Retention and transport of nutrients in a mature agricultural impoundment
Retention and transport of nutrients in a mature agricultural impoundment
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DOI：
10.1029/2012jg002148
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发表时间：
2013-03
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影响因子：
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通讯作者：
S. Powers;J. P. Julian;M. Doyle;E. Stanley
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作者：
S. Powers;J. P. Julian;M. Doyle;E. Stanley
在世界农业地区，用于灌溉、牲畜浇水和水电的小型蓄水池比比皆是。这些人工水体中的许多都处于很好的位置，可以拦截化肥径流和污染物，但可能容易受到长期沉积、管理干预或失败的影响。我们研究了美国威斯康星州农业地区一座有100年历史的小水坝建造的成熟的、充满泥沙的径流蓄水池中的溶质滞留情况。为此，我们通过包含湿地的系统测量了无机和有机溶质的瞬时净通量。蓄水池是硫酸盐的持久净汇，只有在温暖的季节，才是硝酸盐、铵和可溶性活性磷的净汇。硝酸盐与硫酸盐滞留也呈负相关，提示硝酸盐刺激硫酸盐的产生。蓄水水力学随后通过管理操作(大坝拆除)进行了改变，使平均水上旅行时间减少了约40%。操作后，溶质时间序列的自回归模型表明，硝酸盐、硫酸盐、铵和可溶性活性磷的平均净保留率下降。溶解有机氮和溶解有机磷瞬时净出口量的变异性(变异系数)也有所下降。这些生物地球化学变化与基于水力学的预测(缩短了水的旅行时间)是一致的，除了水库脱水后立即释放的铵。我们的结果强调了水库-湿地生态系统的生物地球化学重要性，这些生态系统随着蓄水沉积而扩张，但受到基础设施老化的威胁。建议在堤坝治理和地表水污染治理中考虑水库湿地。
Small impoundments intended for irrigation, livestock watering, and hydropower are numerous in agricultural regions of the world. Many of these artificial water bodies are well positioned to intercept fertilizer runoff and pollutants but could be vulnerable to long‐term sedimentation, management intervention, or failure. We examined solute retention in a mature, sediment‐filled, run‐of‐river impoundment created by a small, >100 year old dam in agricultural Wisconsin, United States. To do so, we measured instantaneous net fluxes of inorganic and organic solutes through the system, which contained wetlands. The impoundment was a persistent net sink for sulfate and, during the warm season only, a net sink for nitrate, ammonium, and soluble reactive phosphorus. There was also a negative relationship between nitrate and sulfate retention, suggestive of nitrate‐stimulated sulfate production. Impoundment hydraulics were then altered by a management manipulation (dam removal) that caused mean water travel time to decrease by approximately 40%. Following manipulation, autoregressive modeling of solute time series indicated a decrease in mean net retention of nitrate, sulfate, ammonium, and soluble reactive phosphorus. There was also a decrease in the variability (coefficient of variation) of instantaneous net exports of dissolved organic nitrogen and dissolved organic phosphorus. These biogeochemical changes were consistent with predictions based on hydraulics (reduced water travel time), with the exception of ammonium release immediately following reservoir dewatering. Our results emphasize the biogeochemical importance of reservoir‐wetland ecosystems, which are expanding with impoundment sedimentation but are threatened by infrastructure aging. We suggest that reservoir wetlands be considered in the management of dams and surface water pollution.