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排序方式: 共有193条查询结果,搜索用时 15 毫秒
1.
The interstitial water composition (
, alkalinity, Ca2+, Mg2+, Sr2+, Na+, K+) and the cation exchange capacity (CEC) were determined for the muddy sediments of the continental shelf off the Gironde Estuary (France), in the area where the sediment represents the deposit of the muddy suspension of the river. In comparison with seawater concentrations, the pore waters below 10 cm depth, show depletions of
and Ca2+ and below a 30 cm depth show depletions of Mg2+. Inversely, the upper 10 cm an enrichment of Ca2+ concentration, and an increase of K+ concentration to a 40 cm depth. High values of
are observed at the top 4 cm. Alkalinity enrichment is observed along the length of the core. Applying the alkalinity models for the sediment below a 10 cm depth demonstrates generally that calculated alkalinities are higher than the measured ones. Ca2+ dissolution occurs at the first 10 cm and authigenic carbonate precipitation starts beneath that level. Mg2+ depletion is accompanied by bicarbonate loss. This proves that Mg2+ depletion is due to a Mg-silicate reaction. The result of the CEC does not confirm the Mg2+ uptake by clay minerals in exchangeable site, under reducing conditions. Diffusion and bioturbation play an important role in the pore water concentration at the top of the core. 相似文献
2.
B. Velimirov 《Marine Ecology》1980,1(2):155-168
Abstract. An experiment to test C have's hypothesis on temperature dependent MgCO3 concentrations in marine calcareous skeletons was undertaken by transplanting colonies of Heliopora coerulea. The corals were transferred from a shallow lagoon with high average temperatures to the outer bottom of a fringing reef, 16 m depth, with low average temperatures. Against expectation, a statistically significant increase of average mol % concentrations from 0.48 to 0.54 % for upper growth regions and from 0.49 to 0.62% for lower growth regions was obtained. Temperature records during the experimentation period and the above data indicate that the mol% MgCO3 concentration in the skeleton of living Heliopora colonies increases when transplanted to an environment with a lower temperature average than that of their original growth site, and with seasonal temperature fluctuations which are smaller in the experimental site than in the control site. Temperature fluctuations at the control site were up to 2.5 times greater than at the experimental site for most of the observation months. This supports the conclusion that the parameters a) minimum temperature and b) temperature stability of the environment are essential for the incorporation of Mg into the carbonate skeleton matrix of marine organisms. Within this study the results of a quantitative chemical analysis of the carbonate skeleton of H. coerulea are presented and growth data of transplanted colonies compared with those from the control site. 相似文献
3.
A Reflection on Mg, Cd, Ca, Li and Si Isotopic Measurements and Related Reference Materials 总被引:6,自引:1,他引:6
Jean Carignan Damien Cardinal Anton Eisenhauer Albert Galy Mark Rehkamper Frank Wombacher Nathalie Vigier 《Geostandards and Geoanalytical Research》2004,28(1):139-148
This contribution aims to report the reflections we had with the scientific community during two international workshops on reference materials for stable isotopes in Davos (2002) and Nice (2003). After evaluating the isotopic homogeneity of some existing reference materials, based on either certificates, literature data or specific inter-laboratory rounds, we confirm these as primary reference materials or propose new ones relative to which stable isotope compositions should be reported. We propose DSM-3 for Mg, NIST SRM 915a for Ca, L-SVEC for Li and NBS28 for Si. Cadmium does not yet have a well identified delta zero material, although three commercial mono-elemental Cd solutions have yielded the same isotopic composition relative to one another. In order to scale the linearity of any mass spectrometer, some secondary reference materials are also proposed: Cambridge-1 solution for Mg, the "Münster-Cd" and JEPPIM Cd solutions for Cd and the "Big Batch" silicate for Si. The team from Nancy propose to prepare a mixed spike solution for Li isotopes. Well-characterised natural samples such as ocean or continental waters, diatoms, sponges, rocks and minerals are needed to validate the entire analytical procedure, particularly to take into account the effect of sample mineralisation and of chemical manipulations for elemental separation prior to analysis. 相似文献
4.
七里坪硼矿床的主要矿石类型从岩石学角度看是方解石岩 ,它们由硼矿物和方解石组成 ,二者都是含硼气液交代白云石大理岩 (围岩 )的结果。矿石的化学成分既富钙又富镁 ,钙来自方解石 ,镁来自硼矿物 ,贫其它成分 ,因此夕卡岩型硼矿床不是传统的镁夕卡岩矿床 ,而是钙镁质夕卡岩矿床。 相似文献
5.
应用信通公司研制的离子质谱计(ST-IMS),建立了地质样品镁同位素分析的实验流程和误差分析方法,为进一步分析微量地质样品中镁同位素组成和分布奠定了基础。 相似文献
6.
7.
本文以水合氯化镁、工业氨水为原料制备出了低硼含量的纯度 >99%的氢氧化镁和氧化镁。利用差热 -热重 (DTA- TG)、X-射线衍射 (XRD)、透射电子显微镜 (TEM)等手段 ,对氢氧化镁的热稳定性、相结构、表观状态以及脱水动力学参数进行了分析。结果为 :氢氧化镁以束状纤维和片状粉末共存 ,在 6 2 3K基本完成脱水反应生成氧化镁 ,其脱水反应的表观活化能 E为135 .4 k J· mol-1,指前因子 A为 5 .15× 10 10 ,反应级数 n为 1.10 相似文献
8.
磷矿石中磷、钙、镁、锶、氟测定方法评述 总被引:2,自引:0,他引:2
本文系统分析了磷矿石高含量磷、钙、镁、锶、氟诸元素存在时对其测定的相互影响及其测定中存在的问题,比较全面地总结了国内分析工作者针对该问题,对诸难测元素在常规分析方法方面的工作进展。 相似文献
9.
10.
在槽式太阳能热发电领域,硝酸镁基熔盐逐渐引起关注。通过六水硝酸镁煅烧法制备无水硝酸镁,采用拉曼、DSC与XRD表征脱水产物,系统研究了环境压力、脱水温度与时间对六水硝酸镁脱水和水解的影响。结果表明,六水硝酸镁在煅烧过程中水解为碱式硝酸镁Mg_3(OH)_4(NO_3)_2,在水溶液中进一步分解为Mg(OH)_2。随着煅烧温度和时间的增加,脱水产物中的含水量逐渐减少,同时水解产物Mg_3(OH)_4(NO_3)_2含量逐渐增加。真空环境下煅烧,可显著降低硝酸镁的水解反应。六水硝酸镁在真空环境下230℃煅烧1.5 h,所制备的无水硝酸镁中水解产物含量为3.63%。制备的硝酸镁可进一步用于硝酸镁基熔盐的研究。 相似文献