Study On Total Dissolved And Particulate Amino Compounds In Atmospheric Aerosol In Qingdao

Organic nitrogen is an important component of nitrogen-containing compounds in atmospheric aerosols, and it might have a significant influence on the nutrition budgets of marine ecosystem and the global nitrogen cycling. Organic nitrogen compounds have various forms in atmospheric aerosols. Amino compounds are the conerned compounds because of their potential roles in ecological processes and plant nutrition. The studies of concentrations, seasonal variations and distributions of amino compounds in the atmospheric aerosols would be helpful to evaluate the roles of organic nitrogen in the global atmospheric nitrogen budget and marine ecosystem.The overall goal of this paper is to characterize dissolved free amino compounds (DFAC), dissolved combined amino compounds (DCAC), total dissolved amino compounds (TDAC), and particulate amino compounds (PAC) in 66 total suspended particles (TSP) samples collected from January 2008 to December 2008 at the coastal area in Qingdao, in order to understand the effects of organic nitrogen on the marine ecosystem. The major results reported here include the concentrations, seasonal variations and distributions of amino compounds, the effects of the different sources of air masses back trajectories on the composition and distribution of amino compounds, and the effects of the dust weather to amino compounds in the aerosol. The conclusions are summarized as follow:The average concentration of particulate matter in 66 TSP samples is 272.3μg·m-3. Throughout the year, the highest concentration of particulate matte is in May with an average concentration of 890.8μg·m-3, and the minimum is in August with average of 123.0μg·m-3. The rank of seasonal distribution is Spring (441.3μg·m-3)> Winter (236.7μg·m-3)> Autumn (206.5μg·m-3)> Summer (145.8μg·m-3).The concentrations of DFAC range from 0.13 to 10.89 nmol·m-3 with an average of 2.23±1.24 nmol·m-3, and the average contribution to TDAC is about 22%. Throughout the year, the highest monthly average concentration of DFAC is 3.9±1.7 nmol·m-3 in May, while the minimum is in September with average 1.1±0.1 nmol·m-3. Concentrations of DFAC vary seasonally, higher values occurring in spring (2.7±1.4 nmol·m-3) and autumn (2.2±1.4 nmol·m-3), lower values occurring in summer (1.93±0.58 nmol·m-3) and winter (1.8±1.0 nmol·m-3). Arginine (Arg), methylamine (MA), alanine (Ala) are the dominant DFAC species, threonine (Thr) also makes great contributions in spring and winter, and methionine sulfoxide (MetSO) accounts for a large proportion in summer and autumn.Concentrations of DCAC range from 0.9 to 33.4 nmol·m-3, and the mean is 7.7±3.0 nmol·m-3, which contributes to TDAC about 78%, about 3 times more than DFAC. The highest is in May, and lowest in October. Seasonal distributions of DCAC concentration are:Spring (9.9±4.5 nmol·m-3)> Summer (7.6±2.7 nmol·m-3>Winter (6.7±1.6 nmol·m-3)> Autumn (5.7±2.9 nmol·m-3). Arg, MA, and Ala are the most prominent contributors in DCAC, in addition, Gly, Ser and Thr's contributions are relatively large in Spring, contribution of Met is more outstanding in Summer and Autumn, and contributions of Ser and Thr account for a large proportion in Winter.The range of TDAC concentration is from 2.4 to 40.9 nmol·m-3, with an average of 9.9±3.8 nmol·m-3, and the average contribution to TAC is about 58%. Throughout the year, the highest is in May (19.2±9.6 nmol·m-3), and lowest in October (6.0±1.6nmol·m-3). Seasonal distributions are as follows:the maximum is in Spring (12.6±4.7 nmol·m-3), and then Summer (9.5±3.2 nmol·m-3), Winter (8.5±2.2 nmol·m-3), and minimum Autumn (8.0±4.0 nmol·m-3). Arg, MA and Ala are the major contributors to TDAC. In addition, Gly, Ser, Thr contribute larger in spring, and Ser, larger in summer, Thr, Ser larger in winter, which is similar with DCAC.PAC concentrations range from 0.7 to 76.1 nmol·m-3, with an average of 7.1±4.3 nmol·m-3, and the average contribution to TAC is 42%, less than TDAC. Arg, Asp, Glu, Ala, Orn is major contributors to PAC. PAC concentration in May (16.46±19.65 nmol·m-3) is the highest, in June (3.3±1.5 nmol·m-3) minimum, seasonal trend is obvious:Spring (9.3±8.2 nmol·m-3)> Winter (6.7±3.0 nmol·m-3)> Autumn (5.6±1.7 nmol·m-3)> Summer (4.8±2.3 nmol·m-3). Arg, Ala, Asp, Glu, Ser, Met, Orn in PAC are prominent in the four seasons, and Gly also has a large contribution in the spring.Three days air mass back trajectories were caculated of the 66 TSP samples by the U.S. National Oceanic and Atmospheric Administrat ion (NOAA) backward trajectory model (HYSPLIT), and it turns out that the samples mainly influenced northerly continental sources, southerly continental sources, and marine sources. The concentrations are the highest in the samples influenced by southerly continental sources, and lower in samples influenced by northerly continental sources, lowest in samples influenced by marine sources. Affected by different sources, amino compounds vary differently in different forms. In dissolved and particulate amino compounds, protein amino compounds are highest in samples influenced by marine sources, and non-protein amino compounds are highest in samples influenced by southerly continental sources.TDAC contributes to total dissolved organic nitrogen (DON) with an average of 10.8%±9.3%, and DCAC is the larger contributor, averaged 8.4%±7.4%. Arg and MA are the largest contributors, followed by Ala, Met, Ser, His.