【作者】 石金辉；

【导师】 高会旺； 张经；

【作者基本信息】 中国海洋大学 ， 环境科学， 2011， 博士

【摘要】 大气氮沉降是海洋氮营养物质的重要来源,能够对海洋生态系统产生重要影响。大气沉降中的氮组分主要包括具有生物活性的无机氮,此外有机氮也是大气沉降中的重要组分,这些有机氮是否具有生物活性取决于它的化学形态和来源,因此,认识大气有机氮的组成、来源和浓度水平对评价大气氮沉降对海洋生态系统的影响具有十分重要的科学意义。中国近海是全球氮沉降的高值区,但这一估计仅包括了无机氮,而我国在化肥生产与使用、化石燃料燃烧以及地表扬尘等方面可能具有强的有机氮排放源,目前只包括无机氮的入海通量可能低估了大气氮沉降对中国近海的贡献,因此在中国近海开展大气气溶胶中有机氮的研究是十分必要而且具有重要的科学意义。本论文以青岛近岸、千里岩海岛和黄海为主要研究区域,研究气溶胶中的氮组分、尤其是水溶性有机氮的分布特征、组成和来源,以及大气沉降对黄海氮营养物质的贡献及其与水华生物响应之间的关系,获得的主要认识如下:青岛大气气溶胶中水溶性有机氮对总氮的贡献为23.7±16.5%,其平均浓度为256±303 nmol·m^-3,显著高于世界其他地区,我国具有较强的NOx、NH₃、挥发性有机物等有机氮前体排放源是造成气溶胶中有机氮浓度较高的主要原因。季节变化显示,有机氮浓度在冬、春季节较高,秋、夏季节较低。不同天气状况下,气溶胶中有机氮浓度存在显著性差异,烟霾和雾天时有机氮浓度为晴天时的2³倍,表明气溶胶中有机氮主要来自二次气溶胶,有机氮与NO₃^-和NH₄⁺之间存在显著正相关关系支持了这一观点。冬季采暖期间有机氮浓度较之采暖前有统计意义上的升高,这一结果提供了大气有机氮来自化石燃料燃烧的直接证据。溶解性氨基化合物对有机氮的贡献为7.5±5.0%,结合态是氨基化合物的主要存在形态,约为游离态的3倍。精氨酸、甲胺、丙氨酸是青岛气溶胶中最主要的氨基化合物,气团来源和天气条件不同影响氨基化合物的浓度和组成。尿素氮对有机氮的贡献为8.6±6.2%,与世界其他地区相比较,青岛气溶胶中尿素浓度较高,我国尿素的大量使用所带来的局地强排放源是造成这一结果的主要原因。千里岩气溶胶中有机氮对总氮的贡献为22.8±12.9%,与青岛及世界其它地区的平均值相当。有机氮的平均浓度为111±81 nmol·m^-3,明显高于世界其他地区,但低于青岛的结果。千里岩上风向上京、津等大城市高浓度污染物的远距离输送是造成这一结果的主要原因。千里岩气溶胶中有机氮的季节变化趋势与青岛相同。在不同天气状况下,与青岛相似,有机氮浓度也存在显著性差异,但变化幅度小于青岛。有机氮与NO₃^-、NH₄⁺、K⁺、Cl-和Ca²⁺之间存在正相关关系,表明千里岩大气有机氮主要来自人为污染及地表扬尘的贡献。溶解性氨基化合物对有机氮的贡献为12.4±12.6%,Arg和MA是最主要的氨基化合物,MA与NH₄⁺、NO₃^-和SO42-之间的相关关系表明其主要来自人为源的贡献。千里岩气溶胶中尿素浓度高于世界其他地区未受污染大气中的结果,但低于青岛。季节变化趋势为春、冬季较高、夏、秋季较低,与青岛的一致。尿素氮对有机氮的贡献为5.3±3.8%,千里岩气溶胶中的有机氮组分,除了尿素和氨基化合物外尚有约80%未能被认识。在南海,气溶胶中有机氮对总氮的贡献约为30%,在黄海和青岛这一比例约为20%。有机氮浓度在青岛气溶胶中最高,黄海次之,南海最低。在中国近海,超过70%的有机氮出现在<2.1μm细粒子上,约10%出现在7.0-11.0μm的粗粒子上,表明了部分有机氮可能来自海盐气溶胶。沙尘期间,气溶胶中有机氮的浓度显著升高,但是有机氮对总氮的贡献降低。在沙尘气溶胶中,有机氮在>2.1μm粗粒子上的贡献升高约20%,表明有机氮可能包含在大的沙尘粒子中和/或吸附在粗的矿物气溶胶表面。因子分析结果表明有机氮主要来自人为污染源,海洋源和地表扬尘的贡献相对较小。在中国近海,气溶胶中尿素对有机氮的贡献约为8%。在非沙尘气溶胶中,50%左右的尿素出现在细粒子上,而在沙尘气溶胶中,这一比例下降为30%。游离氨基酸是有机氮中的少量组分,对有机氮的贡献仅为1%左右。PMF分析表明黄海气溶胶主要有四个源:海洋源、地表扬尘,人为污染和机动车排放。对有机氮的贡献分别为18.0%、25.3%、41.7%、15.0%。估计了2009年2⁴月黄海大气总氮的沉降通量,其中人为污染源贡献了66%,海洋源和地表扬尘分别贡献了10%左右,机动车排放贡献了15%。2007年春季在黄海调查期间,调查海域受到了沙尘暴的影响,沙尘过境后观测到水华的发生。研究了沙尘和非沙尘期间气溶胶中营养盐的浓度、溶解性、粒径分布和沉降通量,结果表明,总悬浮颗粒物（TSP）中总磷、总铁和总无机氮（NH₄⁺, NO2-和NO₃^-）的浓度分别为0.01¹.05μg·m^-3,1.0¹21.8μg·m^-3和1.21²2.28μg·m^-3,最高值均出现在沙尘发生期间采集的气溶胶样品中。平均而言,铁在沙尘和非沙尘气溶胶中的溶解度分别为1.65%和8.46%。颗粒物、NO₃^-和NH₄⁺的粒径分布显示,沙尘期间它们在粗粒子上的贡献较之非沙尘期间分别升高了50%、20%和20%。在沙尘发生期间（3月31日至4月1日）,溶解性铁、溶解性磷和总无机氮的沉降通量分别为非沙尘时的15倍、13倍和5倍左右。沙尘发生时伴随的降雨对沙尘粒子有明显的清除作用,通过沙尘期间表层海水中铝的增量推算总沉降通量,结果显示,在这次沙尘事件中,溶解性铁、溶解性磷和无机氮的总沉降通量分别42.5±10.9 mg·m-2,10.3±2.6 mg·m-2和77.2±19.8 g·m-2,其中湿沉降在总沉降中占主导。沙尘期间,大气氮沉降是黄海中部表层营养盐的主要来源,约为海洋向上输送通量的6倍,磷的大气输入与海洋的输入相当。比较营养盐的大气输入和浮游植物的需求,发现沙尘沉降带来的氮几乎可以满足水华发生时生物生长的需要,沙尘带来的Fe则远超过水华生物生长的需要量。格兰杰因果关系检验结果显示沙尘沉降带来的氮、磷和铁是沙尘发生3⁵天后水华生物响应的格兰杰原因,因此,在这次事件中,沙尘沉降与水华发生存在因果关系,沙尘带来的营养盐的加富效应是水华发生的关键因子。更多还原

