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1.
Vertical profiles of dissolved and particulate 210Po and 210Pb were measured across the redox transition zone at Station F1 in Framvaren Fjord, Norway. In this fjord, a sharp decrease in pH above the O2/H2S interface facilitates the aerobic dissolution of MnO2. In contrast, Fe(II) concentrations begin to increase only at the O2/H2S interface depth. Activity profiles reveal that dissolved 210Po and 210Pb are sequestered efficiently by particulates in surface waters. As polonium-210 and lead-210 activities descend down into the aerobic manganese reduction (AMR) zone, they are remobilized during the reductive dissolution of the carrier phase oxyhydroxides. Both 210Po and 210Pb are highly enriched at the O2/H2S interface where an active community of microbes, such as anoxygenic phototrophs (e.g., Chromatium, Chlorobium sp.), thrives. The coincident peaks in 210Po, 210Pb and microbial biomass suggest a strong biological influence on the behavior of these radionuclides. There is a strong covariance between the vertical distribution of Mn and Pb, indicating that their redox cycling is closely coupled and is likely microbially mediated. 相似文献
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This paper reports that stoichiometric, amorphous, and uniform Er2O3 films are deposited on Si(001) substrates by a radio frequency magnetron sputtering technique. Ellipsometry measurements show that the refractive index of the Er2O3 films is very close to that of a single layer antireflection coating for a solar cell with an air surrounding medium during its working wavelength. For the 90-nm-thick film, the reflectance has a minimum lower than 3% at the wavelength of 600 nm and the weighted average reflectances (400--1000 nm) is 11.6%. The obtained characteristics indicate that Er2O3 films could be a promising candidate for antireflection coatings in solar cells. 相似文献
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ZHANG Naixing SONG Jinming CAO Conghu REN Rongzhu WU Fengcong ZHANG Shaoping SUN Xu 《海洋学报(英文版)》2012,31(1):73-82
The influence of macronitrogen (NO - 3 and NH + 4 ) addition with Ulva pertusa on dissolved inorganic carbon system in seawater was studied. The results indicate that p(CO 2 ) and HCO 3 concentration decrease significantly, while pH and CO 2- 3 concentration increase significantly. When the concentration of NO 3 was less than 71 μmol/dm 3 or NH + 4 was less than 49.7 μmol/dm 3 , dissolved inorganic carbon (DIC) absorption rates by Ulva pertusa generally increased with the increasing of nitrogen concentration. The DIC decreased 151 μmol/dm 3 with the addition of 71 μmol/dm 3 NO 3 and decreased 232 μmol/dm 3 with the addition of 49.7 μmol/dm 3 NH + 4 after the experiment compared with DIC measured without nitrogen addition. A significant negative-correlation was found between c(DIC) and growth rate (μ) of Ulva pertusa (r = -0.91, P <0.000 1, n=11). NH + 4 had more influence on the species of inorganic carbon system than NO 3 . 相似文献
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Geometry and vibrational frequencies of the ground state of Si2O2 molecule are studied using density function theory (DFT) at the level of cc-pvtz and 6-311++G**. It is found that the optimizing value by B3lyp/cc-pvtz is closer to the experimental data. The excited properties under different external electric fields are also investigated by the time-dependent-DFT method. Transitions from the ground state of Si2O2 molecule to the first singlet state under different external electric fields can take place more easily. The corresponding absorption spectral line is about 360 nm in wavelength and the excitation energy is about 3.4 eV. 相似文献
6.
