共查询到20条相似文献，搜索用时 171 毫秒
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利用free-drift开放反应系统,在恒压力(1×105Pa)、恒温度(25.0℃±0.2℃)环境下,研究人工海水中近溶解、沉淀平衡状态时二氧化碳分压(pCO2)的变化对文石溶解、沉淀速率及其动力学方程的影响。每组实验中通入混合气体的pCO2分别为2300×10-6和320×10-6两种,并保持通入气体的pCO2恒定,通过实验得到了这两种pCO2环境下,文石的溶解和沉淀速率及动力学方程。研究结果表明:(1)文石在近溶解、沉淀平衡附近,溶解速率相对于Ac(碳酸盐碱度值)或?(饱和度)的变化速率要大于沉淀速率相对于Ac或?的变化速率;(2)Ac相同时,pCO2越高,溶解速率越高,沉淀速率越低;?相同时,亦是如此;(3)溶解实验中,在?0.8的区间内,反应液和混合气体之间pCO2平衡,反应级数n介于9～10之间;沉淀实验中,文石的反应级数介于2.0～3.2之间。 相似文献
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土霉素在牙鲆体内的药代动力学研究 总被引：1，自引：0，他引：1
采用高效液相色谱法为定性、定量手段,研究土霉素在牙鲆(Paralichthys olivaceus)体内的药代动力学过程,采用DAS(Drug and Statistics)药代动力学程序对数据进行分析.结果表明,牙鲆单剂量口服土霉素后(200 mg/kg),血药经时过程符合二室模型,主要动力学参数如下:吸收半衰期(T(1/2)a)为10.043 h,单剂量给药后牙鲆体内出现最高质量分数的时间(Tmax)为4.000 h,单剂量给药后牙鲆体内最高血药质量分数(Cmax)为0.54 mg/L,药时曲线下总面积(CAU0-72)为17.15 (mg*h)/L,吸收速率常数(Ka)为0.223,消除速率常数(k)为0.476 h-1.牙鲆肌肉中土霉素的经时过程符合一级吸收一室模型,主要动力学参数:T(1/2)a为74.893 h,Tmax为4.000 h,Cmax为3.58 mg/L,CAU0-72为148.56 (mg*h)/L,Ka为0.731,k为2.991 h-1.牙鲆肝脏中土霉素的经时过程符合一级吸收一室模型,主要动力学参数:T(1/2)a为31.376 h,Tmax为4.000 h,Cmax为13.78 mg/L,CAU0-72为494.14 (mg*h)/L,Ka为0.876,k为4.940 h-1. 相似文献
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运用实验模拟的手段,对铀(U)、钍(Th)在碳酸钙-海水界面的附着行为进行了初步研究,通过测定相关的分异系数(D)定量评估了文石和方解石两种碳酸钙矿物对U和Th的捕集作用。实验结果显示,不仅U和Th之间存在显著差异,而且两种碳酸钙矿物之间也存在明显不同。U介于碳酸钙和海水之间的分异系数(DU)分别在1.5~3.5(文石)和0.04~0.19(方解石)区间内变化,分异行为非常微弱但其分异系数随着碳酸钙沉淀速率的增加而逐渐上升。这表明U元素主要是以共沉淀的方式进入到文石或方解石沉淀中,但由于其在海水溶液中主要以2 22 3UO(CO)nn的形式存在,因而只能以占据晶格缺陷的方式进入碳酸钙。与之相反的是,文石和方解石都对Th表现出极强的捕集能力,所测定的分异系数(DTh)分别在240~6 330(文石)和430~6 160(方解石)范围内变化,但DTh与碳酸钙沉淀速率之间无明显关联。Th在碳酸钙表面的附着行为可界定为单纯的吸附作用,这一行为应与Th主要以Th(OH)4的形式赋存于溶液中有关。 相似文献
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云南湖泊的碳酸盐沉积 总被引：11，自引：1，他引：11
云南湖泊多属中等矿化度的淡水湖泊,碳酸盐沉积物处于缓慢的积累过程。就其外形和成分可分为微粒碳酸盐、颗粒碳酸盐、生物贝壳碳酸盐和陆源碎屑碳酸盐。颗粒碳酸盐多分布在特定环境的湖区,集合粒成因与微生物的生物化学沉积作用有关;球状粒为微晶方解石组成,由藻群落及其代谢物形成的微环境对方解石缓慢沉淀有利;鲕状粒的形成可能与湖泊不定期干涸引起镁、钙比值变化及方解石、文石交替沉淀有关。微粒方解石是碳酸盐沉积的主要矿物形式,局部湖区形成的以颗粒碳酸盐为主的堆积体是云南湖泊早期碳酸盐沉积作用的主要特点。 相似文献
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南海东北部海区碳酸钙的饱和面、溶跃面和补偿深度 总被引：2，自引：0，他引：2
南海东北部碳酸钙地球化学研究得出:上层海水中方解石饱和度450—550％,文石饱和度250—350％.300m以深下层海水方解石与文石饱和度和深度的对数直线相关.深层水中二氧化碳含量0.03mmo1·dm~-3,碳酸根含量0.094mmol·dm~(-3),碳酸氢根含量2.35mmol·dm~(-3)总二氧化碳2.48mmo1·dm~(-3);方解石的饱和面1630m,溶跃面3000m,补偿深度4600m,文石饱和面435m,补偿深度1000m. 相似文献
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通过对青藏高原东南缘560 cm的寇查湖湖心矿物组成、碳酸盐矿物含量以及方解石中镁含量分析,表明方解石中镁含量可能是一个潜在的湖泊盐度指标.湖泊沉积物中总碳酸盐含量有时并不与环境介质的变化一致,其原因主要是沉积物中总碳酸盐主要由方解石组成,而高盐度水体中有较少的方解石的形成.根据5个"CAMS年代分析建立的年代模式,重... 相似文献
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M. D. Kravchishina A. Yu. Lein A. S. Savvichev L. E. Reykhard O. M. Dara M. V. Flint 《Oceanology》2017,57(1):174-191
