Particle size-based evaluation of stormwater control measures in reducing solids, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs).

This study evaluates the effectiveness of various stormwater control measures (SCMs) in removing polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), both in dissolved forms and associated with different-sized solids. The SCMs evaluated include biofilters, a hybrid biofilter + media filter, a retention pond, and treatment trains with hydrodynamic separators and cartridge filters. The targeted particle size fractions were clay (0.7-2.7 µm), fine silt (2.7-20 µm), coarse silt (20-63 µm), and sand (>63 µm), along with their associated PAHs and PCBs. Samples were collected from multiple storm events at the inlets and outlets of these SCMs on current and former military bases in the Southwestern and Northwestern US. The study found that coarse particles (>20 µm) contained significantly higher fractions of organic carbon (foc), which correlated with higher concentrations of contaminants in these particulates. All SCMs effectively reduced particulate-bound contaminants, especially within the coarse particle fractions, but the removal of aqueous phase contaminants was generally minimal. Despite the overall effectiveness of the SCMs, maintenance challenges-such as biofilter erosion and insufficient cleanout of cartridge filters-can hinder their performance. The study highlights the importance of considering particle size and its relationship to contaminant distribution to comprehensively assess the performance of stormwater control measures and the potential for sediment recontamination.