Marine nitrogen fixation as a possible source of atmospheric water-soluble organic nitrogen aerosols in the subtropical North Pacific

[摘要] Water-soluble organic nitrogen (WSON) in marineatmospheric aerosols affect the water solubility, acidity, andlight-absorbing properties of aerosol particles, which are importantparameters in assessing both the climate impact and the biogeochemicalcycling of bioelements. Size-segregated aerosol and surface seawater (SSW)samples were simultaneously collected over the subtropical North Pacific toinvestigate the origin of WSON in the marine atmosphere. The fine-mode WSONconcentration (7.5  ±  6.6 ngN m −3 ) at 200–240 ∘  Ealong 23 ∘  N, defined as the eastern North Pacific (ENP), wassignificantly higher than that (2.4  ±  1.9 ngN m −3 ) at135–200 ∘  E, defined as the western North Pacific (WNP).Analysis of the stable carbon isotope ratio of water-soluble organic carbon(WSOC; δ 13 C WSOC ) together with backward trajectoryindicated that most of the observed WSON in the fine particles in the ENPoriginated from the ocean surface. We found positive relations amongnitrogen-fixation rate, dissolved organic nitrogen (DON) in SSW, and theWSON concentrations. The result suggests that reactive nitrogen (DON andammonium), produced and exuded by nitrogen-fixing microorganisms in SSW,contributed to the formation of WSON aerosols. This study provides newinsights into the role of ocean-derived reactive nitrogen aerosolsassociated with marine microbial activity.

[学科分类] 大气科学