海洋生物固氮作用研究进展

近年来,海洋生物固氮作用研究已成为海洋氮循环研究热点之一,因为它补充了海洋中的结合态氮,影响着海洋氮储库的收支平衡,进而调控海洋的初级生产力,并因此与海洋颗粒有机碳的迁出以及海洋对大气CO2的吸收密切相关.海洋生物固氮作用的研究主要是在近30a开展起来的,现有观点认为全球海洋生物固氮速率为100～200 Tg/a.15↑N2示踪法和乙炔还原法是最重要的生物固氮速率实测方法,而硝酸盐异常指数法、15↑N同位素收支平衡法、卫星遥测法等则是重要的间接估测方法.束毛藻曾被认为是全球海洋最重要的固氮生物,但近年来也发现了固氮生物在微微（pi-co）级和微（nano）级的分布,表明以往基于束毛藻的固氮速率可能是被低估的.海洋生物固氮作用营养盐限制的研究主要集中在铁和磷这2个元素的作用,但目前尚无定论.在中国边缘海生物固氮作用的研究还很匮乏,少数研究表明除黑潮区外,由束毛藻所支持的固氮速率并不高.就海洋固氮作用研究的未来发展,指出今后必须在更大时空尺度上开展海洋生物固氮作用研究,以弥补现有实测数据的不足,并获取固氮微生物种类组成的准确信息,在确定海洋生物固氮作用控制因素的同时,追踪新固定氮的流向,进而为海洋氮循环提供准确信息.     

改性粉煤灰性质及其封堵油层大孔道效果

粉煤灰是燃煤火力发电厂的废弃物,由大小不等、结构疏松的非晶质玻璃相球形颗粒组成,其主要化学成分是铝硅酸盐,具有来源广和成本低等特点。在水热条件下,Holler和Wirsching首先利用粉煤灰与碱（NaOH或KOH）作用合成了沸石。针对油田封堵油层孔隙即改善注水井吸水效果的实际需求,在总结和吸取粉煤灰和沸石颗粒封堵油层孔隙矿场施工成功经验和不足基础上,探索了水热条件下粉煤灰部分转化为沸石的配方组成和工艺条件,研究了改性粉煤灰组成和外观结构特征,评价了改性粉煤灰的封堵效果,分析了改性粉煤灰封堵作用机理。研究结果对改善油层孔隙封堵效果、提高油田注水效率具有重要应用价值。     

Electron loss and the determination of electron concentrations in theD-region

The most meaningful way to compare observations of the daytimeD-region under all ionization conditions, for the purpose of improving our understanding of this region, would appear to be through use of the effective electron recombination coefficient, =q/[e]², whereq is the ionization production rate, and where [e] is the electron concentration. This ratio apparently increases monotonically with decreasing altitude, and is much less variable than its componentsq and [e]. This parameter appears eminently suitable as a best first order solution to [e] after determiningq. For nighttime conditions, is more sensitive toq. However, an accurate but simple formula exists for the calculation of electron concentrations.     

黄山东镁铁超镁铁杂岩中的辉石化学成分研究

通过对黄山东镁铁超镁铁杂岩的辉石化学成分研究，证明辉石的化学成分受寄主岩石类型的制约，从超镁铁岩相到角闪辉长岩相斜方辉石的化学成分由富ＭｇＯ、ＳｉＯ＿２、Ａｌ＿２Ｏ＿３、Ｃｒ＿２Ｏ＿３到富ＦｅＯ、ＴｉＯ＿２、ＣａＯ、ＭｎＯ；单斜辉石化学成分由富Ａｌ＿２Ｏ＿３、Ｃｒ＿２Ｏ＿３、Ｎａ＿２Ｏ、ＭｇＯ到富ＦｅＯ、ＭｎＯ、ＣｏＯ。在同一寄主岩石中，单斜辉石比斜方辉石富ＴｉＯ＿２、Ａｌ＿２Ｏ＿３、Ｃｒ＿２Ｏ＿３、ＣａＯ和Ｎａ＿２Ｏ，贫ＭｇＯ、ＳｉＯ＿２、ＭｎＯ和ＦｅＯ。根据辉石化学成分特征得出黄山东杂岩形成于岛弧环境，为上地幔石榴二辉檄榄岩部分熔融形成的拉斑玄武岩岩浆结晶分异作用的产物。     

