Hydrochemistry and Isotope Hydrology for Groundwater Sustainability of the Coastal Multilayered Aquifer System (Zhanjiang, China)

Abstract

Groundwater sustainability has become a critical issue for Zhanjiang (China) because of serious groundwater level drawdown induced by overexploitation of its coastal multilayered aquifer system. It is necessary to understand the origins, material sources, hydrochemical processes, and dynamics of the coastal groundwater in Zhanjiang to support its sustainable management. To this end, an integrated analysis of hydrochemical and isotopic data of 95 groundwater samples was conducted. Hydrochemical analysis shows that coastal groundwater is fresh; however, relatively high levels of Cl − , Mg 2+ , and total dissolved solid (TDS) imply slight seawater mixing with coastal unconfined groundwater. Stable isotopes ( 18 O and 2 H) values reveal the recharge sources of groundwater in the multilayered aquifer system. The unconfined groundwater originates from local modern precipitation; the confined groundwater in mainland originates from modern precipitation in northwestern mountain area, and the confined groundwater in Donghai and Leizhou is sourced from rainfall recharge during an older period with a colder climate. Ionic relations demonstrate that silicate weathering, carbonate dissolutions, and cation exchange are the primary processes controlling the groundwater chemical composition. Declining trends of groundwater level and increasing trends of TDS of the confined groundwater in islands reveal the landward extending tendency of the freshwater-seawater mixing zone.

Characterization of seasonal groundwater origin and evolution processes in a geologically heterogeneous catchment using geophysical, isotopic and hydro‐chemical techniques (Lough Gur, Ireland)

“…An indicator of cation sources associated with silicate weathering is the milligram equivalent ratio of [(Na + + K + )/Cl − ], where a ratio greater than 1 indicates release of cations from silicate weathering and a ratio of 1 or less suggests dissolution from other geological materials (Mukherjee & Fryar, 2008; Zhou et al, 2017) (Figure S3).…”

“…The plot of (Cl − + SO 4 2− ) versus HCO 3 − (Figure 8d) shows that groundwater samples under low flow conditions mainly plot above the 1:1 line, indicating that carbonate dissolution may be the dominant material source of the chemical composition of this groundwater. In contrast, groundwater samples under high flow conditions plot on both sides of the 1:1 line, indicating both carbonate dissolution and silicate weathering are the main material sources of the hydro‐chemical composition of groundwater (Zhou et al, 2017).…”

Systematic Analysis of Geothermal Resources in the Coastal Bedrock Area of Chunxiao Town (China) by Using Geochemistry and Geophysics Methods

“…The methods used in this study include hydrogeochemical method and geophysical method. Hydrogeochemical method is one of the most direct and effective ways to understand the migration and evolution of hydrochemical components in a region [24]. In this study, Langelier-Ludwig graphic method and Piper three-line graphic method were used to analyze the hydrochemistry evolution characteristics of surface water and groundwater, and ratios of ion components were used to eliminate the interference from seawater to coastal water.…”

Groundwater Quality Assessment in a Karst Coastal Region of the West Aurunci Mountains (Central Italy)

“…73 groundwater samples were collected from 2016 to 2018 and analysed to evaluate the main geochemical processes controlling the groundwater evolution in this hydrogeological system. With the aim of identifying the potential seawater intrusion in this coastal region, several water quality indicators and some diagrams, which use hydrochemical parameters, have been applied in this case study [21][22][23][24][25][26][27][28][29][30].…”