Groundwater Chemical Characteristics and Analysis of Their Controlling Factors in an Alluvial Fan of Jianjiang River

Abstract

The Jianjiang alluvial fan is one of the frontal alluvial fan clusters in the Longmen Mountains of the Chengdu Plain. In order to study the groundwater chemical characteristics and controlling factors, we collected 30 groups of groundwater samples on site in May 2018. Descriptive statistical analysis, Piper diagrams, ArcGIS spatial analysis, ion-scale coefficients, and other methods were used to analyze the chemical types and ion spatial distribution characteristics. The main factors controlling the chemical evolution processes of the groundwater and the main sources of ions are discussed. The northeast area of the alluvial fan contains mostly weakly acidic waters, accounting for 13.33%, the rest being weakly alkaline. Groundwater chemical types included HCO3·SO4-Ca, HCO3-Ca, HCO3·SO4-Ca·Mg, and HCO3·SO4-Ca·Na, and all groundwater was freshwater. The main ion spatial variation coefficient were between 0.22 and 0.91, and the variability was moderate. The chemical evolution processes of groundwater was mainly controlled by leaching, and human activities have certain influence. The effect of evaporation and concentration, and atmospheric rainfall, and alternating cation adsorption were not obvious.