;Co、Cr、Mn、Ni和As主要是受成土母质等自然因素的影响;据模糊综合评判的结果,研究区70个样点,有13个是中污染程度,23个属于轻污染,28个是警戒程度,6个样点处在安全范围内;从空间分布上看,重金属含量的高值区主要集中在黄水河下游的诸由观镇和徐福镇,说明污水灌溉给当地土壤造成了一定程度的重金属污染.

Farmland soils in sewage irrigation area at Longkou City were collected,soil pH together with the heavy metal content were tested. Taking 70 soil points as the study object,this paper investigated the source of heavy metals in this area based on the correlation analysis and PCA of multivariate statistical analysis theory. We studied the spatial variation and distribution characteristics about heavy metals using both the theory of geostatistics and GIS spatial interpolation method. At last,the heavy metal pollution was evaluated in the way of Nemerow Index and improved fuzzy evaluation method. It turned out that,9 kinds of heavy metal elements in the soil of research area had a certain degree of enrichment,among them the average of Cd was 3. 06 times as high as the background value,and its enrichment was most severe. The result of Nemerow Index showed that,the values of comprehensive pollution index of Cu,Cd and Pb respectively were 7. 06,6. 10 and 5. 54,and they all belonged to high levels of pollution. According to the results of correlation analysis and principal component analysis,Cu,Zn together with Pb,Cd were mainly affected by human factors,sewage irrigation was their common pollution factor,the pollution sources for the first two heavy metals included excessive use of chemical fertilizers and pesticides in agricultural production and the accumulation of long time,whereas pollution from northern coal mining and coal gangue piled up as well as plating,machinery manufacturing and other industrial pollution were the pollution sources of the latter two elements.Other elements（ Co,Cr,Mn,Ni and As） were mainly influenced by natural factors such as parent material. Comprehensive evaluation results showed that,among the 70 points,13 points had moderate pollution,23 points belonged to light pollution,28 points were at alert level,6 points were in the safe range. From the perspective of spatial distribution,high value areas of heavy metal contents were mainly concentrated in towns of Zhuyouguan and Xufu. This showed that,sewage irrigation caused a certain degree of heavy metal pollution to local soil.