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51.
Vertical measurements of , and N2O concentrations, and uptake, and oxidation rates were measured at 5 sites in western Cook Strait, New Zealand, between 31 March and 3 April 1983. Nitrate increased with depth at all stations reaching a maximum of 10.5 μg-atom at the most strongly stratified station whereas was relatively constant with depth at all stations (~0.1 μg-atom ). The highest rates of oxidation generally occurred in the near surface waters and decreased with depth. N2O levels were near saturation with respect to the air above the sea surface and showed no obvious changes during 24 h incubation. oxidation by nitrifying bacteria may account for about 30% of the total utilization (i.e. bacterial+agal) and, assuming oxidation through to , may supply about 40% of the algal requirements of in the study area. These results suggest that bacterial nitrification is of potential importance to the nitrogen dynamics of the western Cook Strait, particularly with respect to the nitrogen demands of the phytoplankton. 相似文献
52.
It is necessary to pay more attention to the durability of concrete undergoing freeze-thaw cycles and seawater attack simultaneously.Investigated are the effects of water-binder ratio,fly ash (FA) contents and air-entraining agent on resistance to frost and chloride diffusion of marine concrete blended with FA in natural seawater.The results show that fly ash does not improve the frost resistance of concrete but can improve its resistance to chloride diffusion by addition of less than 30%.The resistance to frost and chloride diffusion of FA concrete can be improved with the decrease of water-binder ratio,and FA may improve both of them simultaneously only being mixed with air-entraining agent.A ratio (named as R) of the frost-resisting durability factor to chloride diffusion coefficient can be used to evaluate the durability of marine concrete.Scanning electron microscope (SEM) analyses are consistent with the evaluations by the value of R. 相似文献
53.
Dissolved inorganic carbon (DIC) and its carbon isotopic composition in sediment pore waters from the Shenhu area,northern South China Sea 总被引:2,自引:0,他引:2
Tao Yang Shao-Yong Jiang Jing-Hong Yang Ge Lu Neng-You Wu Jian Liu Dao-Hua Chen 《Journal of Oceanography》2008,64(2):303-310
The Shenhu area is one of the most favorable places for the occurrence of gas hydrates in the northern continental slope of
the South China Sea. Pore water samples were collected in two piston cores (SH-A and SH-B) from this area, and the concentrations
of sulfate and dissolved inorganic carbon (DIC) and its carbon isotopic composition were measured. The data revealed large
DIC variations and very negative δ
13C-DIC values. Two reaction zones, 0–3 mbsf and below 3 mbsf, are identified in the sediment system. At site SH-A, the upper
zone (0–3 mbsf) shows relatively constant sulfate and DIC concentrations and δ
13C-DIC values, possibly due to bioturbation and fluid advection. The lower zone (below 3 mbsf) displays good linear gradients
for sulfate and DIC concentrations, and δ
13C-DIC values. At site SH-B, both zones show linear gradients, but the decreasing gradients for δ
13C-DIC and SO4
2− in the lower zone below 3 mbsf are greater than those from the upper zone, 0–3 mbsf. The calculated sulfate-methane interface
(SMI) depths of the two cores are 10.0 m and 11.1 m, respectively. The depth profiles of both DIC and δ
13C-DIC showed similar characteristics as those in other gas hydrate locations in the world oceans, such as the Blake Ridge.
Overall, our results indicate an anaerobic methane oxidation (AMO) process in the sediments with large methane flux from depth
in the studied area, which might be linked to the formation of gas hydrates in this area. 相似文献
54.
区域地下水溶解性碳的时空变化特征研究对于认识区域物质循环和能量传递及推动区域生态可持续发展具有重要意义。本研究在青海湖流域冻结期和融化期分别收集了地下水、河水和湖水样品,研究了环青海湖地下水在冻结期和融化期的溶解性碳特征,并探究了不同类型地下水的溶解性碳特征及其对不同冻融时期的响应,最后揭示了环湖区域不同水体的溶解性碳的差异特征及影响因素。结果表明:冻结期地下水、河水和湖水的溶解性无机碳(DIC)均相对高于融化期,溶解性有机碳(DOC)均相对低于融化期。地下水、河水和湖水的溶解性碳均主要以DIC为主,DIC在溶解性碳的占比高达92%。地下水的DIC平均含量在基岩裂隙水、水量中等和浅埋藏的水文地质条件下相对较高,DOC平均含量在基岩裂隙水、水量丰富和浅埋藏的水文地质条件下相对较高。地下水的DIC在湖滨平原砂砾石层、淤泥质砂层潜水和水量中等的水文地质条件下受冻融期影响较大,DOC在基岩裂隙水和水量贫乏的水文地质条件下受冻融期影响较大。湖水的DIC和DOC均远高于河水和地下水。河水的DIC在融化期和冻结期均低于地下水,DOC在融化期高于地下水,在冻结期低于地下水。 相似文献
55.
