Spatial distributions of dicarboxylic acids, ω-oxoacids, pyruvic acid and α-dicarbonyls in the remote marine aerosols over the North Pacific

Abstract

To better understand the sources and atmospheric processing of organic aerosols in the remote marine atmosphere, aerosol (TSP) samples were collected over the North Pacific (13°14′N-53°37′N and 140°46′E-179°54′W) in May–July, 2010 during a cruise of T/V Oshoro Maru, and studied for dicarboxylic acids (C2–C11), ω-oxoacids, pyruvic acid and α-dicarbonyls as well as organic and elemental carbon, water-soluble organic carbon and total nitrogen. Over the North Pacific, diacids are most abundant followed by ω-oxoacids and α-dicarbonyls. Although the molecular compositions of diacids are generally characterized by the predominance of oxalic (C2) acid, we found a predominance of succinic (C4) acid in four samples, which were collected in the central northern North Pacific. We consider that photochemical degradation of unsaturated fatty acids emitted from the ocean surface is the main source of C4 over the central northern North Pacific, where Chlorophyll-a maximized during the cruise. Moreover, seven samples collected in the central northern North and western North Pacific shows predominance of malonic (C3) acid over C4, suggesting the photochemical degradation of C4 to C3. Spatial distributions of diacids, ω-oxoacids and α-dicarbonyls together with total carbon and water soluble total nitrogen contents showed higher abundances in the coastal western North Pacific followed by the central northern North and subtropical Pacific, signifying that continental aerosols are transported long distances to the remote marine atmosphere.