【Abstract】 Atmospheric nitrogen deposition provides an important supply of nutrients to the oceans and exerts a large influence on marine ecosystem. Beside bioavailability inorganic nitrogen, water soluble organic nitrogen is an important component in atmospheric nitrogen deposition. The bioavailability of water soluble organic nitrogen varied a lot in different components and it is also associated with their origins. To evaluate the effect of atmospheric nitrogen deposition to the marine ecosystem, the composition, sources and abundance of organic nitrogen should be determined. It was reported that a high value occurred in the China Sea has on the global map of atmospheric nitrogen deposition. However, these estimates only reflect contribution from inorganic nitrogen. In China, however, there are strong emission sources of organic nitrogen on fossil fuels, fertilizer production and application and aeolian dust. The current estimates of atmospheric nitrogen input to the China Sea should be significantly underestimated. Determination of organic nitrogen in the atmospheric aerosols over the China Sea would fill up knowledge gap on organic nitrogen and improve accuracy of atmospheric nitrogen input to the China sea. This thesis aims to characterize nitrogen species in aerosols over Qingdao, Qianliyan Island and Yellow Sea. The sources, compositions, distributions and abundance of water soluble organic nitrogen （ON） in aerosols, and the atmospheric nutrients input to the Yellow Sea and associated with the bloom biota responses are investigated. The main results are listed as below.In Qingdao, the contribution of particulate ON to total nitrogen （TN） is 23.7±16.5%. The mean concentration of ON is 256±303 nmol·m^-3 and much higher than those reported world widely, which was attributed to strong emissions of ON precursors such as NOx, NH3, soot and VOC in China. The ON concentration shows the high values occur in winter and spring, and the low values occur in autumn and summer. The concentration of ON in aerosols was found to be associated with the weather conditions. During haze and fog episodes, the concentrations of particulate ON are 2³ times higher than those during clear weather conditions, indicating a significant contribution of ON from secondary atmospheric reactions. ON shows strong correlation to NO₃^- and NH₄⁺ that further support this point. During the winter heating period, the ON concentration in aerosols shows statistically significant enhancement, suggesting a primary emission of ON from fossil fuels combustion. Water soluble total amino compounds contributes 7.5±5.0% to total organic nitrogen in aerosols. Combined amino compounds （CAC） accounts for the major portion of the amino compounds and its concentration is about 3 times greater than that of free amino compounds （FAC）. Arginine （Arg.）, methylamine （MA） and alanine （Ala） typically are the most abundant amino compounds in Qingdao. The transport path and the origin of air mass and weather conditions during the collection of aerosols appears to influence the concentrations and compositions of FAC and CAC. Urea contributes 7.5±5.0% to total organic nitrogen. The urea concentrations in Qingdao are higher than those reported for the other regions in the world, probably due to strong emissions derived the high usage of urea as