Contamination characteristics of polychlorinated naphthalenes in the agricultural soil of two industrial cities in South Korea

This study investigates the contamination characteristics of polychlorinated naphthalenes (PCNs) in the rice paddy soils of two industrial cities (Pohang and Ulsan) in South Korea. The paddy soils were collected from 40 sites in the paddy fields near industrial complexes in both cities. The mean concentration of Σ₅₅ PCNs was 145.9 ± 101.7 pg/g and 95.4 ± 41.4 pg/g for the soils in Pohang and Ulsan, respectively. The toxic equivalents (TEQs) of Σ₂₈ PCNs ranged from 0.007 pg-TEQ/g to 0.069 pg-TEQ/g in Pohang, and 0.015 pg-TEQ/g to 0.046 pg-TEQ/g in Ulsan. The PCN profiles were dominated by lower chlorinated homologues such as tetra- and tri-CNs for both cities, which are associated with the historical use of technical products, or more specifically, Halowaxes (HW 1099, 1031, 1013, and 1001). The results of the principal component analysis (PCA) indicate that the historical residues from the technical products contributed to the PCN contamination, but the influence of combustion sources was also observed with a high fraction of combustion-related congeners. Based on this study, we can expect that rice grown in these paddy fields will accumulate PCNs and other combustion-related pollutants, strongly suggesting the necessity for multimedia (e.g., air, soil, water, and rice) monitoring and human exposure assessments of PCNs.