Hydrochemical processes and evolution of karst groundwater in the northeastern Huaibei Plain, China

Qian, Jiazhong; Peng, Yinxue; Zhao, Weidong; Ma, Lei; He, Xiaorui; Lu, YueHan

Hydrochemical processes and evolution of karst groundwater in the northeastern Huaibei Plain, China | Processus hydrochimiques et évolution des eaux souterraines karstiques dans le nord-est de la Plaine d’Huaibei, Chine Procesos hidroquímicos y evolución del agua subterránea kárstica en el noreste de la llanura de Huaibei, China 中国淮北东北部岩溶地下水的化学过程和演化 Processos hidrogeoquímicos e evolução cárstica das águas subterrâneas no nordeste da Planície de Huaibei, China

2018

Major ion geochemistry reveals that the hydrochemical evolutionary process of karst groundwater in the northeastern Huaibei Plain, China, consists of three sub-processes: the dissolution of dolomite, gypsum dissolution with dedolomitization, and mixing with overlying pore water. Understanding hydrochemical evolution has been an important topic in understanding the history, status, and dynamics of the groundwater flow system. The presented study found a hydrochemical boundary roughly corresponding to the thickness of overlying strata equating to 50 m depth, indicating two flow compartments participating in different hydrological cycles—a local shallow rapidly replenished compartment showing lower and more stable main ion concentrations, and a regional deep-flow compartment showing higher and sporadic concentrations of Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻ and SO₄²⁻, as well as high total dissolved solids (TDS), total hardness, and sodium adsorption ratio (SAR). In areas with aquifers with low water transmitting ability, groundwater samples show a high chloride ratio and elevated TDS values, indicating salinization of groundwater due to stagnant water flows. Analyses of the data on the saturation indexes and mineral solutions, in tandem with trilinear diagram analysis and petrological observations, indicate that dedolomitization is the dominant process controlling the chemical characteristics of karst groundwater in the study area. Groundwater and pore-water mixing was also observed at the later evolutionary stage of groundwater flow, demonstrating frequent groundwater/pore-water interactions where groundwater is recharged by pore water due to lower groundwater level in the study area.

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