| 碳氮氧同位素解析典型岩溶流域地下水中硝酸盐来源与归趋 |
| 摘要点击 2771 全文点击 719 投稿时间：2020-10-08 修订日期：2020-11-01 |
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| 中文关键词 硝酸盐 氮氧同位素 碳同位素 SIAR模型 来源解析 岩溶水 |
| 英文关键词 nitrate nitrogen and oxygen isotopes carbon isotope SIAR model sources identification karst groundwater |
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| 中文摘要 |
| 利用多同位素（C、N和O）和水化学方法解析贵州八步地下河流域水体中硝酸盐（NO3-）来源与转化过程，利用SIAR模型定量计算NO3-不同输入端的贡献比例.结果表明，研究区地下水NO3-污染严重，近38%的地下水样品NO3-超过饮用水限值.地下水的δ15N-NO3值介于2.3‰~30.33‰，均值9.68‰，δ18O-NO3值介于2.65‰~13.73‰，均值6.64‰，δ18O-H2O值介于-8.83‰~-7.37‰，均值-8.18‰.同位素组成（δ15N-NO3、δ18O-NO3和δ18O-H2O）指示硝化作用主导着流域内氮素循环.硝化作用产生的硝酸加速了碳酸盐岩溶解，导致地下水中δ13CDIC与δ15N-NO3存在显著负相关性（P<0.001），说明δ13CDIC与δ15N-NO3相结合是判断岩溶水中NO3-转化的有效手段.地下水和地表水中NO3-主要来源于土壤氮、粪肥污水和铵态氮肥料，其对地下水中NO3-贡献率分别为36.19%、33.71%和30.1%，对地表水贡献率分别为39.15%、36.08%和24.77%.岩溶流域内污水处理应同时去除污水中的NO3-和NH4+，农业区应科学施肥，以有效降低地下水中NO3-的补给通量. |
| 英文摘要 |
| Multiple isotopes (C, N, and O) and hydrochemical data were used to trace the sources and fate of nitrate in ground and surface waters of the Babu subterranean stream watershed in Guizhou Province. The origin of nitrate in the water samples was also quantitatively analyzed by the SIAR model. Approximately 38% of the groundwater samples were not drinkable because the nitrate exceeded the drinking water standard, thereby indicating that the groundwater was seriously polluted by nitrate. The ranges of δ15N-NO3, δ18O-NO3, and δ18O-H2O in groundwater were 2.30‰-30.33‰ (mean of 9.68‰), 2.65‰-13.73‰ (mean of 6.64‰), and -8.83‰﹣-7.37‰ (mean of -8.18‰), respectively. Based on the stable isotopic compositions (δ15N-NO3, δ18O-NO3, and δ18O-H2O), nitrification was the dominant process in the basin. The nitric acid produced by nitrification promoted the dissolution of carbonate rocks, thereby leading to a significantly negative correlation (P<0.001) between the carbon isotope of dissolved inorganic carbon (δ13CDIC) and δ15N-NO3 and indicating that δ13CDIC, combined with δ15N-NO3, is effective in exploring the fate of nitrate in karst groundwater. The nitrate in the ground and surface waters mainly originated from soil N, manure and sewage, and ammonium nitrogen fertilizer. The results of the SIAR model showed that the contributions of soil N, manure and sewage, and ammonium nitrogen fertilizer were 36.19%, 33.71%, and 30.10% in groundwater, respectively, and 39.15%, 36.08%, and 24.77% in surface water, respectively. Therefore, it would be more effective to reduce the nitrate recharge flux in groundwater by simultaneously removing nitrate and ammonium nitrogen during wastewater treatment and by adopting scientific fertilization technology in agricultural areas. |
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