大气有机氮沉降及其对海洋生态系统的影响

Atmospheric Organic Nitrogen Deposition and Significance in Marine Ecosystem

有机氮是大气中含氮物质的重要组成部分。大气中有机氮化合物的种类繁多,按其存在的形态可分为:氧化型、还原型以及生物/颗粒型有机氮,这些有机氮可来自自然源和人为源的直接释放,也可来自于无机氮与碳氢化合物间的大气化学反应。大气有机氮对海洋的输入不仅可以促进海洋初级生产力的增长、进而增加二氧化碳的吸收速率,还可能影响海洋生态系统的结构和功能。分析了海洋大气有机氮沉降的最新研究进展,结果表明:气溶胶中的有机氮在总氮中所占的比例为39.6%±14.7%;陆地雨水中以有机形式存在的溶解氮为30.2%±15.0%,而海洋上,溶解有机氮可达到雨水中总氮的62.8%±3.3%。可见,目前仅包括无机氮沉降的入海通量可能低估了1/3。因此,开展大气有机氮沉降的研究,有助于评价有机氮在全球氮循环中的作用,以及对海洋生态系统的短期和长期的影响。

Organic nitrogen is a quantitatively important ganic forms of nitrogen both in wet and dry deposition can be component in the atmospheric deposition. These ordivided into three types： oxidized, reduced and biological/particulate atmospheric organic nitrogen. They could be released directly from both natural and anthropogenic sources including terrestrial vegetation, soils, oceans, fertilizers, biomass burning and fossil-fuel combustion, and also produced through atmospheric reactions between NOx and volatile organic carbons. Atmospheric organic nitrogen may not only accelerate primary productivity and the corresponding enhanced anthropogenic CO2 uptake, but also affect ecosystem composition or function by its substantive deposition to the oceans. This paper has reviewed the results in the recent studies of organic nitrogen in atmospheric deposition. The compiled data set shows that organic nitrogen contributes up to 39.6% ± 14.7% of the total aerosol nitrogen. In rainwater from continental locations, 30.2% ± 15.0% of the dissolved nitrogen is present in organic forms, while in remote marine rains, organic nitrogen makes up 62.8% ± 3.3% of the total nitrogen in rain samples. Atmospheric nitrogen flux to the worldg ocean would be one third more as compared to the previous estimation （only inorganic nitrogen） if organic nitrogen was considered. The studies of organic nitrogen in the atmospheric deposition would be helpful for evaluating the roles of organic nitrogen in the global atmospheric nitrogen budget and marine ecosystem on short or long time scale.