Hydrological tracers for assessing transport and dissipation
processes of pesticides in a model constructed wetland system

Groundwater quality in urban catchments is endangered by the input of biocides, such as those used in facade paints to suppress algae and fungal growth and washed off by heavy rainfall. Their retention in storm water infiltration systems (SIS) depends, in addition to their molecular properties, on chemical properties and structure of the integrated soil layer. These soil properties change over time and thus possibly also the relevance of preferential flow paths, e.g. due to ongoing biological activity. To investigate the mobility of biocides in SIS, we analyzed the breakthrough of differently adsorbing tracers (bromide, uranine, sulforhodamine B) and commonly used biocides (diuron, terbutryn, octhilinone) in laboratory column experiments of undisturbed soil cores of SIS, covering ages from 3 to 18 years. Despite similar soil texture and chemical soil properties, retention of tracers and biocides differed distinctly between SIS. Tracer and biocide breakthrough ranged from 54% and 5%, to 96% and 54%, respectively. We related the reduced solute retention to preferential transport in macropores as could be confirmed by brilliant blue staining. Our results suggest an increasing risk of groundwater pollution with increasing number of macropores related to biological activity and the age of SIS.

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“…Similar transport characteristics of UR and SRB in the beginning of the experiment were observed e.g. in the study conducted by 70 .…”

Section: Resultssupporting

confidence: 85%

Urban storm water infiltration systems are not reliable sinks for biocides: evidence from column experiments

Bork

Lange

Graf‐Rosenfellner

et al. 2021

Sci Rep

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“…Saline solution (NaCl) was used as a pollutant for the conservative tracer and the dye FB291 (CAS Number: 56548‐64‐2) was used as a strongly sorptive molecule (Berez et al., 2016). The combination of tracers with different sorptive properties allowed to distinguish between organic pollutant transport and phase partitioning in lab‐scale constructed wetlands (Fernandez‐Pascual et al., 2020). The initial salt concentrations were adjusted to prevent density‐driven flow during mixing with NaCl (500 mg·L −1 ) (Nagaoka & Ohgaki, 1990) or to avoid precipitation of FB291 (150 mg·L −1 ).…”

Section: Tracer Recirculation In Bench‐scale River Channelmentioning

confidence: 99%

Pollutant Dissipation at the Sediment‐Water Interface: A Robust Discrete Continuum Numerical Model and Recirculating Laboratory Experiments

Drouin

Fahs

Droz

et al. 2021

Water Resources Research

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More than one-third of globally available freshwater resources is used for human activities, and freshwater pollutions by macro-and micro-pollutants are recurring and widespread (Sousa et al., 2018). Rivers are the most sensitive environmental compartments to pollution hazards, especially low Strahler order rivers, which may receive proportionally larger loads of pollutants relative to their water discharge (Honti et al., 2018; Munz et al., 2011). Hyporheic zone processes in rivers affect both biogeochemical activities and pollutant mixing in the sediment bed (Boano et al., 2014). Despite decades of intense research on the hyporheic zone, the dynamics of hyporheic zone processes remain partly unresolved. In particular, current approaches often fail to identify and hierarchize the predominant factors controlling interactions between pollutants and river sediment beds in the hyporheic zone. Hyporheic processes controlling pollutant transformation mainly occur at the sediment-water interface (SWI) where dissolved species (e.g., organic matter, nitrates, oxygen, etc.) from the overlying water or the groundwater mix within the riverbed sediment, resulting in various redox gradients, themselves controlling the pollutant fate in rivers (Byrne et al., 2014). Hydrological conditions in rivers, including the succession of low flow and flooding events, vertical surface-groundwater exchanges, and geomorphological variations of river reaches, affect the transport of dissolved pollutants at the SWI (Briggs et al., 2014; Dwivedi et al., 2018; Lansdown et al., 2015). In addition, the propensity of a pollutant to sorb and degrade within the sediment bed controls its accumulation in the hyporheic zone (Liao et al., 2013). Sorption typically increases the pollutant mean residence time in the sediment bed and alters its distribution across the hyporheic zone (Ren & Packman, 2004a, 2004b). Hence, the interplay between hydraulic processes and pollutant partitioning at the SWI currently limits our understanding of pollutant fate in river systems (Krause et al., 2017). In this context, the characterization of hyporheic exchanges in rivers can rely on laboratory tracer experiments (Liao et al., 2013). Tracers can be used as surrogates of pollutants that may facilitate investigations of

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Hydrological tracers for assessing transport and dissipation processes of pesticides in a model constructed wetland system

Cited by 2 publications

References 13 publications

Urban storm water infiltration systems are not reliable sinks for biocides: evidence from column experiments

Urban storm water infiltration systems are not reliable sinks for biocides: evidence from column experiments

Pollutant Dissipation at the Sediment‐Water Interface: A Robust Discrete Continuum Numerical Model and Recirculating Laboratory Experiments

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