Monitoring polycyclic aromatic hydrocarbon concentrations and distributions in rice paddy soils from Gyeonggi-do, Ulsan, and Pohang

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants that are released by incomplete combustion of carbon-containing materials. The top soils of rice paddies were collected from Gyeonggi-do (18 sites), Ulsan (20 sites), and Pohang (19 sites) in Korea to assess the spatial distribution and potential sources of PAHs. The total concentrations of 15 PAHs in the soils were 19.53–672.93, 125.01–3106.27, and 51.94–8106.21 mg/kg in Gyeonggi province, Ulsan, and Pohang, respectively. The concentration of 7 key carcinogenic PAHs were followed the order: Pohang (38.54–4826.63 ng/g) > Ulsan (28.54–1561.39 ng/g) > Gyeonggi province (19.53–206.51 ng/g). Three-ring PAHs were predominant in the soils from Gyeonggi-do while 3–5 ring compounds were abundant in the agricultural soils from the two industrial regions (Ulsan and Pohang). The PAH isomeric diagnostic ratios indicated that PAH contamination in the two cities mainly originated from pyrogenic sources. The principal component analysis indicated that pyrogenic coal burning and residential biomass combustion were major contributors to the soil contamination in the two cities. The transportation of PAHs through the air from industrial complexes and high volume of traffic may influence the PAHs distribution in the soils of the two cities in Korea.