Determination of fluxes and mass transfer coefficients of polychlorinated biphenyls (PCBs)

Abstract

This study evaluated a modified water surface sampler (MWSS) in terms of deposition characteristics of atmospheric polychlorinated biphenyls (PCBs). Water was employed as a collection surface for the atmospheric PCBs. The main difference between the MWSS and previous WSSs was its cover which prevented the deposition of particles and minimized wind effects. Therefore, lower particle-phase deposition fluxes were observed. Moreover, preventing wind from the water surface, which was the collection surface, caused lower dissolved phase fluxes and mass transfer coefficients (MTCs). Forty-eight flux and ambient air samples were taken by using an MWSS and a high volume air sampler (HVAS), respectively. The average dissolved phase PCB fluxes were 5.92 +/- 5.37 ng/m(2)-day. Particle phase PCB fluxes were also determined by attaching a filter to the sampler. The particle phase flux ratio was 14% of the total flux, which was much smaller than previously reported ones. This difference was mainly due to the cover layer which minimized the wind effects. 4- CBs and lower chlorinated PCBs were dominant in the samples. Homolog groups obtained from both the MWSS and HVAS were highly correlated. This result indicated that both samplers collected similar atmospheric PCBs. Then, MTCs were calculated for each PCB congener. To calculate the MTCs, dissolved phase PCB fluxes were divided by gas-phase PCB concentration. The average MTC was determined to be 0.25 +/- 0.23 cm/s which was smaller than the previously reported MTCs. This result illustrated that the MWSS configuration allowed us to determine the minimum MTCs and gas transfers to the water.