Hydrogeochemical characteristics and evolution simulation of groundwater in basalts on the Leizhou Peninsula, Guangdong, China

Softwares for hydrochemical analysis and water-rock interaction are used to perform the hydrogeochemical analysis and flow path simulation of groundwater on the Leizhou Peninsula. Simulations of water-rock interactions are made in the directions of groundwater runoffs in the east and west from the recharge area of terrace I to the discharge area of terraces II and III. The research results show that groundwater may undergo a series of water-rock interactions, including dissolution or precipitation of gypsum, kaolinite, Ca-smectite, illite, chlorite, diopside, goethite and hematite and dissolution or escape of carbon dioxide. The quantities of dissolved or precipitated goethite, hematite and diopside are far smaller in the east flow direction than in the west flow direction. Dissolution of goethite and hematite occurs only in a couple of water sample sites, whereas in most water sample sites they are in a saturated state and precipitated from groundwater. Dissolution of carbon dioxide occurs at most water sample sites. The quantity of dissolved carbon dioxide is relatively large and its saturation index increases with increasing concentration of carbon dioxide in the water. The carbon dioxide may escape from water after it reaches saturation. Thus the results of modeling of water-rock interaction are conducive to revealing the evolution mechanism of the groundwater chemical environment in the study area.