Estimating groundwater discharge into Minjiang River estuary based on stable isotopes deuterium and oxygen-18
Estimating groundwater discharge into Minjiang River estuary based on stable isotopes deuterium and oxygen-18
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基于稳定同位素氘和氧-18估算流入闽江口的地下水流量
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
Ma, Zhi-Yong1
中科院分区：
文献类型：
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作者：
Zhang, Bin1;Guo, Zhan-Rong1;Gao, Ai-Guo1;Yuan, Xiao-Jie1;Li, Kai-Pei1;Ma, Zhi-Yong1
通过对降水、地表水和地下水中的氢、氧-18同位素组成特征的分析，揭示降水的同位素效应，地下水的成因和演化，估算不同水体之间的混合过程和排入闽江口的地下水。夏季降水的氢、氧同位素组成以重同位素亏损较多。两种水样的δ18O和δD曲线均位于福州本地气象水线上。这两种水样分别来自闽江河口北岸山区和山前平原丘陵地区的裂隙地下水和浅层地下水。对比表明，两种类型的水样分别来自闽江口北岸的裂隙地下水和浅层地下水。从闽江口南岸山前平原和丘陵地区采集的浅层地下水样品大多落在低分子量线的右下部。低分子量线上两条拟合线的交点非常接近当地5-9月农业灌溉期间大气水同位素组成的加权平均值。结果表明，北岸地下水主要来自大气降水补给，而南岸地下水在入渗过程中同时来自灌溉水和大气降水，并伴随着不同程度的蒸发。除闽江口两侧的地下水外，南岸地下水还以大气降水补给为主。裂隙带的裂隙水也局部补给河口。将线性端元混合模型、数字高程模型和地下水文分析相结合，定量研究了地下水对河口的贡献以及不同水源之间的混合过程。模拟结果表明，河口淡水区地下水的最大混合比高达8.8%，其中裂隙水占0.4%。在河口咸水区，淡水(河流水和地下水)与海水的比例为53：47。保守估算的闽江口地下水流量为87.0m~3/S，占枯水期闽江径流量的12.8%。
Through analyzing the characteristics of deuterium and oxygen-18 composition in precipitation,surface water and groundwater,this paper will reveal the isotopic effects of precipitation,the origin and evolution of groundwater,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 δ18O 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 groundwater 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 irrigation water and meteoric water accompanied by a different degree of evaporation during the infiltration process.In addition to the groundwater from both sides of Minjiang River estuary,fracture water from the fracture zone also locally recharge into the estuary.The linear end member mixing model,the digital elevation model and the underground hydrologic 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% of the fracture water.In the saltwater zone of the estuary,the ratio of freshwater(river water and groundwater) to seawater is 53∶47,which includes approximately 1.7% of groundwater.The conservative estimate of groundwater discharge into the Minjiang River estuary is 87.0 m3/s which accounts for 12.8% of the Minjiang River runoff during the dry season.