Background, aim, and scope

The release of trace elements (TE) associated with the development of human activities has accelerated since the nineteenth century, leading to the pollution of river systems. Despite a drastic reduction in industrial inputs in northern Europe, diffuse pollution originating from urban areas still prevents achieving the good status required by the European Water Framework Directive. The objectives of the current study, which is a part of a wider project, were to determine the impact of hydrological dynamics on the total exports of TE from an urban catchment and to develop an assessment tool to evaluate the level of contamination of a catchment based on its specific particulate TE fluxes.

Materials and methods

Accordingly, this research investigated the behavior of TE contamination in a 950 km² catchment (Orge River, France) showing a strong urbanization gradient in downstream direction. Particulate and dissolved samples were collected in the river during a hydrological year at four stations reflecting the increasing urbanization gradient. Trace element concentrations were measured in the samples using inductively coupled plasma/mass spectrometry (ICP-MS). Daily and annual TE fluxes were calculated at the four stations to evaluate the contribution of urban areas to the total TE exports from the catchment.

Results

The quantification of TE fluxes showed that up to 70% of particulate Cu, Zn, Sb, and Pb exported by the Orge River originated from the urban areas located in the lower catchment portions, especially during average water flow periods characterized by frequent rain events. Moreover, the results show that 50% of the dissolved fluxes of Cu, Zn, and Pb are supplied by urban areas during the entire year, regardless of hydrological conditions, and that the specific contribution of floods to these fluxes (i.e., the June 2016 event) is lower than that in other catchments because of the continuous supply of dissolved metal fluxes to the river in this urbanized environment.

Conclusion

These results underline the need to integrate all hydrological conditions for the management of TE contamination in urban areas and not to focus on storm events only. Finally, based on a literature survey, the ratios of specific fluxes were homogeneous across different highly urbanized catchments, and they could be used as a tool to compare the levels of anthropogenic pressure in these contrasted study sites. This observation demonstrates the similar impacts of societal development on urban river geochemistry worldwide, although they occurred during different time periods.

中文翻译：

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流域尺度上城市地区微量元素通量的时空变化定量

背景，目的和范围

自19世纪以来，与人类活动发展相关的微量元素（TE）的释放加速了，导致了河流系统的污染。尽管北欧的工业投入急剧减少，但城市地区产生的弥漫性污染仍然无法达到欧洲水框架指令要求的良好状态。作为一项更广泛项目的一部分，本研究的目标是确定水文动力学对城市集水区TE总出口量的影响，并开发一种评估工具来评估基于集水区的集水区的污染水平。其特定的颗粒TE通量。

材料和方法

因此，这项研究调查了950 km ²集水区（法国奥尔格河）中TE污染的行为，表明下游方向上的城市化梯度很强。在水文年期间，在四个站点的河流中收集了颗粒状和溶解性样本，反映出城市化梯度不断增加。使用电感耦合等离子体/质谱法（ICP-MS）测量样品中的痕量元素浓度。计算了四个站点的日和年TE通量，以评估城市地区对流域总TE出口的贡献。

结果

对TE通量的定量分析表明，奥尔格河出口的高达70％的颗粒状Cu，Zn，Sb和Pb来自位于下游集水区的市区，特别是在降雨频繁的平均水流时期。此外，结果表明，全年（不论水文条件如何），城市地区都提供了50％的溶解的铜，锌和铅通量，洪水对这些通量的具体贡献（即2016年6月事件）低于其他流域，因为在这种城市化环境中向河流不断供应溶解的金属通量。

结论

这些结果表明，有必要整合所有水文条件，以管理城市地区的TE污染，而不仅仅是关注暴风雨事件。最后，根据文献调查，在不同高度城市化的集水区，特定通量的比率是均匀的，它们可以用作比较这些对比研究地点的人为压力水平的工具。这项观察表明，尽管社会发展发生在不同的时间段，但它们对全世界城市河流地球化学的影响是相似的。