矿区地下水硝酸盐来源的解析

Tracking the Source of Nitrate Pollution in Groundwater in Mining Area Based on Dual Isotope and IsoSource Model

石拐矿区是内蒙古重要的煤炭供应地,地下水受到矿山活动的影响,面临着污染和水质异常等问题,为保障该地区居民的饮水安全,矿区地下水的硝酸盐污染分布特征分析和污染源追踪具有重要意义。该文通过双同位素对石拐矿区的地下水硝酸盐污染源进行定性分析,分析其污染特征和同位素特征值,利用IsoSource模型定量评估地下水中硝酸盐中不同来源的贡献率。结果表明,研究区有40%的取样点硝酸盐超标,有显著的空间特征和时间特征。沿着地下水流向,矿区下游及居民区上游硝酸盐浓度超标,居民区硝酸盐浓度在雨季有明显增幅。地下水的δ^(15)N-NO_(3)^(-)的变化范围为0.07‰~2.69‰,δ^(18)O-NO_(3)^(-)的变化范围在-5.09‰~-2.85‰。根据不同污染源的同位素值范围,确定土壤有机氮和NH_(4)^(+)硝化是地下水硝酸盐的主要来源,且距离矿区越近,土壤有机氮的贡献率越高。

Shiguai mining area is an important coal supply area in Inner Mongolia.The groundwater is affected by mining activities and faces problems such as pollution and abnormal water quality.To ensure the safety of drinking water for residents in the area,the analysis of the distribution characteristics of nitrate pollution in the groundwater and the tracking of pollution sources are of important significance.The groundwater nitrate pollution source in Shiguai mining area was qualitatively tracked through dual isotopes,and its pollution characteristics and isotopic characteristics were analyzed.The IsoSource model was used to quantitatively evaluate the contribution rates of different sources of nitrate in groundwater.The results showed that 40%of the sampling points in the study area exceeded the nitrate standard,with significant spatial and temporal characteristics.Along the flow of groundwater,the nitrate content in the downstream of the mining area and the upstream of the residential area exceeded the standard.The variation range ofδ^(15)N-NO_(3)^(-)of groundwater is 0.07‰~2.69‰,and the variation range ofδ^(18)O-NO_(3)^(-)is-5.09‰to-2.85‰.According to the isotope range of different pollution sources,it is determined that soil organic nitrogen and NH_(4)^(+)nitrification are the main sources of groundwater nitrate,and the closer to the mining area,the higher the contribution rate of soil organic nitrogen.