Quantifying an aquifer nitrate budget and future nitrate discharge using field data from streambeds and well nests
Quantifying an aquifer nitrate budget and future nitrate discharge using field data from streambeds and well nests
复制标题
使用河床和井巢的现场数据量化含水层硝酸盐预算和未来硝酸盐排放
DOI：
10.1002/2016wr018976
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发表时间：
2016
影响因子：
5.4
通讯作者：
H. Mitásová
中科院分区：
文献类型：
--
作者：
T. Gilmore;D. Genereux;D. Solomon;K. Farrell;H. Mitásová
在河床下和井中进行的新型地下水采样（年龄、通量和硝酸盐）用于估算(1)受污染的无承压含水层中硝酸盐储量（dSNO3 /dt）的当前变化率，以及(2)未来的[NO3−]FWM（地下水排放中流量加权平均硝酸盐浓度）和fNO3（从含水层到溪流的硝酸盐通量）。dSNO3 /dt的估计表明，在采样时（2013年），含水层中硝酸盐的储存量以每年（平均= - 9 mmol/m2yr）的速度减少，相当于硝酸盐补给输入速度的十分之一。这与近年来地下水补给[NO3−]缓慢减少的数据一致。关于未来的[NO3−]FWM和fNO3，基于井数据的预测显示，在21世纪40年代初趋于平稳之前，在~ 5年后会立即下降，下降速度会更快。基于河床数据的预测通常显示，到本世纪20年代末，未来的[NO3−]FWM和fNO3会增加，随后会减少，到本世纪40年代趋于平稳。差异显示了直接利用地下水-地表水界面信息来量化地下水硝酸盐对地表水质量未来影响的潜在价值。反硝化动力学的选择同样重要；与零级动力学相比，一阶速率定律使未来[NO3−]FWM和fNO3（峰值较低，最小值较高）的估计值趋于平衡，因为遗留的硝酸盐从含水层中被冲走。关于非点源含水层污染的主要基本问题可以在没有复杂的数值模型或长期监测计划的情况下得到回答。
Novel groundwater sampling (age, flux, and nitrate) carried out beneath a streambed and in wells was used to estimate (1) the current rate of change of nitrate storage, dSNO3 /dt, in a contaminated unconfined aquifer, and (2) future [ NO3− ]FWM (the flow‐weighted mean nitrate concentration in groundwater discharge) and fNO3 (the nitrate flux from aquifer to stream). Estimates of dSNO3 /dt suggested that at the time of sampling (2013) the nitrate storage in the aquifer was decreasing at an annual rate (mean = −9 mmol/m2yr) equal to about one‐tenth the rate of nitrate input by recharge. This is consistent with data showing a slow decrease in the [ NO3− ] of groundwater recharge in recent years. Regarding future [ NO3− ]FWM and fNO3 , predictions based on well data show an immediate decrease that becomes more rapid after ∼5 years before leveling out in the early 2040s. Predictions based on streambed data generally show an increase in future [ NO3− ]FWM and fNO3 until the late 2020s, followed by a decrease before leveling out in the 2040s. Differences show the potential value of using information directly from the groundwater—surface water interface to quantify the future impact of groundwater nitrate on surface water quality. The choice of denitrification kinetics was similarly important; compared to zero‐order kinetics, a first‐order rate law levels out estimates of future [ NO3− ]FWM and fNO3 (lower peak, higher minimum) as legacy nitrate is flushed from the aquifer. Major fundamental questions about nonpoint‐source aquifer contamination can be answered without a complex numerical model or long‐term monitoring program.