Mobilization of natural arsenic in groundwater:targeting low arsenic aquifers in high arsenic occurrence areas

研究表明饮用水中微小数量的砷会对人类健康产生不利影响.世界上居住在贫穷地区的人数超过了100万,目前他们正直接饮用来自含水层中砷离子含量(>10μg/L)非安全标准的地下水.砷有时称为毒中之王,在水环境中常常以五价氧化物形式出现.自2000年以来,许多国家开始执行更为严格的10μg/L(WHO认可的居民安全饮水标准)饮用水标准,可以确定地说,在世界范围内的饮用水中检测到砷的情况越来越多.亚洲地区砷中毒的人数比世界其他地区总和还多.最受影响的地区位于南亚和东南亚富砷带,环绕恒河一雅鲁藏布江-梅克纳河三角洲及恒河平原上游的冲洪积扇含水层、红河三角洲、湄公河和伊洛瓦底江;在中国境内包括内蒙黄河冲积盆地,山西大同盆地、新疆准噶尔盆地,其中的地下水富含砷和氟化物而引发砷中毒和氟中毒.尽管还未完全掌握其中的水文地质及生物地球化学作用的详细过程,但对大多数沉积介质含水层,在还原条件下砷离子容易从沉积介质转移到地下水中.孟加拉研究实例表明地质时期尺度的冲刷降低了沉积介质中的As和有机物含量从而形成低砷地下水.这一认识为孟加拉国的降砷策略提供了科学指导,是未来水文学,矿物学,地质学和生物地球化学方面很有意义的研究方向,并有利于地砷病区低砷地下水的可持续利用.

Mobilization of natural arsenic in groundwater: targeting low arsenic aquifers in high arsenic occurrence areas

Chronic exposure to minute amounts of arsenic in drinking water has been shown to adversely affect human health.Over 100 million people,many living in poor areas of the world,are currently exposed to unsafe level of arsenic(>10μg/L)in drinking water derived from aquifers.Arsenic,sometimes known as the King of Poisons,is a group VA element commonly found as an oxyanion in aqueous environment.Since 2000,testing for arsenic when many countries moved to implement a more stringent drinking water standard of 10 μg/L(the WHO recommended safe level for human consumption)has now unequivocally established the world wide occurrence of elevated As in drinking water,especially in ground water.More people are affected by arsenic poisoning in Asia than in the rest of the world combined.The most affected areas are the South and Southeast Asian Arsenic Belt,encompassing the deltas of the Ganges-Brahmaputra-Meghna river and the alluvial fan aquifers in the upstream areas of the Ganga plains,the deltas of the Red river,Mekong river and Irrawaddy river.In China,the alluvial basins of the Yellow River in Inner Mongolia,the Datong and Taiyuan basins of Shanxi,and the Dzungaria basin of Xinjiang produce groundwater rich in arsenic and fluoride,causing arsenicosis and fluorosis.In most sedimentary aquifers,reducing conditions-tend to mobilize arsenic from sediment to groundwater,although the detailed processes of hydrological and biogeochemical interactions remain to be fully understood.Cases studies from Bangladesh are used to illustrate that flushing over geological time scales lowers the sediment mobilizable As and organic matter content,resulting in low As groundwater.Such understanding has guided the As mitigation policy in Bangladesh.A worthwhile future research direction is to understand the hydrological,mineralogical geological and biogeochemical factors that contribute to the sustainable use of low As aquifers in endemic area of As.