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 sigmaPCBs and sigmaPCDD/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 sigmaPCBs and sigmaPCDD/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 sigmaPCBs yr(-1) for PCBs and 1300 kg sigmaPCDD/Fs yr(-1). Furthermore, it is suggested that marine aerosol plays an important role in scavenging atmospheric contaminants.

GEM/POPs: a global 3-D dynamic model for semi-volatile persistent organic pollutants – Part 2: Global transports and budgets of PCBs

“…For example, it is noticeable that Atlantic region was a receptor and the deposition was an important process for the heavier PCB congeners in that region. Relative high dry deposition flux was found around 30 • N to 86 • N in the Atlantic area and the highest value was 500 pg/m 2 /day at 53 • N. This distribution was associated with the high air concentration in that area and consistent with the distribution and magnitude estimated by Jurado et al (2004). Wet deposition flux of PCB180 also presented a correlation to its air concentration: a peak value was predicted from 30 • N to 86 • N. Particle scavenging dominated the wet removal process (Jurado et al, 2005), which agrees with the prediction by GEM/POPs that 92% of the total deposition flux for PCB180 in the meridional region of Atlantic Ocean between 1 • E-20 • E was due to wet scavenging.…”

“…Compared to other studies (e.g. Jurado et al, 2004), GEM/POPs captured the general pictures of global PCB depositions. For example, it is noticeable that Atlantic region was a receptor and the deposition was an important process for the heavier PCB congeners in that region.…”

Atmospheric Dry Deposition of Polychlorinated Dibenzo-p-Dioxins/Dibenzofurans (PCDD/Fs) and Polychlorinated Biphenyls (PCBs) in Southern Taiwan

“…Deposition of SOCs in air can be divided into dry and wet deposition; both processes contribute significantly to the removal of these SOCs (Jurado et al, 2004). When SOCs are emitted into the atmosphere, they can be partitioned between the gas and particulate phases based on their concentrations, vapor pressures, the atmospheric temperature, and the concentration of particles within it (Hoff et al, 1996).…”

Spatio-temporal variations and influencing factors of polycyclic aromatic hydrocarbons in atmospheric bulk deposition along a plain-mountain transect in western China

“…Besides the sources emission, the meteorological parameters are also decisive factors for the deposition fluxes. For example, temperature can affect the vapor-particle partitioning for SOCs (Jurado et al, 2004). And the intensity, form (rain or snow) and rate of precipitation, wind speed and humidity could have impacts on the washout ratio and/or dry deposition speed, which will cause the variation of deposition fluxes (Lei and Wania, 2004;Li et al, 2009).…”