No abstract

Although Dehui City has excellent agricultural conditions, long-term large-scale over-cultivation and human activities in recent years have caused significant changes in the local groundwater chemical characteristics. This study analyzes the causes, evolution, and prediction of groundwater chemistry via multi-disciplinary theoretical cross-cutting methods, such as groundwater ion composition-ratio analysis and groundwater influencing factor analysis, and artificial neural networks. The lithological characteristics of the groundwater aquifer were combined with ion composition-ratio mapping to explore the cause of groundwater chemistry composition in the study area. Piper three-line diagrams and Gibbs diagrams were used to analyze the evolution characteristics and influencing factors of groundwater chemistry in the study area. Based on these data, time series predictions were made for hydrochemical data. The results demonstrate that the chemical origins of groundwater in the study area are mainly background stratum and cation exchange, influenced by human activities. The main factors of groundwater chemical characteristics have changed from rock weathering to evaporation/precipitation in the past two decades. The hydrochemical characteristics changed from secondary alkalinity to secondary salinity. The predicted data from long short-term memory neural networks indicated that groundwater would continue salinization without the changes in the conditions, leading to land degradation in the study area.

The unreasonable development and utilization of groundwater in Dehui City, China, has resulted in poor groundwater quality conditions. Based on the collection of a large amount of groundwater chemical data and hydrogeological data collected by Dehui City from 1992 to 2015, this paper uses hydrogeological analysis, graphic and other methods and ArcGIS toolbox to analyze the groundwater quality of this City. The study shows that the concentration of groundwater chemical components in the vicinity of the Songhua River is decreasing with time, and the concentration of groundwater chemical components in other regions is increasing with time. The increase of chemical concentrations are affected by human activities and water-rock interaction. The decrease of groundwater chemical concentration in Songhua River area is caused by the mixing between dilute river water and groundwater.