a fertilizer in China.In Qianliyan, the ON contribution to TN is 22.8±12.9%, agreeing with those averaged values observed in Qingdao and the other regions in the world. The ON mean concentration is 111±81 nmol·m-3, much higher than that of the other regions in the world, but lower than that of Qingdao. This result may be due to the long-range transport of high levels of anthropogenic components from the big cities such as Beijing and Tianjing upwind of Qianliyan. The seasonal trend of ON concentration is consistent with that of Qingdao. The concentration of ON in aerosols, like Qingdao, is also significantly affected by the weather conditions. ON shows significant correlation to NO₃^-, NH₄⁺, K⁺, Cl- and Ca²⁺, indicating that the anthropogenic input and continental-derived dust are the major sources of ON in Qianliyan. Water soluble total amino compounds contributes 12.4±12.6% to total organic nitrogen. Arg. and MA typically are the most abundant amino compounds. MA shows significant correlation to NH₄⁺, NO₃^- and SO42-, suggesting that anthropogenic source is the major provider of MA. The urea concentrations in Qianliyan are lower than those of Qingdao, but higher than those reported for the other regions in the world where are not influenced by the polluted air mass. The urea concentration shows the high values occur in winter and spring, and the low values occur in autumn and summer, agrees with that of Qingdao. Urea contributes 5.3±3.8% to total organic nitrogen, therefore, about 80% of ON in Qianliyan aerosols are unidentified in this study. ON contribute ³0% of the total water-soluble particulate nitrogen over the South China Sea and ²0% over the Yellow Sea and in Qingdao. On average, the ON concentration over the Yellow Sea is higher than that of over the South China Sea, but lower than that of Qingdao. Over the marginal sea of China, more than 70% of the ON exist in the fine mode particles （<2.1μm）. About 10% of the ON exists in the 7.0-11.0μm large particles and the part of the ON might be entrained sea-salt particles. During the dust storm periods, the concentrations of ON in the dust aerosols significantly increase but the contribution of ON to the total nitrogen decrease. In the dust aerosols, the contribution of ON increase by 20% in the coarse mode （>2.1μm）, indicating the entrainment of large soil particles or dust material and/or the adsorption of coarse minerals on the aerosols. Factor analysis indicates that ON mainly originate from anthropogenic sources while a relatively small amount is from marine and crustal sources. Urea, on the average, represents ⁸% of the total ON over the marginal sea of China. In the non-dust aerosols, ⁵0% of urea exists in the fine mode over the Yellow Sea and Qingdao, but the percentage decrease to ³0% in the dust aerosols. Free amino acids is generally a minor component of the ON, only accounting for～1% of the total ON. Positive matrix factorization analysis indicates that ON mainly