南海氮循环几个重要过程研究的新进展

边缘海连接陆地和开阔大洋,是氮循环过程非常活跃和复杂的区域.南海是世界上最大的边缘海之一,是研究边缘海氮循环的热点区域.重点总结和归纳了南海外源氮输入、上层水体氨氮动力学过程和水体颗粒氮动力学过程的新进展:南海氮循环过程广泛受到人为活动的影响,表现为人为排放进入南海的外源氮持续增加;南海上层水体氨氮的动力学过程与营养盐跃层有关,并受到黑潮入侵的影响;上层水体中不同颗粒氮同位素信号高度相似,表明氮元素的快速运转;有别于其他陆架边缘海,南海颗粒氮同位素特征在向下传输过程中存在显著改变

A Review on the Younger Dryas Event

发生在12.9~11.6 kA bP的一次北半球气候快速变冷——新仙女木(yd)事件在过去30年来一直是古气候研究的热点。当下由于人类活动引起全球变暖,研究类似的快速气候变化事件及其触发机制对于预测未来气候变化具有重要意义。然而时至今日,科学界对yd事件的发生时间、气候效应、触发机制及其全球性意义依然存在很大争议。对比多个高分辨率记录探讨了yd事件的发生时间及其年代学意义,详细总结了南、北半球中高纬地区及低纬地区近年来新发现的yd事件的记录及其气候效应,重点讨论了yd事件触发机制假说的发展与争议,并结合yd事件的研究现状提出了未来研究热点和重要方向。The Younger Dryas(YD) event which lasted from 12.9 ~ 11.6 ka BP is a rapid return to near-glacial conditions with a major impact on global climate that punctuated last glacial-Holocene transition period.The YD event was firstly found in records of mid-high latitude Northern Europe and North Atlantic vicinities and later identified broadly in North Pacific Oceans,Asia,North America,tropics and even in South Hemisphere.The mechanism of YD event is not clear although tremendous efforts have been paid over the past 30 years.Even the precise timing,duration and global impact remain ambiguous.The understanding of the magnitude of YD-like event in temporal and spatial scales andits forcing mechanism may help us to forecast the possible environmental and ecological impacts in global scale due to anthropogenic forcing.This article reviewed the progress of studies on the YD event,including the most recent dating of the onset and geographic pattern of climatic impacts,and particularly the triggering mechanisms proposed in recent years.The disparities of precise dates among records for the YD onset may result from counting mistakes,regional environmental responses and rapid fluctuation of atmospheric14 C.Globally,the YD event was characterized by abrupt climate change with increasing anomalies in magnitude toward the poles and opposite signs between Hemispheres,which modulated by bipolar seesaw mechanism.It is generally accepted that the YD event is caused by a slowdown Atlantic Meridional Overturning Circulation(AMOC).However,the triggering mechanism of this slowdown is debatable.Besides the earliest hypothesis of Lake Agassiz outburst,alternative mechanisms such as meltwater discharge into Arctic Ocean,extraterrestrial impact or atmospheric circulation forcing have been proposed under various supportive evidences.Tropical processwas suggested to play an additional role in abrupt climate change,of which high latitude was thought to be the modulator.The newest hypothesis suggested that YD event was an integral part of natural climate oscillation rather than a freak excursion.Finally,future directionstohave a complete understanding of the mechanisms of YD event are provided.国家自然科学基金项目重大研究计划“南海水体硝酸盐动力学与水团示踪”(编号:91328207);国家自然科学基金面上项目“中国边缘海沉积物氮同位素时空变化与控制因子”(编号:41176059)资

Source apportionment of water-soluble ions in spring TSP of Pengjia Islet, Taiwan

