Seasonal and spatial distributions of polycyclic aromatic hydrocarbons in surface water of the Taehwa River in the largest industrial city in South Korea

Abstract

Surface water samples were collected from 18 stations along the Taehwa River in Ulsan, the largest industrial city in South Korea, to investigate the levels, compositional patterns, spatial distribution, and potential sources of polycyclic aromatic hydrocarbons (PAHs). The mean concentration of Sigma 15 PAHs in surface water across all sampling sites was 120 ng L-1, ranging from 82.1 to 245 ng L-1. Benz[a]anthracene concentrations during summer, fall, and winter exceeded the threshold values established by the Canadian Water Quality Guidelines. Particulate PAHs were more abundant than dissolved PAHs, and low-molecular-weight compounds, particularly phenanthrene, were predominant. PAH concentrations were higher in fall and winter than in spring and summer. In the upstream area, PAH levels and profiles were mainly influenced by non-point sources (e.g., illegal burning and agricultural waste incineration), whereas midstream and downstream levels were attributed to emissions from vehicles and petrochemical industrial facilities. The increasing pollution load downstream indicated that river flow rate was a key factor affecting PAH levels in surface water. Total suspended solids and total organic carbon also contributed to elevated PAH levels near industrial areas. This study is the first to investigate spatial variations in PAH concentrations along the Taehwa River in Ulsan, providing valuable insights for future regulation and management strategies targeting industrial emissions and non-point source pollution.