The global increase of urban impervious land cover poses a significant threat to the integrity of river ecosystems. Hence, it is critical to assess the efficiency of green roofs (GR) to mitigate the negative impacts of urbanization on river ecosystems, such as thermal surges and pollutants. In this study, we evaluated the ecohydrological behaviour of two fully established GR under differing management regimes at the Chicago Botanical Gardens from July to September 2019. The drainage outflow from a non-vegetated roof, a managed GR (perennial native and non-native plants) and an unmanaged GR (perennial natural prairie vegetation) were monitored, and thermal dynamics, dissolved organic matter (DOM) composition and nitrate concentration assessed. The managed GR runoff had a lower DOC concentration and less humic-like DOM signal (SUVA₂₅₄) compared to the unmanaged GR. In contrast, lower concentrations of nitrate and more recalcitrant DOM (less protein-like compounds relative to humic-like compounds) were associated with the unmanaged GR. The unmanaged GR also displayed a greater capacity to reduce thermal surges associated with storm events. Our study provides new information on the implications of GR management for water quality with particular relevance to the urban stream syndrome. Further, the impacts of GR management on the mitigation of thermal surges and DOM composition can help to improve future GR design, as these ecohydrological responses have been largely overlooked to date. Our findings can support future urban planning, particularly for scenarios where green infrastructures are used to mitigate the impacts of climate change on urban river ecosystems.

中文翻译：

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绿色屋顶植被管理改变了缓解水质和温度的潜力

全球城市不透水土地覆盖的增加对河流生态系统的完整性构成了重大威胁。因此，评估绿色屋顶 (GR) 的效率对于减轻城市化对河流生态系统的负面影响（例如热浪涌和污染物）至关重要。在这项研究中，我们评估了 2019 年 7 月至 9 月芝加哥植物园在不同管理制度下两种完全成熟的 GR 的生态水文行为。 ) 和未管理的 GR（多年生天然草原植被），并评估了热动力学、溶解有机物 (DOM) 组成和硝酸盐浓度。受管理的 GR 径流具有较低的 DOC 浓度和较少的类腐殖质 DOM 信号（SUVA₂₅₄) 与非托管 GR 相比。相比之下，较低浓度的硝酸盐和更顽固的 DOM（相对于腐殖质类化合物较少的类蛋白质化合物）与未管理的 GR 相关。未管理的 GR 还显示出更大的能力来减少与风暴事件相关的热浪。我们的研究提供了关于 GR 管理对水质的影响的新信息，特别是与城市河流综合症相关。此外，GR 管理对缓解热浪涌和 DOM 组成的影响有助于改进未来的 GR 设计，因为迄今为止这些生态水文响应在很大程度上被忽视了。我们的研究结果可以支持未来的城市规划，特别是对于使用绿色基础设施减轻气候变化对城市河流生态系统影响的场景。