The increasing urbanization and land development poses significant water quality challenges in urban areas. Stormwater control measures, such as bioretention basins, are implemented to mitigate these issues by managing storm volumes and improving water quality. Despite their widespread use, the effectiveness of bioretention basins in removing pollutants, particularly heavy metals and polycyclic aromatic hydrocarbons (PAHs), remains unclear. This study evaluates the treatment efficiency of two stormwater bioretention basins (Kyle and TPC) situated within the critical Edwards Aquifer recharge zone in Texas. Over a 1-year period, influent and effluent samples were collected and analyzed to assess removal of heavy metals and PAHs. Soil samples were also collected to assess the distribution of metals in basin soil. The results reveal significant differences in removal efficiency for Fe, Cu, and Zn between the two basins. Within Kyle, there was a significant load reduction of Fe (77%), Cr (74%), and Cu (65%). Within TPC, a significant load reduction was observed for Fe (68%), Cu (84%), and Zn (82%). The results from soil samples indicated significant difference between summer and winter samples for Fe, Mg, Zn and Pb in Kyle while Pb was the only metal that significantly varied between seasons in TPC samples. The high molecular weight PAHs detected in TPC suggested that the sources likely originated from industrial and transportation activities. These results carry significant implications for the operation and maintenance protocols governing such basins, necessitating careful consideration of their impact on groundwater quality and the broader ecosystem.
Keywords: Aquifer protection; Bioretention; Heavy metals; Polycyclic aromatic hydrocarbons; Stormwater.
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