Spatial distributions and source identification of PCDD/Fs and PCBs in soils and pine needles in the multi-industrial city of Ulsan, South Korea

The spatial distribution and contamination patterns of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in soil and pine needles from the multi-industrial city of Ulsan, South Korea were assessed. The mean concentrations of Σ₁₇ PCDD/Fs, Σ₁₂ dl-PCBs, and Σ₇ I-PCBs were 78 pg/g dw, 90 pg/g dw, and 453 pg/g dw in the soil and 6 pg/g ww, 31 pg/g ww, and 166 pg/g ww in the pine needles, respectively. The mean concentrations of PCDD/Fs, dl-PCBs, and I-PCBs in the soil at industrial sites (138, 184, and 453 pg/g dw) were significantly higher than those at urban (47, 33, and 186 pg/g dw) and suburban sites (48, 49, and 234 pg/g dw). In the pine needles, although PCDD/F and PCB levels were higher at several industrial sites, mean concentrations at the industrial (6, 31, and 166 pg/g ww), urban (4, 29, and 143 pg/g ww), and suburban (4, 31, and 169 pg/g ww) sites were comparable, indicating that atmospheric transport plays a crucial role in spreading contamination throughout the study area. Higher chlorinated PCBs were predominant in the soils, while PCDFs and lower chlorinated PCBs were more common in the pine needles, reflecting the distinct physicochemical properties and interactions of these chemicals with each medium. Principal Component Analysis (PCA) revealed industrial combustion as the main source of PCDD/Fs and PCBs, with Aroclors identified as an additional source of PCBs. Suburban areas were influenced by both local sources and pollutants transported from urban and industrial areas. This study highlights that industrial activities and atmospheric transport significantly contribute to the widespread contamination of PCDD/Fs and PCBs in Ulsan.