Study On Amino Compounds In Aerosol And Rainwater Over The East China Sea And The Yellow Sea

Organic nitrogen is a quantitatively important component of fixed nitrogen in atmospheric aerosol and rainwater. The inputs of organic nitrogen to oceans may not only induce an enhancement of marine primary productivity but also influence the ecosystem structure and function. There are various organic nitrogen compounds in atmosphere. Amino acids and urea as two possible candidates of organic nitrogen component may have an immediate influence to the marine ecosystem since they can be utilized by plants and microorganism directly. The study on concentrations,sources and distributions of amino acids and urea may have an important significance to understand the effects of atmospheric organic nitrogen to marine ecosystem.In this study, we focused on atmospheric aerosols and rainwater collected in the marginal seas of China. 46 total suspended particulate samples, 9 size-segregated particles samples and 18 rainwater samples were collected during four cruises, which were over the Yellow Sea from Oct. to Nov., 2006 and Mar. to Apr., 2007, over the East China Sea from Nov. to Dec. , 2006 and Feb. to Mar., 2007, respectively. These aerosol and rainwater samples were applied to analyze the concentration of free and combined amino acids, primary amines and urea. The information on concentrations, size distributions and composition characteristics of amino compounds in the atmospheric aerosol and rainwater over the Yellow Sea and East China Sea were presented. The conclusions were summarized as follow:In the Yellow Sea, the average concentration of dissolved free amino compounds (DFAC) in aerosols in autumn was 857.6 pmolN·m^-3, slightly higher than that in spring during non-dust event (730.3 pmolN·m^-3). The concentration of DFAC in spring during dust event was 1078.7 pmolN·m^-3, obviously higher than that during non-dust aerosols. In the East China Sea, the concentration of DFAC in winter aerosols was 797.1 pmolN·m^-3, and similar to that measured in winter. Dissolved combined amino compound (DCAC) was the major composition type in aerosols over the marginal seas of China, accounting 70%⁹0% to the total amino compounds. The concentration of DCAC in spring aerosols over the Yellow Sea during dust event was 7360.5 pmolN·m-3, which was 3 times higher than that in non-dust aerosol. The concentration of DCAC in winter aerosol over the East China Sea was 3180.9 pmol·m-3, similar amount in spring was also detected.In the Yellow Sea rainwater, the average concentrations of DFAC amd DCAC were 5.3μmolN·L^-1 and 27.0μmolN·L^-1 in autumn, respectively and the corresponding concentrations were 6.2μmolN·L^-1 and 44.9μmolN·L^-1 in spring. In the East China Sea rainwater, the average concentrations of DFAC amd DCAC in winter were 5.7μmolN·L^-1and 44.8μmolN·L^-1, respectively, higher than those in spring, which were 4.8μmolN·L^-1 and 24.5μmolN·L^-1, respectively. Similar to the aerosols, the combined amino compound was also the major composition type in marine rainwater, accounting～85% to the total amino compounds.In the Yellow Sea aerosol and rainwater, the average concentrations of urea were 12.7nmolN·m-3 and 16.4μmolN·L^-1 in autumn, respectively and the corresponding concentrations were 8.1 nmolN·m-3and 56.2μmol·L^-1 in in spring (non-dust). The concentration of urea in spring dust samples was 19.9 nmolN·m-3, significantly higher than that in non-dust samples. In the East China Sea, the average concentrations of urea in aerosols were 7.9nmolN·m-3 and 9.8 nmolN·m-3 in winter and spring, respectively and the corresponding concentrations in rainwater were 11.4μmol·L^-1 and 21.4μmol·L^-1. The average scavenging ratio for the removal of urea during wet precipitation was 2700～2900kg·L^-1, higher than those for atmospheric mineral matters or other particles.In marine aerosols, Ser, Thr, Gly, Ala and MA were the most abundant DFAC, accounting for～55% of the DFAC pool. Ser, Thr and Gly were the most abundant DCAC, accounting for 30%⁴0% of the DCAC pool. In marine rainwater, Ser, Thr, Gly and Ala were the dominant DFAC species, accounting for about 50% of the DFAC pool. Asp,Glu and Ser were the major components of the DCAC pool in spring rainwater. Asp,Glu,Ser,Arg and Gly+Thr were the most abundant DCAC in winter and spring, accounting for more than 70% of the DCAC pool.The distributions of DFAC and DCAC basically showed bi-modal size distribution in marine aerosols except for dust aerosols in spring over the Yellow Sea, which presented a single peak distributions. Two peaks of DFAC and DCAC in marine aerosols presented in the range of 0.43μm～0.65μm and >7.0μm, and 1.1μm～3.3μm and 7.0μm～11μm, respectively. During the dust event, the single peak of DFAC and DCAC showed in the coarse particles, the range of 4.7μm～7.0μm and 2.1μm～3.3μm, respectively.In marine aerosols, the size distribution of urea showed no pronounced difference among cascade stages, but the size distributions of urea in different seasons present different characteristics. In the East China Sea aerosols, the contributions of urea in fine particles (<2.1μm) in winter and spring were 30% and 40%, respectively and the corresponding contributions were about 42% and 35% in the range of 2.1μm～7.0μm. In the Yellow Sea aerosols, there was little difference of the urea contributions in autumn between the fine particles (<2.1μm) and coarse particles (>2.1μm), which was both approximately 50%. In spring, most urea existed in fine particles less than 2.1μm in non-dust aerosols, which was 67.8%. In contrast, the urea contribution in coarse particles (7.0μm～11μm) was much higher in dust aerosols than in non-dust aerosols.The statistic results indicated that the distributions of DFAC, DCAC and urea in the Yellow Sea and the East China Sea aerosols were dominated by different factors in different seasons. DFAC and urea were mainly derived from continental sources, and urea in spring aerosols were associated with the sublimation of urea in soils. The sources of DCAC in aerosols were more complicated, which were affected by marine and continental sources, together.