于2010年春季,在台湾省北部东海海域彭佳屿岛采集了60个总悬浮颗粒(TSP)样品,用离子色谱测定了8种水溶性离子(Na~+、Mg~(2+)、; Ca~(2+)、K~+、NH_4~+、Cl~-、SO_4~(2-)和NO_3~-)浓度.结合HYSPLIT气团后向轨迹模型、离子化学计量学关系、; 离子相关性分析和主成分分析,探讨了彭佳屿岛春季TSP中水溶性离子的主要来源.结果表明:彭佳屿岛春季TSP中水溶性离子质量浓度顺序依次为SO_4~; (2-)(7.704.53)mug/m~3> Cl~-(6.17 3.85)mug/m~3>Na~+(4.59 ; 2.28)mug/m~3>NO_3~-(4.24 3.07)mug/m~3>NH_4~+(1.53 ; 1.20)mug/m~3>Ca~(2+)(0.95 1.47)mug/m~3>Mg~(2+)(0.59 ; 0.30)mug/m~3>K~+(0.310.17)mug/m~3.其中Cl~-、Na~+和Mg~(2+)全部来源于海洋源;K~+来源较多,除了; 海洋源外,煤和生物质燃烧以及陆源矿物等都可能是彭佳屿岛春季TSP中K~+的来源;60%的Ca~(2+)来源于当地的建筑粉尘;77%的SO_4~(; 2-)源于煤和生物质燃烧释放;NO_3~-主要源于汽车尾气、煤和生物质燃烧等释放;NH_4~+主要来源于二次气溶胶和生物质燃烧等.通过整合本研究; 与前人的观测,发现在春季从中国东北至西北太平洋开阔海域,TSP中Cl~-、Na~+和Mg~(2+)的浓度在空间上呈现逐渐升高趋势,而Ca~(2+; )、K~+、NH_4~+、SO_4~(2-)和NO_3~-的浓度在空间上呈现逐渐下降趋势,显示了TSP中不同水溶性离子在海洋大气传输过程中的空间; 变化特征.In spring of 2010, sixty total suspended particulate (TSP) samples we; collected in Pengjia Islet, northern sea of Taiwan, China. The; concentrations of water-soluble ions (Na~+, Mg~(2+), Ca~(2+), K~+,; NH_4~+, Cl~-, SO_4~(2-) and NO_3~-) in the TSP samples were extracted; and then determined using an Ion Chromatography. Using these data, we; investigated the sources of water-soluble ions by a multiple-technique; analysis combining with the HYSPLIT model, ion stoichiometry,; correlation analysis of water-soluble ions and primary component; analysis. According to a decreasing order in the average mass; concentration, these ions ranked as SO_4~(2-)(7.704.53)mug/m~3,; Cl~-(6.173.85)mug/m~3, Na~+(4.592.28)mug/m~3, NO_3~-(4.24 3.07)mug/m~3,; NH_4~+(1.531.20)mug/m~3, Ca~(2+)(0.951.47)mug/m~3,; Mg~(2+)(0.590.30)mug/m~3 and K~+(0.310.17)mug/m~3. The sea water was; identified as the dominant source for Cl~-, Na~+ and Mg~(2+). Besides; the contribution from the sea salt, the K~+ had other sources, such as; coal and biomass burning, and mineral etc. 60% Ca~(2+) came from the; local construction dust, while 77% SO_4~(2-) originated from coal and; biomass burning. The NO_3~- dominantly sourced from the vehicle exhaust,; coal and biomass burning, while NH_4~+ totally originated from the; second inorganic aerosol and biomass burning. By combining our results; with previous findings, in spring, the concentrations of Cl~-, Na~+ and; Mg~(2+) in TSP increased gradually from the Northeast of China to the; Northwest Pacific Ocean; on the contrary, the Ca~(2+), K~+, NH_4~+,; SO_4~(2-) and NO_3~- in TSP decreased gradually. The spatial; characteristics of different water-soluble ions in TSP were associated; with their long-range transport in the marine boundary layer.国家973计划项目; 国家自然科学基金项目台湾海峡联合基金资助项目; 东华理工大学校科技创新团队科研启动基金项目; 江西省教育厅科技项目;; 东华理工大学博士科研启动基金项

Atmospheric Deposition Connected with Marine Primary Production and Nitrogen Cycle: A Review

