Inherent and external factors influencing the distribution of PAHs, hydroxy-PAHs, carbonyl-PAHs and nitro-PAHs in urban road dust

Abstract

The distribution and fate of hazardous polycyclic aromatic hydrocarbons (PAHs) and their associated transformed PAHs products (TPPs) notably carbonyl-PAHs (CPAHs), hydroxy-PAHs (HoPAHs), and nitro-PAHs (NPAHs) on urban road surfaces are influenced by diverse factors to varying extent. The pollutants are eventually transported to urban receiving waters via stormwater runoff posing risks to human and ecosystem health. In order to formulate an effective mitigation strategy, it is essential to comprehensively examine the role of both inherent and external factors in the distribution and fate of these hazardous pollutants, and thus, the need for this study. The research study showed that commercial land use has the highest cumulative concentration of PAHs and TPPs. Antecedent dry days (ADDs) has an inverse influence on the distribution of the total concentrations of low-molecular weight PAHs (LMW-PAHs), PAHs, and (PAHs + TPPs) irrespective of the type of land use, whilst there was no major influence on the total concentrations of high molecular weight PAHs (HMW-PAHs), and TPPs. The high volatility of LMW-PAHs compared to HMW-PAHs is considered to account for the decreasing concentration of LMW-PAH with increasing ADD. Particle size range has significant inverse influence on the cumulative concentration of pollutants across all land uses, since smaller particles are characteristically associated with larger surface area leading to the higher sorption of pollutants. Multivariate analysis of the influential factors indicated that two particle size ranges (0.45–150 μm and 150–425 μm) constitute the major influential factors on the distribution and fate of PAHs and TPPs in urban road dust. Greater quantum of pollutants are sorbed to the 0.45–150 μm particles due to the relatively higher specific surface area (SSA), concentration of total organic carbon (TOC) and total suspended solids (TSS) concentration. Therefore, it is critical to effectively remove finer particles from road surfaces in order to reduce exposure to hazardous pollutants.