Origins and fate of polycyclic aromatic hydrocarbons (PAHs) in sustainable drainage systems (SuDS) in a Scottish urban area: Implications for groundwater systems

Increasing urbanisation and the effects of climate change have resulted in a decrease in water quality and availability worldwide. At the same time, flooding in urban areas has become one of the most prevalent natural disasters worldwide. Sustainable drainage systems (SuDS) are resilient stormwater management solutions that can help reduce flooding by mimicking natural drainage processes and promoting infiltration. Numerous studies have focused on the benefits SuDS provide. But, to date, studies fail to investigate the risks that detention basins pose to groundwater quality, particularly the potential for infiltration of stormwater pollutants such as polycyclic aromatic hydrocarbons (PAHs). To address this important knowledge gap, this study combines gas chromatography–mass spectrometry (GC–MS) techniques for PAHs characterisation with numerical modelling tools to investigate organic pollutant infiltration patterns. We find that high levels of PAHs originating from urban areas are temporarily stored in SuDS basins and are likely to reach shallow water tables within one year. Multiple factors such as vegetation, precipitation, drainage area size, total organic carbon content in the soil and soil saturation influence the PAHs infiltration rates within the basins. More broadly, this study highlights the need for more research regarding SuDS dynamics to prevent both flooding and groundwater deterioration.