| 滇池周边浅层地下水硝酸盐来源及转化过程识别 |
| 摘要点击 2959 全文点击 881 投稿时间：2022-11-29 修订日期：2023-01-08 |
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| 中文关键词 硝酸盐 氮氧同位素 滇池 浅层地下水 转化过程 |
| 英文关键词 nitrate nitrogen and oxygen isotope Dianchi Lake shallow groundwater transformation process |
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| 中文摘要 |
| 明确硝酸盐的主要来源及转化过程对地下水氮污染防治和水资源开发利用具有重要意义.为了探明滇池周边浅层地下水中硝酸盐污染现状及来源，于2020年雨季（10月）和2021年旱季（4月）在滇池周边共采集73个浅层地下水样，运用水化学和氮氧同位素（δ15N-NO3-、δ18O-NO3-）识别浅层地下水中硝酸盐的空间分布、来源及转化过程，并结合同位素混合模型（SIAR）定量评价不同来源氮对浅层地下水硝酸盐的贡献.结果表明，旱季浅层地下水中有40.5%的采样点ρ（NO3--N）超过地下水质量标准（GB/T 14848）Ⅲ类水质规定的20 mg·L-1，雨季超过47.2%的采样点ρ（NO3--N）超过20 mg·L-1.氮氧同位素和SIAR模型分析结果证明了土壤有机氮、化肥氮、粪肥和污水氮是浅层地下水硝酸盐的主要来源，以上氮源对旱季浅层地下水中硝酸盐的贡献率分别为13.9%、11.8%和66.5%，对雨季的贡献率分别为33.7%、31.1%和25.9%，而大气氮沉降贡献率仅为8.5%，对该区浅层地下水中硝酸盐来源贡献较小.硝化作用是旱季浅层地下水中硝态氮转化的主导过程，雨季以反硝化作用为主，且反硝化作用雨季比旱季明显. |
| 英文摘要 |
| Elucidating the main sources and transformation process of nitrate for the prevention and control of groundwater nitrogen pollution and the development and utilization of groundwater resources has great significance. To explore the current situation and source of nitrate pollution in shallow groundwater around the Dianchi Lake, 73 shallow groundwater samples were collected in the rainy season in 2020(October) and dry season in 2021(April). Using the hydrochemistry and nitrogen and oxygen isotopes(δ15N-NO3- and δ18O-NO3-), the spatial distribution, source, and transformation process of nitrate in shallow groundwater were identified. The contribution of nitrogen from different sources to nitrate in shallow groundwater was quantitatively evaluated using the isotope mixing model(SIAR). The results showed that in nearly 40.5% of sampling points in the shallow groundwater in the dry season, ρ(NO3--N) exceeded the 20 mg·L-1 specified in the Class Ⅲ water quality standard for groundwater(GB/T 14848), and in more than 47.2% of sampling points in the rainy season, ρ (NO3--N) exceeded 20 mg·L-1. The analysis results of nitrogen and oxygen isotopes and SIAR model showed that soil organic nitrogen, chemical fertilizer nitrogen, and manure and sewage nitrogen were the main sources of nitrate in shallow groundwater; these nitrogen sources contributed 13.9%, 11.8%, and 66.5% to nitrate in shallow groundwater in the dry season and 33.7%, 31.1%, and 25.9% in the rainy season, respectively. However, the contribution rate of atmospheric nitrogen deposition was only 8.5%, which contributed little to the source of nitrate in shallow groundwater in the study area. Nitrification was the leading process of nitrate transformation in shallow groundwater in the dry season, denitrification was the dominant process in the rainy season, and denitrification was more noticeable in the rainy season than that in the dry season. |
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