Center for Applied Geoscience, University of Tübingen, Hölderlinstr. 12, 72074 Tübingen, Germany.
Center for Applied Geoscience, University of Tübingen, Hölderlinstr. 12, 72074 Tübingen, Germany.
Sci Total Environ. 2019 Mar 15;656:1250-1260. doi: 10.1016/j.scitotenv.2018.11.379. Epub 2018 Nov 27.
Interpreting the fate of wastewater contaminants in streams is difficult because their inputs vary in time and several processes synchronously affect reactive transport. We present a method to disentangle the various influences by performing a conservative-tracer test while sampling a stream section at various locations for chemical analysis of micropollutants. By comparing the outflow concentrations of contaminants with the tracer signal convoluted by the inflow time series, we estimated reaction rate coefficients and calculated the contaminant removal along a river section. The method was tested at River Steinlach, Germany, where 38 contaminants were monitored. Comparing day-time and night-time experiments allowed distinguishing photo-dependent degradation from other elimination processes. While photo-dependent degradation showed to be highly efficient for the removal of metroprolol, bisoprolol, and venlafaxine, its impact on contaminant removal was on a similar scale to the photo-independent processes when averaged over 24 h. For a selection of compounds analyzed in the present study, bio- and photodegradation were higher than in previous field studies. In the Steinlach study, we observed extraordinarily effective removal processes that may be due to the higher proportion of treated wastewater, temperature, DOC and nitrate concentrations, but also a higher surface to volume ratio from low flow conditions that favorizes photodegradation through the shallow water column and a larger transient storage than observed in comparable studies.
解释废水中污染物在溪流中的命运是困难的，因为它们的输入随时间变化，并且几个过程会同时影响反应性迁移。我们提出了一种方法，通过在不同位置对溪流段进行采样以进行痕量污染物的化学分析，同时进行保守示踪剂测试，从而可以将各种影响分开。通过将流出污染物的浓度与由流入时间序列卷积的示踪剂信号进行比较，我们估计了反应速率系数，并计算了沿河道段的污染物去除率。该方法在德国 Steinlach 河进行了测试，在那里监测了 38 种污染物。比较日间和夜间实验可以区分光依赖性降解与其他消除过程。虽然光依赖性降解对 metroprolol、bisoprolol 和 venlafaxine 的去除非常有效，但在 24 小时平均值上，其对污染物去除的影响与光非依赖性过程相当。对于本研究中分析的化合物选择，生物和光降解的效率高于以前的现场研究。在 Steinlach 研究中，我们观察到特别有效的去除过程，这可能是由于处理过的废水比例较高、温度、DOC 和硝酸盐浓度较高，但也由于低流量条件下的表面积与体积比较大，有利于通过浅水层进行光降解，以及比在可比研究中观察到的更大的暂存区。
