Spatial distribution of heavy metals in the surface soil of source-control stormwater infiltration devices – Inter-site comparison

• Published in: The Science of the total environment 2017-02, Vol.579, p.881-892
• Main Authors: Tedoldi, Damien, Chebbo, Ghassan, Pierlot, Daniel, Branchu, Philippe, Kovacs, Yves, Gromaire, Marie-Christine
• Format: Article
• Language: English
• Subjects: Contamination; Earth Sciences; Engineering Sciences; Environmental Engineering; Environmental Sciences; Hydrology; Metals; Runoff infiltration; Sciences of the Universe; Soil; Spatial distribution; Sustainable urban drainage systems
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2016.10.226

Stormwater runoff infiltration brings about some concerns regarding its potential impact on both soil and groundwater quality; besides, the fate of contaminants in source-control devices somewhat suffers from a lack of documentation. The present study was dedicated to assessing the spatial distribution of three heavy metals (copper, lead, zinc) in the surface soil of ten small-scale infiltration facilities, along with several physical parameters (soil moisture, volatile matter, variable thickness of the upper horizon). High-resolution samplings and in-situ measurements were undertaken, followed by X-ray fluorescence analyses and spatial interpolation. Highest metal accumulation was found in a relatively narrow area near the water inflow zone, from which concentrations markedly decreased with increasing distance. Maximum enrichment ratios amounted to >20 in the most contaminated sites. Heavy metal patterns give a time-integrated vision of the non-uniform infiltration fluxes, sedimentation processes and surface flow pathways within the devices. This element indicates that the lateral extent of contamination is mainly controlled by hydraulics. The evidenced spatial structure of soil concentrations restricts the area where remediation measures would be necessary in these systems, and suggests possible optimization of their hydraulic functioning towards an easier maintenance. Heterogeneous upper boundary conditions should be taken into account when studying the fate of micropollutants in infiltration facilities with either mathematical modeling or soil coring field surveys. [Display omitted] •Concerns about the fate of urban pollutants within the soil of infiltration devices.•Experimental assessments of ten study sites with contrasting characteristics.•Surface concentrations are spatially structured with respect to the inflow area.•Contamination patterns bear the signature of non-uniform infiltration fluxes.•These findings should be accounted for in SUDS design, maintenance, and modeling.