Appropriate stoichiometric ratios of dissolved organic carbon and nitrate can trigger a transition in nitrate removal in groundwater around plateau lakes, Southwest China

文献类型： 外文期刊

第一作者： Cui, Rongyang

作者： Cui, Rongyang;Chen, Anqiang;Hu, Wanli;Fu, Bin;Cui, Rongyang;Liu, Gangcai;Cui, Rongyang;Zhang, Dan

作者机构：

关键词： Groundwater; Nitrate pollution; Dissolved organic carbon; Nitrate removal

期刊名称：SCIENCE OF THE TOTAL ENVIRONMENT （ 影响因子：9.8； 五年影响因子：9.6 ）

ISSN： 0048-9697

年卷期： 2024 年 916 卷

页码：

收录情况： SCI

摘要： Increasing dissolved organic carbon (DOC) in groundwater as a carbon source for microorganisms that stimulate nitrate attenuation is considered a sustainable strategy to mitigate nitrate pollution in groundwater. However, little is known on the stoichiometric ratio of DOC and nitrate required in groundwater nitrate reduction processes, which has become an obstacle for evaluating the current status of DOC limitations on nitrate reduction. Here, the NO3--N and DOC concentrations in groundwater around 8 plateau lakes were investigated, and a microcosm experiment was performed to elucidate the effects of different DOC:NO3--N levels in groundwater on NO3--N reduction, and the current status of DOC limitations on groundwater NO3--N reduction around 8 lakes was further evaluated. The results indicated that nearly 41 % of the groundwater NO3--N concentrations exceeded the WHO threshold for drinking water (11.3 mg L-1) and 79 % of the groundwater DOC concentrations exceeded 5 mg L-1. The differences in groundwater NO3--N and DOC concentrations among the 8 lakes were controlled by the intensity of agricultural and human activities and hydrogeological background. The stoichiometric ratio of DOC:NO3--N regulated the NO3--N reduction process, and groundwater NO3--N accumulation rate appeared to become limited and sharply decreased when the DOC concentration was approximately 10 mg L-1 or when the DOC:NO3--N ratio was close to 1:1, and the DOC:NO3--N ratio threshold for limiting the NO3--N reduction process was approximately 2.25. Based on this threshold, >33 %-86 % of the groundwater samples around the 8 plateau lakes were strongly limited in the reduction of groundwater NO3--N due to a lack of sufficient DOC provides energy for heterotrophic microorganisms. Additionally, we highlight that the sustainable strategy of increasing DOC to stimulate groundwater NO3- attenuation should be combined with short-term strategies to jointly coordinate and control groundwater NO3- pollution.

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