Proximity of Field Distribution of Polycyclic Aromatic Hydrocarbons to Chemical Equilibria among Air, Water, Soil, and Sediment and Its Implications to the Coherence Criteria of Environmental Quality Objectives

The proximity of PAHs distribution to the equilibrium states among air, soil, water, and bottom sediment was assessed for future risk management and coherence test among environmental quality objectives (EQOs) in these media. Concurrently measured concentration data in the four media were used. In the study areas (Seoul, Shihwa/Banwol, and Taegu), nonequilibrium states prevailed among air, soil, and water except for some light PAHs between air and water. Elevated concentration in soil particularly caused significant deviation from equilibrium between soil and other media. Coherence criteria among these media should be determined based on steady state (not equilibrium) conditions. Sediment was in or near equilibrium with soil for all PAHs, indicating that sediment quality is closely related to soil quality and that the coherence between the EGOs of the two media is required in the study areas. As the concentration ratio of individual PAHs for a given medium pair was found to vary up to 4 orders of magnitude across the study areas, a factor of 10 as a threshold criterion for incoherence is apparently too strict to apply to the national scale of Korea.