浒苔对NH+4-N与NO-3-N吸收的相互作用 总被引：1，自引：0，他引：1
在国内首次研究了大型海洋绿潮藻浒苔(Ulva prolifera)对NH4+-N与NO 3--N两种氮源的选择吸收作用。结果表明:当两种氮源等浓度比例存在时,随着NH4+-N与NO3--N浓度升高,藻体对NH4+-N的吸收速率逐渐升高,而对NO3--N吸收受到抑制;当NO3--N和NH 4+-N高浓度比存在时,藻体对NH4-N的吸收速率随着NO3--N/NH4+-N比例的升高和NH4-N浓度的下降而降低;当NO3--N和NH4+-N低浓度比存在时,藻体对NH+4-N保持较高的吸收速率,而对NO3--N的吸收效率随着NO3--N浓度的降低而降低;浒苔具有同时利用水体中较高浓度的NH+4-N和NO3--N的能力,只有当NH4+-N或NO3--N浓度较低时,才以吸收相对应的氮源为主。这说明浒苔能够快速、大量地吸收水体中氮源,为爆发性增殖贮备物质条件。同时,即便两种氮源同时存在,浒苔对NH+4-N的吸收速率也远高于对NO3--N的吸收速率,因此,控制NH4+-N的大量输入仍是预防浒苔绿潮爆发的关键。 相似文献
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以I.A.M.收集的培养基Ⅱ为基本培养基,采用单因子和L16(45)正交设计法,进行了舟形藻BT001对N、P、Fe、Si四种营养盐最适需求的研究,并在此基础上,研究了尿素对正交优化组合的影响以及以尿素作为氮源对正交优化组合的影响。结果表明,N、P、Fe、Si四种营养盐最佳单因子水平为:KNO3,300mg/L;Na2HPO4·12H2O,40mg/L;FeCl3,4mg/L;Na2SiO3·9H2O,200mg/L。四种营养盐正交组合水平为:KNO3,150mg/L;Na2HPO4·12H2O,40mg/L;FeCl3,4mg/L;Na2SiO3·9H2O,200mg/L。在正交组合水平基础上,添加16mg/LCO(NH2)2,可更好的促进该藻的生长和繁殖。在8天的培养中,最大细胞相对生长率可达0.1577。在等摩尔氮源的条件下,以CO(NH2)2代替正交优化水平组合中的KNO3对舟形藻BT001进行11天的培养。结果表明,以CO(NH2)2为氮源的藻细胞最大生长密度可达2.69×105cell/ml,明显地高于硝酸钾作为氮源培养的藻细胞密度。 相似文献
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Vertical gas profiles of N2, N2O and O2were obtained in intact sediment cores from a Tagus estuary salt marsh using membrane inlet mass spectrometry. This technique allows direct measurements of dissolved gas concentrations with minimal disturbance. O2concentrations decreased sharply with depth, becoming undetectable below 14mm. Denitrification products (N2and N2O) occurred in the surface layer of the sediment where O2was present. Diffusion of N2and N2O from the anaerobic zone, denitrification in anaerobic microsites and aerobic denitrification are possible explanations for this observation. N2was the sole product of denitrification in control sediment cores probably because of the great demand for electron acceptors in this sediment. The addition of NO3 − and CH3CO2 − increased the concentrations of N2and N2O in the sediment. Significantly higher concentrations in treated cores occurred between 1·5 and 2·0cm for N2and between 0·5 and 1·5cm for N2O. The peak in N2concentration occurred in the anaerobic zone of the sediment, close to the aerobic–anaerobic interface while the peak in N2O concentration occurred above this interface where concentrations of O2were approximately 10μM. This is indicative that, in this sediment, production of N2O is less sensitive to the presence of O2than reduction of N2O to N2. 相似文献
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This paper evaluates the simultaneous measurement of dissolved gases (CO2 and O2/Ar ratios) by membrane inlet mass spectrometry (MIMS) along the 180° meridian in the Southern Ocean. The calibration of pCO2 measurements by MIMS is reported for the first time using two independent methods of temperature correction. Multiple calibrations and method comparison exercises conducted in the Southern Ocean between New Zealand and the Ross Sea showed that the MIMS method provides pCO2 measurements that are consistent with those obtained by standard techniques (i.e. headspace equilibrator equipped with a Li–Cor NDIR analyser). The overall MIMS accuracy compared to Li–Cor measurements was 0.8 μatm. The O2/Ar ratio measurements were calibrated with air-equilibrated seawater standards stored at constant temperature (0 ± 1 °C). The reproducibility of the O2/Ar standards was better than 0.07% during the 9 days of transect between New Zealand and the Ross Sea.The high frequency, real-time measurements of dissolved gases with MIMS revealed significant small-scale heterogeneity in the distribution of pCO2 and biologically-induced O2 supersaturation (ΔO2/Ar). North of 65°S several prominent thermal fronts influenced CO2 concentrations, with biological factors also contributing to local variability. In contrast, the spatial variation of pCO2 in the Ross Sea gyre was almost entirely attributed to the biological utilization of CO2, with only small temperature effects. This high productivity region showed a strong inverse relationship between pCO2 and biologically-induced O2 disequilibria (r2 = 0.93). The daily sea air CO2 flux ranged from − 0.2 mmol/m2 in the Northern Sub-Antarctic Front to − 6.4 mmol/m2 on the Ross Sea shelves where the maximum CO2 influx reached values up to − 13.9 mmol/m2. This suggests that the Southern Ocean water (south of 58°S) acts as a seasonal sink for atmospheric CO2 at the time of our field study. 相似文献
