Tuesday Poster Session - Source control measures - Monitoring & modelling

Microplastics are not frequently studied in stormwater runoff and receiving urban soil. Existing urban soil studies focusing on microplastics generally do not include other urban pollutants which may be related. This study provides a comprehensive overview of pollution in urban soils receiving road runoff. It builds on a previous study of a highway bioswale which analyzed tire wear particles and found a link between plastic litter and microplastics. In this study, sites include three roadsides with levels of traffic ranging from 3000 to 17000 vh/d and one parking lot outfitted with bioretention cells, located in the Île-de-France region to the North East of Paris. At each site, composite soil samples were collected at locations receiving stormwater runoff and analyzed for plastic litter, microplastics, tire and road wear particles, and heavy metals. In addition, chemical analysis for tire wear associated compounds and ecotoxicity studies of soil and its leachate will complement this data. Preliminary results show that concentrations for all pollutants decrease as the distance increases from the road. It is suspected that tire and road wear particles are correlated with metals. Further, the results suggest that microplastics, in the analysed size range, also more likely derived from atmospheric deposition than fragmentation of plastic litter. 

Urban rainwater runoff is increasingly recognized as a valuable resource in the context of water scarcity exacerbated by climate change. Nevertheless, runoff quality is often compromised by micropollutants originating from building materials, such as pesticides leaching from bituminous roof sheets. This study focuses on emissions of 2-methyl-4-chlorophenoxyacetic acid (MCPA), a herbicide commonly associated with green roofs and bituminous roofing materials. Given the limited availability of field measurements and the high costs of extensive monitoring campaigns, we employed a controlled laboratory setup to calibrate a pollutant transport model using Iber software water quality module. The calibration demonstrates the feasibility of reproducing MCPA transport dynamics within urban runoff systems, although further refinement is required to enhance accuracy. Future work will incorporate uncertainty and sensitivity analyses to evaluate the influence of key factors on model performance, thereby improving predictive capacity and supporting the development of robust management strategies for urban runoff quality. 

Stormwater runoff transports contaminants from urban infrastructure, automotive wear, industrial activities, and other sources into water bodies, while conventional monitoring focuses on known pollutants, leaving many emerging or unregulated compounds undetected. To obtain a comprehensive pollution profile, two retention-soil-filter (RSF) sites in Luxembourg were selected. (i) Raemerich, influenced by industrial and vehicular activities, and (ii) Grass Steinfort, representing road and rooftop runoff. First flushes were collected and analyzed for conventional water quality parameters, followed by combined suspect and non-target screening. Preliminary results show Raemerich runoff is heavily polluted, with COD (0-175 mg/L), and TSS (2-1378 mg/L) far exceeding levels at Steinfort. Inorganic pollutants including Na⁺, Cl⁻ , SO₄²⁻ , Br⁻ , and Mg²⁺ were consistently higher than Steinfort, peaking during rainfall-driven wash-off. Metals of concern included Mo, Ni, and V, reaching 14, 16, and 6 mg/L, respectively. Suspect screening detected eight priority contaminants at Raemerich (2a-3a/3c confidence), highlighting diverse pollution sources. Industrial markers 5-methyl-1H-benzotriazole and tributyl phosphate were prominent in inlet and RSF effluent, while pharmaceuticals (ibuprofen, lidocaine) and pesticides (propiconazole, isoproturon) were also observed. Lower but recurrent levels of DEET and Bisphenol A-d16 reflected general urban contamination. RSF effluent showed reduced intensities, for ibuprofen, lidocaine, and isoproturon, suggesting partial attenuation. However, key contaminants persisted in RSF effluent, showing that RSF inadequately remove micropollutants and require optimization. 

