Temporal Variations of Water Chemistry in the Wet Season in a Typical Urban Karst Groundwater System in Southwest China

Min Xiao, Zenglei Han, Sen Xu and Zhongliang Wang
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Min Xiao: Tianjin Key Laboratory of Water Resources and environment, Tianjin Normal University, Tianjin 300387, China
Zenglei Han: Tianjin Key Laboratory of Water Resources and environment, Tianjin Normal University, Tianjin 300387, China
Sen Xu: Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China
Zhongliang Wang: Tianjin Key Laboratory of Water Resources and environment, Tianjin Normal University, Tianjin 300387, China

IJERPH, 2020, vol. 17, issue 7, 1-14

Abstract: It is important to investigate temporal variations of water chemistry for the purpose of improving water quality in karst groundwater systems. Groundwater samples were collected daily under various land uses of Guiyang. Major ions and stable carbon isotope composition of dissolved inorganic carbon (δ 13 C DIC ) were analyzed to understand the biogeochemical processes. The water chemistry was dominated by Ca 2+ , Mg 2+ , HCO 3 - , and SO 4 2- , which mainly derived from the dissolution of carbonate rocks (limestone and dolomite) and oxidation of sulfide. The groundwater was defined as of the HCO 3 -Ca Mg and HCO 3 ?SO 4 -Ca?Mg type, according to its hydrochemical characteristics. Results suggested that hydrochemical concentrations changed quickly, in response to rainfall events. The fast response revealed that karst groundwater was easily impacted by rainfall and anthropogenic inputs according to temporal variation of water chemistry. The distribution of DIC (dissolved inorganic carbon) and δ 13 C DIC showed that DIC is mainly sourced from soil CO 2 (g) influx and carbonate dissolution. δ 13 C DIC and major ions ratios suggested that carbonate minerals were dissolved by H 2 SO 4 at groundwater in wooded area, contributing an important source for DIC due to the slight enrichment of heavy δ 13 C DIC . More negative δ 13 C DIC values were observed after rainfall reflected the fact that soil CO 2 (g) and organic carbon oxidation influxes accounted for a large share during DIC formation. Various δ 13 C DIC and hydrochemical patterns were observed under various land use and human activity conditions. Meanwhile, relative high nitrate loads were found in groundwater after rainfall, suggesting high anthropogenic inputs following rainwater as having side effects on water quality. This study suggests that water chemistry and isotopic proof provide a better understanding of water quality and carbon dynamics responding to rainfall events in the karst groundwater systems.

Keywords: water chemistry; dissolved inorganic carbon; carbon isotope; carbonate rock weathering; groundwater (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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