Coupling stable isotopes and water chemistry to assess the role of hydrological and biogeochemical processes on riverine nitrogen sources
Coupling stable isotopes and water chemistry to assess the role of hydrological and biogeochemical processes on riverine nitrogen sources
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耦合稳定同位素和水化学来评估水文和生物地球化学过程对河流氮源的作用
DOI：
10.1016/j.watres.2018.11.082
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发表时间：
2019
期刊：
影响因子：
12.8
通讯作者：
Dingjiang Chen
中科院分区：
文献类型：
--
作者：
Minpeng Hu;Yanmei Liu;Yufu Zhang;R;y A. Dahlgren;Dingjiang Chen
准确的源识别是优化水污染控制策略的关键。虽然双稳定同位素（15 N-NO3-/18 O-NO3-）方法已被广泛应用于区分河流氮（N）的来源，但由于流域N动态的时间变异性大，以往研究中通常使用的相对较短（<1年）的15 N-NO3-/18 O-NO3-记录往往阻碍严格的评估。在许多以前的研究中，通过建模方法估计土壤和地下水中的遗留氮源对河流氮输出的贡献也缺乏来自补充信息的验证，例如多种稳定同位素。本研究综合了3年的河水、地下水和降雨的15 N-NO3-/18 O-NO3-和2 H-H2O/18 O-H2O稳定同位素和水化学观测资料，对永安流域（2474 km 2）的氮素动态和来源进行了研究。非点源氮污染占主导地位，并表现出相当大的季节和空间变异的N形态和浓度。δ 15 N-NO3-和δ 18 O-NO3-的变化表明，河流氮素的动态变化受贡献源、硝化和反硝化作用以及水文过程的调控。对于三个检查集水区和整个流域，缓慢的地下水和地下水流量占河流排放量的75%以上，可能是氮输送到河流的主要水文途径。河流NO3−来源因主要土地利用而异（p < 0.001），其中地下水（60%）、废水（35%）和土壤（50%）的贡献最大，分别发生在农业、住宅和森林集水区。对于整个流域，地下水（约50%）和土壤氮（>30%）是主要的河流NO3-来源，这意味着相当大的潜在的N污染的遗产效应。结果与观察到的一氧化二氮动态和N源在以前的建模研究中确定的一致。作为第一次尝试应用多种同位素示踪剂探索和量化N转化和运输途径，这项研究提供了一个综合的方法来验证和了解在世界各地的许多流域中观察到的N污染的遗留效应。这项研究强调，在许多流域的河流氮污染控制需要特别注意地下水恢复和土壤氮管理，除了氮输入控制策略。
Accurate source identification is critical for optimizing water pollution control strategies. Although the dual stable isotope (15N-NO3-/18O-NO3-) approach has been widely applied for differentiating riverine nitrogen (N) sources, the relatively short-term (<1 yr)15N-NO3-/18O-NO3-records typically used in previous studies often hinders rigorous assessment due to high temporal variability associated with watershed N dynamics. Estimated contributions of legacy N sources in soils and groundwater to riverine N export by modeling approaches in many previous studies also lack validation from complementary information, such as multiple stable isotopes. This study integrated three years of multiple stable isotope (15N-NO3-/18O-NO3-and2H-H2O/18O-H2O) and hydrochemistry measurements for river water, groundwater and rainfall to elucidate N dynamics and sources in the Yongan watershed (2474 km2) of eastern China. Nonpoint source N pollution dominated and displayed considerable seasonal and spatial variability in N forms and concentrations. Information from δ15N-NO3-and δ18O-NO3-indicated that riverine N dynamics were regulated by contributing sources, nitrification and denitrification, as well as hydrological processes. For the three examined catchments and entire watershed, slow subsurface and groundwater flows accounted for >75% of river discharge and were likely the major hydrological pathways for N delivery to the river. Riverine NO3−sources varied with dominant land use (p < 0.001), with the highest contributions of groundwater (60%), wastewater (35%), and soil (50%) occurring in agricultural, residential and forest catchments, respectively. For the entire watershed, groundwater (∼50%) and soil N (>30%) were the dominant riverine NO3−sources, implying considerable potential for N pollution legacy effects. Results were consistent with observed nitrous oxide dynamics and N sources identified in previous modeling studies. As the first attempt to apply multiple isotope tracers for exploring and quantifying N transformation and transport pathways, this study provides an integrated approach for verifying and understanding the N pollution legacy effects observed in many watersheds worldwide. This study highlights that river N pollution control in many watersheds requires particular attention to groundwater restoration and soil N management in addition to N input control strategies.