基于稳健统计的土壤环境背景值研究及应用

Determination and Application of Soil Environmental Background Concentrations Based on Robust Statistics

使用稳健统计方法中的位置估计量和尺度估计量对我国某受到人为干扰的地下水水源地C层土壤重金属的背景值进行了研究．结果表明，稳健统计方法对样本中的异常值有较高的耐抗性，计算结果与常规方法相近，因而适用于某些人为干扰地区的土壤环境背景值研究．对该水源地背景值的计算表明，该地区C层土壤Cu，Ph，Cd，Cr，As和№的背景值中心分别为21．2，32．5，0，103，60．3，11．0和0．012mg／kg，其中w（Pb），W（cd）和W（As）高于山东省平均值．6种重金属的阈值分别为29．0，43．7，0．143，93．5，21．0和0．080mg／kg，均小于全国平均上限值，但其中Pb，Cr，As的阈值高于土壤环境质量一级标准．基于该地区背景值的污染累积指数评价表明，该地区主要重金属污染物为Pb和Hg，主要污染区为污水沟渠周边，污染深度为1-3m．

The methods of location and scale estimates from robust statistics were applied to determine the background concentrations of heavy metals in the C soil horizon in an anthropogenically influenced groundwater resource area. The results showed that the robust statistical method was much more resistant to exceptional values in the samples. And, the new method had similar predictions to conventional methods. Therefore, it can be applied to the study of soil environmental background concentrations for certain areas influenced by human activities. The background concentrations in the deep stratum in the investigation area were 21.2 mg/kg for Cu, 32.5 mg/kg for Pb, O. 103 mg/kg for Cd, 60.3 mg/kg for Cr, 11.0 mg/kg for As and 0.012 mg/kg for Hg, with values of Pb, Cd and As higher than the average values in Shandong province. The thresholds were 29.0 mg/kg for Cu, 43.7 mg/kg for Pb, 0.143 mg/kg for Cd, 93.5 mg/kg for Cr, 21.0 mg/kg for As and 0.080 mg/kg for Hg, which were lower than those of the national averages. However, the upper limits of Pb, Cr and As were higher than the primary soil environmental quality standards. Based on these values, the pollution accumulation index showed that the primary heavy metal pollutants in this area were Pb and Hg, and the main contaminated area was located around the sewage ditches in depths of 1 m to 3 m.