飞凤山处置场地下水水化学、氢氧稳定同位素特征及其指示意义

Groundwater Hydrochemical and Hydrogen and Oxygen Stable Isotopic Features and Implications in Feifengshan Disposal Repository

飞凤山低中放固体废物处置场是中国西南地区极为重要的核废料处置场。处置场位于四川省北部山区,地层是一套志留系泥页岩,属于传统意义上的低渗透性岩类,但处置场地下水特征与低渗透性岩类中地下水活动规律不符。为了研究处置场地下水特征与补排关系,通过现场调查、取样分析等手段,测定处置场及其周边地下水的化学特征及同位素,分析地下水补给、径流、排泄关系,掌握地下水的基本规律。研究表明:飞凤山处置场地下水化学类型主要为HCO3-Ca型,处置场降水井地下水化学类型为HCO3-(K+Na)·Ca;研究区氢氧同位素数据表明飞凤山地区凉水井一带及处置场T06取样点附近受降雨直接快速补给,其他区域大气降水入渗地下过程中一定程度受到了蒸发作用的影响;处置场降水井地下水来源虽然是大气降雨,但其补给高程较其他区域更高,且径流通道是处置场SE-NW方向的裂隙密集带。在区域及处置场范围,存在一种地下水通过裂隙密集带径流补给的形式,从而形成了处置场降水井附近的远源补给。

Feifengshan low-intermediate radioactive solid waste disposal repository,located in the northern mountain areas in Sichuan Province,is an extremely important nuclear waste disposal in Southwest China. The stratum ofthe disposal site is a set of Silurian shale,belonging to the traditional low permeability rock,however,thegroundwater characteristics of the site did not conform to the groundwater activity law in low-permeability rock. To study the groundwater characteristics of the site and the relationship between recharge and discharge,various of measures were taken,such as on-site investigation and sample analysis,to determine the groundwater characteristics and isotopes at the disposal site and its surroundings,to analyze the relationship between groundwater recharge,runoff and discharge,and to grasp the basic laws of groundwater. The study demonstrated that themainly groundwater hydrochemical type of the disposal site was HCO3-Ca and that of the precipitation well was HCO3- (K + Na) ·Ca;the hydrogen and oxygen isotopic data of the study areas indicated that the cold water wells and the T06 sampling site were directly recharged by rainfall,while the other areas were more or less affected by evaporation during the atmospheric precipitation into ground;The ground water source of the precipitation wells was rainfall and the recharge elevation was higher than other areas and the runoff channels were the fissure dense zones passing through the SE-NW direction. Within the region and the disposal site,there was ground water replenished through the fissure of the site,which was regarded as a remote source supply for the precipitation wells of the disposal site.