Multiple processes affecting surface seawater N20 satura- tion anomalies in tropical oceans and Prydz Bay, Antarc- tica     

CHEN Liqi  ZHAN Liyang  XU Suqing  ZHANG Jiexia  ZHANG Yuanhui  XU Guojie 《极地研究(英文版)》2012,(2):87-94

Abstract We analyzed the N20 content of surface seawater sampled from Prydz Bay, Antarctica, on a cruise track between 30°S and 30°N during the twenty-second Chinese National Antarctic Research Expedition during austral summer, 2006. The surface water showed an average pN20 value of 311.9a：7.6 nL.L-1 （14.1：t：0.4 nmol-Ll）, which was slightly undersaturated. The air-sea N2O flux in the region was -0.3±0.8 p.mol.mE,dl; howeveh N20 in the surface water was oversaturated in most stations along the cruise track. Saturation anomalies were greater than 10%, with a maximum of 54.7% being observed at the Eqaator, followed by 31% at 10°N in the Sulu Sea. The air-sea fluxes at these locations were 12.4 and 4 μmol-mLd-1, respectively. Overall, the results indicated that surface water in Prydz Bay was near equilibrium with atmospheric N20, and that ocean waters in lower latitudes acted as a N20 source. Physical processes such as stratification, ice-melt water dilution, and solar radiation dominate the factors leading to N20 saturation of surface water of Prydz Bay, while biological production and upwelling are primarily responsible for the N20 oversaturation of surface water observed in subtropical and tropical regions along the cruise track.  相似文献   

Mineral chemistry of a Cenozoic igneous complex,the Urumieh–Dokhtar magmatic belt,Iran: Petrological implications for the plutonic rocks          下载免费PDF全文

Maryam Honarmand  Nematollah Rashidnejad Omran  Franz Neubauer  Ghasem Nabatian  Mohammad Hashem Emami  Manfred Bernroider  Jamshid Ahmadian  Mohammad Ebrahimi  Xiaoming Liu 《Island Arc》2016,25(2):137-153

The Niyasar plutonic complex, one of the Cenozoic magmatic assemblages in the Urumieh‐Dokhtar magmatic belt, was the subject of detailed petrographic and mineralogical investigations. The Niyasar magmatic complex is composed of Eocene to Oligocene mafic rocks and Miocene granitoids. Eleven samples, representing the major rock units in the Niyasar magmatic complex and contact aureole were chosen for mineral chemical studies and for estimation of the pressure, temperature, and oxygen fugacity conditions of mineral crystallization during emplacement of various magmatic bodies. The analyzed samples are composed of varying proportions of quartz, plagioclase, K‐feldspar, hornblende, biotite, titanite, magnetite, apatite, zircon, garnet, and clinopyroxene. Application of the Al‐in‐hornblende barometer indicates pressures of around 0.2 to 0.4 kbar for the Eocene–Oligocene mafic bodies and around 0.5 to 1.7 kbar for the Miocene granitoids. Hornblende‐plagioclase thermometry yields relatively low temperatures (661–780 °C), which probably reflect late stage re‐equilibration of these minerals. The assemblage titanite–magnetite–quartz as well as hornblende composition were used to constrain the oxygen fugacity and H₂O content during the crystallization of the parent magmas in the Miocene plutons. The results show that the Miocene granitoids crystallized from magmas with relatively high oxygen fugacity and high H₂O content (~5 wt% H₂O). The Miocene granitoids show similar range of oxygen fugacity, H₂O contents and mineral chemical compositions, which indicate a common source for their magmas. Although the crystallization pressures of the Miocene plutons discriminate various categories of plutonic bodies emplaced at depths of about 5.7–6.5 km (Marfioun pluton), about 4.2 km (Ghalhar pluton) and 1.9–2.3 km (Poudalg pluton), they were later uplifted to the same level by vertical displacement of faults. The emplacement depths of the Niyasar plutons suggest that the central part of the Urumieh‐Dokhtar magmatic belt has experienced an uplift rate of ca. 0.25–0.4 mm/yr from the Miocene onwards.  相似文献   

Geochemical characteristics of deposits from the 2011 Tohoku‐oki tsunami at Hasunuma,Kujukuri coastal plain,Japan          下载免费PDF全文

Tetsuya Shinozaki  Yuki Sawai  Junko Hara  Minoru Ikehara  Dan Matsumoto  Koichiro Tanigawa 《Island Arc》2016,25(5):350-368

