Centre for Hydrology, University of Saskatchewan, Canada; Global Institute for Water Security, University of Saskatchewan, Canada.
Centre for Hydrology, University of Saskatchewan, Canada; Global Institute for Water Security, University of Saskatchewan, Canada.
Sci Total Environ. 2019 Apr 20;662:110-120. doi: 10.1016/j.scitotenv.2019.01.091. Epub 2019 Jan 21.
Seasonal snowcovers release nutrients accumulated over the winter during spring snowmelt and this can be an important part of the annual biogeochemical cycling of chemicals and their loading to soils and water bodies. The characteristics of this load are controlled by snowmelt dynamics and the physical and chemical properties of the snowpack, which are affected by overwinter and snowmelt metamorphism, refreezing of meltwater, and ion exclusion from snow crystals. Rain-on-snow (ROS) events can accelerate and modify the snowpack discharge process. The interplay of these processes can cause microscale flow heterogeneity and preferential flow pathways (PFP). Previous experimental work has examined PFP and ion elution processes in snowpacks, but their combined effect on the spatial and temporal characteristics of snowmelt ion elution remains uncertain. In this research, two controlled laboratory experiments were performed to investigate the role of PFP and ROS in controlling snow ion release to runoff. These involved the high frequency monitoring of flow and meltwater concentrations during snowmelt induced by radiation-convection (RC) processes and rain-on-snow (ROS). Results showed that when ROS was included, PFP was responsible for the transport of 68% and 73% of the total NO and PO load discharged during the early snowmelt phase recorded by the experiment. However, this initial load increased to 95% and 75% when ROS was removed, causing the release of more than 20% of the total snowpack NO and PO during the first 1.5% of melt. Small intensity ROS may refreeze in the snowpack, which may affect the ability of lateral flow to deliver snow ions located beyond the leading edge of PFP.
季节性积雪在春季融雪期间释放冬季积累的养分，这可能是化学物质年生物地球化学循环及其向土壤和水体加载的重要组成部分。这种负荷的特征受融雪动力学以及积雪的物理和化学性质控制，而积雪的物理和化学性质又受到越冬和融雪变质、融水再冻结以及雪晶中离子排除的影响。雨夹雪（ROS）事件会加速并改变积雪的排放过程。这些过程的相互作用会导致微尺度流的非均质性和优先流路径（PFP）。先前的实验工作已经研究了积雪中的 PFP 和离子洗脱过程，但它们对融雪离子洗脱的时空特征的综合影响仍不确定。在这项研究中，进行了两项受控实验室实验，以研究 PFP 和 ROS 在控制积雪离子释放到径流中的作用。这些实验涉及在辐射对流（RC）过程和雨夹雪（ROS）引起的融雪过程中高频监测流量和融水浓度。结果表明，当包括 ROS 时，PFP 负责在实验记录的早期融雪阶段中输送总 NO 和 PO 负荷的 68%和 73%。然而，当 ROS 被去除时，这个初始负荷增加到 95%和 75%，导致在最初 1.5%的融雪期间释放了超过 20%的总积雪 NO 和 PO。强度较小的 ROS 可能在积雪中再冻结，这可能会影响侧向流输送位于 PFP 前缘以外的积雪离子的能力。
