Chemical Characteristics of Flow Driven by Rainfall and Associated Impacts on Shallow Groundwater Quality in a Karst Watershed, Southwest China

摘要

Monitoring from 2016 to 2018 was used to investigate seasonal variation of chemical characteristics and define the water quality status within a subsurface river system in a karst region of Southwest China. For this, the water quality index (WQI) and principal component analysis (PCA) were employed. Results showed that baseflow and constituents, i.e., TN, TP, NO_2~-N, and SO_4~(2-) exhibited seasonal variation. Arsenic and selenium were the main pollutants found in the river system of the Houzhai river basin. Total dissolved solids (TDS), pH, selenium, TP, NO_2~--N, and TN were obviously impacted by precipitation during the precipitation-derived flow processes. The groundwater quality was categorized as "very poor" throughout the entire monitoring period, with WQI values ranging from 62 to 70. In particular, TN, TP, selenium, and arsenic scores ranged from 80 to 100, which are considered unsuitable for potable water use. In order to ensure the safety of groundwater as a potable water source, administrators must recognize the importance of preventing the cross-contamination of surface water and groundwater to guarantee the safety of water and the health of local residents in karst areas.