大气沉降通过为海洋提供外源性氮、磷和铁等微量元素,可显著影响海洋氮、碳循环过程,并产生气候效应。一方面促进海洋初级生产和生物固氮,增强海洋吸收二氧化碳的能力;另一方面影响海洋氮、碳循环路径,增加海洋生物源气溶胶排放量,间接影响气候变化。由于大气沉降对海洋生态系统及气候变化的重要影响,相关科学问题已成为海洋科学与大气科学交叉研究的热点,被多个国际研究计划列为核心研究内容。在大气污染物排放持续增加与沙尘事件频发的背景下,大气沉降对我国东部陆架海(黄海、东海)及其邻近西北太平洋碳、氮循环过程的影响日趋增强,因此该海区已成为大气沉降及其气候影响研究的代表性海域。结合分子生物学和实验生态学手段理解大气沉降影响下的海洋初级生产过程,利用同位素示踪技术研究大气沉降对海洋氮循环的影响,以及获得大气沉降影响下海洋生物源气溶胶排放的观测证据将是未来研究的重点方向。Atmospheric Deposition( AD) provides external nutrients such as nitrogen( N),phosphorus( P)and iron( Fe) supporting the growth of phytoplankton in oceans and thereby exerts obvious impacts on carbon and nitrogen cycles and climate change associated.Specifically,the external nutrients derived from atmospheric deposition can promote the marine primary production and nitrogen fixation that enhance the ocean capacity in absorbing CO2; AD may also change a few pathways of carbon and nitrogen cycles in oceans and increase the emissions of biogenic aerosol and radioactive gases such as N2 O,DMS,etc.Due to the underlying important impacts on climate and environmental change,AD and processes related have become the hot topics of multidisciplinary studies in the areas of ocean and atmospheric sciences,and the focus of some international core projects such as Surface OceanLower Atmosphere Study( SOLAS),an International Study of Marine Biogeochemical Cycles of Trace Elements and Their Isotopes( GEOTRACES) and Integrated Marine Biogeochemistry and Ecosystem Research( IMBER).With the severe air pollution and high frequencies of Asian dust events,as the downwind areas of big cities and dust sources,the East China Sea and adjacent North Pacific have received increasing influences of AD.Limited studies showed that the increase of AD indeed caused significant influence on carbon and nitrogen cycles in these immediately related oceanic areas and the study there would have a signature effect on global oceans.A multidisciplinary study on the impacts of AD in oceans,e.g.,combing molecular biology and experimental ecology techniques to study primary production processes,utilizing isotopic techniques to trace the change of the nitrogen cycle,new evidences of ocean-biogenic aerosol emissions,etc.would be the focus in the future.国家重大科学研究计划项目“大气物质沉降对海洋氮循环与初级生产过程的影响及其气候效应”(编号:2014CB953700)资

高分散度铜基甲醇合成催化剂的研究

高分散度铜基甲醇合成催化剂的研究李基涛高利珍张伟德陈明树（厦门大学化学系物理化学研究所361005）70年来甲醇合成催化剂被广泛关注，特别是60年代后期英国ICI公司发明低温低压铜基甲醇合成催化剂以来，人们对铜基甲醇合成催化剂的制备与表征进行了深入地...国家自然科学基金;固体表面物理化学国家重点实验室资

Land use effect and hydrological control on nitrate yield in subtropical mountainous watersheds

Nitrate export in small subtropical watersheds is rarely observed and the estimation of individual land use nitrate yield from a mixed combination within catchments has scarcely been studied. In this study the nitrate concentrations at 16 nested catchments in the Chi-Chia-Wan watershed in Central Taiwan were measured during 2007–2008. A 3-layer TOPMODEL was applied to estimate daily discharge for ungauged sub-catchments. The observed nitrate concentrations and the simulated discharges were used for nitrate flux estimations through four flux methods. Meanwhile, a new deconvolution computation was developed to resolve the nitrate yield of each land use from within the mixed combinations. <br><br> The results showed that the observed mean NO<sub>3</sub>-N concentration in relatively pristine catchments was approximately 0.145 ± 0.103 mg l<sup>−1</sup>, which is comparable with other forestry catchments around the world. However, the higher rainfall/runoff, substantial N deposition, and other nitrogen sources resulted in significantly higher annual export of approximately 238–1018 kg-N km<sup>−2</sup> yr<sup>−1</sup>. Our deconvolution computation showed that the background yield of natural forestry was ~351 ±62 kg-N km<sup>−2</sup> yr<sup>−1</sup>. On the other hand, the extremely high nitrate yield of active farmland was ~308, 170 ± 19 241 kg-N km<sup>−2</sup> yr<sup>−1</sup> due to over-fertilization. The deconvolution computation technique is capable of tracing the mixed signals at the outlet back to the nitrate productions from varied land use patterns. It advances the application of river monitoring network. The typical values of nitrate yields can serve as a guideline for land management. Comparing the nitrogen input and output, we found some nitrogen missing in the cycling which may indicate certain removal processes and we therefore suggest further study to be carried out to fully understand nitrogen cycling in subtropics

