Phytoplankton biomass and size fractions in surface waters of the Australian sector of the southern ocean     

Wendy Ehnert  C. Peter McRoy 《Journal of Oceanography》2007,63(2):179-187

We collected surface water along the 142nd E meridian from Tasmania to Antarctica in December 1999. We measured temperature, salinity and total chlorophyll a; additionally, we collected suspended particle size fractions and used fluorometric analysis to determine the quantity of chlorophyll a in each of four cell size classes: picoplankton (<3 μm), two nanoplankton fractions (3–10 μm and 10–20 μm) and microplankton (> 20 μm). Changes in temperature and salinity show that we crossed 6 water masses separated by 5 fronts. We found low abundance (<0.2 mg m⁻³) of chlorophyll in all size classes, with the exception of higher values near the continent (0.2 to 0.4 mg m⁻³). Lowest chlorophyll values (<0.1 mg m⁻³) were found in the Polar Frontal Zone (51° to 54°S). Microplankton made up the largest portion of total chlorophyll throughout most of the region. We conclude that biomass of all phytoplankton fractions, especially pico-and nanoplankton, was constrained by limiting factors, most probably iron, throughout the region and that ecosystem dynamics within a zone are not circumpolar but are regionalized within sectors.  相似文献   

Spring and summer phytoplankton communities in the Chukchi and Eastern Beaufort Seas   总被引：2，自引：0，他引：2  

Victoria Hill  Glenn Cota  Dean Stockwell 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3369

Phytoplankton pigments and size-fractionated biomass in the Chukchi and Beaufort Seas showed spatial and temporal variation during the spring and summer of 2002. Cluster analysis of pigment ratios revealed different assemblages over the shelf, slope and basin regions. In spring, phytoplankton with particle sizes greater than 5 μm, identified as diatoms and/or haptophytes, dominated over the shelf. Smaller (<5 μm) phytoplankton containing chlorophyll b, most likely prasinophytes, were more abundant over the slope and basin. Due to extensive ice cover at this time, phytoplankton experienced low irradiance, but nutrients were near maximal for the year. By summer, small prasinophytes and larger haptophytes and diatoms co-dominated in near-surface assemblages in largely ice-free waters when nitrate was mostly depleted. Deeper in the water column at 1–15% of the surface irradiance larger sized diatoms were still abundant in the upper nutricline. Phytoplankton from the shelf appeared to be advected through Barrow Canyon to the adjacent basin, explaining similar composition between the two areas in spring and summer. Off-shelf advection was much less pronounced for other slope and basin areas, which are influenced by the low-nutrient Beaufort gyre circulation, leading to a dominance of smaller prasinophytes and chlorophytes. The correlation of large-sized fucoxanthin containing phytoplankton with the higher primary production measurements shows promise for trophic status to be estimated using accessory pigment ratios.  相似文献   

铅锌矿山开发导致的重金属在环境介质中的积累   总被引：35，自引：4，他引：35  

杨元根  刘丛强  张国平  吴攀  朱维晃 《矿物岩石地球化学通报》2003,22(4):305-309

以连续提取法和相关性分析研究了土法冶炼锌、铅锌和矿山开采导致的重金属在废渣及环境介质土壤、溪流沉积物中的积累，并分析了其环境危害性。结果显示，贵州赫章土法炼锌导致的重金属Pb、Zn、Cd在环境介质中的积累相当高。水城杉树林铅锌矿山开采引起的重金属积累则相对较低，但也明显高于背景值；土壤和沉积物中的铁矿物对重金属有强烈的固定作用。除残渣态外，Pb、Zn在土壤、炼锌废渣中主要呈铁锰氧化物结合态，沉积物中则为碳酸盐结合态。可交换态Pb、Zn含量变异较大，但在炼锌废渣、土壤中含量明显高于河流沉积物，暗示铅锌矿开发对土壤环境的潜在危害更大。  相似文献   

黄河下游泥沙淤积的经验统计关系   总被引：4，自引：0，他引：4  

许炯心 《地理研究》1997,16(1):23-30

以黄河下游历年实测水文泥沙资料为基础,运用多元回归分析方法,建立了下游河道淤积量与淤积强度的经验统计关系。揭示了不同粒径组泥沙的来量和它们在全沙中所占的比率对下游河道淤积特征的影响。同时,研究了高含沙洪水及清水基流对下游河道淤积的影响。  相似文献   

A preliminary estimate of how stream water age is influenced by changing runoff sources in the Nagqu river water shed,Qinghai-Tibet Plateau     

Yuheng Yang  Baisha Weng  Denghua Yan  Xiaoyan Gong  Yanyu Dai  Yongzhen Niu 《水文研究》2021,35(10):e14380

  相似文献   

Rutile R632 – A New Natural Reference Material for U‐Pb and Zr Determination          下载免费PDF全文

Emelie Axelsson  Jonas Pape  Jasper Berndt  Fernando Corfu  Klaus Mezger  Michael M. Raith 《Geostandards and Geoanalytical Research》2018,42(3):319-338

