区域尺度土壤环境地球化学基线估算方法及其应用研究

区域土壤环境地球化学基线可为区域尺度地球表层系统中物质变化提供丰富的数据信息,并可据此评价自然和人为活动对土壤环境中化学物质浓度变化的影响.本研究以长江、珠江三角洲地区As、Cd、Hg、Pb、Se等10种微量元素的土壤环境地球化学基线为例,探讨了运用累积频率曲线法和土壤面积加权平均法分别估算了不同类别土壤和整个区域土壤的环境地球化学基线,取得了较为一致的结果.并通过基线比较反映地球化学富集作用和人为活动对土壤环境中微量元素积累与污染的影响.较为典型的是近20年来珠江三角洲地区农业土壤中Cd由过去0.035mg/kg增加到目前的0.13～0.22mg/kg,Hg也由过去的0.045mg/kg增加到目前的0.15mg/kg左右,区域化污染趋势已经显现.

Researches on the Estimate Methods and Applications of Soil Environmental Geochemical Baseline at a Regional Scale

Regional soil environmental geochemical baseline is a base tool for studying material changes in the earth surface system at a regional scale as well as for the assessment of natural and human activities impacts on the changes of chemical elemental contents in the soil environment. We choose the Yangtze River Delta (YRD) region and Pearl River Delta (PRD) region as cases to estimate the regional soil environmental geochemical baseline of ten trace elements including As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn, Se. Two methods including cumulative distribution frequency (CDF) and average estimation based on weighted soil area were applied to estimate the baseline of different soil categories at a regional scale and the whole region, respectively. A consistent result was obtained based on the two methods, implying the feasibility of the methods for baseline estimation. The estimated baselines were further used to assess the impacts on accumulation and contamination of trace elements caused by geochemical enrichment and human activities in YRD and PRD regions. For the instance of PRD region, Cd level has increased from 0.035 mg/kg to 0.13-0.22 mg/kg and Hg level has increased from 0.045mg/kg to 0.15mg/kg by compared the baselines to soil environmental background levels investigated 20 years ago. Such a change implies a typical trend of heavy metal contamination in soil at a regional scale.