originate from four sources; they are marine, crustal, anthropogenic, and vehicles exhaust sources, respectively. Marine sources contribute 18.0%, crustal sources 25.3%, anthropogenic sources 41.7% and mobile emission sources 15.0% of total ON variance in the aerosol samples over the Yellow Sea. The deposition fluxes of total nitrogen in the Yellow Sea from February to April 2006 are estimated. The contribution of anthropogenic sources to the TN deposition is predominant among these four sources with the value of 66%. The other sources contributions are 9.8% of marine sources, 9.2% of crustal sources and 15% of vehicles exhaust sources, respectively.A cruise campaign in spring 2007 over the Yellow Sea ran into a couple of Asian dust episodes which were followed by blooms. The particle nutrients and iron concentrations, their solubility, size distributions and deposition fluxes during the dust and normal days were investigated. The concentrations of total P, total Fe and TIN （NH₄⁺, NO2- and NO₃^-） in TSP vary from 0.01 to 1.05μg·m^-3, 1.0 to 121.8μg·m^-3 and 1.21 to 22.28μg·m^-3 with the maximum concurrently with the dust storm events. On average, the solubility of Fe is 1.65 % in the dust aerosols and 8.46 % in the non-dust aerosols, respectively. The size distributions of particle mass, NO^3- and NH₄⁺ exhibit that their contributions increase by about 50%, 20% and 20% in the coarse mode, respectively, during the dust storm relatives to the normal days. During this dust event （31 March to 1 April, 2007）, the dry deposition fluxes of soluble iron, soluble phosphorus and total inorganic nitrogen increase by a factor of ¹5, ¹3 and 5 relative to the non-dust level, respectively. The dust deposition scavenged by the precipitation accompanied with dust is extrapolated using the dissolved Al increment in the surface ocean. The result shows that the total atmospheric deposition for soluble Fe, soluble P and inorganic nitrogen over the Yellow Sea during the dust episodes are 42.5±10.9 mg·m-2, 10.3±2.6 mg·m-2 and 77.2±19.8 g·m-2, respectively, of which the wet depositions of nutrients is absolutely governed in the total depositions. During the dust event, the atmospheric input instead of the oceanic input from bottom dominates the supplies of nutrients in the surface water in the central Yellow Sea. When comparing estimations of the dust-derived nutrient supplies with plankton community needs, we found that the dust-derived N supply nearly satisfied the bloom phytoplankton need in the initiation of bloom; while, the dust-derived Fe supply far exceeded the total need of bloom biota. Granger causality test result shows that the dust-derived N, P and Fe depositions are the Granger causes of the subsequent biological response with 3-5 days extra lags, suggesting that the dust deposition has causality with the initiation of spring bloom in this case and the fertilization effect of dust-derived nutrients is the key factor in causing this spring bloom.更多还原