Tracing organic matter composition and distribution and its role on arsenic release in shallow Cambodian groundwaters
Tracing organic matter composition and distribution and its role on arsenic release in shallow Cambodian groundwaters
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DOI：
10.1016/j.gca.2016.01.010
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发表时间：
2016-04-01
影响因子：
5
通讯作者：
Ballentine, Christopher J.
中科院分区：
文献类型：
--
作者：
Lawson, Michael;Polya, David A.;Ballentine, Christopher J.
利用溶解有机碳的生物地球化学过程被广泛认为是南亚和东南亚沉积物中砷释放到浅层地下水的原因。该地区大部分人口稠密国家的主要饮用水源中，这种已知致癌物已积累到危险的高浓度。据认为，有机物的地表来源和沉积来源对这些含水层中的溶解有机碳都有贡献。然而，负责驱动砷释放的有机碳源的识别仍然是谜，甚至有争议。在这里，我们提供了迄今为止最广泛的审讯地下和地表沃茨的同位素签名在柬埔寨的一个已知的砷热点。我们目前的氚和放射性碳的数据表明，通过池塘和/或粘土窗口的补给可以运输年轻的，表面衍生的有机物进入地下水的深度为44米的自然流动条件下。年轻的有机质占主导地位的溶解有机碳库在地下水，是在这些地表水源附近，我们认为这可能是一个区域的关系。在远离地表水接触的地方，溶解有机碳代表了年轻的地表和较老的沉积衍生有机物质的混合物。因此，地下水-地表水的相互作用强烈地影响着溶解有机碳的平均年龄，以及这种年龄在整个现场的空间分布。砷的动员率似乎是由这些地下水中存在的溶解有机物的年龄控制。浅层地下水（20米）中的砷浓度。我们认为，虽然砷的释放率是最大的浅层含水层沉积物中，砷的释放也发生在更深的含水层沉积物，因此仍然是一个重要的过程中控制砷的空间分布在东南亚的地下水。我们的研究结果表明，任何改变地下水补给来源或补给时间尺度的人为活动也可能导致这些地下水中溶解有机碳的天然组成发生变化。这种变化有可能影响该地区当前地下水砷危害的空间和时间演变。(C)2016年6月，作者。爱思唯尔有限公司出版
Biogeochemical processes that utilize dissolved organic carbon are widely thought to be responsible for the liberation of arsenic from sediments to shallow groundwater in south and southeast Asia. The accumulation of this known carcinogen to hazardously high concentrations has occurred in the primary source of drinking water in large parts of densely populated countries in this region. Both surface and sedimentary sources of organic matter have been suggested to contribute dissolved organic carbon in these aquifers. However, identification of the source of organic carbon responsible for driving arsenic release remains enigmatic and even controversial. Here, we provide the most extensive interrogation to date of the isotopic signature of ground and surface waters at a known arsenic hotspot in Cambodia. We present tritium and radiocarbon data that demonstrates that recharge through ponds and/or clay windows can transport young, surface derived organic matter into groundwater to depths of 44 m under natural flow conditions. Young organic matter dominates the dissolved organic carbon pool in groundwater that is in close proximity to these surface water sources and we suggest this is likely a regional relationship. In locations distal to surface water contact, dissolved organic carbon represents a mixture of both young surface and older sedimentary derived organic matter. Ground-surface water interaction therefore strongly influences the average dissolved organic carbon age and how this is distributed spatially across the field site. Arsenic mobilization rates appear to be controlled by the age of dissolved organic matter present in these groundwaters. Arsenic concentrations in shallow groundwaters (20 m) groundwaters. We suggest that, while the rate of arsenic release is greatest in shallow aquifer sediments, arsenic release also occurs in deeper aquifer sediments and as such remains an important process in controlling the spatial distribution of arsenic in the groundwaters of SE Asia. Our findings suggest that any anthropogenic activities that alter the source of groundwater recharge or the timescales over which recharge takes place may also drive changes in the natural composition of dissolved organic carbon in these groundwaters. Such changes have the potential to influence both the spatial and temporal evolution of the current groundwater arsenic hazard in this region. (C) 2016 The Authors. Published by Elsevier Ltd.