铬污染场地调查数据评估与暴露浓度估计

针对某铬污染场地调查采样得到的1 269个土壤w(TCr)和w〔Cr(Ⅵ)〕,分别采用检出限替代法和Walsh's Test方法分析了未检出值和潜在的异常值.结果表明,异常值的取舍对数据的统计分析结果影响较大,结合该铬污染场地的实际情况和采样记录,最终保留了潜在异常值. 分别采用Q-Q图示法和假设检验方法探讨了该铬污染场地土壤w(TCr)和w〔Cr(Ⅵ)〕的数据分布形态发现,二者均不符合3种常见的分布形态(即正态分布、对数正态分布和Gamma分布),因此,采用基于切比雪夫不等式的非参数方法计算该铬污染场地调查数据的95%UCL(置信区间上限值),确定w(TCr)和w〔Cr(Ⅵ)〕的暴露值分别为0.285 6%和0.022 7%. 

Estimating Exposure Point Concentrations and Evaluating Survey Data for a Chromium-Contaminated Site

Non-detection values and potential outliers in the analytical results of the total chromium content and the hexavalent chromium of 1269 soil samples collected from a contaminated site were respectively analyzed by detection limit alternative method and Walsh's Test method. The results showed that the statistical analysis of survey data was seriously affected by the options of outliers. The presence of potential outlier was finally determined by the actual situation from the sampling sites and the sampling records. The distribution patterns of analytical data of contents of TCr and Cr(Ⅵ) were investigated by using the Quantile-Quantile plot and hypothesis testing methods. The results showed:the analytical results of contents of TCr and Cr(Ⅵ) in soil samples did not match with three common distribution functions (i.e., normal, lognormal and Gamma). The exposure point concentration of TCr and Cr(Ⅵ) in the contaminated soil at the site were finally calculated by the non-parametric UCL method based on the Chebyshev inequality and showed proportions of 0.2856% and 0.0227% respectively.