Abstract
Groundwater in coastal aquifers is often affected by seawater intrusion, resulting in water quality deterioration. Using groundwater influenced by seawater intrusion for irrigation can lead to crop failure, erosion of machinery and pipes, and adverse effects on farming. In this study, the results of water testing, methods of statistical analysis, ion ratios, a Piper diagram, and a variety of groundwater irrigation suitability models were used to analyze the chemical composition of groundwater and the influence of seawater intrusion. The result shows that the content of Na+, K+, Ca2+, Mg2+, Cl−, and SO42− in groundwater would increase due to seawater intrusion, and the increasing trend was consistent with the freshwater–seawater mixing line. With the deepening of seawater intrusion, the hydrochemical type gradually changes from Ca-HCO3·Cl to Na·Mg-Cl·SO4 and then to Na-Cl type, and the source of hydrochemical composition changes from “Rock Weathering Dominance” to “Evaporation Dominance”. When the Cl− concentration is greater than 7.1 meq/L, groundwater will corrode pipelines and instruments; when greater than 28.2 meq/L, excessively high salinity of groundwater will have adverse effects on planting; and when greater than 14.1 meq/L, the groundwater hardness is too high, which may make the groundwater unsuitable for cultivation.
Highlights
Groundwater is an important part of the water cycle and the main source of water in many parts of the world [1,2,3]
The maximum, minimum, average, and coefficient variation (CV) of each parameter were calculated, and the main ion boxplot was drawn with Origin
A Piper diagram is a graph commonly used in hydrogeochemical analysis [27], it directly reflects the hydrochemical characteristics by the main used in hydrogeochemical analysis [27], it directly reflects the hydrochemical characteristics by the percentage of anion and anion milligram equivalent
Summary
Groundwater is an important part of the water cycle and the main source of water in many parts of the world [1,2,3]. Due to the change in groundwater hydrodynamic conditions, the process of seawater invaded into freshwater aquifers on land is called seawater intrusion [10]. Seawater intrusion can be generally divided into two categories according to its formation cause, invasion route, and occurrence process: The first is the impact of various natural factors (such as climate change or sea level rise) and human factors (mainly excessive groundwater exploitation), which causes seawater to invade the coastal freshwater aquifer through the groundwater system, and generally occurs relatively slowly, causing a gradual disaster; the other type mainly occurs in estuarine areas, through the ocean surface, upstream invasion along the river, especially affected by storm surge, sea flow, tide, current, wind direction, and wind.
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