The integrated impacts of natural processes and human activities on groundwater salinization in the coastal aquifers of Beihai, southern China

Li, Qinghua; Zhang, Yanpeng; Chen, Wen; Yu, Shaowen

The integrated impacts of natural processes and human activities on groundwater salinization in the coastal aquifers of Beihai, southern China | Impacts intégrés des processus naturels et des activités humaines sur la salinisation des aquifères côtiers de Beihai, Chine du Sud Los impactos integrados de los procesos naturales y de las actividades humanas en la salinización del agua subterránea en los acuíferos costeros de Beihai, sur de China 自然过程及人类活动对中国南部北海沿海含水层地下水盐化作用的综合影响 Os impactos integrados de processos naturais e atividades humanas na salinização das águas subterrâneas nos aquíferos costeiros de Beihai, sul da China

2018

Li, Qinghua | Zhang, Yanpeng | Chen, Wen | Yu, Shaowen

Salinization in coastal aquifers is usually related to both seawater intrusion and water–rock interaction. The results of chemical and isotopic methods were combined to identify the origin and processes of groundwater salinization in Daguansha area of Beihai, southern China. The concentrations of the major ions that dominate in seawater (Cl⁻, Na⁺, Ca²⁺, Mg²⁺ and SO ₄²–), as well as the isotopic content and ratios (²H, ¹⁸O, ⁸⁷Sr/⁸⁶Sr and ¹³C), suggest that the salinization occurring in the aquifer of the coastal plain is related to seawater and that the prevailing hydrochemical processes are evaporation, mixing, dissolution and ion exchange. For the unconfined aquifer, groundwater salinization has occurred in an area that is significantly influenced by land-based sea farming. The integrated impacts of seawater intrusion from the Beibuwan Gulf and infiltration of seawater from the culture ponds are identified in the shallowest confined aquifer (I) in the middle of the area (site BBW2). Leakage from this polluted confined aquifer causes the salinization of groundwater in the underlying confined aquifer (II). At the coastal monitoring site (BBW3), confined aquifer I and lower confined aquifer II are heavily contaminated by seawater intrusion. The weak connectivity between the upper aquifers, and the seaward movement of freshwater, prevents saltwater from encroaching the deepest confined aquifer (III). A conceptual model is presented. Above all, understanding of the origin and processes of groundwater salinization will provide essential information for the planning and sustainable management of groundwater resources in this region.

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