Authigenic minerals were studied in Holocene shelf sediments of the Laptev Sea (cold methane seep site, water depth 71 m). The study presents the first finds of large hard carbonate concretions with Mg-calcite cement in recent sediments of the Arctic shelf seas. These concretions differ from previously reported glendonites and concretions from bottom sediments of the White Sea, Kara Sea, Sea of Okhotsk, etc. A study of the morphology, microstructure, and composition of these newly reported concretions revealed the multistage formation of carbonates (structural varieties of Mg-calcite and aragonite). It was shown that organic matter played an important role in the formation of authigenic carbonates, i.e., in the formation of sedimentary–diagenetic Mg-calcite. The role of methane as a possible source for authigenic carbonate formation was estimated. It was found that methane-derived Mg-calcite accounts for 17–35% of concretion materials. Mg-calcite had δ13С-Сcarb values between–24 and–23‰ and δ13С-Сorg values between–44.5 and–88.5‰. 相似文献
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The behavior of transition metals (Co, Ni, Cu and Zn) on precipitation of manganese oxides from seawater pumped up from a
well at the site of the Marine Science Museum, Tokai University, and collected from several tanks along the water supply system
to an aquarium was investigated. The distribution coefficients of cobalt and nickel between manganese oxides and seawater
were different at different sampling points along the water supply system. At sampling points with high rates of manganese
oxide precipitation, the distribution coefficients were about one order of magnitude smaller than those at the points with
low precipitation rates, while there were no remarkable differences in the distribution coefficients of copper and zinc among
the sampling points. The distribution coefficients of minor transition metals, with the exception of copper, observed at the
points with low precipitation rates were comparable to those measured experimentally using manganese dioxides. 相似文献
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We report the abundant occurrence of authigenic Fe-rich carbonate, high Mg-calcite (HMC) and low Mg-calcite from 11 cores recovered from the Krishna–Godavari Basin (K–G Basin), Bay of Bengal. The cores were collected as part of the Indian gas hydrate exploration program on board R/V Marion Dufresne (MD-161: May, 2007) in different environments, including mounds (mud diapirs), mass flows, and hemipelagic sediments over a range of water depths from 647 to 2079 m. Authigenic carbonates range in size from 1 mm to 12 cm and display various morphologies like roundish or platy (micro-) nodules and tube-like forms. From the cores, 173 carbonate samples have been investigated for their depth distribution, mineralogy, geochemical and stable isotopic composition. The stable carbon isotopic composition of 46 out of 88 