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The distribution of diatoms in surface sediments in the Minjiang Estuary, southeast China, was investigated in2009. Total 56 species and other species belonging to 25 genera were identified, among them 11 species were dominant over 5%. Dominant species included Actinocyclus ehrenbergii, Coscinodiscus curvatulus, C. divisus, C.jonesianus, C. radiatus, C. rothii, C. subtilis, Cyclotella stylorum, Epithemia hyndmanii, Hydrosera whampoensis,and Trachyneis aspera. Diatom abundance varied spatially, with the absolute abundance of diatoms ranging from13 valves/g to 11×104 valves/g, and averaging 2.5×104 valves/g. A canonical correspondence analysis(CCA) was used to explain the relationships between diatom distribution and sediment properties in the Minjiang Estuary.CCA revealed that the major elements(Fe_2O_3, Na_2O, CaO, MgO, TiO_2, SiO_2, Al_2O_3, and K_2O) were closely related to diatom abundance. Four diatom assemblages were distinguished, representing different sediment properties,which may assist late Quaternary palaeoceanographic reconstructions of the Minjiang Estuary. 相似文献
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The δ13C and δ15N of particulate organic matter (POM) sampled from the Weddell Sea in 1986 and 1988 ranged from −30.4 to − 16.7%o and from −5.4 to +41.3%o, respectively. These large variations in POM δ13C and δ15N may reflect spatial/temporal changes in the concentrations and isotope abundances of CO2(aq.) and NH4+, respectively. Elevated isotope values were found exclusively in POM in or closely associated with sea ice, which may be the source of the 13C- and 15N-enriched sediments observed in this region. 相似文献
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甲壳动物的卵巢发育及卵黄发生受到体内各种内分泌激素的调控。本文研究了两组不同饲料—脂类营养平衡组(A组,含有磷脂和HUFA)和不平衡组(B组,缺乏磷脂和HUFA)对中华绒螯蟹卵巢发育及卵黄发生的激素调控,运用放射免疫法和放射化学法分别测定了处于不同卵黄发生期的中华绒螯蟹的肝胰腺、卵巢、血淋巴中孕酮(PG)、雌二醇(E2)的含量及中华绒螯蟹大颚器(MO)合成与分泌甲基法尼酯(MF)的速率。结果表明:1)中华绒螯蟹体内三种组织(肝胰腺、卵巢和血淋巴)中均存在PG和E2,PG可能为E2的前体;2)早熟蟹的MO合成MF速率远远大于正常发育的幼蟹,MF的大量合成与分泌是促使早熟蟹产生的主要内分泌因素;3)B组饲料(含猪油)喂养的河蟹其MO合成MF的速率均高于A组饲料(含鱼油),且B组饲料的早熟蟹转化PG速度比B组饲料的早熟蟹快;4)PG和E2的脂类结合部位能结合外源性卵黄蛋白原(Vg),通过血淋巴的运输被卵泡细胞胞吞,最终与卵母细胞内的内源性Vg结合,共同形成卵黄体;5)多不饱和脂肪酸(如EPA和DHA)可能会抑制类固醇激素的产生。研究表明,MF是中华绒螯蟹的促性腺激素,具有促使PG合成和E2转化的作用,它们共同诱导河蟹卵巢发育及卵黄发生。 相似文献
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Distribution of major and trace elements in surface sediments of Hangzhou Bay in China 总被引：2，自引：0，他引：2
LIU Shengf LIU Yanguang YANG Gang QIAO Shuqing LI Chaoxin ZHU Zhiwei SHI Xuefa 《海洋学报(英文版)》2012,31(4):89-100
The Inductively Coupled Plasma Optical Emission Spectrometer was used to analyze sediment samples collected from the Hangzhou Bay to determine major and trace elemental concentrations. Based on these concentrations, the study area can be classified into three geochemical provinces. Province I covers the northern Hangzhou Bay area and contains high concentrations of Al2 O3 , Fe2 O3 , MgO, Na2 O, K2 O, MnO, Cr, Cu, Ni, Pb, V, Co and Zn. Province III is located in the western Hangzhou Bay, near the Qiantang River mouth, and contains high concentrations of SiO2 , Na2 O, P2 O5 , TiO2 , Cr, Sr, Zr. Province II is located in the middle and eastern Hangzhou Bay, with the medium concentrations of major and trace elements. The results also demonstrate that the grain size is the dominating factor controlling the spatial variations of elemental concentrations, and the Changjiang River （Yangtze River） and Qiantang River sediments play an important role in the distribution of these elements. Anthropogenic impact on heavy metal concentrations （especially Cr, Sr and Zr） can be detected in the surface sediments near the Qiantang River mouth. 相似文献