正Amounts of lithium-containing salt lake brine resources are widely distributed in the four provinces named Qinghai,Tibet,Inner Mongolia and Xinjiang province,especially the salt lakes in Qinghai-Tibet Plateau are abundant of 相似文献
56.
The major ion composition of Great Artesian Basin groundwater in the lower Namoi River valley is relatively homogeneous in chemical composition. Traditional graphical techniques have been combined with multivariate statistical methods to determine whether subtle differences in the chemical composition of these waters can be delineated. Hierarchical cluster analysis and principal components analysis were successful in delineating minor variations within the groundwaters of the study area that were not visually identified in the graphical techniques applied. Hydrochemical interpretation allowed geochemical processes to be identified in each statistically defined water type and illustrated how these groundwaters differ from one another. Three main geochemical processes were identified in the groundwaters: ion exchange, precipitation, and mixing between waters from different sources. Both statistical methods delineated an anomalous sample suspected of being influenced by magmatic CO2 input. The use of statistical methods to complement traditional graphical techniques for waters appearing homogeneous is emphasized for all investigations of this type. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
57.
Is Precipitation the Dominant Controlling Factor of High Inorganic Nitrogen Content in the Changjiang River and Its Mouth? 总被引:1,自引:1,他引:0
沈志良 《中国海洋湖沼学报》2003,21(4):368-376
The main reasons for the high content of inorganic N and its increase by several times in the Changjiang River and its mouth during the last 40 years were analysed in this work. The inorganic N in precipitation in the Changjiang River catchment mainly comes from gaseous loss of fertilizer N, N resulting from the increases of population and livestock, and from high temperature combustions of fossil fuels. N from precipitation is the first N source in the Changjiang River water and the only direct cause of high content of inorganic N in the Changjiang River and its mouth. The lost N in gaseous form and from agriculture non-point sources fertilizer comprised about 60% of annual consumption of fertilizer N in the Changjiang River catchment and were key factors controlling the high content of inorganic N in the Changjiang River mouth. The fate of the N in precipitation and other N sources in the Changjiang River catchment are also discussed in this paper. 相似文献
58.
Churyumov Klim I. Luk'yanyk Igor V. Berezhnoi Alexei A. Chavushyan Vahram H. Sandoval Lourdes S. Palma Alejandro A. 《Earth, Moon, and Planets》2002,90(1-4):361-368
We present a preliminary analysis of medium resolution optical spectra of comet C/2000 WM1 (LINEAR) obtained on 22 November
2001. Theemission lines of the molecules C2, C3, CN, NH2,H2O+ and presumably CO (Asundi and triplet bands) and C2
-were identified in these spectra. By analysing the brightnessdistributions of the C2, C3, CN emission lines along theslit of the spectrograph we determined some physical parameters of theseneutrals, such as their
lifetimes and expansion velocities inthe coma. The Franck–Condon factors for the CO Asundi bands and C2
- bands were calculated using a Morse potential model. 相似文献
59.
INTRODUCTIONMarinemicroalgaeacquiretheirinorganiccarbonforphotosynthesisfromseawaterwhereinorganiccarbonmaybepresentasfreeCO2 ,H2 CO3andHCO-3 andCO2 -3 .TheproportionsofdifferentDICformsareprimarilyrelatedtopH ,andtotemperatureandsalinitytoalessextent.ThetotalDICisashighas2mmol Linseawa terbutthisismainlyintheformofHCO-3 .InnormalpHrangeof7.8-8.2inseawater,HCO-3 accountsfororethan 90 %ofthetotalDIC,whilefreeCO2 islessthan1 % .TheequilibriumconcentrationoffreeCO2 isonly1 2 μm… 相似文献
60.
本文运用磁场的最小方差分析法和磁场-电子密度的相关分析法分析了欧洲空间局Giotto飞船对P/Grigg-Skjellerup(简称G-S)彗星弓激波附近磁场和电子能流的部分观测数据.结果表明彗星附近存在大量的频率靠近新生水族离子回旋频率的波动,它们是由彗星新生水族离子环流激发的低频左旋电磁波.波在近似平行于磁场方向传播,斜传播角小于15°.电子数据和磁场数据相关分析表明即使在离彗星很远的地方仍然存在压缩波. 相似文献