This meta-analysis integrates data from 182 runoff events across 15 urban catchments representing diverse land uses and seasonal conditions to prioritize metals of concern in urban discharges. Using a data-driven risk assessment, concentrations and risks of 20 metal(loid)s were compared against international databases and regulatory thresholds to consider both acute and chronic effects and bioavailability for seven metals. Event- and site-level analyses revealed large temporal and spatial variability driven by specific emission sources, land use, and seasonal hydrology. Spatially, “Parking/Road”, “Main Road/Highway”, and “Mixed Urban” catchments contributed most to overall metal loads and risk levels. Seasonally, snowmelt showed higher total concentrations and acute/chronic risks (due to elevated TSS and pH), while stormwater contained relatively higher dissolved and bioavailable fractions; only Co and Al showed notable chronic risk on the bioavailable fraction in snowmelt, whereas Cu and Pb did so in stormwater. Overall, Zn, Cu, Al, Fe, and Co ranked as the highest-risk metals, followed by Mn, V, Ba, and Ni. Results highlight the need for dynamic, chemistry-dependent management that integrates targeted source reduction, solids management, and treatment, while considering both metal speciation and runoff chemistry.

Current literature shows the ubiquitous occurrence of per- and polyfluoroalkyl substances (PFAS) in drinking water, rainwater, and soil/sediments. However, there are few data specifically quantifying their transport or mitigation within stormwater infrastructure (Bodus et al., 2024). This study presents the results of an extensive direct monitoring study of two wet ponds, constructed stormwater wetlands, and bioretention cells in Wilmington, NC, USA.  Data will answer the following questions: How much PFAS treatment do several common stormwater control measures (SCMs) provide? Which pollutant removal mechanisms found in standard designs are most effective at PFAS capture? Paired inlet and outlet event-based, composite samples are collected during natural rain events and analyzed for a suite of North Carolina’s most common PFAS compounds.  Data collection is currently ongoing and is expected to continue through June, 2026. 

In order to study the reactive transport of metallic micropollutants within stormwater infiltration infrastructures, a geochemical model describing the release of five trace elements from stormwater infiltration basin sediments, as a function of pH, was constructed. The modelling methodology presented combines experimental data from pH-dependent leaching tests with geochemical modelling using PHREEQC software. This work is carried out based on pre-existing experimental results on a sample dating from approximately 10 years after the structure was built (1991), and completed by leaching tests in accordance with standard NF EN 14429 on a sample from the same basin, taken in 2020. The model is calibrated by iteratively comparing measured and modelled concentrations of released major and trace elements followed by a corresponding adjustment of the model parameters. The model constructed from historical data is able to reproduce global trends for the release of 3 of the 5 trace metals studied in the dissolved fraction and to provide a first indication on the role of the different mineral phases and organic matter in the release mechanisms. Additional pH-dependent leaching tests allow to extend the pH range studied, as well as to improve the description of the organic matter and of the proposed mineral assemblage. Establishing a robust geochemical model under static conditions is an essential step prior to integrating a model describing contaminant transport in a stormwater infiltration basin. 

Combined sewer overflows (CSOs) occur when the discharge in combined sewer systems exceeds the hydraulic capacity of the WWTP and storage volume in the system is reached. This results in the discharge of untreated wastewater/stormwater mixtures into receiving water bodies. In addition to conventional contaminants, CSOs convey a broad spectrum of micropollutants, from domestic and non-domestic sewage (e.g. pharmaceuticals, personal care product residues) and from surface runoff (e.g. pesticides, and microplastics). In this study, Nature-based solutions (NBS) were developed for the treatment of CSO discharges within the Sûre catchment, a cross-border area between Luxembourg, Germany and Belgium (Wallonie). Locally available materials were selected and subsequently characterized for their suitability as substrates in retention soil filters. Under controlled mesocosm conditions (i.e. synthetic water, spiked active ingredients, constant temperature), these systems achieved removal efficiencies exceeding 92% for 18 targeted micropollutants, in average. Furthermore, locally produced biochars were evaluated as potential admixture components to conventional sand substrates to enhance micropollutant removal from CSO discharges. The outcomes of this first phase have been used to design pilot plants that are installed in the Sûre catchment, both in Luxembourgish and Belgian sides. The presentation will also contain first results obtained from these pilots. 

