Water Environmental Characteristics and Eutrophication Evaluation of Alpine Karst Mountains in Huanglong, Sichuan, China

Abstract

Travertine deposits are formed after CO 2 is degassed from deep karst water at the Huanglong Scenic Area, a World Natural Heritage Site. In recent years, various levels of eutrophication have occurred in travertine waters, resulting in large areas of algal mats that have severely affected the continued deposition of travertine and its appreciable value. The research on hydrochemical types, hydrochemical components, and pollution characteristics of surface water and groundwater in Huanglong National Scenic Area, a World Natural Heritage, is beneficial to the evaluation and management of regional water resources and landscape development. In June 2022, 14 groups of surface water and groundwater samples were collected from Huanglong. Mathematical statistics were used to analyze the water’s chemical characteristics, the Piper three-plot was used to analyze the water’s chemical types, and Gibbs and Gaillardet model were used to discuss the sources and influencing factors of main ions in surface water. The eutrophication degree of regional water was evaluated by the single factor index method. The results show that most of the groundwater in the study area belongs to weakly alkaline water. The cations are mainly Ca 2+, the anions are mainly HCO 3 –, and the hydrochemical type is HCO 3 –Ca. The major contribution of TDS comes from Ca 2+ and HCO 3 – . According to the analysis of water–rock model, the hydrochemical origin of surface water in the study area is mainly controlled by rock weathering, and most ions are influenced by the water–rock interaction of carbonate rocks, with the existence of reverse cation exchange. The spatial and temporal distribution characteristics of nitrogen, phosphorus, and carbon are obvious. Eutrophication evaluation showed that Huanglong was in a medium eutrophication state.

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