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Seasonal Variation and Gas/Particle Partitioning of PCBs in Air from Central Urban Area of an Industrial Base and Coastal City –Tianjin, China

Category: Air Toxics

Volume: 15 | Issue: 3 | Pages: 1059-1071
DOI: 10.4209/aaqr.2015.01.0035
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Zhi-Yong Li , Yu-Ling Zhang, Lan Chen

  • School of Environmental Science and Engineering, North China Electric Power University, No.689 Huadian Road, Baoding 071000, China

Highlights

In China, the research on gas/particle partitioning of PCBs is still at a early stage.
Four seasonal samples were collected for analysis of 86 congeners.
The results for three models indicated the non-equilibrium state of gas-particle partitioning.
The TEQ for dl-like PCBs was as high as 144.878 fg/m3.


Abstract

The 26 air samples were collected from Tianjin urban areas from July 2010 to May 2011 for the analysis of 86 PCB congeners to investigate the gas/particle partitioning of PCBs. The total PCBs concentration (in pg/m3) ranged from 31.28 to 650.33 (mean: 273.77) and showed a significantly seasonal variation as summer > autumn > spring > winter. Gas PCBs accounted for 80.79% of total PCBs. The fraction of each gas PCB homolog increased with the decreasing chlorine atoms. The contribution of gas PCBs to total PCBs showed a strong seasonal variation with summer (94.07%) > autumn (78.91%) > spring (78.19%) > winter (56.02%). Tri-, tetra- and penta-PCBs were the predominantly homologs in Tianjin atmosphere. The natural logarithm of partial pressure of PCBs were well correlated with the inverse absolute environmental temperature (R = 0.79). The steep slope of –4933.64 obtained from Clausius–Clapeyron (C.C) plot indicated the influence of local PCBs sources. In generally, the C.C slopes and the surface-air exchange enthalpy (∆HSA) for different PCB homologs increased with the increasing chlorine atoms. The fraction of particle bound PCBs were underestimated for PCBs with PL0 > 10–3.85 Pa and overestimated for PCB congeners with PL0 < 10–3.85 Pa by Junge-Pankow model. The logarithm of particle/gas partitioning coefficients (log KP) of PCBs were well correlated with the logarithm of respective sub-cooled vapor pressures (log PL0) (R = 0.72) and the octanol-air partition coefficient (log KOA) (R = 0.77). The slopes for log KP against log PL0 and log KOA plots were –0.44 and 0.48, deviated significantly from the expected –1 and +1 for the equilibrium state of gas/particle partitioning, possibly explained by the emission of PCBs and particles from the local industries and other sources. The TEQ concentrations (fg/m3) for 12 dioxin-like PCB congeners ranged from 35.628 to 612.796 with the mean value as 144.878.

Keywords

PCBs Gas/particle partitioning Clausius-Clapeyron plot Sub-cooled vapor pressure Octanol-air partition coefficient


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