基于PPC模型与RI指数法的茶产地土壤重金属污染评价

以某喀斯特山区茶产地表层土壤为研究对象,依托GIS空间分析技术,采用投影寻踪聚类(PPC)模型和潜在生态风险指数(RI)法两种较新的评价方法对土壤重金属污染进行综合评价。投影寻踪聚类模型将236个土壤样本中的Hg、As、Cd、Pb、Cr含量指标作为多维投影参数寻求其最优投影方向,由投影指标函数得出土壤重金属污染投影值来反映重金属含量的特征,建立投影寻踪聚类模型,从而得出研究区土壤重金属污染实际现况,结合潜在生态风险指数法,进一步对研究区土壤重金属污染风险程度和演变趋势进行预测。结果表明:(1)在指标投影方向上Hg和As对研究区土壤污染影响最大,Cd对土壤污染影响最小;(2)根据PPC评价标准,研究区土壤环境质量状况良好,无污染的样点区域达到96.61%,清洁占总样点数的30.08%,尚清洁占总样点数的66.53%;(3)在潜在生态风险上存在低度、中度,分别占采样点的89.41%和10.59%,风险程度较低,但有向中度演变的趋势;(4)在污染情况上,清洁和尚清洁的空间分布广阔,轻度污染进行内插后空间分布不明显。本文研究结果有利于综合评价该地的土壤环境质量状况,在实践中将为喀斯特山区的土壤资源的管理和茶叶种植区的合理布局起到参考作用。

Assessment of Heavy Metal Pollution in Tea-planting Soils Based on PPC Model and RI Index Method

Taking the topsoils of the tea-planting area in Karst mountainous regions of Guizhou Province as the study object, based on GIS spatial analysis technology, projection pursuit cluster (PPC) model and potential ecological risk index (RI), as two new evaluation methods, were used to comprehensively evaluate the heavy mental pollution in soil. PPC model takes the contents of Hg, As, Cd, Pb and Cr in 236 soil samples as the multi-dimensional projection parameter to seek its optimal projection direction, obtains the projection value of soil heavy mental pollution by the function of projection index to reflect the characteristic of heavy metal content, establishes the poly class model of projection pursuit, knows the actual situation of soil heavy mental pollution, and further to predict the pollution degree of soil heavy metals and its evolution trend in the study area combined with the method of potential ecological risk index. The results showed that: 1) Hg and As had the greatest influences on soil pollution in the projection direction of index, while Cd had minimal impact on soil pollution. 2) according to the criteria of PPC evaluation, soil environmental quality in the study area was in good condition, the areas of no-pollution level accounted for 96.61% of the study area, the numbers of clean level and still clean level accounted for 30.08% and 66.53% of the total samples, respectively. 3) There were low level and moderate level in the potential ecological risk, accounted for 89.41% and 10.59% of the total samples, respectively, their risk degree were low, but trended to worsen into moderate level. 4) On pollution level, the clean level and still clean level distributed widely in the study area, the spatial distribution of light pollution level was not obviously after interpolation. The above results are favorable for the comprehensive evaluation of soil environmental quality and can play a reference role in the management of soil resources and the rational distribution of tea-planting in Karst areas.