Department of Physical Geography and Quaternary Geology, Svante Arrhenius väg 8C, Stockholm University, SE-106 91 Stockholm, Sweden.
Environ Int. 2011 Feb;37(2):435-42. doi: 10.1016/j.envint.2010.11.006. Epub 2010 Dec 4.
Limited data on the pollution status of spatially extensive water systems constrain health-risk assessments at basin-scales. Using a recipient measurement approach in a terminal water body, we show that agricultural and industrial pollutants in groundwater-surface water systems of the Aral Sea Drainage Basin (covering the main part of Central Asia) yield cumulative health hazards above guideline values in downstream surface waters, due to high concentrations of copper, arsenic, nitrite, and to certain extent dichlorodiphenyltrichloroethane (DDT). Considering these high-impact contaminants, we furthermore perform trend analyses of their upstream spatial-temporal distribution, investigating dominant large-scale spreading mechanisms. The ratio between parent DDT and its degradation products showed that discharges into or depositions onto surface waters are likely to be recent or ongoing. In river water, copper concentrations peak during the spring season, after thawing and snow melt. High spatial variability of arsenic concentrations in river water could reflect its local presence in the top soil of nearby agricultural fields. Overall, groundwaters were associated with much higher health risks than surface waters. Health risks can therefore increase considerably, if the downstream population must switch to groundwater-based drinking water supplies during surface water shortage. Arid regions are generally vulnerable to this problem due to ongoing irrigation expansion and climate changes.
关于空间广阔水系污染状况的数据有限，这限制了流域尺度的健康风险评估。本研究采用受纳体测量方法，以咸海流域（涵盖中亚大部分地区）的地下水-地表水系统为例，结果表明，由于铜、砷、亚硝酸盐的浓度较高，以及一定程度上的滴滴涕（DDT），农业和工业污染物会对下游地表水造成累积健康危害，超过了指导值。鉴于这些高影响污染物，我们进一步对其上游时空分布进行了趋势分析，研究了主要的大规模扩散机制。DDT 母体与其降解产物的比例表明，地表水中的排放物或沉积物可能是近期或正在发生的。在河水中，铜浓度在春季解冻和融雪后达到峰值。河水中砷浓度的高空间变异性可能反映了其在附近农田表土中的局部存在。总体而言，地下水的健康风险比地表水高得多。如果下游人口在地表水短缺期间必须改用地下水作为饮用水供应，那么健康风险可能会大大增加。由于持续的灌溉扩张和气候变化，干旱地区通常容易受到这个问题的影响。
