Chemical characterization of aerosols over the Atlantic Ocean and the Pacific Ocean during two cruises in 2007 and 2008

To help understand the chemical properties of marine aerosols and the long-distance transport of continental aerosols to remote oceanic regions, total suspended particulates (TSP) samples were collected over the Atlantic Ocean and the Pacific Ocean during two cruises in September-December 2007 (cruise I) and March-April 2008 (cruise II) aboard the M/V Oceanic II. Data were analyzed and interpreted with the aid of back trajectory, principal component, and multiple linear regression analyses. Compared with the results over the South Pacific from 2 decades ago, the non-sea-salt sulfate (NSS-SO₄^2-) concentrations over the South Pacific have increased by a factor of ∼1.5, while the NO₃^- concentration has remained constant. On average, NSS-SO₄^2- accounted for 30-52% of the total SO₄^2- during the two cruises. Chloride deficit was observed in all samples, with NSS-SO₄^2- being the preferred species for acid displacement over the South Pacific and the Mediterranean Sea. Persistent clean marine air masses were only observed over the northern Atlantic and South Pacific during cruise I, while more frequent impacts of continental air (dust, biomass burning, and industrial plumes) were observed during cruise II. Combined with the NAAPS aerosol maps, these results indicate that during cruise II, (1) southern Atlantic was influenced by Southern Africa and the interhemisphere transport of biomass burning plumes in Central Africa, (2) northern Atlantic was under the combined pollution plumes of Sahara dust intrusion and biomass burning, and (3) the Mediterranean Sea was affected by the mixed pollution from biomass burning and industrial contamination, as well as Saharan dust.