measured carbonate samples are around −50‰ which allows the differentiation into methane-related carbonates (HMC), especially at Sites 8 and 15, but also in low abundance at Sites 1, 5, 9 and 12. Results indicate that the carbonates at Site 8 and 15 represent paleo methane seepage locations. The Fe-rich carbonates occur abundantly at many sites in the K–G Basin. Their varying carbon isotopic composition indicates that probably not only sulfate reduction through organic matter degradation but also methanogenesis are the responsible processes for their formation. 相似文献
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墨西哥湾波候统计特性分析 总被引：2，自引：0，他引：2
简要介绍了波候的概念,简述Ｗｅｉｂｕｌｌ分布及对数一正态分布的拟合方法,提出最大熵分布拟合有效波高、峰周期分布的新方法;选取半封闭海湾墨西哥湾内水深不同、地理位置不同的六个观测站一年的连续资料,以上述三种拟合方法对其有效波高,峰周期概率分布进行拟合,并与观测直方图进行比较检验,结果表明,在墨西哥海湾内,最大熵分布优于对数－正态分布,对数－正态分布优于Ｗｅｉｂｕｌｌ分布。 相似文献
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Catherine Pierre Germain Bayon Marie-Madeleine Blanc-Valleron Jean Mascle Stéphanie Dupré 《Geo-Marine Letters》2014,34(2-3):253-267
On the passive margin of the Nile deep-sea fan, the active Cheops mud volcano (MV; ca. 1,500 m diameter, ~20–30 m above seafloor, 3,010–3,020 m water depth) comprises a crater lake with hot (up to ca. 42 °C) methane-rich muddy brines in places overflowing down the MV flanks. During the Medeco2 cruise in fall 2007, ROV dives enabled detailed sampling of the brine fluid, bottom lake sediments at ca. 450 m lake depth, sub-surface sediments from the MV flanks, and carbonate crusts at the MV foot. Based on mineralogical, elemental and stable isotope analyses, this study aims at exploring the origin of the brine fluid and the key biogeochemical processes controlling the formation of these deep-sea authigenic carbonates. In addition to their patchy occurrence in crusts outcropping at the seafloor, authigenic carbonates occur as small concretions disseminated within sub-seafloor sediments, as well as in the bottom sediments and muddy brine of the crater lake. Aragonite and Mg-calcite dominate in the carbonate crusts and in sub-seafloor concretions at the MV foot, whereas Mg-calcite, dolomite and ankerite dominate in the muddy brine lake and in sub-seafloor concretions near the crater rim. The carbonate crusts and sub-seafloor concretions at the MV foot precipitated in isotopic equilibrium with bottom seawater temperature; their low δ13C values (–42.6 to –24.5‰) indicate that anaerobic oxidation of methane was the main driver of carbonate precipitation. By contrast, carbonates from the muddy lake brine, bottom lake concretions and crater rim concretions display much higher δ13C (up to –5.2‰) and low δ18O values (down to –2.8‰); this is consistent with their formation in warm fluids of deep origin characterized by 13C-rich CO2 and, as confirmed by independent