Emerging and legacy PAHs in urban soils of four small cities: Concentrations, distribution, and sources

Polycyclic aromatic hydrocarbons (PAHs) are widespread organic contaminants in the environment, much being accumulated in soils. Although their concentrations in large cities have been studied, their levels in small cities were less studied. This study determined the concentrations, distributions, and sources of 16 USEPA priority PAHs (legacy PAHs) and 6 emerging PAHs in urban soils of four small cities. A total of 100 soil samples were collected in Florida, USA. The average ∑16-PAHs in urban soils of Clay county, Ocala, Pensacola, and West Palm Beach were 1821, 2748, 3115 and 4055 μg kg^-1, respectively. Based on benzo[a]pyrene-equivalent (BaP-EQ), the 7 USEPA carcinogenic PAHs (7cPAHs) and 3 emerging carcinogenic PAHs (3cPAHs) in urban soils in Clay County averaged 223 and 3703, Ocala 319 and 4521, Pensacola 302 and 5423, and West Palm Beach 449 and 5916 μg kg^-1, respectively. Although ∑7cPAHs in 87-89% of samples were lower than the Florida Soil Cleanup Target Levels (FSCTLs) for industrial sites at 700 μg kg^-1, ∑3cPAHs were 13-18 times greater than ∑7cPAHs. Based on the PMF model and molecular diagnostic ratios, soil PAHs were dominated by similar sources in small cities, mainly from pyrogenic sources including biomass, coal and coke combustion and vehicle emissions. It is important to evaluate both legacy and emerging PAHs concentrations in urban soils when considering soil remediation and human health risk assessment.