Interpreting the seasonal and long-term trend of nitrate in both groundwater and spring water in a typical headwater wetland with well-defined groundwater flow pathways
Interpreting the seasonal and long-term trend of nitrate in both groundwater and spring water in a typical headwater wetland with well-defined groundwater flow pathways
复制标题
解释具有明确地下水流路径的典型水源湿地地下水和泉水中硝酸盐的季节和长期趋势
DOI：
10.2166/ws.2016.047
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Xing Li
中科院分区：
文献类型：
--
作者：
Yingjie Cao;C. Tang;Z. Han;Sako Yoko;Xing Li
水源地硝酸盐行为的时间尺度问题（季节变化和长期趋势）与其水文过程密切相关。在日本千叶县一个典型的农业水源集水区，地下水硝酸盐浓度呈上升趋势，而泉水，在我们的监测期间，观察到大幅下降的趋势。两个关键问题，（1）多个流动路径的识别和（2）不同途径的停留时间的评估，强调揭示控制硝酸盐趋势的不同模式的因素。研究了土壤水沿坡谷沿着的垂直流动、地下水沿坡谷的侧向流动和地下水沿坡谷的深层流动3种主要流动途径。不同的时间尺度的三个流动路径被识别。根据土壤水分收支方程计算出VF的停留时间为9-10年，利用氯氟碳化物示踪法估算出LG的表观年龄为41年。地下水中NO3−的增加趋势与历史硝酸盐负荷一致。春季NO3-的下降趋势主要受LF的硝酸盐行为影响，2000年以来由于氮肥负荷的减少，LF的硝酸盐行为大幅下降。
Time scale problems of nitrate behavior (i.e. seasonal variation and long-term trend) in headwater are closely related to its hydrological process. In a typical agricultural headwater catchment in the Chiba prefecture, Japan, the groundwater nitrate concentration showed an increasing trend, while for spring water, a substantial decreasing trend was observed during our monitoring period. Two key issues, (1) identification of multiple flow pathways and (2) evaluation of the residence time for different pathways, were emphasized to reveal the factors controlling the different patterns of nitrate trend. Three major flow pathways including vertical soil water flow (VF), lateral groundwater flow (LG) and deep groundwater flow (DG) along the upland-slope-valley were discriminated. Different time scale of three flow pathways was identified. The residence time of VF was calculated as 9–10 years based on the soil water budget equation and the apparent age of LG was estimated as 41 years by chlorofluorocarbons traces. The increasing trend of NO3− in groundwater agreed well with the historical nitrate loading. And the decreasing trend of NO3− in spring was mainly influenced by nitrate behavior of LF, which substantially decreased due to reduction of nitrogen fertilizer loadings since 2000.