Title: Polycyclic Aromatic Hydrocarbons in Urban Environments: A Potential Role for Pervious Concrete

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant toxic organic pollutants that are ubiquitous in the environment, including stormwater runoff. Asphalt and concrete are impervious to urban runoff and therefore do not allow water to be filtered by the underlying soil. Pervious concrete is a specialized alternative to impervious surfaces such asphalt and traditional concrete. The incorporation of fly ash into concrete is common practice. However, its use in pervious concrete is poorly understood in terms of environmental quality. The presence of polycyclic aromatic hydrocarbons (PAHs) in the fly ash could leach when exposed to large volumes of rainwater. Furthermore, the carbon content of fly ash could theoretically increase the concrete’s adsorption capacity for organic contaminants. Local stormwater and sediments were analyzed to determine organic contaminant loadings. Pyrene and Fluoranthene were the only organic contaminants repeatedly identified in both stormwater and sediments. Runoff samples had concentrations in the range of 11–191 mg/L. Sediment samples ranged from 2.3 ´ 10¹–1.3 ´ 10⁴ mg/kg. Different pervious concrete formulations (0 – 40% fly ash, 2 – 14% carbon) were exposed to solutions to determine the potential for PAH leaching. Additionally, the formulations were spotted with motor oil and their desorption profile studied. Leaching studies using both distilled water and acidified water (pH 4.2) showed most PAHs were undetectable. Three positives resulted in concentrations below 1.0 mg/L. Both fly ash percentage and carbon content formulations showed impacts on motor oil retention. The 30% fly ash formulation retained 92% of the motor oil after being leached with 20 L of water while 0% fly ash retained only 83%. Increasing carbon content from 2% to 14% resulted in an increase in motor oil retention from 80% to 89% for the 20% fly ash formulations. This preliminary investigation into fly ash amended pervious concrete has shown that the pavement should not be a major source of PAHs due to water infiltration. Furthermore, this study indicates a positive environmental impact by increasing hydrocarbon retention.