Assessment of metal and PAH profiles in SUDS soil based on an improved experimental procedure

Abstract

The increasing use of infiltration-based systems for stormwater management questions the soil's ability to act as a long-term filter for runoff contaminants, and brings about operational matters regarding the most effective maintenance practices to enhance contaminant retention in SUDS. This paper reports the vertical extent of metal and PAH contamination in the soil of seven source-control devices in operation for more than 10 years, assessed via a two-step sampling strategy to optimize the representativeness of the contamination profiles. Metal distribution was typically characterized by a significant surface buildup, followed by a decrease in concentrations with increasing depth, usually coming close to the background values. PAH were more heterogeneously distributed with depth, but their accumulation was globally restricted to the upper 10-40 cm. This indicates an interesting potential for pollution interception by the upper horizons of soil, but does not necessarily prevent from downward fluxes, even while measuring low surface contents, as deeper strata may have lesser retention capacities. Specific amendments of the surface soil may help prevent this problem. Surface soil renewal - which would be necessary over 2.5-30 cm in four sites, according to the "strictest" standards for soil remediation - may regenerate the soil's sorption potential, but such a practice could disrupt the interactions with the local ecosystem, so this should be carried out exceptionally and not as a preventive measure.

Stochastic Method for Evaluating Removal, Fate and Associated Uncertainties of Micropollutants in a Stormwater Biofilter at an Annual Scale

“…The filter media in the BFS was sampled in April 2017 according to the method developed by Tedoldi et al [24], which relies on a sampling procedure in two phases. First, the surface of the BFS was sampled using an identical high-resolution grid in each section of the BFS ( Figure 2a); each sample was dried, sieved to 2 mm, homogenized and analysed for Cu, Zn and Pb using portable X-ray fluorescence spectrometry.…”

Zirconium deficit as a tracer of urban sediment accumulation in Sustainable Urban Drainage Systems – Application to the calibration of a filtration model

“…As regards the "exception sites" with dissimilar behaviors, it should be underlined that the Greffiere facility was implemented in a residential area with a priori low suspended solid loads, while the heterogeneity observed in the Chanteraines and Compans3 swales may be attributed to an uneven mixture of the soil material during their construction. In the former case, this would also explain the dissimilarity in Zr profiles between the contaminated and the reference zones (Figure 5b), which was also visible with the distribution of other metals or pedological parameters such as cation exchange capacity or carbonates (Tedoldi et al, 2017b). In the latter case, not only was the differential between the sediment and soil relatively small, but also the operating time of the system (1 year) was probably insufficient to observe a significant sediment buildup in the swale.…”

“…In Compans1 and 2, the cross-sections showed that Zr deficit was globally restricted to the upper 5 centimeters alongside the road; the rest of the filter strips displayed almost uniform contents (Figure 4). In the most contaminated zone of the other facilities, Zr content generally tended to increase with depthwhich, as for the cartographies, was the opposite trend compared to metals (Tedoldi et al, 2017b). In comparison with the reference profiles, which showed little variability, Zr deficit in the contaminated zone was visible up to a depth of 5 to 15 cm ( Figure 5).…”

Retention and transport processes of particulate and dissolved micropollutants in stormwater biofilters treating road runoff

“…Soil sampling A sample of BFS filter media was collected before installation; in addition, a soil sampling campaign was conducted in April 2017, after 13 months of operation. During this campaign, a cartography of the soil's surface contamination was established using X-ray fluorescence and used to identify eight zones of similar contamination for core sampling according to the method developed by Tedoldi et al (2017). In each zone, 2-4 cores were collected, divided into three depth segments: 0-5 cm, 5-15 cm and 15-50 cm, and combined to form composite samples for each depth.…”