广东省土壤砷元素空间变异与环境意义

利用广东省260个土壤剖面数据,开展区域尺度下的土壤砷（As）元素质量分数的空间分布和垂直变异研究。结果显示,研究区土壤砷的几何平均质量分数为10.4 mg.kg-1,高于全国的平均水平9.6 mg.kg-1。表层土壤As的上基线质量分数为23.4 mg.kg-1。土壤As的空间分布特征主要决定其成土母岩的类型,主要表现为A、B、C 3层土壤As的空间展布形式相似,高As背景质量分数主要分布于石灰岩和砂页岩地区。此外,由A层至C层,As质量分数呈逐渐增加的趋势（由低到高依次为10.4 mg.kg-1,10.7 mg.kg-1,11.3 mg.kg-1）,但无底层富集特征,这种垂直变异特征与低有机质含量和强烈的土壤侵蚀作用有关。计算得出,研究区由土壤侵蚀引发的流入周边水体的土壤As每年可高达1 040 t。

Spatial variation and environmental indications of soil arsenic in Guangdong province

Total of 260 soil profiles were reported to investigate the arsenic spatial distribution and vertical variation. The arsenic geometric mean concentration of 10.4 mg·kg^-1 was higher than that of China. An upper baseline concentration of 23.4 mg·kg^-1 was estimated for surface soils. Arsenic spatial distributions presented the similar patterns that high arsenic concentration mainly located in limestone and sandshale areas, indicating that soil arsenic distribution was dependent on bedrock properties. From A- to C-horizon arsenic geometric mean concentrations had an increasing tendency of 10.4, 10.7 to 11.3 mg·kg^-l. This vertical variation may be related to the lower soil organic matter and soil degradation and erosion. Consequently, the soil arsenic export into surface and groundwater would reach 1 040 t·a^-1 in the study area.