Aerosols as a source of dissolved black carbon to the ocean

溶解黑碳（dissolved black carbon, DBC）在开阔大洋的年龄可达上万年，是海洋中到目前为止已知的年龄最老、最大的惰性溶解有机碳。因此海洋溶解黑碳的源汇问题是全球碳循环研究的重要部分。该研究团队通过测定2015年春季东、黄海以及西北太平洋的气溶胶中水溶性有机碳(water soluble organic carbon, WSOC)、水溶性黑碳 (water soluble black carbon, WSBC)的含量，并结合超高分辨质谱---傅里叶变换离子回旋共振质谱 (FT-ICR-MS)，解析了海洋气溶胶中溶解黑碳的浓度以及分子组成。进一步分析发现气溶胶中溶解黑碳的浓度与水溶性有机碳浓度显著高度相关。预测的未来生物质燃烧以及沙尘输送的变化可能增加大气沉降溶解黑碳的通量，影响区域甚至全球碳库。该研究结果将有助于把溶解黑碳纳入到海洋碳循环研究模型中。 近海海洋环境科学国家重点实验室助理教授鲍红艳为论文第一作者，高树基教授为共同通讯作者。【Abstract】Dissolved black carbon (DBC) is the largest known slow-cycling organic carbon pool in the world’s oceans. Atmospheric deposition could significantly contribute to the oceanic DBC pool, but respective information is lacking. Here we estimate that, during the dust outbreak season, the atmospheric dry deposition of water-soluble black carbon (WSBC) is～ 40% of the riverine input to the China coastal seas. The molecular composition of atmospheric WSBC determined by ultrahigh-resolution mass spectrometry, reveals similar soil-derived sources as for riverine discharge. WSBC is significantly positively correlated with water-soluble organic carbon (WSOC) in marine aerosols, and water-soluble black carbon contributes on average 2.8 ± 0.65% to the total WSOC. Based on this relationship, the global atmospheric deposition of DBC to the ocean is estimated to be 1.8 ± 0.83 Tg yr−1. Anticipated future changes in biomass burning and dust mobilization might increase these numbers, with consequences for regional ecosystems and global carbon reservoirs.This study was funded by the Major State Basic Research Development Program of China (973 program) (No. 2014CB953702) and the China Postdoctoral Science Foundation (No. 2013M540529). Hanse-Wissenschaftskolleg (the Institute for Advanced Study in Germany) is acknowledged for its support of Dr. H. Bao. 本研究受到973项目“不同营养水平下海洋氮循环关键过程及其对大气物质沉降的响应”（No.2014CB953702）以及中国博士后科学基金（No.2013M540529）的资助； 鲍红艳博士在德国的工作受到德国Hanse-Wissenschaftskolleg奖学金的资助

Ambient nitrate switches the ammonium consumption pathway in the euphotic ocean

高树基教授研究团队的研究论文，以现场原位速率观测与环境因子调查，证明了环境硝酸盐浓度是调控海洋真光层不同氨氮消耗途径的关键因子。硝酸盐通过影响浮游植物对于氨氮吸收的能力，决定了真光层内氨氮的氧化路径强弱，刻画了海洋真光层氮循环的微结构。高树基团队利用同位素示踪培养技术，围绕南海和西北太平洋真光层内硝化作用和浮游植物氨氮吸收速率的垂直分布特点及其动力学特征进行研究。首次提出硝酸盐浓度通过影响不同浮游植物类群对于氨氮的吸收能力，从而调控真光层的氨氮消耗途径。研究团队的万显会博士为成果的第一作者，近海海洋环境科学国家重点实验室的戴民汉教授，史大林教授、张瑶教授、盛华夏博士后、祝依凡，以及澳大利亚联邦科学与工业研究组的Tom Trull教授和美国Bigelow海洋实验室的Mike Lomas教授为成果的共同完成人。【Abstract】Phytoplankton assimilation and microbial oxidation of ammonium are two critical conversion pathways in the marine nitrogen cycle. The underlying regulatory mechanisms of these two competing processes remain unclear. Here we show that ambient nitrate acts as a key variable to bifurcate ammonium flow through assimilation or oxidation, and the depth of the nitracline represents a robust spatial boundary between ammonium assimilators and oxidizers in the stratified ocean. Profiles of ammonium utilization show that phytoplankton assemblages in nitrate-depleted regimes have higher ammonium affinity than nitrifiers. In nitrate replete conditions, by contrast, phytoplankton reduce their ammonium reliance and thus enhance the success of nitrifiers. This finding helps to explain existing discrepancies in the understanding of light inhibition of surface nitrification in the global ocean, and provides further insights into the spatial linkages between oceanic nitrification and new production.This work is supported by the National Natural Science Foundation of China through grants 91328207, Science Fund for Creative Research Groups of the National Natural Science Foundation of China through grants 41721005 and National Basic Research Program of China (973 Program) through grants 2014CB953702, 2015CB954003. T.W.T. was supported by an MEL Visiting Scholar award. 成果获得了国家重点基础研究发展计划（2014CB953702, 2015CB954003），国家自然科学基金委“创新研究群体项目”（41721005）以及重点基金（91328207）的资助

