西藏雅鲁藏布江上游及狮泉河流域高砷地表水环境效应

Yarlung Tsangpo and Shiquan River are the most important water sources for drinking and irrigating in the southern and western Tibet. Arsenic enrichment in Shiquan River and upstream of Yarlung Tsangpo were revealed in the former studying. The concentration of arsenic can be up to 252μg/L and 83μg/L in the Shiquan River and upstream of Yarlung Tsangpo River water respectively, which is much higher than the limits value of 10μg/L for drinking water. However, the environmental effects of elevated arsenic concentration in the drainages have not been studied yet for the local special conditions of geography. According to the geography conditions, this area can be divided into two types which are the pasturing area in the upstream where is arid-semiarid higher altitude plateau and the farm belt in the downstream where is relatively lower altitude and wetness. The bioavailablity of arsenic in the environmental mediums and accumulation in food chains in different geography conditions of Tibet will be studied in this project. The environmental effects of arsenic in the different geographic conditions in Tibet will also be investigated based on a detailed arsenosis epidemiology survey and sampling in the arsenic elevated and contral areas. This study will provide some scientific evidences for the potential arsenosis prevention in this area.

西藏雅鲁藏布江及狮泉河分别是藏南及藏西最为重要的城镇及农牧饮用水源，此前的研究发现日喀则以西的雅鲁藏布江上游及狮泉河大部分流域地表水存在砷的超常富集，狮泉河水砷含量可达252μg/L，雅鲁藏布上游江支流多雄藏布河水砷含量达83μg/L，都远高于10μg/L的饮用水限值标准。由于特殊的地理环境条件，其生态环境效应研究尚属空白。本项目拟在前期研究工作基础上，对该流域不同地质地貌气候（即上游高寒干旱半干旱高原牧区和下游相对低海拔温湿河谷农区）条件下环境介质中砷的生物有效性以及食物链累积过程进行研究，根据不同区域居民饮食结构的差异计算不同地理单元高砷区居民砷摄入量，并通过详细的地方性砷中毒流行病学调查以及生物学指标分析，客观评估西藏高砷区在不同地质地貌气候条件下的环境效应，从而为该区可能存在或潜在的地方性砷中毒防治提供科学依据。

已按计划完成了该项目的主要研究内容和目标。 . 通过详细系统的野外踏勘、样品采集和实验分析，较为系统地对青藏高原主要流域（包括狮泉河、雅鲁藏布江、怒江、金沙江、澜沧江）环境介质中砷的形态、分布、运移等环境地球化学行为进行了深入细致的研究。研究表明，西藏地区部分流域砷的异常与该区强烈的地热活动有关，稀释及沉积物的吸附作用对河水砷含量降低具有重要作用，沉积物中砷的吸附相主要为铁氧化物/氢氧化物、粘土矿物和锰矿物，其中铁的相关矿物吸附了超过80%的溶解态砷。并利用吸附实验数据、河流水As含量、沉积物对砷的吸附量以及河流基础水文数据，首次对源于西藏的主要河流向下游的As输送通量进行了估算。. 通过对研究区地方性砷中毒流行病学调查，首次在西藏地区发现了饮水型地方性砷中毒人群的存在。通过对当地人群的头发、指甲等人体生物学指标中砷的含量分析，客观评估了西藏地区砷的人体健康环境效应，可为西藏地区地方性砷中毒防治提供重要的科学依据。

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