Size distributions of organic nitrogen and carbon in remote marine aerosols: Evidence of marine biological origin based on their isotopic ratios

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Size-segregated aerosol samples were collected over the western North Pacific in summer 2008 for the measurements of organic nitrogen (ON) and organic carbon (OC). ON and OC showed bimodal size distributions. Their concentrations showed positive correlation with those of biogenic tracers, methanesulfonic acid (MSA) and azelaic acid (C9). We found that average ON and OC concentrations were twice greater in aerosols collected in the oceanic region with higher biological productivity than in the regions with lower productivity. The average ON/ OC ratios are higher (0.49 ± 0.11) in more biologically influenced aerosols than those (0.35 ± 0.10) in less influenced aerosols. Stable carbon isotopic analysis indicates that marine-derived carbon accounted for ~46-72% of total carbon in more biologically influenced aerosols. These results provide evidence that organic aerosols in this region are enriched in ON that is linked to oceanic biological activity and the subsequent emissions to the atmosphere.
2010-03-23