Nitrate flux from aquifer storage in excess of baseflow contribution during a rain event.
Nitrate flux from aquifer storage in excess of baseflow contribution during a rain event.
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DOI：
10.1016/s0043-1354(01)00246-9
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发表时间：
2002-02
期刊：
影响因子：
12.8
通讯作者：
M. Iqbal
中科院分区：
文献类型：
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作者：
M. Iqbal
通过水流线分离法计算了由暴雨引起的基岩含水层的硝酸盐通量。爱荷华州雪松河（Cedar River）一次20毫米降雨所产生的水文曲线分为以下三个部分：恒定基流、雨水和超过基流的含水层释放的水。利用氧同位素、溶解硝酸盐和水流进行分离。峰值放电时间为33h。在此期间，超过基流的含水层储水量占总放水量的36%。雨水和暴雨前基流当量分别为17%和47%。瞬时放电中硝酸盐浓度在8.6 ~ 10.0mg/L之间。雨水和基流中的平均浓度分别为3.7和9.8mg/L。在峰值流量的33h内，共输送硝酸盐3.6×105mol。大约35% （1.3×105mol）的质量来自含水层储存，超过了基流的贡献。雨水和恒定基流当量分别为7% （2.6×104mol）和58% （2.1×105mol）。含水层中大量硝酸盐的释放表明，当地地质有利于雨水的垂直补给，这导致含水层内流体压力的增加，迫使地下水侧向排放到溪流中。这种观察结果还表明，在暴风雨期间，含水层实际上被冲走了，从而限制了农业来源的硝酸盐的长期积累。
Nitrate flux from a bedrock aquifer due to a storm was calculated by hydrograph separation. The hydrograph generated by a 20-mm rain in Cedar River of Iowa was separated into the following three components: the constant baseflow, the rainwater, and the water released from aquifer in excess of baseflow. The separation was conducted by using oxygen isotopes, dissolved nitrate, and stream discharge. The peak discharge was 33h long. During this period, the water released from the aquifer storage in excess of baseflow was 36% of the total discharge. The rainwater and the pre-storm baseflow equivalents were 17% and 47%, respectively. The nitrate concentrations in the instantaneous discharge ranged between 8.6 and 10.0mg/L. The average concentrations in the rainwater and the baseflow were 3.7 and 9.8mg/L, respectively. A total of 3.6×105mol of nitrate was transported by the stream during the 33h of peak discharge. Approximately 35% (1.3×105mol) of this mass was derived from the aquifer storage in excess of baseflow contribution. The rainwater and the constant baseflow equivalents were 7% (2.6×104mol) and 58% (2.1×105mol), respectively. The release of a significant amount of nitrate from the aquifer suggests that the local geology is favorable for vertical recharge of rainwater which causes an increased fluid pressure within the aquifer forcing ground water to discharge laterally into the stream. Such observation also implies that the aquifer is effectively flushed out during storms, thus restricting long term build-up of nitrate from agricultural sources.