北京市通州区地下水分层质量评价及水化学特征

Assessment of Groundwater Quality of Different Aquifers in Tongzhou Area in Beijing Plain and Its Chemical Characteristics Analysis

为准确掌握通州地区地下水质量状况,并从水化学角度探讨其分布特征.基于研究区的地质和水文地质条件,将2008年6月采集的151个地下水样分为浅、中、深层.按照F值评分法进行了分层综合质量评价.并采用数理统计方法,分别计算了上游、中游和下游每一个含水层特征指标算数平均值和方差.结果表明研究区内地下水均属于偏碱性水,地下水由浅到深,水质的均一性增强,水质逐渐变好.浅、中、深层地下水超Ⅲ类水的面积分别为884、599和94 km2.研究区超标组分主要为TDS、硬度、氨氮、氟化物和总铁(包含Fe3+和Fe2+),且多数超标样点属于浅层和中层水样.浅层地下水化学类型主要为HCO3-Ca·Mg型和HCO3·Cl-Ca·Na·Mg型,中深层地下水化学类型则主要由于Na+、SO2-4和Cl-浓度的上升,多数表现为HCO3-Na·Ca型和HCO3·SO4-Na·Ca型共同组成.浅层地下水水质主要受人类活动的影响,而中、深层地下水水质变差的原因则是人类活动和天然劣质水存在的双重因素所致.

In order to evaluate the groundwater quality of Tongzhou area in Beijing Plain and to discuss the characteristics of its distribution by the view of hydrochemistry,a total of 151 groundwater samples,collected within study area in the dry period of 2008according to the geological and hydrogeololgical condition of Tongzhou area,were classified as shallow,middle and deep groundwater,respectively. Based on the data,the groundwater quality was evaluated by the method of F value. The mean and variance of main chemical constituents of groundwater samples were presented. Almost all the quaternary groundwater of Chaobai river pluvial fan belonged to the alkaline water type. The evaluation results based on the analysis results showed that from shallow to deep,the quality of groundwater in Beijing became better. The total areas of groundwater belonging to class Ⅳ and Ⅴ area were 884 km2,599 km2and94 km2respectively for shallow,middle and deep groundwater. The evaluation results showed that the main exceeding chemical constituents were TDS,hardness,NH+4,F-and total Fe. Most exceeding samples belonged to middle and deep aquifers. The main types of shallow groundwater were HCO3-Ca·Mg-and HCO3·Cl-Ca·Na·Mg,while the chemical types of mid-deep groundwater were mostly HCO3-Na·Ca-and HCO3·SO2-4-Na·Ca type due to the increased Na+,SO2-4and Cl-concentration. Study results showed that the quality of shallow groundwater became worse mainly due to human activities. The deterioration of groundwater quality in mid-deep aquifers was due to both human activities and natural occurrence of poor-quality water.