Wet Deposition of Persistent Organic Pollutants to the Global Oceans

Wet deposition fluxes of polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins and furans to the Atlantic Ocean have been estimated by combining meteorological satellite data and measured atmospheric field concentra tions. They are then compared to other atmospheric depositional mechanisms on a global scale. Additional features not treated in traditional studies are addressed such as contaminant adsorption onto raindrops and enhancement of dry gaseous diffusive fluxes due to rain-induced turbulence. Wet deposition estimates show a high spatial and seasonal variability, with maxima located in the Intertropical Convergence Zone (ITCZ) and in low-temperature regions. Seasonal variability reflects the northward shift of ITCZ in July. Average wet deposition fluxes estimated for the Atlantic Ocean in this study are 110 and 45 ng m^-2 yr^-1 for ΣPCB and ΣPCDD/Fs, respectively. Furthermore, the total wet deposition to the Atlantic results in 4100 kg yr^-1 (ΣPCB) and 2500 kg yr^-1 (ΣPCDD/Fs). Model validation shows good agreement with available coastal data measurements of wet deposition fluxes. When compared to other atmospheric depositional mechanisms and during precipitation events, wet deposition is found to be dominant. However, when raining events and non-raining time periods are integrated, air−water diffusive exchange fluxes acquire an important role, which can be dominant in some regions and for some POPs.