铅锌矿区土壤重金属空间变异及其污染风险评价——以四川汉源富泉铅锌矿山为例

采用地统计学中的普通克里格和概率克里格研究了汉源富泉铅锌矿区土壤重金属的空间变异特征、污染情况以及空间分布的影响因素。结果表明,土壤样本的Cd、Pb和Zn的平均值分别为(10.92±12.22)mg·kg-1、(657.92±1031.87)mg·kg-1和(1549.06±1915.55)mg·kg-1,空间变异呈团状分布,变异方向主要发生在东北-西南方向;3种元素高值区主要集中在北偏东矿山尾矿堆积的区域,其次为临近矿山靠近公路农田土壤部分,低值区主要集中在西北方向;研究区东北、东南区域3种重金属元素超标概率最大,西北区域超标概率最小。由于土壤重金属空间分布的影响因素主要为外源污染,对成矿元素的污染,应采取矿产资源开采与环境协调发展的途径;对伴生污染元素,应根据土壤的污染程度,采用一定富集或耐性能力的植物进行修复或开发利用,防止重金属对生态环境的污染。

基于GIS的凯江流域农田重金属污染评价研究

采用单因子污染指数法(Pi)对四川盆地丘陵区凯江流域农田耕层土壤(0~20 cm)中4种重金属污染风险进行评价,并基于GIS平台,结合反比距离权重法(IDW)、径向基函数法(RBF)、普通克里格法(OK)、析取克里格法(DK)和概率克里格法(PK)分析研究区重金属的空间分布特征。结果表明,凯江流域土壤Cd、Hg、As和Pb平均含量分别为0.35、0.10、7.77mg·kg^-1和22.54 mg·kg^-1,在空间分布上土壤Cd、As和Pb总体呈现以两个高值为中心向四周递减的趋势,土壤Hg则呈现西部高、东部低的特征。单因子污染指数评价结果表明,土样Cd、As、Hg和Pb的污染超标率(Pi≥1)分别为7.5%、0.5%、0和0。前4种空间插值的分级面积统计结果表明,研究区域土壤Pb、Hg和As均无污染超标,土壤Cd超标面积(Pi≥1)为0.14%~1.06%;概率克里格法风险评估结果表明,土壤Hg、Pb分别在Pi>0.3和Pi>0.2条件下无高风险概率,在阈值为1.0条件下,受到As污染的高概率(0.8~1.0)区域有1.05%,0.16%的区域面积有Cd污染超标风险(P=1.0)。因此,该区部分农田土壤主要受到Cd污染。

Contribution to sample failure probability plot and its solution by Kriging method

To analyze the effect of the region of the model inputs on the model output,a novel concept about contribution to the sample failure probability plot(CSFP) is proposed based on the contribution to the sample mean plot(CSM) and the contribution to the sample variance plot(CSV).The CSFP can be used to analyze the effect of the region of the model inputs on the failure probability.After the definition of CSFP,its property and the differences between CSFP and CSV/CSM are discussed.The proposed CSFP can not only provide the information about which input affects the failure probability mostly,but also identify the contribution of the regions of the input to the failure probability mostly.By employing the Kriging model method on optimized sample points,a solution for CSFP is obtained.The computational cost for solving CSFP is greatly decreased because of the efficiency of Kriging surrogate model.Some examples are used to illustrate the validity of the proposed CSFP and the applicability and feasibility of the Kriging surrogate method based solution for CSFP.