Jin Zanfang, Qin Xue, Chen Lingxiao, Jin Mantong, Li Feili
College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, China.
J Contam Hydrol. 2015 Jun-Jul;177-178:64-75. doi: 10.1016/j.jconhyd.2015.02.008. Epub 2015 Mar 19.
The West Lake is a World Heritage site in the West Lake watershed in eastern China. In this study, the hydrogeological and dual isotopic approaches were integrated to evaluate the seasonal and spatial variations of nitrate (NO3(-)) in the West Lake watershed, and to characterize NO3(-) sources and transformations. The results revealed that the geochemical facies of the water samples were dominated by Ca(2+)+Na(+)-HCO3(-)+SO4(2)(-) in the surface water and transfer water, Ca(2+)+Na(+)-HCO3(-) and Ca(2+)+Na(+)-SO4(2-) in the groundwater, which most likely reflect natural reactions and anthropogenic inputs. About 13% of the groundwater samples containing NO3(-) exceeded the World Health Organization (WHO) standard of 10 mg N L(-1). NO3(-) was the dominant form of total nitrogen (TN) and was the main surface water contaminant in the West Lake watershed. The δ(15)NNO3 and δ(18)ONO3 values indicated that the dominant NO3(-) sources in surface water were soil nitrogen (soil N) and chemical fertilizers, while the main NO3(-) sources in groundwater were soil N from the forest, chemical fertilizers and manure in the tea garden, domestic sewage from the small, old residential area in the forest as well as urban areas. The distribution of NO3(-) in groundwater was strongly influenced by land use. Results also suggest that there was significant nitrification in surface water and groundwater in the West Lake watershed, and that there were also denitrification processes in groundwater. The annual net fluxes of TN, NO3(-), and NH4(+) into the West Lake were 2.0×10(4), 4.0×10(3), and 1.31×10(4) kg as N, respectively.
西湖是中国东部西湖流域的世界遗产地。在本研究中，综合运用水文地质和双同位素方法来评估西湖流域硝酸盐（NO₃⁻）的季节和空间变化，并确定NO₃⁻的来源和转化特征。结果表明，地表水和输水的水样地球化学相以Ca²⁺+Na⁺-HCO₃⁻+SO₄²⁻为主，地下水以Ca²⁺+Na⁺-HCO₃⁻和Ca²⁺+Na⁺-SO₄²⁻为主，这很可能反映了自然反应和人为输入。约13%的含NO₃⁻地下水样本超过了世界卫生组织（WHO）规定的10 mg N L⁻¹标准。NO₃⁻是总氮（TN）的主要形态，也是西湖流域地表水中的主要污染物。δ¹⁵N-NO₃和δ¹⁸O-NO₃值表明，地表水中NO₃⁻的主要来源是土壤氮（soil N）和化肥，而地下水中NO₃⁻的主要来源是森林中的土壤氮、茶园中的化肥和粪便、森林中小型老旧居民区以及城市地区的生活污水。地下水中NO₃⁻分布受土地利用影响强烈。结果还表明，西湖流域地表水和地下水中存在显著的硝化作用，地下水中也存在反硝化过程。进入西湖的TN、NO₃⁻和NH₄⁺的年净通量分别为2.0×10⁴、4.0×10³和1.31×10⁴ kg（以N计）。
