地下水中氮污染主要包括铵态氮和硝态氮,特别是当铵(NH₄⁺)作为地下水的主要污染物时,由于其在含水层中迁移规律复杂,且难以去除,成为研究该问题的难点。在奎河徐州段两岸通过钻孔对浅层地下水进行取样测试分析,研究区浅层地下水中氮的存在形式主要为NH₄⁺,其次为NO₃^-。通过对δ¹⁵N-NH₄⁺同位素分析可知,地下水中约27.3%的NH₄⁺来源于化肥,约72.7%NH₄⁺来自于动物粪便、生活污水等高δ¹⁵N值的污染源;对δ¹⁵N-NO₃^-同位素分析可知,地下水中约有15.2%的NO₃^-来源于化肥和土壤有机氮,63.6%的NO₃^-来源于动物粪便和污水;约21.2%的地下水样本中δ¹⁵N-NO₃^-值超出了污染源的同位素值,可能产生了反硝化作用。

Nitrogen pollution in groundwater is mainly caused by the intrusion of ammonium nitrogen and nitrate nitrogen. Especially when ammonium (NH₄⁺) is the major pollutant in groundwater, studying its distribution characteristics will be difficult as its migration law in aquifers is complicated and the pollutant is hard to be removed. Through boring holes at both banks of Kuihe River in Xuzhou city, we collected water samples to analyze nitrogen pollution. Test results showed that the main existence form of nitrogen in the study area was NH₄⁺, followed by NO₃^-. Isotopic analysis of δ¹⁵N-NH₄⁺ showed that 27.3% of NH₄⁺ in the groundwater was from chemical fertilizer and the rest was from the sources with high δ¹⁵N, such as animal manure and domestic sewage, etc. On the other hand, isotopic analysis of δ¹⁵N-NO₃^- showed that 15.2% of NO₃^- was from chemical fertilizer and soil organic nitrogen and 63.6% of that was from animal manure and sewage. Test and analysis of groundwater also showed that about 21.2% of samples were with higher isotope values than the pollution source, reflecting the denitrification in shallow groundwater at the study area.