Atmospheric dry deposition of persistent organic pollutants to the Atlantic and inferences for the global oceans

Abstract

Atmospheric deposition to the oceans is a key process affecting the global dynamics and sinks of persistent organic pollutants (POPs). A new methodology that combines aerosol remote sensing measurements with measured POP aerosol-phase concentrations is presented to derive dry particulate depositional fluxes of POPs to the oceans. These fluxes are compared with those due to diffusive air−water exchange. For all polychlorinated biphenyl (PCB) congeners and lower chlorinated dibenzo-p-dioxins and furans (PCDD/Fs), air−water exchange dominates the dry deposition mechanism. However, this tendency reverses in some areas, such as in marine aerosol influenced areas and dust outflow regions, consistent with the important variability encountered for the depositional fluxes. Seasonal variability is mainly found in mid-high latitudes, due to the important influence of wind speed enhancing dry deposition fluxes and temperature as a driver of the gas-particle partitioning of POPs. The average dry aerosol deposition flux of ΣPCBs and ΣPCDD/Fs to the Atlantic Ocean is calculated to be in the order of 66 ng m-2 yr-1 and 9 ng m-2 yr-1 respectively. The total dry aerosol deposition of ∑PCBs and ∑PCDD/Fs to the Atlantic Ocean is estimated to be 2200 kg yr-1 and 500 kg yr-1, respectively, while the net air−water exchange is higher, 22000 kg ∑PCBs yr-1 for PCBs and 1300 kg ∑PCDD/Fs yr-1. Furthermore, it is suggested that marine aerosol plays an important role in scavenging atmospheric contaminants