永定河上游山间盆地地下水质量评价与水化学特征分析

摘要

为准确掌握永定河上游山间盆地地下水质量状况，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65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。开展了TDS、Ca2+、NO3-和硬度与取样深度的相关性分析。结果表明，延庆盆地内水样基本均属于偏碱性水，垂向上，延庆盆地地下水由浅到深，地下水水质逐渐变好，且随着深度增大，水样的pH值有增大趋势。横向上，上游地下水水质好于中游，中游好于下游；深层地下水已经出现较差和极差点。在上游地区基本以HCO3-Ca·Mg为主，水质趋同性好，分层特征较弱；在中游地区，大部分中层地下水中的Na+浓度升高，开始出现HCO3-Ca·Na·Mg型，水质分层特征明显。到了下游地区， Na+和Mg2+浓度快速升高，许多水样表现为HCO3-Na·Mg·Ca型和HCO3·SO4-Na·Ca·Mg型。越往下游，地下水的化学组分更趋于复杂，一方面表征了其多源输入的特征，另一方面反映了人类活动影响强度的增强。%In order to evaluate the groundwater quality of Yongding River upstream mountain basin and to discuss the characteristics of its distribution by the view of hydrochemistry, a total of 65 groundwater samples, collected within YanQing basin in the dry period of 2008 according to the geological and hydrogeololgical condition of Yanqing basin, were classify shallow, middle and deep groundwater respectively. Based on the data, the groundwater quality is evaluated by the method of F value. The mean and variance of main chemical constituens of groundwater samples were presented.. Also , the relationship between the depth of the samples and the concentration of TDS,Ca2+, Cl-, NO3-,pH, EC, hardness were analysed. The results show that most groundwater belong to Alkaline water. From shallow to middle, and then to deep, the quality of groundwater in Beijing is getting better. In the horizontal, from the fanhead area to middle area and then to the edge of the fan, groundwater become worse. The worst groundwater samples, i.e. V class of groundwater have been appeared in deep groundwater aquifer.At the fanhead area, the consternation of groundwater is low, the Layered characteristics is not very obvious, the watertype is HCO3-Ca·Mg mainly. At the middle area of the basin, the consternation of Na+and Cl- become higher, HCO3-Ca·Na·Mg water appear, the difference of different aquifers is becoming obvious. The groundwater at the edge of the fan appeared complex relatively, several samples were HCO3-Na·Mg·Ca and HCO3· SO4-Na·Ca·Mg, this results is identical with the Characteristics of the multi-source input on the other hand, this reflect the influence of human activities intensity enhancement.