Octanol−Air Partition Coefficient for Describing Particle/Gas Partitioning of Aromatic Compounds in Urban Air

Abstract

Atmospheric concentrations and particle/gas partition coefficients were measured for PAHs, PCBs, and PCNs in urban Chicago during February/March 1995. Average (n = 15) concentrations (pg m-3) were ΣPAH = 58 000, ΣPCB = 350, and ΣPCN = 68. The partitioning of these compounds between the particle phase and the gas phase was investigated and compared to the adsorption (Junge−Pankow) model, which utilizes the subcooled liquid vapor pressure as a fitting parameter, and the K OA absorption model. The K OA model was able to resolve differences between ortho-chlorine substituted groups of PCBs which correlations against were not able to explain. Partitioning of PCNs was also well described by the K OA model. For PAHs, sorption onto particles agreed with both models when the wind was predominantly from the SW sector. When air was sampled from the NE sector, PAHs showed enrichments in the particle phase relative to the chlorinated aromatics in log−log plots of the particle/gas partition coefficient, K P versus Enrich ment factors calculated as K P (PAH)/K P (multi - ortho PCB) were 27−100 from the NE sector compared to 2−4 for the SW sector. This suggests source region effects on K P for PAHs. It is hypothesized that the enrichment may be due to nonexchangeable PAHs trapped inside combustion aerosols or a result of a slow re-equilibration of these aerosols as they are diluted in ambient air.

Evaluation of a Conceptual Model for Gas-Particle Partitioning of Polycyclic Aromatic Hydrocarbons Using Polyparameter Linear Free Energy Relationships

“…Previous studies showed that the model of Finizio could underestimate the PAH partitioning constants by more than 1 order of magnitude. 9,16,17 In the present study, predictions made with the Dachs-Eisenreich model (i.e., adding the contribution of adsorption onto soot) increased the magnitude of K P but not substantially (Table 1 and Figure S9). This may not be surprising if we consider that the partitioning process was mainly dominated by absorption into organic matter ( Figure S10).…”

“…13,16 However, analyte nonexchangeability in the atmosphere could only be expected under low relative humidity and temperature, such as in the free troposphere, due to kinetic constraints caused by slow diffusion in glassy or semisolid bulk organic matter. 58−60 Such conditions may have hardly affected the aerosols studied here, which were transported mostly close to sources and within the boundary layer.…”

Short- and Medium-Chain Chlorinated Paraffins in Air and Soil of Subtropical Terrestrial Environment in the Pearl River Delta, South China: Distribution, Composition, Atmospheric Deposition Fluxes, and Environmental Fate

“…47 Light congeners have stronger tendency to pass to the vapor phase and can undergo atmospheric transport by air masses, while heavier congeners, bound on particles, are more likely to deposit to adjacent areas. Therefore, atmospheric transport is an important pathway for the movement of light contaminants from sources to distant regions, 48 while atmospheric deposition is the main process contributing to air-to-soil transport of heavy contaminants to regions in the proximity of sources. 20 A fractionation was also discovered for CP congeners in the PRD, especially for SCCPs, with a trend toward increasing levels of light congeners (e.g., C 10−11 Cl 5−6 ) and decreasing levels of heavy congeners (e.g., C 12−13 Cl 7−10 ) from the industrialized Dongguan and Guangzhou to the rural Huizhou City (based on the average abundance within the same city, Figures 4 and S4, Supporting Information).…”

Atmospheric Concentrations and Phase Partitioning of Polycyclic Aromatic Hydrocarbons in Izmir, Turkey

“…Partitioning of atmospheric organic compounds between the gas and particle-phases is parameterized using the gas/particle partition coefficient, K P (m 3 mg À1 ) [33]:…”

“…The octanol-air partitioning coefficient (K OA ) can be used to predict K P with the assumption of predominant distribution process is absorption [33]. The relationship between K P and K OA is:…”