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An integrated study involving sedimentology, mineral chemistry and spectroscopy highlights a distinctive compositional evolution of Cretaceous glauconite within the Ukra Hill Member. Glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf. The concentration of glauconite steadily increases towards the maximum flooding surface, maximizing around 50%, and sharply falls at the onset of progradation. Unlike most Phanerozoic examples, Ukra glauconite forms by the variable degree of replacement of quartz, feldspar and mica grains. XRD, FEG-SEM and spectroscopy of glauconite pellets indicate an ‘evolved’ stage of maturation. Mossbauer spectroscopy reflects a minor substitution of Al3+-Fe3+ (total) in tetrahedral sites and significant substitution of the same in octahedral sites. A consistently high value of K2O as well as Fe2O3 contradicts the two popular theories, ‘layer lattice’ and ‘verdissement’, and support replacement origin of glauconite in a high aSi+ and high aK+ pore water environment. Incipiently formed glauconite records a marginal increase in K2O content accompanied by release of Al2O3 and SiO2 to form evolved glauconite pellets; those forming within quartz grains involve an addition of Fe2O3 (total) content during maturation. The minimal increase in K2O content of incipiently formed glauconite, best exhibited by those formed within quartz grains is possibly related to stratigraphic condensation. Compositional evolution like this is exhibited by Precambrian glauconites involving abiotic substrates, but is unusual for the Phanerozoic. Original K2O and Fe2O3 (total) content of glauconites is reduced around peripheries and fractures during diagenesis, adding to compositional variability. 相似文献
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可口革囊星虫(Phascolosoma esculenta)重组铁蛋白富集Pb2+等重金属特性和功能研究 总被引：1，自引：1，他引：0
利用可口革囊星虫重组铁蛋白富集Pb2+、Fe3+、Cd2+、Cr3+、Cu2+、Mn2+、Sn2+和Zn2+等8 种重金属离子后, 通过透射显微镜和傅里叶红外光谱测定蛋白的超微结构变化和内部基团特性。以 天然的马脾铁蛋白为对照, 观察重组铁蛋白与天然铁蛋白的差别。结果显示, 重组铁蛋白富集Pb2+ 和其它7 种重金属离子后蛋白体积大小与重金属离子种类直接相关。重组铁蛋白相对天然铁蛋白来 说在富集不同种类重金属离子后, 除了非特异性酰胺特征峰和蛋白特征峰外, 还出现一些专门富集 某些重金属离子的特异基团, 如:-CH3、-CH2-、-CH-、-NH-、-SO3-、-COOH、-S=S-和-C-S-C 等。 通过细胞实验进一步验证了铁结合蛋白能够通过富集重金属离子Pb2+来保护小鼠成骨前体细胞 MRC3T3-E1, 使细胞的死亡率明显降低(P<0.05). 相似文献
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The potential of benzo[ a]pyrene (BaP) quinones (diones) to stimulate NAD(P)H-dependent hydroxyl radical (·OH) production (2-keto-4-methiolbutyric acid (KMBA) oxidation) by digestive gland microsomes of M. edulis was studied using iron/EDTA as a promotor of the Haber-Weiss reaction (O2− + H2O2 = ·OH + OH− + O2). Stimulation of basal rates of KMBA oxidation was observed for all three diones. Stimulation was similar for the 1,6- and 3,6-diones, but much less for the 6,12-dione, and greater for the NADH than the NADPH-dependent reaction, viz. % increases of 78 to 333 (NADH) compared to 0 to 78 (NADPH). Maximal KMBA oxidation was obtained at dione concentrations of 12.5 to 50 μm. Inhibition of KMBA oxidation by Superoxide dismutase and catalase indicated the involvement of respectively Superoxide anion radical (O2−) and hydrogen peroxide (H2O2) in 1,6-dione stimulated NADPH-dependent · OH formation. The apparent Km values of xenobiotic-stimulated KMBA oxidation were lower for BaP-diones than for the model redox cycling quinone menadione (2-methyl-1,4-naphthoquinone), viz. in μm, 0.6 to 14.6 (NADH) and 4.4 to 28.5 (NADPH) compared to 315 to 457 (NADH) and 72 to 103 (NADPH). The results are consistent with metabolism of BaP to diones and resultant enhanced generation of oxyradicals being a potential mechanism of pollutant-mediated toxicity in molluscs. 相似文献
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Controversies over the origin of globally distributed Cretaceous red beds have mainly focused on climate vs. weathering with potential hydrothermal influence. In comparison to Cretaceous Oceanic Red Beds, Cretaceous lacustrine red beds exhibit chronological inconsistencies and their diverse tectonic settings suggest differing genetic mechanisms. In this paper, Early Cretaceous red beds in the North Yellow Sea Basin, one of Mesozoic rift basins in eastern China that are associated with multi-phase magmatic activities, was chosen to document potential hydrothermal impact. Geological and geochemical analyses show that these red beds were syndepositional products developed in shallow to moderately