Are the ratios of the two concentrations at steady state in the medium pairs of air-water, air-soil, water-soil, water-sediment, and soil-sediment?

Abstract

For optimization and evaluation of a steady state multimedia model, concurrent multimedia monitoring data of steady state are necessary. In the lack of emission rate information, the primary aim of the present work was to assess if five concentration ratios (CRs) (Cwater/Cair, Csoil/Cair, Csediment/Csoil, Cwater/Csoil, and Csediment/Cwater) of chemical compounds are at steady state in South Korea. A total of 16,676 CRs values were calculated using 74,641 concurrent multimedia (air, water, soil and sediment) monitoring data from 96 areas for 45 semi-volatile organic compounds (polychlorinated dibenzo-p-dioxins/furans, polybrominated diphenyl ethers, phthalates, and polycyclic aromatic hydrocarbons). Test of steady state indicated that CR is statistically at steady state with an overall occurrence rate of 70% of the 223 tested cases while the rates of individual chemical groups were 94.5%, 88%, 82.5%, and 37.6% for polycyclic aromatic hydrocarbons, phthalates, polybrominated diphenyl ethers, and polychlorinated dibenzo-p-dioxins/furans, respectively. About 83% of the steady state CRs resulted from scattering of two concentrations in each of the medium pairs without a certain temporal trend while the rest due to closely co-varying two concentrations. Analysis of the 95% confidence interval of the fugacity ratio indicated that CRs at steady state may occur in equilibrium state with higher chances than CRs at unsteady state. A total of 156 point values representing the CRs at steady state were determined that can be used for optimization and evaluation of steady state one-box multimedia models. However, potential influences of the uncertainties of the values arisen from the scattering of the concentration data should quantitatively be assessed in the model optimization and evaluation.