青岛大气气溶胶中水溶性有机氮对总氮的贡献

Contribution of Water Soluble Organic Nitrogen to Total Nitrogen in Atmospheric Aerosols in Qingdao

有机氮是大气气溶胶中重要的氮组分,其沉降入海后不仅能够促进海洋初级生产力的增长,还可能影响海洋生态系统的群落结构.利用2008年1～12月在青岛采集的64个总悬浮颗粒物样品,分析了其中水溶性有机氮的浓度.气溶胶中有机氮的浓度为30～2 073 nmol.m-3(100～12 157μmol.g-1),以12月浓度最高,3、4月次之,6～9月最低,年平均浓度为430nmol.m-3(2 323μmol.g-1).有机氮对总氮的平均贡献为(37.5±21.6)%,其中12月的贡献最大,9月最小.不同天气过程显著影响气溶胶中有机氮的浓度分布,烟霾和雾天时气溶胶中有机氮的浓度分别为789 nmol.m-3和412 nmol.m-3,约为晴天时的4倍和2倍,但颗粒物的浓度与晴天时相比并没有明显地增加;沙尘天气时大气颗粒物浓度约为晴天时的5倍,但有机氮的浓度仅为晴天时的1.4倍;降雨对气溶胶中有机氮具有明显的清除作用,雨后样品中有机氮的浓度为57 nmol.m-3,较之雨前降低了80%.

Organic nitrogen （ON） is a quantitatively important component of reactive nitrogen in atmospheric aerosols. Deposition of ON in seawater from atmosphere could enhance primary productivity, as well as with the changes in the phytoplankton community composition. 64 total suspended particles （TSP） samples collected at Qingdao from January to December in 2008 were applied to analyze the concentrations of water soluble organic nitrogen in aerosols. Concentrations of ON in Qingdao aerosols ranged from 30 to 2 073 nmol.m^-3 （ 100-12 157μmol·g^-1） , with the highest values occurring in December, followed in March and April and the lowest values in June to September. ON mean concentration in TSP in 2008 was 430 nmol.m^-3 （2 323 μmol.g^-1 ）. The contribution of ON to total nitrogen （TN） was （37.5 ± 21.6）%, with the maximum presenting in December and the minimum in September. The distribution of organic nitrogen in aerosols was significantly affected by the weather conditions. During haze and fog episodes, the concentrations of ON in the aerosols were 789 nmol·m^-3 and 412 nmol·m^-3, respectively, 4 times and twice higher than that during clear episodes. However, the particle mass concentrations in haze and fog days were comparable with that in clear days. During dust episodes, the concentration of particles was 5 times higher than that during clear episodes while ON concentration slightly enhanced 0.4 times. The ON concentration in aerosols after raining was 57 nmol·m^-3, decreased 80% than that before raining due to the efficient wet scavenging.