Identification of the sources and fate of NO3--N in shallow groundwater around a plateau lake in southwest China using NO3- isotopes (δ15N and δ18O) and a Bayesian model.
Identification of the sources and fate of NO3--N in shallow groundwater around a plateau lake in southwest China using NO3- isotopes (δ15N and δ18O) and a Bayesian model.
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DOI：
10.1016/j.jenvman.2020.110897
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发表时间：
2020-06
影响因子：
8.7
通讯作者：
Rongyang Cui;Bin Fu;Kunming Mao;Anqiang Chen;Dan Zhang
中科院分区：
文献类型：
--
作者：
Rongyang Cui;Bin Fu;Kunming Mao;Anqiang Chen;Dan Zhang
洱海是我国西南高原地区第二大淡水来源地，NO3 −-N污染严重威胁着洱海周边浅层地下水水质，进而影响湖泊水质和人体健康。我们在2018年和2019年的旱季和雨季采集了SG样品，并通过NO3−同位素和水化学方法确定了SG中NO3−-N的潜在来源及其归宿。结果表明，丰水期农田土壤中NO3--N浓度远高于枯水期居民区土壤中NO3--N浓度。δ 15 N-NO3-和δ 18 O-NO3-的变化幅度较大（农田分别为-12.78 ‰ ~+18.10‰和-27.62 ‰ ~+23.07‰，居民区分别为-5.34 ‰ ~+34.54‰和-20.04 ‰ ~+17.47‰），表明SG中NO3−-N具有多源性。农田NO3--N在旱季主要来源于化肥氮（NF，36%）、土壤氮（SN，33%）和粪污（M&S，24%），在丰水期主要来源于SN（61%）和NF（33%）。居民区的NO3--N在旱季主要来源于M&S（57%）、SN（23%）和NF（14%），在雨季主要来源于SN（50%）、NF（25%）和M&S（24%）。SG中氮素转化以反硝化作用为主。洱海东岸是污染最严重的SG区，NO3--N主要来源于NF。洱海西岸NO3--N污染呈现出多源性，且从高海拔向湖滨逐渐减缓。SG受NF、SN和M&S的氮污染，沿着流路流入洱海。因此，减少土壤氮素浓度、减少化学氮肥施用量、改善污水处理设施是缓解SG硝酸盐污染的重要途径。
Pollution by NO3−-N seriously threatens the quality of shallow groundwater (SG) around Erhai Lake, which is the 2ndlargest source of freshwater in the plateau area in southwest China; further, NO3−-N affects the lake water quality and human health. We collected SG samples during the dry and wet seasons in 2018 and 2019, and the potential NO3−-N sources and their fates were identified in SG by NO3−isotopes and hydrochemical methods. Our results showed that the NO3−-N concentrations in the SG in the wet season in farmland were far higher than those in the dry season in residential areas. The high variation in δ15N–NO3-and δ18O–NO3-(from −12.78‰ to +18.10‰ and −27.62‰ to +23.07‰, respectively, in the farmland and from −5.34‰ to +34.54‰ and −20.04‰ to +17.47‰, respectively, in the residential area) indicated multiple NO3−-N sources in the SG. The NO3−-N in the farmland mainly originated from chemical nitrogen fertilizer (NF, 36%), soil nitrogen (SN, 33%) and manure and sewage (M&S, 24%) in the dry season and from SN (61%) and NF (33%) in the wet season. The NO3−-N in the residential area mainly originated from M&S (57%), SN (23%) and NF (14%) in the dry season and from SN (50%), NF (25%) and M&S (24%) in the wet season. Nitrogen transformation was dominated by denitrification in the SG. The most polluted SG area was observed on the east bank of Erhai Lake, NO3−-N mainly originated from NF. But the NO3−-N pollution slowed down from high altitude to lakeside and had multiple NO3−-N sources on the west bank of Erhai Lake. The SG was contaminated by nitrogen from NF, SN and M&S along the flow path and flowed into Erhai Lake. Therefore, reducing soil nitrogen concentrations and chemical nitrogen fertilizer applications and improving sewage facilities are significant ways to mitigate nitrate pollution in the SG.