Distribution and sources of polycyclic aromatic hydrocarbons in soils along the Shatt Al-Arab River Delta in southern Iraq

Abstract

The soil samples from 0–10 cm depth were collected from three areas (Center of Basrah – CB, Garmat Ali – GA, and Abu Al-Khasib – AK) located along the Shatt Al-Arab River (SR) delta in southern Iraq to estimate the distribution and sources of polycyclic aromatic hydrocarbons (PAHs). The PAH total concentrations in the soils decreased significantly from CB (72.16 ng/g dry weight (DW)), GA (36.48 ng/g DW), to AK (17.30 ng/g DW) gradually indicating the impact of pollution emissions on the distribution of PAHs in soils. The low (2 and 3 ring) and high (4, 5, and 6 ring) molecular weight PAHs accounted for 14%, 16%, 37%, 21%, and 12% respectively in CB soil, 24%, 31%, 29%, 7%, and 10% in GA soil and 40%, 29%, 17%, 8%, and 8% in AK soil. The high molecular weight PAHs predominated in CB soils and the low molecular weight PAHs dominated in GA and AK soils suggesting a difference in emission sources between the studied areas. The PAH diagnostic ratios and principal component analysis (PCA) indicated that PAHs in soils of the SR delta essentially originated from traffic and industrial emissions and biomass and grass/wood/coal combustion. The PAH atmospheric transport from CB area might impact the PAH distribution in the soils of AK area. The risk assessment of the soils has been performed. The total toxic equivalent concentrations (Bapteq) of PAHs in the examined areas did not exceed the Dutch target values suggesting that no carcinogenic risk for the SR delta soils was found.