Department of Watershed Sciences, Utah State University, 5210 Old Main Hill, Logan, UT, 84332-5210, USA.
Utah Water Research Laboratory, Department of Civil and Environmental Engineering, Utah State University, 8200 Old Main Hill, Logan, UT, 84322-8200, USA.
J Environ Manage. 2021 May 1;285:112127. doi: 10.1016/j.jenvman.2021.112127. Epub 2021 Feb 15.
Non-point source (NPS) pollution remains high in many watersheds despite strategies aimed at reducing such pollution. Beaver (Castor canadensis) activity converts lotic systems to semi-lentic by impounding stream flow and trapping sediments, which have a high affinity for NPS pollutants such as nitrogen (N), phosphorus (P), and heavy metals. This study aimed to identify environmental conditions under which beaver ponds influence the fate and cycling of NPS pollutants. Dissolved and particulate nutrients were sampled upstream and downstream of three headwater beaver ponds differing in age and character through the summer season. Sedimentation rates and sediment concentrations of nutrients and metals were also determined. Results from this study suggest that beaver ponds can attenuate heavy metals at a rate 2 to 4 times greater than a riffle reach (p < 0.05). Metal sequestration scaled with pond age and sediment organic matter content. The oldest and youngest ponds had no significant effect on dissolved nutrients (NO, TDN and SRP) or total P (TP). The middle age pond was a significant TN sink in summer (0.6-0.8 g N m d [p = 0.03]) and influenced dissolved nutrient concentrations differently in spring (21% NO sink [p = 0.03], 61% SRP source [p = 0.05]) compared to summer (34% NO source, 7% SRP sink). This pond had little apparent effect on TP loads during the study period but accumulated a total of 146 g m of phosphorus in the sediments suggesting that beaver ponds may reach their phosphorus sequestration potential within the first few years of pond development and then subsequently act as a weak SRP source. We use a theoretical relationship describing sediment-water interactions to show that biogeochemical processing in a beaver pond is optimized at intermediate levels of pond nutrient supply and residence time. If beaver ponds are to be considered as an option for landscape scale restoration, this theoretical relationship may be useful for predicting the effects of beaver ponds on water chemistry, and aid in the interpretation of variable water quality results from inherently heterogeneous environments.
尽管已经采取了旨在减少非点源污染的策略，但许多流域的非点源污染仍然很高。海狸（Castor canadensis）的活动通过拦截水流和捕获沉积物将流水系统转化为半静水系统，而沉积物对氮（N）、磷（P）和重金属等非点源污染物具有很高的亲和力。本研究旨在确定海狸池塘影响非点源污染物命运和循环的环境条件。本研究在夏季通过三个不同年代和特征的源头海狸池塘，在上游和下游采集溶解态和颗粒态养分。还确定了沉积物中养分和金属的沉降速率和浓度。本研究的结果表明，海狸池塘可以以比急流区高 2 到 4 倍的速度衰减重金属（p<0.05）。金属固定与池塘年龄和沉积物有机质含量成正比。最古老和最年轻的池塘对溶解态养分（NO、TDN 和 SRP）或总磷（TP）没有显著影响。中年池塘是夏季 TN 的重要汇（0.6-0.8 g N m d [p=0.03]），并在春季以不同的方式影响溶解态养分浓度（21%的 NO 汇 [p=0.03]，61%的 SRP 源 [p=0.05]），而不是夏季（34%的 NO 源，7%的 SRP 汇）。该池塘在研究期间对 TP 负荷没有明显影响，但在沉积物中积累了总共 146 g m 的磷，这表明海狸池塘可能在池塘发展的最初几年内达到其磷固定潜力，然后随后成为 SRP 的弱源。我们使用描述沉积物-水相互作用的理论关系表明，海狸池塘中的生物地球化学过程在池塘养分供应和停留时间的中等水平下得到优化。如果海狸池塘被视为景观尺度恢复的一种选择，那么这个理论关系可能有助于预测海狸池塘对水质的影响，并有助于解释从固有异质环境中获得的可变水质结果。
