Department of Geography and Environmental Studies, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada.
Department of Geography and Environmental Studies, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada.
Sci Total Environ. 2019 Feb 20;652:278-288. doi: 10.1016/j.scitotenv.2018.10.242. Epub 2018 Oct 19.
In some cold regions up to 97% of the chloride (Cl) entering rivers and lakes is derived from road salts that are applied to impervious surfaces to maintain safe winter travel conditions. While a portion of the Cl applied as road salt is quickly flushed into streams during melt events via overland flow and flow through storm sewer pipes, the remainder enters the subsurface. Previous studies of individual watersheds have shown that between 28 and 77% of the applied Cl is retained on an annual basis, however a systematic evaluation of the spatial variability in Cl retention and potential driving factors has not been carried out. Here we used a mass balance approach to estimate annual Cl retention in 11 watersheds located in southern Ontario, Canada, which span a gradient of urbanization. We evaluated the influence of multiple landscape variables on the magnitude of Cl retention as well as the long-term rate of change in stream Clconcentration for the same systems. We found that mean annual Cl retention ranged from 40 to 90% and was higher for less urbanized watersheds and for watersheds with urban areas located farther from the stream outlet. This result suggests that less urbanized watersheds and ones with longer flow pathways have more Cl partitioned into storage and hence the potential for legacy Cl effects on aquatic organisms. While we did measure statistically significant increasing trends in stream Cl concentration in some watersheds, there was no consistent relationship between the long-term rate of change in stream Cl concentrations and patterns of urbanization and the magnitude of Cl retention. Based on our results we present a detailed conceptual model of watershed Cl dynamics that can be used to guide future research into the mechanisms of Cl retention and release within a watershed.
在一些寒冷地区，进入河流和湖泊的氯（Cl）有高达 97%来自于用于保持冬季道路安全的道路盐。尽管一部分道路盐中的 Cl 会在融雪期间通过地表径流和雨水管道迅速冲入溪流，但其余部分会进入地下。先前对个别流域的研究表明，每年有 28%至 77%的应用 Cl 被保留下来，然而，对 Cl 保留的空间变异性及其潜在驱动因素尚未进行系统评估。在这里，我们使用质量平衡方法来估计位于加拿大安大略省南部的 11 个流域的年度 Cl 保留量，这些流域跨越了城市化程度的梯度。我们评估了多种景观变量对 Cl 保留量的影响，以及同一系统中溪流 Cl 浓度的长期变化率。我们发现，年平均 Cl 保留量范围为 40%至 90%，在城市化程度较低的流域和城市区域离溪流出口较远的流域中，Cl 保留量较高。这一结果表明，城市化程度较低和流程路径较长的流域中，更多的 Cl 被分配到存储中，因此对水生生物产生氯代物影响的可能性更大。虽然我们确实在一些流域中测量到 Cl 浓度的统计上显著增加趋势，但在溪流 Cl 浓度的长期变化率与城市化模式和 Cl 保留量之间没有一致的关系。基于我们的结果，我们提出了一个详细的流域 Cl 动态概念模型，可用于指导未来对流域内 Cl 保留和释放机制的研究。