deep lacustrine environments and that they were influenced by hydrothermal activity. Major and trace elements, including enhanced Al2O3-normalized Fe2O3 and Fe2O3 (total) values, Al/(Al + Fe + Mn) and (Fe + Mn)/Ti ratios, Ni-Co-Zn and Fe-Mn-(Ni + Co + Cu)*10, ∑REE-La/Yb, the concentrations of hydrothermally-related ions, invalid redox indicators of trace elements, abnormally high Fe2O3 (total) content, positive Eu anomaly, correlation of Fe2O3 (total) and Eu anomaly, and vitrinite reflectance (Ro) vs. total organic carbon (TOC), all show strong hydrothermal fluid influence and heating effects. By integrating and comparing data from previous studies, we propose a hydrothermally affected sedimentation model for Cretaceous red beds and associated sediments in magma-activated lacustrine basins, and conclude that the enriched metallic ions introduced by the hydrothermal fluids may be the most significant reason for the deposition of the red beds, and the flushed ferric ions, accompanied by hydrothermal fluid, are the main ions that are hosted inside hematite causing the red sediment. This model can be applied to similar lacustrine basins that experience strong magmatic activity. 相似文献
19.
T. Yoshinari M. A. Altabet S. W. A. Naqvi L. Codispoti A. Jayakumar M. Kuhland A. Devol 《Marine Chemistry》1997,56(3-4)
Nitrous oxide (N2O) is a trace gas that is increasing in the atmosphere. It contributes to the greenhouse effect and influences the global ozone distribution. Recent reports suggest that regions such as the Arabian Sea may be significant sources of atmospheric N2O.In the ocean, N2O is formed as a by-product of nitrification and as an intermediary of denitrification. In the latter process, N2O can be further reduced to N2. These processes, which operate on different source pools and have different magnitudes of isotopic fractionation, make separate contributions to the 15N and18O isotopic composition of N2O. In the case of nitrification in oxic waters, the isotopic composition of N2O appears to depend mainly on the 15N/14N ratio of NH+4 and the 18O/16O ratio of O2 and H2O. In suboxic waters, denitrification causes progressive 15N and 18O enrichment of N2O as a function of degree of depletion of nitrate and dissolved oxygen. Thus the isotopic signature of N2O should be a useful tool for studying the sources and sinks for N2O in the ocean and its impact on the atmosphere.We have made observations of N2O concentrations and of the dual stable isotopic composition of N2O in the eastern tropical North Pacific (ETNP) and the Arabian Sea. The stable isotopic composition of N2O was determined by a new method that required only 80–100 nmol of N2O per sample analysis. Our observations include determinations across the oxic/suboxic boundaries that occur in the water columns of the ETNP and Arabian Sea. In these suboxic waters, the values of δ15N and δ18O increased linearly with one another and with decreasing N2O concentrations, presumably reflecting the effects of denitrification. Our results suggest that the ocean could be an important source of isotopically enriched N2O to the atmosphere. 相似文献
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The degree of atmospheric saturation for O2, Ar, and N2 gases in water can be determined to accuracies of ±0.1–0.3% using mass spectrometry to determine the gas ratios and Winkler titrations for oxygen analysis. We describe methods used to obtain this level of accuracy and precision. Oxygen accuracy of ±0.1% can be obtained by careful attention to standardization using KIO3 standards that have been corrected for impurities. Accurate O2/Ar and O2/N2 gas ratios (±0.1–0.2%) are obtainable by measuring the mass ratios against the atmosphere if the effect of different gas concentrations on the performance of the mass spectrometer are taken into account. Oxygen and argon saturation values have been determined previously to accuracies of less than or equal to ±0.1%, but published estimates of the saturation value for nitrogen differ by more than 1%. We have redetermined the N2 saturation value at 19°C and zero salinity to be 0.92% greater than the results reported in the work of Weiss (1970). 相似文献