万山汞矿区表层土壤汞迁移

水土流失是土壤退化的根本原因,是最严重的生态环境问题之一。目前对喀斯特山区土壤侵蚀研究已经进入成熟阶段,但对以典型喀斯特山区为背景、汞污染严重地区因土壤侵蚀发生的汞迁移的研究却很少。本文基于GIS平台,借助通用土壤流失方程(RU-SLE)模型评估研究区侵蚀强度,对万山汞矿区(167.4km2)因土壤侵蚀造成的汞迁移进行了研究。结果表明,万山土壤侵蚀模数为0～600884t·km-2·a-1,微度侵蚀和剧烈侵蚀面积占全区总面积的76.6%,其中剧烈侵蚀对土壤总侵蚀量的贡献率达到90.5%。全区因土壤侵蚀发生的土壤汞(THg)流失量高达505kg·a-1,迁移速率为3.02kg·km-2·a-1。土地利用方式和坡度是影响汞流失的重要因素。旱地和灌木林最易发生汞流失,流失量分别为175和319kg·a-1。本研究不仅为当地治理水土流失、制定水土保持方案奠定了可靠的科学依据,也为当地环境汞污染治理提供了有力的数据支持。

Surface soil mercury translocation in Wanshan mercury mining area of Southwest China

Water and soil loss is the main cause of soil degradation, and one of the most serious ecological environmental problems. Many achievements have been obtained in the study of soil erosion in Karst region, but few studies are conducted on the mercury (Hg) translocation induced by soil erosion in seriously Hg-polluted areas of typical Karst regions. Selecting the Wanshan Hg mining area (167.4 km2) of Southwest China as study area and by using geographic information system (GIS) and a revised universal soil loss equation (RUSLE), this paper assessed the intensity of soil erosion and the surface soil Hg translocation via soil erosion. In the mining area, soil erosion modulus was in the range of 0-600884 t·km-2·a-1, and the areas with slight and severe erosion occupied 76.6% of the total, among which, the area with severe erosion made up 90.5%. On annual basis, the surface soil Hg loss was up to 505 kg·a-1, and the Hg loss rate was 3.02 kg·km-2·a-1. Land use type and slope gradient were the main factors affecting the Hg loss, and Hg loss easily occurred on the farmland and shrub land in steep zones, with an amount of 175 and 319 kg a-1, respectively. This study not only provided scientific basis for the control of water and soil erosion in the study area, but also supplied data support for the management of Hg pollution of local ecosystems.