Advances in Earth Science ›› 2012, Vol. 27 ›› Issue (12): 1344-1352. doi: 10.11867/j.issn.1001-8166.2012.12.1344

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Environmental Tracers (δ 2H-δ 18O, δ 34S, δ 13C) as Indicators of Seawater Intrusion Processes in the Coastal Karst Area

Yang Jilong 1, Han Dongmei 2, Su Xiaosi 3, Xiao Guoqiang 1,Zhao Changrong 1, Song Qingchun 4,  Wang Na 5   

  1. 1.Tianjin Institute of Geology and Mineral Resources, Tianjin300170, China; 
    2.Key Laboratory of Water Cycle & Related Land Sarface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing100101, China;
    3.College of Environment and Resources,Jilin University, Changchun130026, China;
    4.Liaoning Investigation Insititute of Hydrogeology and Engineering Geology, Dalian116037, China;
    5.No.2 Geological Brigade of Hebei Geology and Mineral Exploration Bureau, Tangshan063000, China
  • Received:2012-03-20 Revised:2012-06-24 Online:2012-12-10 Published:2012-12-10

Yang Jilong, Han Dongmei, Su Xiaosi, Xiao Guoqiang,Zhao Changrong, Song Qingchun, Wang Na. Environmental Tracers (δ 2H-δ 18O, δ 34S, δ 13C) as Indicators of Seawater Intrusion Processes in the Coastal Karst Area[J]. Advances in Earth Science, 2012, 27(12): 1344-1352.

Daweijia wellhead field is located at the coastal karst area in north China. Unsustainable groundwater exploitation in recent decades has resulted in severe seawater intrusion in this area. Employing hydrogeological investigations, hydrodynamic monitoring and hydrogeochemical and isotope data analysis, this study analyzed the groundwater hydrodynamic conditions partially controlling seawater intrusion processes, and delineated the mechanism of seawater intrusion in this area. The characteristics of major hydrochemical composition and multi-stable-isotopes (δ2H-δ18O, δ34S, δ13C) in groundwater have been used to identify the main hydrogeochemical behaviors; these were also quantitatively simulated by inverse hydrogeochemical reactions. Seawater intrusion occurs primarily along the permeable fault zone, karst fissures and loose Quaternary strata. The compositions of  δ18O and  δ2H in groundwater show that the critical groundwater recharge source is precipitation. Combined with the Cl- distribution, it can be identified that besides salinity increase accompanying seawater intrusion into fresh water aquifer, evaporation of shallow groundwater also plays an important role in the accumulation of salt in groundwater. Joint analysis of δ34SSO4, δ13CHCO3composition with special anions (e.g., SO2-4,Cl-) reveals that brackish and saline groundwater are not the results of a simple mixture between seawater and fresh groundwater. Inverse hydrogeochemical modeling can be used to reveal the main hydrogeochemical reactions controlling the hydrochemical evolution of coastal karst aquifers in the study area, including the dissolution of calcite, montmorillonite and gypsum, the precipitation of illite and Ca-Na cation exchange with CO2 extrication.

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