Evidence for dynamic air-water exchange of PCDD/Fs: A study in the RaritanBay/Hudson River Estuary

The first detailed evidence for dynamic air-water exchange of polychlorinat ed dibenzo-p-dioxins and furans (PCDD/Fs) is presented. Samples of air (340 -380 m(3)) and water (33-60 L) were taken simultaneously during July 1998 a t two sites in the lower Hudson River Estuary, NY. The atmospheric gas and particulate phases and the aqueous dissolved and particulate phases were an alyzed for di- to octa-CDD/Fs. All the homologue groups were routinely dete cted by HRGC-HRMS, with detection limits for the homologue groups similar t o 1 pg/sample. Cl(2)DDs, OCDD, and Cl(2)DFs were the most abundant homologu es in the water, and the Cl(2)DDs were the most abundant in the air(4.3-7.6 pg/m(3)). The Cl2DD/Fs and Cl7/8DD/Fs were 25-53% and 78-99% associated wi th the water particulate phase, respectively. The likelihood of sampling ar tifacts influencing the apparent dissolved/particulate partitioning of the higher chlorinated congeners is discussed. Water concentrations were consta nt over the sampling period, while atmospheric concentrations varied with a ir mass origin. The fugacity ratios between the dissolved phase in water an d the gas phase in air were usually similar to 1, implying a net volatiliza tion flux. Evidence for outgassing of the lower chlorinated homologues, obt ained by the simultaneous measurement of air over adjacent land and water, provided further support for the outgassing of the lower chlorinated homolo gues from the water body.