Monitoring of organochlorine pesticides using pine needle, pine bark, and soil samples across South Korea: Source apportionment and implications for atmospheric transport.

Pine needle, pine bark, and soil samples were collected from various regions in South Korea, considering the suitability of vegetation samples as passive samplers. A total of 27 organochlorine pesticides (OCPs) were analyzed using a gas chromatograph/high-resolution mass spectrometer (GC/HRMS). The total concentrations of OCPs ranged between 650 and 3652 pg/g dw in soil, 215 and 1384 pg/g ww in pine needles, and 456 and 1723 pg/g ww in pine bark. Metabolites such as endosulfan sulfate, p,p'-DDE, and p,p'-DDD were dominant in the soil samples, whereas parent compounds were more prevalent in the pine needles. Diagnostic ratios and compositional profiles suggested that potential OCP sources were primarily related to historical use, atmospheric transport, and unintentional byproducts. OCPs that were never used or registered in South Korea were also detected in all sample types, indicating atmospheric transport from source regions. Sites closer to North Korea and China showed higher concentrations of OCPs, with levels gradually decreasing from west to east in the soil, suggesting long-range atmospheric transport from the source regions. Fugacity fractions indicated net volatilization for most compounds, while net deposition was observed for others, suggesting a dynamic equilibrium. This study concludes that atmospheric transport plays a predominant role in the distribution and fate of OCPs in the environment, with no evidence of current local sources.