Hydrogeological characterization and environmental effects of the deteriorating urban karst groundwater in a karst trough valley: Nanshan, SW China

Jiang, Yongjun; Cao, Min; Yuan, Daoxian; Zhang, Yuanzhu; He, Qiufang

Hydrogeological characterization and environmental effects of the deteriorating urban karst groundwater in a karst trough valley: Nanshan, SW China | Caractérisation hydrogéologique et effets environnementaux sur la détérioration d’eaux souterraines karstiques urbaines dans une vallée karstique: Nanshan, Sud-Ouest de la Chine Caracterización hidrogeológica y efectos ambientales del deterioro del agua subterránea urbana a través de un valle kárstico: Nanshan, sudoeste de China 岩溶槽谷地区城市岩溶地下水恶化的水文地质特征及其环境效应 – 中国西南的南山 Caracterização hidrogeológica e efeitos ambientais na deterioração das águas subterrâneas do carste urbano em um vale cárstico: Nanshan, SO China

2018

Jiang, Yongjun | Cao, Min | Yuan, Daoxian | Zhang, Yuanzhu | He, Qiufang

The unique hydrogeology of karst makes the associated groundwater respond quickly to rainfall events and vulnerable to anthropogenic pollutions. In this study, high-frequency monitoring of spring discharge, temperature, electrical conductivity (EC) and pH, along with monthly hydrochemical and microbial analyses, was undertaken at the outlet of Laolondong karst underground river in Nanshan, southwestern China. The aim was to explore the environmental effects of the catchment’s urban area on the karst groundwater resources. The monitoring data of a tracer test and the response of discharge to rainfall events demonstrate that conduits and narrow fissures coexist in the Laolongdong karst aquifer. The EC, Na⁺, Cl⁻ and SO₄²⁻ values (840 μS/cm, 33.7, 38.6 and 137.2 μg/L, respectively), along with high concentrations of fecal coliform bacteria, at the outlet indicate considerable urban pollution in this area. The contaminants sulfate and nitrate showed different relationships with discharge and EC in different stages of a rainfall event. This behavior provided information about aquifer structure and the influence of transport properties. Meanwhile, the hydrological processes of groundwater flow could be modified by urbanization and result in increasing magnitude of urban floods in the underground river. In addition, sulfuric and nitric acids introduced by urbanization not only impact the karst groundwater quality, but also result in a significant perturbation to the carbon cycling system in the karst area.

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