用氢氧稳定同位素评价闽江河口区地下水输入  

Estimating groundwater discharge into Minjiang River estuary based on stable isotopes deuterium and oxygen-18

作　　者：章斌[1] 郭占荣[1] 高爱国[1] 袁晓婕[1] 李开培[1] 马志勇[1] 

机构地区：[1]厦门大学海洋与地球学院,福建厦门361005

出　　处：《水科学进展》2012年第4期539-548,共10页Advances in Water Science

基　　金：福建省重点基金资助项目(2009I0025);国家自然科学基金资助项目(41072174)~~

摘　　要：通过分析闽江河口区降水、地表水和地下水的氢氧稳定同位素特征,揭示降水的环境同位素效应和地下水的形成演化规律,定量评价河口区多种水体的混合过程及地下水输入量。夏季的降水氢氧同位素组成相对贫化,呈现出降雨量效应。在δ18O与δD关系图上,闽江北岸基岩裂隙水、平原及丘陵区浅层地下水均落在福州降水线上,而南岸平原及丘陵区浅层地下水大部分落在福州降水线右下方,其拟合线与降水线交点与5～9月农灌期降水氢氧同位素加权值接近,表明北岸地下水主要来自降水补给,而南岸地下水同时接受灌溉水和降水补给,并在入渗过程中经历了不同程度的蒸发作用。闽江河口段除接受两岸地下水补给外,局部河段还接受断裂带裂隙水补给。将线性端元混合模型、数字高程模型和地下水文分析法结合起来定量评价地下水的输入和各水体的混合过程,结果显示,在河口段淡水区,地下水混合比率上限为8.8%,其中包括0.4%的断裂带裂隙水;在河口段淡咸水混合区,淡水(河水、地下水)和海水的混合比为53∶47,其中地下水的保守混合比率为1.7%;枯水期闽江河口段地下水保守输入量为87.0 m3/s,是闽江径流量的12.8%。Through analyzing the characteristics of deuterium and oxygen-18 composition in precipitation, surface wa- ter and groundwater, this paper will reveal the isotopic effects of precipitation, the origin and evolution of groundwa- ter, and estimate the mixing processes between various water bodies and groundwater discharge into the Minjiang River estuary. The hydrogen and oxygen isotopic compositions of precipitation are more depleted in heavy isotopes during summer, showing the so-called amount effect. The 8180 versus δD plots for two types of water samples are on the Fuzhou local meteoric water line （LMWL）. The two water types are the fissure groundwater and the shallow groundw- ater respectively collected from a mountainous area in the north bank of the Minjing River estuary and a piedmont plain and hilly land. By contrast, the shallow groundwater samples collected from a piedmont plain and hilly land in the south bank of the Minjiang River estuary mostly fall in the lower right side of LMWL. The intersection points of the two fitted lines on LMWL are so close to the weighted average of isotopic composition of meteoric water during the local agricultural irrigation period from May to September. The result shows that the groundwater in the north bank is mainly recharged from meteoric water, while the groundwater in the south bank is simultaneously recharged from both irriga- tion water and meteoric water accompanied by a different degree of evaporation during the infiltration process. In addi- tion to the groundwater from both sides of Minjiang River estuary, fracture water from the fracture zone also locally re- charge into the estuary. The linear end member mixing model, the digital elevation model and the underground hydro- logic analysis are combined to quantitatively study the groundwater contribution to the estuary and the mixing processes among various water sources. The modeling results show that the maximum mixing ratio of groundwater is up to 8.8% in the freshwater zone of the estuary including 0.4%

关 键 词：地下水 河水 海水 氢氧稳定同位素 线性端元混合模型 地下水输入通量 闽江河口区 

分 类 号：P641.3[天文地球—地质矿产勘探]