We examined the geochemical characteristics and temporal changes of deposits associated with the 2011 Tohoku‐oki tsunami. Stable carbon isotope ratios, biomarkers, and water‐leachable ions were measured in a sandy tsunami deposit and associated soils sampled at Hasunuma, Kujukuri coastal plain, Japan, in 2011 and 2014. At this site, the 2011 tsunami formed a 10–30 cm ‐thick layer of very fine to medium sand. The tsunami deposit was organic‐poor, and no samples contained any detectable biomarkers of either terrigenous or marine origin. In the underlying soil, we identified hydrocarbons and sterols derived from terrestrial plants, but detected no biomarkers of marine origin. In the samples collected in 2011, concentrations of tsunami‐derived water‐leachable ions were highest in the soil immediately beneath the tsunami deposit and then decreased gradually with depth. Because of its finer texture and higher organic content, the soil has a higher water‐holding capacity than the sandy tsunami deposit. This distribution suggests that ions derived from the tsunami quickly penetrated the sand layer and became concentrated in the underlying soil. In the samples collected in 2014, concentrations of water‐leachable ions were very low in both soil and sand. We attribute the decrease in ion concentrations to post‐tsunami rainfall, seepage, and seasonal changes in groundwater level. Although water‐leachable ions derived from seawater were concentrated in the soil beneath the tsunami deposit following the tsunami inundation, they were not retained for more than a few years. To elucidate the behavior of geochemical characteristics associated with tsunamis, further research on organic‐rich muddy deposits (muddy tsunami deposits and soils beneath sandy tsunami deposits) as well as sandy tsunami deposits is required.  相似文献   

全球海气系统年代际突变时空特征的模拟评估   总被引：1，自引：0，他引：1  

肖栋  李建平  周秀骥  赵平 《气象学报》2010,68(6):763-778

文中评估了5个耦合模式对1880年至今全球海气系统的年平均年代际突变时空特征的模拟能力。19世纪80年代—20世纪90年代,评估了耦合模式对海表温度(SST)和海平面气压(SLP)的年代际突变水平分布的模拟能力;20世纪70—90年代,评估了耦合模式对70、80和90年代这3次年代际突变大气的四维时空特征的模拟。结果表明,在上述2个时段中,5个耦合模式对SST场中年代际突变分布最主要的空间分布型——太平洋年代际振荡(PDO)没有抓住,可能导致了对SST年代际突变的空间分布的模拟能力较差,也没有模拟出SLP年代际突变的行星及其以上尺度的空间结构。20世纪70—90年代,在对流层中,UKMO-HadGEM1模式较好地模拟出了70年代的热带地区500 hPa气温和位势高度,80年代极地SLP,90年代南、北副热带气温和500 hPa气温的年代际突变的空间分布。GFDL-CM2.1模式部分模拟出了90年代的SST和500 hPa温度场突变的水平分布。其余模式中也有行星及以上尺度的年代际突变发生,虽然所模拟出来的突变的时间和空间分布与实际差异都较大,但说明这些模式可以模拟出大尺度气候系统年代际突变,其中包含的物理过程还有待于进一步的研究。在平流层,肖栋(2008年)指出1994年平流层的降温突变可能是1991年Pinatubo火山爆发所造成的臭氧减少导致的。其中,GFDL-CM2.1和ECHAM5/MPI-OM模式较好地模拟出了平流层在1994年的降温突变,CCSM3和UKMO-HadGEM1模式部分模拟出了平流层的变冷突变,而FGC)ALS-g1.0模式没有模拟出来。分析表明,这可能是FGOALS-g1.0模式没有考虑火山灰或者臭氧的作用所致。  相似文献   

近50年来(1960—2007年)长江流域20 cm口径蒸发皿蒸发量与太阳辐射变化的对比     

郭媛  王艳君  刘长坤 《南京气象学院学报》2012,4(6):496-505

利用长江流域147个气象站点1960—2007年的地面观测数据,通过计算,对比分析了长江流域20 cm口径蒸发皿蒸发量与太阳辐射的变化关系.结果表明:长江流域近50年来蒸发皿蒸发量变化和太阳辐射变化呈显著正相关关系,二者均呈现显著下降趋势,蒸发皿蒸发量随太阳辐射的变化产生相应波动变化,而且中下游地区蒸发皿蒸发量变化受太阳辐射变化的影响程度更为明显;就季节变化而言,春夏秋冬4个季节长江流域蒸发皿蒸发量变化和太阳辐射变化同样呈现明显下降趋势,春、夏、秋3个季节二者变化关系高度相关,这三季对于流域全年蒸发皿蒸发量减少的贡献也最大;长江流域太阳辐射的显著下降是导致20 cm口径蒸发皿蒸发量持续降低的主要原因之一.  相似文献   

