The direct measurement of the dry deposition of organochlorine pesticides and polychlorinated naphthalenes

Between June 1995 and October 1995, simultaneous dry deposition and ambient air samples were collected to characterize the dry deposition of polychlorinated naphthalenes (PCNs) and organochlorine pesticides (OCs) in Chicago, IL.;Average total SigmaPCN concentration was 20 +/- 6.15 pg/m3, similar to the lower range of previously measured urban area concentrations while organochlorine pesticides had similar ambient concentrations. The particle/gas phase distribution for PCNs varied widely among congeners while the SigmaPCN distribution was approximately 50% in each phase while organochlorine pesticides phase distribution varied with molecular weight.;Total (particulate + gas) fluxes were measured for each PCN congener, SigmaPCN and each OC pesticides with the WSS while particulate fluxes were obtained from dry deposition plates. The highest PCN flux was for 4--6(CN) (2.6 ng/m2.d) and the lowest was for another 4 chlorinated naphthalene, 4--7 (CN) (0--06 ng/m2.d). Particulate fluxes for these compounds varied between 0.7 and 2.3 ng/m2.d.;The total flux of OC pesticides ranged from 90--850 ng/m 2.d. The particulate flux was dominated by high molecular weight compounds and ranged from 174 to 486 ng/m2.d. Gas phase fluxes for OCs was 40--928 ng/m2.d while it was 0.8--10 ng/m2.d for SigmaPCN.;Particulate phase dry deposition velocities were calculated using the dry deposition fluxes and ambient concentrations. The average particulate phase dry deposition velocity for OCs was 5.0 +/- 2.0 cm/s while it was 3.0 +/- 2.3 cm/s for PCNs.;Overall gas phase mass transfer for the OCs was 1.16 +/- 0.30 cm/s which agreed well with the modeled value of 0.77 cm/s. The experimental overall mass transfer coefficient for PCN congeners was 0.82 +/- 0.46 cm/s which agreed well with the modeled value for all congeners of 0.55 cm/s.;Back trajectory analysis showed that in the Great Lakes area local volatilization had a greater effect on concentration in the atmosphere than long-range transport. However long-range transport from other countries may also influence the concentration of these compounds where some of these compounds are still in use.