Variation of water quality of underground rivers in uncovered karst regions during the process of urbanization

Underground rivers are the primary form of water resources as well as the most important landscape resources in karst regions in southern China. Their water quality was constantly deteriorated recently by human activities changing. Taking the Shangzhai underground river as an example, this paper addresses this issue based on historical monitoring data. The water quality of this river has experienced stage-wise changes with urbanization, and became the worst in rural-urban conjunctions. The relatively high contribution rates to over standard components are attributed to Mn,NH4+,F- and NO2-. Contaminants come mainly from aquaculture，life，food processing, smelting and manufacturing. Organic contaminants were detected since 2003, and BaP was found over-standard from 2015. The increasing of population and enterprises, the random discharge of waste water and waste residue have led to severe pollution of surface water. The vulnerable antipollution ability of underground river systems in uncovered karst regions are the main reason for underground water deterioration.