evidence, slightly higher heavy rare earth element signatures, the main driver of carbonate precipitation being methanogenesis. Moreover, the benthic activity within the seafloor sediment enhances aerobic oxidation of methane and of sulphide that promotes carbonate dissolution and gypsum precipitation. These findings imply that the coupling of carbon and sulphur microbial reactions represents the major link for the transfer of elements and for carbon isotope fractionation between fluids and authigenic minerals. A new challenge awaiting future studies in cold seep environments is to expand this work to oxidized and reduced sulphur authigenic minerals. 相似文献
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Lin Yuanshao Luo Wenxin Cao Wenqing Guo Donghui Zheng Airong Huang Changjiang 《海洋学报(英文版)》2002,21(1):147-155
The filtration rates of four kinds of bivalves that were cultivated dominantly around Xiamen sea area were measured by using a laboratory flowing system. The experimental results were shown below: (1) Filtration rates were measured in the range of 54 - 74.8 ml/ (g·min) among the four bivalves , sequencing descently Saccostrea cucullata > Sinonovacula constricta > Mytilus viridis > Rudi-tapes philippinarum. (2) The relationship between filtration rates on individual size showed a negative exponential function (FR = aW~b, FR' = aW~(b-1)), with b - 1 =- 0.435 6 and -0.392. (3) Filtration rates on Skeletonema costatum were much higher than on Alexandrium tamarensis and Scripp-silla trochoidea inS. cucullata and R. philippinarum. (4)FR'on algal densities was also shown a negative function (FR' = aD~(b-1)), with b -1 =- 0.143 and -0.215 2 in S. cucullata and R. philippinarum , respectively. 相似文献
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通过室内实验模拟了脊尾白虾（Exopalaemon carinicauda）对苯并[a]芘（benzo[a]pyrene,Ba P）的生物富集,通过非线性曲线拟合获得脊尾白虾对Ba P的富集动力学参数（吸收速率常数k1、释放速率常数k2、生物富集因子BCF、平衡状态下脊尾白虾体内Ba P含量CAmax、生物学半衰期B1/2）.各动力学参数分别为：k1范围为12.34～24.96,平均值为18.80,k2范围为0.06～0.10,平均值为0.08,BCF范围为208.41～248.03,平均值为228.02、CAmax范围为12.40～93.79 ng/g,平均值为46.78 ng/g,B1/2范围为6.89～11.71 d,平均为8.95 d.脊尾白虾对Ba P的吸收速率常数k1、释放速率常数k2、BCF均随外部水体中Ba P浓度的增大而减少,CAmax、B1/2随外部水体中Ba P浓度的增大而增大. 相似文献
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长江河口及邻近海域表层沉积物中铁溶解和磷释放活性的动力学表征 总被引：1，自引：0，他引：1
运用溶解动力学实验及活性连续体模型表征了长江河口至东海邻近海域表层沉积物中铁(Fe)和磷(P)的活性。通过动力学数据拟合得到了活性组分的理论含量m0和表观速率常数k。结果表明,Fe(Ⅱ)普遍存在于表层沉积物中,这应是高活性有机络合态Fe(Ⅲ)絮凝/沉淀到沉积物中后快速还原的结果。沉积物中黏土及总有机碳（TOC）含量对Fe(Ⅱ)的m0及其k值起重要控制作用。从长江河口至邻近海域沉积物中Fe(Ⅱ)均以FeCO3形态为主,FeCO3的溶解及与之相结合磷(主要为交换态P和自生P)的释放导致Fe(Ⅱ)和P具有相似的溶解动力学特征。与吸附于Fe(Ⅱ)矿物相的P相比,与Fe(Ⅱ)矿物相共沉淀的P的m0较高,但k较低。与TOC含量较低的粗粒沉积物中的Fe(Ⅲ)相比,TOC含量较高的细粒沉积物中Fe(Ⅲ)的m0值较小,但k值较大。以上特征是Fe不同的氧化还原过程导致的。Fe(Ⅲ)氧化物的含量(m0)和活性(k)总体上控制着与之相结合P的含量(m0)及溶解活性(k)。虽然传统活性Fe形态分析未能揭示出长江河口沉积物中活性Fe的富集作用,但溶解动力学表征结果表明,Fe的絮凝/沉淀导致河口沉积物中活性Fe的明显富集,且该过程主要发生在盐度明显增加的低盐度河口区。 相似文献