Technical Note: Simultaneous measurement of sedimentary N-2 and N2O production and a modified N-15 isotope pairing technique

National Science Council, Taiwan [NSC 100-2621-M-001-003-MY3]; National Natural Science Foundation of China [NSFC 41176059, B07034]Dinitrogen (N-2) and/or nitrous oxide (N2O) are produced through denitrification, anaerobic ammonium oxidation (anammox) or nitrification in sediments, of which entangled processes complicate the absolute rate estimations of gaseous nitrogen production from individual pathways. The classical isotope pairing technique (IPT), the most common N-15 nitrate enrichment method to quantify denitrification, has recently been modified by different researchers to (1) discriminate between the N-2 produced by denitrification and anammox or to (2) provide a more accurate denitrification rate under considering production of both N2O and N-2. In case 1, the revised IPT focused on N-2 production being suitable for the environments of a low N2O-to-N-2 production ratio, while in case 2, anammox was neglected. This paper develops a modified method to refine previous versions of IPT. Cryogenic traps were installed to separately preconcentrate N-2 and N2O, thus allowing for subsequent measurement of the two gases generated in one sample vial. The precision is better than 2% for N-2 (m/z 28, m/z 29 and m/z 30), and 1.5% for N2O (m/z 44, m/z 45 and m/z 46). Based on the six m/z peaks of the two gases, the N-15 nitrate traceable processes including N-2 and N2O from denitrification and N-2 from anammox were estimated. Meanwhile, N2O produced by nitrification was estimated via the production rate of unlabeled (N2O)-N-44. To validate the applicability of our modified method, incubation experiments were conducted using sediment cores taken from the Danshuei Estuary in Taiwan. Rates of the aforementioned nitrogen removal processes were successfully determined. Moreover, N2O yield was as high as 66 %, which would significantly bias previous IPT approaches if N2O was not considered. Our modified method not only complements previous versions of IPT but also provides more comprehensive information to advance our understanding of nitrogen dynamics of the water-sediment interface

Water and sediment discharge from small mountainous rivers, Taiwan: The roles of lithology, episodic events, and human activities

National Science Council of Taiwan [NSC96-2628-M-001-028]; U.S. National Science Foundation and Naval Oceanographic OfficeTaiwan's natural setting creates highly vulnerable watersheds whose rivers discharge disproportionately large quantities of sediment to the coastal ocean. The 16 Taiwanese rivers analyzed in this article discharge similar to 180 Mt yr(-1) of sediment to the coastal ocean, although totals over the past 20 years have varied between 16 and 440 Mt yr(-1). The mean annual sediment yield of 9500 t km(-2) yr(-1) for the 16 rivers is 60-fold greater than the global yield of 150 t km(-2) yr(-1), but mean yields for the individual rivers vary by more than 2 orders of magnitude, from 500 to 71; 000 t km(-2) yr(-1). Most sediment erosion and delivery occur in response to typhoon-generated floods, as evidenced by the fact that > 75% of the long-term flux occurs in < 1% of the time, about one-third of which reaches hyperpycnal concentrations. Detailed analysis of the 16 watersheds reveals little evidence of any single environmental factor that controls sediment load. The Erren, the highest-yield river on Taiwan, drains an erodible but low-gradient watershed with relatively low runoff. In contrast, three east coast rivers, the Hoping, the Hualien, and the Beinan, have high sediment yields that may be explained by relatively frequent earthquakes coupled with high runoff. Farming and urbanization also have elevated sediment yields in eastern watersheds, whereas Holocene sediments buried in the Taiwan Strait suggest that present-day sediment loads of the western rivers may be no higher than prehuman levels