Combined sewer overflows (CSOs) are a major source of aquatic pollution, particularly microplastics (MPs), as they discharge untreated water during rainfall events. With the expected increase of more intense precipitation, these discharges will play an increasing role in the dispersion of MPs in aquatic ecosystems. Managing these discharges is therefore crucial to reducing urban anthropogenic emissions and the spread of MPs in rivers and oceans. The TRANSPLAST project aims to study MP emissions from CSOs by proposing a multidisciplinary approach. The teamwork of five laboratories (DEEP, IMP, LEHNA, LMFA, LMI) enables field studies to be carried out on a selection of CSOs in the Lyon metropolitan area, laboratory tests with doped model particles and numerical simulations on MPs transfer in CSOs. Each task provides information that feeds into the others. All of these results will help to design innovative strategies for intercepting MPs discharged by CSOs. The design of the model particles demonstrates homogeneous doping and dimensional control, which are essential for monitoring MPs during testing. Batch tests evaluate the effect of particle type and the wastewater/rainwater dilution ratio in order to identify the conditions that promote MPs sedimentation in a combined sewer system during rainfall. Finally, the VICAS protocol is adapted to MPs to measure their settling velocities. 

Urban stormwater sediments can accumulate a broad range of contaminants, yet municipalities often lack the resources for extensive laboratory analyses to determine appropriate management of these sediments. This study evaluates colour analysis, X-ray fluorescence (XRF), and optical microscopy as low-resource methods for characterising sediments and identifying anthropogenic particle sources. The assessment used sediment samples from 17 stormwater ponds and 26 gully pots in Sweden, which were earlier examined for metal and organic contaminants. The colour analysis showed spatial patterns for stormwater pond sediments, with lower anthropogenic pollutant levels and lighter colours in Örebro and darker sediments from Växjö and Stockholm showing higher pollutant concentrations, indicating the potential for colour as preliminary pollution indication. Microscopy revealed different anthropogenic materials, including clothing fibres, plastics, metal fragments, and glass beads, highlighting multiple contributing sources. In contrast, gully pot sediments displayed weaker relationships between colour, metals and pollutants, likely due to difference in catchments characteristics. Overall, the combined methods provided valuable insights into sediment composition and contamination patterns, however, further analysis is needed to confirm the observed trends of colour and pollutant levels. 

Episodic pollution waves from combined sewer overflows significantly affect surface-water quality, as confirmed by multi-year monitoring. Testing of the Proteus multiparameter probe during stormflow events in 2025 showed that it reliably captures wastewater dynamics and that selected parameters match laboratory analyses well. Despite some sensor limitations, the system offers a realistic way to track rapid water-quality changes that traditional sampling cannot capture and may help meet EU UWWTD requirements. 

This study examined whether three tiers of bioanalytical tools, acute toxicity (Microtox®), in-vitro cytotoxicity, and receptor-specific bioassays, can serve as indicators of contaminant burden in sediments from 17 Swedish stormwater ponds which were previously analysed for 259 legacy and contemporary contaminants. Acute toxicity was rarely observed, and Microtox® responses showed no clear correspondence with chemical contamination. In contrast, cytotoxicity derived from methanol-based sediment extracts strongly aligned with chemical contamination indicators, including the number of quantified substances and exceedances of environmental threshold frameworks. Receptor-based assays (estrogenic receptor, aryl hydrocarbon receptor and oxidative stress) revealed widespread biological activities, frequently exceeding benchmark levels derived from reference-compound PNECs, and illustrated mechanistic responses not captured by apical tests. Taken together, the results show that while Microtox® is poorly suited for assessing hazards in organic-rich stormwater sediments, cytotoxicity and receptor-based bioassays provide sensitive and complementary insights into mixture effects and contaminant loading. These findings support integrating effect-based tools with chemical monitoring to improve sediment quality assessment.