Abstract
Abstract Runoff infiltration in Sustainable Drainage Systems enables the interception of a part of urban contaminant fluxes owing to several processes. The soil's ability to retain dissolved pollutants is generally assessed via sorption isotherms obtained from batch studies; however, the experimental points are not always in the same range as runoff concentrations. The present work (i) explores the consequences of modelling runoff–soil interactions from out-of-range equilibrium concentrations and (ii) proposes an improved method to ensure that experimental points fall within the desired range. Uncertainty analysis demonstrates that for a non-linear isotherm, using an extrapolated relationship may introduce significant biases in the ensuing estimations. Therefore, the proposed method consists of anticipating the equilibrium state of batch tests to accurately set the experimental conditions and reach appropriate concentrations. It is successfully applied to the determination of the sorption properties of copper and zinc onto three soils with different electrolyte solutions, as well as those of bisphenol A and three alkylphenols onto one soil. The contrasting affinities between the studied species and the soil materials could be related to their intrinsic properties and the soils' pedological parameters, as well as the presence of salt or dissolved organic ligands which partially inhibited metal sorption.
Highlights
Soil- and media-based Sustainable Drainage Systems (SuDS), which are primarily implemented for stormwater management, have been proven to offer interesting perspectives for the interception of runoff-generated contaminant fluxes (Napier et al 2009), both in the particulate and the dissolved phases (LeFevre et al 2014)
The soil, at thermodynamic equilibrium (Tran et al 2017). This approach has been widely used in the case of SuDS; practical applications of sorption isotherms include (i) comparing different materials used for SuDS design (Gülbaz et al 2015; Huber et al 2016), (ii) evaluating the overall amount of dissolved contaminants that can be retained by the media layer of existing bioretention facilities (Paus et al 2014a), (iii) estimating the risks of metal transfer in roadside embankments (Kluge et al 2014) and (iv) modelling contaminant behaviour within infiltration devices, including event-scale (Winiarski et al 2013; Zhang et al 2016) and long-term assessments (Li & Davis 2008; Quinn & Dussaillant 2014)
The concavity of the curve was visible for zinc at equilibrium concentrations .100 to 200 μg·LÀ1, Figure 3 | Sorption isotherms of (a) copper and (b) zinc for the three soil materials, in the reference conditions: experimental points and adjusted theoretical models
Summary
Soil- and media-based Sustainable Drainage Systems (SuDS), which are primarily implemented for stormwater management, have been proven to offer interesting perspectives for the interception of runoff-generated contaminant fluxes (Napier et al 2009), both in the particulate and the dissolved phases (LeFevre et al 2014) Their retention capacities towards solute species, which originate from a combination of various physicochemical mechanisms (including charge-driven interactions with the soil matrix, coordination, chelation and surface precipitation), are often appraised via sorption isotherms, i.e., global, experimental relationships between solute concentrations and amounts sorbed onto. These ranges may be perfectly suitable for other contexts and types of water, the direct applicability of the isotherms to the case of SuDS soil is probably questionable
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