广西平果铝赤泥堆场对岩溶含水层污染风险评价

Evaluation of the effect of the red mud stack field on the karst groundwater pollution in Pingguo County,Guangxi

为了评估赤泥堆场建设对地下含水层的污染,对堆场周边进行水文地质勘察。采用地球物理探测、钻探、示踪试验等多种技术手段查明堆场周边岩溶管道的分布规律及管道水的流向,并采用压水试验和注水试验测得含水层的渗透系数,在此基础上通过数值模拟计算出各月流经堆场下方的岩溶水流量。采用达西定理计算得到赤泥淋沥液穿透防渗层的时间约为42 a,远超堆场的服务年限(25 a),表明堆场防渗层的设计是合格和可靠的。在赤泥堆场建设20 a后再次对堆场下游及其周边的溶潭水进行地下水水质监测,结果也证实堆场下游及其周边地下水未因赤泥渗漏而污染。

In order to evaluate the groundwater pollution likeliness and degree due to the construction of the red mud dumps,we have conducted a detailed hydro-geological investigation around the red mud stack fields. During the hydro-geological investigation,the distribution of karst pipelines and the flow directions of groundwater in them were identified by geophysical prospecting,drilling,tracer test and other technical measures. The permeability coefficient of karst aquifer was also determined by the water pressure tests and the injection tests. After that,we have been keeping the monthly groundwater current volume checked under the red mud dumps by way of hydro-geological numerical simulation. In the simulation process,a GMS software coupling with a trench package has been used to simulate the groundwater system working manner including the fissure flow（ linear flow） and pipeline flow（ nonlinear flow）. Then the penetration time of red mud leakage through the impervious barrier in red mud stack has been calculated according to Darcy law. The results of our simulation show that the penetration time is 42 years,which is much longer than the service life of the red mud dumps,which is calculated as just 25 years. Seeing the fact that when the stack fields finish their design service life,they would have been given up and then would be covered by impervious geomembrane. From then on the stacked mud won ＇t no longer be chased away by wind or drenched by rains,though there would remain leakage in red mud and be drained away by the expected waste conduit to be laid out.This implies that there will be no longer leakage penetrating through the impervious barrier and the groundwater in the area under study,neither will there be threatened by the pollution of the red mud dumps. That is why the design of the impervious barrier in the red mud dumps should be regarded as eligible and reliable. The results of our investigation of the groundwater quality in the puddles in the past 20 years after the red mud dumps construction and the monitoring data show that the groundwater around and the downstream of the red mud dumps haven＇t been polluted by the red mud leakage.