A new natural rutile reference material is presented, suitable for U‐Pb dating and Zr‐in‐rutile thermometry by microbeam methods. U‐Pb dating of rutile R632 using laser ablation ICP‐MS with both magnetic sector field and quadrupole instruments as well as isotope dilution‐thermal ionisation mass spectrometry yielded a concordia age of 496 ± 2 Ma. The high U content (> 300 μg g^?1) enabled measurement of high‐precision U‐Pb ages despite its young age. The sample was found to have a Zr content of 4294 ± 196 μg g^?1, which makes it an excellent complementary reference material for Zr‐in‐rutile thermometry. Individual rutile grains have homogeneous compositions of a number of other trace elements including V, Cr, Fe, Nb, Mo, Sn, Sb, Hf, Ta and W. This newly characterised material significantly expands the range of available rutile reference materials relevant for age and temperature determinations.  相似文献   

柱色谱分离-分子筛络合洗脱过程中正构烷烃单体碳同位素分馏研究     

董浩伟  赵佳玉  曾凡刚  谢曼曼  尚文郁  王淑贤  孙青 《岩矿测试》2021,(3):349-357

应用气相色谱-气体同位素质谱(GC-C-IRMS)分析正构烷烃单体碳同位素之前,需要对饱和烃样品中正构烷烃和异构烷烃进行预分离、富集,在预分离和富集过程中正构烷烃单体碳同位素是否发生分馏是高精度分析正构烷烃单体碳同位素比值(δ~(13)C)的关键。本文以正构烷烃混合溶液为对象,利用柱色谱、5■分子筛络合、环己烷-正戊烷混合溶剂两次洗脱,GC-C-IRMS分析正构烷烃单体碳同位素,研究前处理过程中正构烷烃单体碳同位素是否发生分馏。结果表明:使用柱色谱分离前后,多数正构烷烃单体碳同位素比值相差-0.2‰～0.2‰;当5■分子筛不完全络合时,未络合的正构烷烃单体碳同位素比值偏重约0.7‰,可能发生了微弱的碳同位素分馏,但并未影响洗脱后的正构烷烃单体碳同位素比值;使用环己烷-正戊烷混合溶剂洗脱前后,碳同位素比值相差-0.2‰～0.5‰,以同样方式洗脱第二次,获得的正构烷烃单体碳同位素比值与模拟样品相差-0.3‰～0.2‰。分析不同回收率(20%)正构烷烃的单体碳同位素比值,处理前后的差值基本在0.3‰以内,可见当正构烷烃回收率低至20%左右时,其单体碳同位素仍未发生明显分馏。柱色谱分离-5■分子筛络合-混合溶剂洗脱方法适用于回收率大于20%的正构烷烃单体碳同位素分析。  相似文献   

高分辨率模式雷达回波预报能力分析   总被引：1，自引：1，他引：0  

刘静  才奎志  谭政华 《气象》2019,45(12):1710-1717

利用2018年7—8月GRAPES_3 km、东北短临(WRFRUC)高分辨率模式综合雷达回波预报数据和辽宁省SWAN雷达组合反射率(MCR)实况,基于邻域法FSS评分指数,分析模式在台风北上和副热带高压边缘暴雨过程中的雷达回波预报能力。结果表明:两家模式在不同降水过程中对小阈值雷达回波有较好的预报技巧,随着回波量级增大,模式预报FSS逐渐减小,雷达回波55 dBz时,FSS甚至为0。当邻域半径是3时,35 dBz以下的回波预报中GRAPES模式在台风北上暴雨中的预报技巧低于副热带高压边缘,35 dBz则相反。WRFRUC模式始终表现为台风北上暴雨中预报较好。当邻域半径9时,WRFRUC模式在台风暴雨中的FSS评分高于GRAPES模式,GRAPES模式在副热带高压暴雨中的FSS评分始终高于WRFRUC模式。GRAPES和WRFRUC模式的最大FSS评分技巧均出现在邻域半径是11时,分别为0.239和0.195。GRAPES模式中FSS评分在12 h逐小时预报中前3个时次较强,WRFRUC模式则表现为中间时次强,两头弱。  相似文献   

Molecular weight distribution,analytical and spectroscopic characterization of humic fractions sequentially isolated by organic solvents from a brown coal humic acid     

Nicola Senesi  Sandor Sipos 《Organic Geochemistry》1985,8(2):157-162

A sequential fractionation procedure employing a series of selected mild organic solvents of different polarity has been applied for the isolation of chemically different organic fractions from a brown coal humic acid. Elemental composition, molecular weight distribution, i.r. and electron spin resonance analysis were carried out on the isolated humic fractions. They were characterized by: (a) a low polydispersity, (b) a decreasing aliphatic and increasing aromatic character along the series, (c) very different molecular weight which significantly correlated with E₄/E₆ ratios (particle aggregation and molecular association) and free radical concentrations (chemical and biochemical activity). Significant correlations were found between physico-chemical parameters of the isolated humic fractions, i.e. M_n, M_w, E₄/E₆ ratios, spins/g contents and the dielectric constants of the solvents used. This suggested the efficiency of the applied procedure in isolating chemically different organic fractions from the bulk, original humic acid.  相似文献   

ON THE NUMBER OF FRACTIONS TO COMPUTE TRANSPORT OF SEDIMENT MIXTURES     

Pedro A. BASILE Center for Hydroenvironmental Research  National University of Rosario   《国际泥沙研究》2001,16(3)

1 INTRODUCTIONMany hydro-momhological mathematical models neglect the innuence of river bed maerialheterogeneity and its time and space changes during transport and related erosion/dePosition processes. Inthese models a rePresentative diameter of the river bed grain-size distribution (for examPle d5o) isspecified as initial data in each comPutational point of the modeled domain. Different d5o can be assignedto each ghd point but temPoral changes in bed material gradation cannot be simula…  相似文献