PARENT SESSION

1K - Tropospheric Fate
Hall 13
8:30 AM - 12:30 PM, Monday, 28 April 2003
Chair: Harner, T.¹, ¹
Co-chair: Halsall, C.¹, ¹

(MO13/7) Importance of black carbon adsorption on the partitioning of ambient PCDD/Fs in a coastal urban environment.

Lohmann, Rainer¹, Eisenreich, Steven², Jones, Kevin¹, ¹ Lancaster University, Lancaster, England, UK² Rutgers University, New Brunswick, NJ, USA

ABSTRACT- Consecutive 12 hour day-night air samples (ca. 500m³ each) were taken over 7 days at 3 land-based sites and an over-water site in coastal New Jersey (NJ) in July 1998, in a campaign designed to shed light on factors controlling ambient PCDD/F concentrations and their gas-particle partitioning. The sampling sites were chosen to reflect contrasting environments: urban/industrial from the centre of New York (NY) (Liberty Science Center, LSC); coastal Atlantic (Sandy Hook, SH); suburban NJ (New Brunswick, NB); and over-water in Raritan Bay. Despite proximity to the major NY/NJ conurbation, ambient PCDD/F concentrations in the region were low: Mean Cl4-8DD/Fs and TEQ (in fg/m³) were: 1,400 and 16 at NB; 1000 and 9.5 over RB; 880 and 8.5 at LSC; and 830 and 6.6 at SH. Mono-, di- and tri-chlorinated PCDD/Fs were also measured and dominated ambient concentrations. Gas-particle partitioning coefficients, K_p = c_part/c_gas/TSP, were calculated and correlated with the respective sub-cooled liquid vapour pressures, p_L, or octanol-air partitioning coefficients, K_oa. Correlations were equally good with either descriptor and highly significant (P = 0.01) at all sites. Atmospheric concentrations at LSC, supported by dynamic to air-water exchange of PCDD/Fs, varied little over the course of the sampling campaign. Gas-particle correlations appeared at equilibrium at LSC, with a mean slope of −1 (p_L) or +1 (K_oa), whereas slopes were shallower at the sites more affected by advective transport (SH) or local source inputs (NB). Normalisation of partitioning constants to organic (f_OC) or elemental carbon (f_EC) fractions did not improve regressions. However, the Koa-model in general overpredicted gaseous concentrations, suggesting that further (ad)sorption has to be incorporated into gas-particle partitioning models.

Key words: dioxins and furans, gas-particle partitioning, black carbon, organic matter