University of Strasbourg, CNRS, ENGEES, ICube, UMR 7357, F-67000 Strasbourg, France; University of Strasbourg, CNRS, UMR7362, LIVE, 67000 Strasbourg, France.
University of Strasbourg, CNRS, ENGEES, ICube, UMR 7357, F-67000 Strasbourg, France.
Sci Total Environ. 2022 Oct 20;844:157097. doi: 10.1016/j.scitotenv.2022.157097. Epub 2022 Jun 30.
In the context of stormwater management in urban areas, more knowledge is needed about sustainable urban drainage systems (SUDS)' long-term performance. This article reports robust calibration of a portable X-ray Fluorescence Analyzer (pXRF) for a purpose of metal accumulation diagnosis in two stormwater constructed wetlands (SCWs). Two 9-year-old SCWs located in Eastern France and composed of a sedimentation pond and a vertical-flow reed-bed filter (RBF#1) respectively a horizontal-flow RBF (RBF#2) are studied. A focus is made on the RBFs where five target metals (Cr, Cu, Ni, Pb, Zn) are monitored to fulfill three objectives: i) develop a robust analyzing method for both field and laboratory scale; ii) compute a distribution mapping of the metals on the substrate; and iii) identify and quantify contamination hotspots. pXRF measurements present an opportunity for a quick field diagnosis of such ageing systems once calibrated. An optimal 63 s beam shooting time was selected for analyses, and optimal particle size distribution was set below 250 μm. As water content is known to be a critical factor influencing measuring quality, correction factors were determined to allow for field campaign up to 30 % of water content. Metals are more accumulated in RBF#1 than in RBF#2 because of the particle size distribution and hydraulic regime of the RBFs. Moreover, RBF#1 displays a higher metal accumulation at the water supply outputs while the distribution pattern in RBF#2 is more diffuse. Only 34 %, resp. 22 % of RBF#1 and RBF#2 surface is contaminated, with corresponding concentrations ranging among the highest 50 % and 25 % concentrations. Eventually, the RBF#1 upper layer (0-5 cm) higher organic matter content generates more metal retention than its deeper layer whereas in RBF#2 metal concentration is homogeneous along depth. These results can be useful to optimize the long-term maintenance and possibly the sizing of such systems.
在城市雨水管理的背景下，需要更多关于可持续城市排水系统（SUDS）长期性能的知识。本文报告了一种便携式 X 射线荧光分析仪（pXRF）的稳健校准，该分析仪用于诊断两个雨水构造湿地（SCW）中的金属积累。两个位于法国东部的 9 年历史的 SCW 分别由一个沉淀池和一个垂直流芦苇床过滤器（RBF#1）以及一个水平流 RBF（RBF#2）组成。研究的重点是 RBF，在那里监测了五种目标金属（Cr、Cu、Ni、Pb、Zn），以实现三个目标：i）为现场和实验室规模开发一种稳健的分析方法；ii）计算金属在基质上的分布图谱；iii）识别和量化污染热点。经过校准后，pXRF 测量为这种老化系统的快速现场诊断提供了机会。选择了最佳的 63 秒射束拍摄时间进行分析，并将最佳的颗粒尺寸分布设置为低于 250μm。由于水含量已知是影响测量质量的关键因素，因此确定了校正因子以允许在水含量高达 30%的野外考察中使用。由于 RBF 的颗粒尺寸分布和水力条件，RBF#1 中的金属积累比 RBF#2 更多。此外，RBF#1 在供水出口处显示出更高的金属积累，而 RBF#2 的分布模式则更加扩散。只有 34%，分别为 RBF#1 和 RBF#2 表面的 22%受到污染，相应的浓度范围在最高的 50%和 25%浓度之间。最终，RBF#1 的上层（0-5cm）较高的有机物含量比其深层产生更多的金属保留，而在 RBF#2 中，金属浓度沿深度均匀分布。这些结果可用于优化此类系统的长期维护和可能的尺寸设计。