2004/2005年冬季强寒潮事件与大气低频波动关系的研究   总被引：22，自引：4，他引：18  

马晓青  丁一汇  徐海明 《大气科学》2008,32(2):380-394

2004/2005年冬季中国出现了两次大范围寒潮过程,造成长时期的降温和严寒天气,从而改变了从1986年以来中国大部分地区连续出现18个暖冬的局面。利用2004年10月1日～2005年3月31日中国740站逐日平均温度和NCEP/NCAR的逐日高度场和风场资料,分析了2004/2005冬季的强寒潮事件,并对寒潮爆发的周期、低频波动特征及其影响寒潮爆发的可能原因进行研究。结果表明:2004/2005年冬季两次主要强寒潮事件（12月22日～1月1日和2月14～21日）是在强10～20天低频振荡背景下发生的。在一次季节内低频振荡过程中,寒潮经历了高空形势相似的3个阶段,它们分别是乌拉尔东侧阻塞脊建立、阻塞脊下游横槽发展、横槽转竖与南支槽耦合重建东亚大槽最后导致寒潮爆发。进一步分析表明,乌拉尔东侧阻塞脊和里海高度脊是导致这两次寒潮的主要系统。研究还表明在寒潮爆发过程中,10～20天低频波动在40°N南北独立传播,南北波列耦合寒潮全面爆发;寒潮爆发后期低频波动引起我国东南部低空辐散异常、高空辐合异常,从而导致我国南部地区偏北风增强,使寒潮向南爆发程度和高空东亚急流明显加强。  相似文献   

Early generation of 20S-5α(H),14α(H),17α(H)- and 5α(H),14β(H),17β(H)-steranes in low salinity lacustrine shales     

Maowen Li  Steve R. Larter  Bowen Mei 《Organic Geochemistry》1994,22(6)

A quantitative sterane biomarker study was conducted on a series of paralic freshwater lacustrine shale samples ranging in maturity from immature to near oil window maturity taken from Section 3 of the Shahejie Formation (Es3) in the Liaohe Basin, N.E. China. Concentrations of 5α(H),14α(H),17α(H)-20S and 5α(H),14β(H),17β(H)-steranes remain nearly constant throughout the sample suite. However, the decrease in the absolute concentrations of the 20R-5α(H),14α(H),17α(H)-C₂₉ steranes with increasing maturity results in an increase in the conventionally defined maturity parameters, 20S/(20S + 20R)-ααα and αββ/(ααα + αββ) sterane ratios. In addition, the data suggest that relatively early generation of 5α(H),14α(H),17α(H)-20S and 5α(H),14β(H),17β(H)-steranes has occurred in lacustrine sediments with a vitrinate reflectance 0.3% (R_o). The data provide strong support for the major importance of relative thermal stability of epimers, but do not exclude the possibility of isomerization as a viable mechanism for production.  相似文献   

Benthic community response to habitat variation: A case of study from a natural protected area,the Celestun coastal lagoon     

Daniel Pech  Pedro-Luis ArdissonNorma A. Hernández-Guevara 《Continental Shelf Research》2007

Little information currently exists on spatial and temporal benthic community variations in tropical coastal lagoons. Here, the benthic community response to habitat variation in the Celestun coastal lagoon, northwest Yucatan peninsula, was seasonally examined during the 1994–1995 climatic cycle into a grid of 12 sampling sites distributed along the salinity gradient of the lagoon. Habitat variation was assessed through physical factors associated both to the water column (e.g. salinity) and the bottom sediment (e.g. sand, silt and clay fractions). The benthic community response was assessed through species diversity measures and abundance. Under the influence of climatic seasonality, variations in habitat conditions followed by changes in the benthic community characteristics were expected. Results from two-way ANOVAs showed that for the period of study, Celestun lagoon was more heterogeneous along the spatial axis of variability than along the temporal one. Multiple regression analysis showed that salinity was spatially the main factor influencing the benthic community characteristics. Temporally, the sediment characteristics were observed to exert significant effects on the species diversity characteristics but not on abundance. Other variables assessed (dissolved oxygen, pH, temperature and water column transparency) exhibited no significant covariance with species diversity and abundance. Since generated from historical data, these results have the potential to be useful as a benchmark to the establishment of monitoring programs in the light of the increasing anthropogenic pressure on the natural resources of the lagoon and surrounding coastal area.  相似文献   

YCJF20型冲击反循环钻机进行地下 连续墙成槽施工技术     

杨东河  刘珂  夏小兴  王国伟  张永春  李绍琳 《探矿工程》2018,45(11):65-68

成槽施工是地下连续墙施工的重要工序,厦门地铁3号线湖滨东路站地下连续墙施工中采用YCJF20型冲击反循环钻机冲击钻进法进行成槽施工。介绍了YCJF20型钻机的主要技术参数、特点和工作原理,以及导墙和导孔施工、钻机布置、泥浆制备、冲钻成槽等成槽施工过程。  相似文献   

Changes of Air–sea Coupling in the North Atlantic over the 20th Century   总被引：1，自引：0，他引：1  

YANG Yun  WU Lixin 《大气科学进展》2015,32(4):445-456

Changes of air–sea coupling in the North Atlantic Ocean over the 20 th century are investigated using reanalysis data,climate model simulations, and observational data. It is found that the ocean-to-atmosphere feedback over the North Atlantic is significantly intensified in the second half of the 20 th century. This coupled feedback is characterized by the association between the summer North Atlantic Horseshoe(NAH) SST anomalies and the following winter North Atlantic Oscillation(NAO). The intensification is likely associated with the enhancement of the North Atlantic storm tracks as well as the NAH SST anomalies. Our study also reveals that most IPCC AR4 climate models fail to capture the observed NAO/NAH coupled feedback.  相似文献