Atmospheric Occurrence and Deposition of Polycyclic Aromatic Hydrocarbons in the Northeast Tropical and Subtropical Atlantic Ocean

Abstract

Atmospheric transport and deposition of polycyclic aromatic hydrocarbons (PAHs) over tropical oceans has not yet been studied even though tropical oceans account for 35% of the global oceans. Here we show the results from measurements of gas- and aerosol-phase PAHs and dry deposition samples in the NE tropical Atlantic Ocean atmosphere, a region between 26 degrees and 21 degrees N, off shore of the Saharan desert. The results show that PAHs concentrations are high at the coastal ocean (15-20 ng m(-3) for sum of 27 gas-phase individual PAHs) and decrease by a factor of 2-3 at open ocean (26 degrees W). The spatial variability observed is consistent with dilution, reaction, and deposition during transport. Atmospheric dry deposition velocities ranged between 0.1 and 0.3 cm s(-1) with higher deposition velocities for the more volatile PAHs. Outbreaks of Saharan Dust significantly increase the deposition rates of PAHs. The occurrence and deposition of PAHs in tropical regions is complex and results from the interplay of a number of processes, such as wind speed, aerosol loads, important sources from West Africa, processes controlling the diurnal variability, and sequestration driven by high primary productivity regions. The measured average atmospheric residence times of gas- and aerosol-phase PAHs are 3.7 and 3.5 days, respectively.

Particulate PAHs and n-alkanes in the air over Southern and Eastern Mediterranean Sea

“…The minimum concentrations were measured offshore in T 3-3(1) , T 6-8 and T 8-9 . Concentrations presented in this work were for most PAHs lower than those found previously in the Black and Eastern Mediterranean Sea (CastroJimenez et al, 2012;Tsapakis and Stephanou, 2005), Pacific and Atlantic Oceans (Xu et al, 2012;Nizzetto et al, 2008;Del Vento and Dachs, 2007); on the other hand, our values were in agreement with data reported for Indian Ocean air (Liu et al, 2014) and Mediterranean sub-basins (Castro-Jim enez et al, 2012), as well as with cruise measurements performed in the south-eastern Mediterranean in summer 2010 (Mulder et al, 2014). The seasonality of emissions, the different maritime traffic in these regions or its combination with various cruise routes distinctly influenced by in land combustion sources on land (biomass burning, power plants etc.…”

Organophosphate Ester (OPE) Flame Retardants and Plasticizers in the Open Mediterranean and Black Seas Atmosphere

“…A value of 0.2 cm s −1 (173 m d −1 ) for v d has been chosen as representative of marine aerosols at high sea. 35 This value has been previously used in the estimation of the dry deposition of other organic contaminants such as PCDD/Fs and PAHs over the Mediterranean Sea. 9,13 However, a degree of uncertainty (factor of 3) is associated to this calculation due to the lack of measurements of v d during the cruises.…”

Atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) to a coastal site of Hong Kong, South China

“…(particle) in Galveston Bay (Park et al, 2001), 19.70 ng m À3 (gas) and 1.05 ng m À3 in the coastal areas of tropical and subtropical Atlantic Ocean (Del Vento and Dachs, 2007), respectively. Compared with these two regions, PAH contamination in this coastal site of Hong Kong was in a low to medium level.…”