金川超镁铁质岩体矿物化学特征及矿物地质温度计、压力计研究

根据金川超镁铁质岩体主要造岩矿物和副矿物的共生组合关系及各种矿物的化学成分特点；选用５种较成熟、使用较方便的矿物地质温度计、压力计（主要是辉石温压计和角闪石压力计），对岩体形成的温、压条件进行了估算，其结果为：成岩温度为１０００～１３００℃（上限可到１４００～１５００℃），成岩压力约为５×１０￣８～１１×１０￣８ｐａ。金川超镁铁质岩体的主要岩石类型为尖晶石二辉橄榄岩，这一岩石类型在复杂体系相关系图中的稳定区域大致处于５×ｌ０￣８～１５×１０￣８ｐａ的范围，这与矿物温压计估算的成岩温压条件是一致的。     

A note on the chemical composition of lake water in the Laguna Amarga,a saline lake in Patagonia,Chile

The chemical composition of lake water in Laguna Amarga, a small, shallow, saline lake near the Torres del Paine National Park (at 51°S), Chilean Patagonia, was studied in January, 1993. The water was strongly alkaline (pH 9.4) conductivity was 71.4 mS cm^–1, and salinity was 77 g L^–1. The major ions were sodium and sulphate.     

东台吉乃尔盐湖卤水的相化学研究（Ⅱ）—冬夏季卤水蒸发实验

为了研究东台吉乃尔盐湖卤水蒸发时的相化学，确定钾、镁和锂盐的结晶特性，在实验室内２５℃等温蒸发实验基础上和自然条件下进行了冬夏季日晒蒸发试验．东台吉乃尔盐湖卤水是由氯化钠饱和的多组分复杂体系构成的．卤水中存在的离子是Ｎａ＋、Ｋ＋、Ｍｇ２＋、Ｌｉ＋、Ｃａ２＋、Ｂ３＋、ＳＯ４２－和Ｃｌ－．试验数据与Ｎａ＋、Ｋ＋、Ｍｇ２＋Ｃｌ－、ＳＯ４２－ＫＨ２Ｏ五元体系介稳平衡数据进行了讨论和比较．Ａｕｔｅｎｒｉｅｔｈ相图被用来表示各数据间的关系和证明冬夏季蒸发时结晶行为的差别．     

Crystal structure refinement of hendricksite,A Zn- and Mn-rich trioctahedral potassium mica: A contribution to the crystal chemistry of zinc-bearing minerals

Summary The crystal structure of hendricksite, a trioctahedral mica of biotite type, characterized by high Zn²⁺ and Mn²⁺ contents has been refined by least square methods. The structural formula is: (K_0.89Na_0.10Ba_0.04)(Mg_1.57Zn_0.54Mn _0.40 ²⁺ Fe _0.25 ²⁺ Al_0.07Ti_0.07Cr_0.01)(Si_2.92Al_1.08)O₁₀ (OH)₂. The space group isC2/m and the cell parameters are:a=5.340(2) Å,b=9.524(2) Å,c=10.235(3) Å, =100.07(2)^o, the cell volume isV=497.98 ų. The final unweightedR=0.072. Average cation-anion distances in polyhedra are: T–O=1.659 Å, M(1)–O=2.093 Å, M(2)–O=2.088 Å, A–O_long=3.316 Å and A–O_short=3.004 Å; A is the alkaline cation. The rotation angle of tetrahedra is =6.7°. The analysis of electron densities, of the dimensions and distorsions of polyhedra shows that Zn²⁺ is exclusively in octahedral sites; there is no order between six-fold coordinated cations. A comparison between the structural features of hendricksite and those of the two main end-members of biotites, phlogopite and annite, is presented.The effect of the strong covalence of Zn–O bonds is particularly visible on the dimensions and orientations of the thermal ellipsoids of octahedral sites M(1) and M(2) which contain zinc. In all the published structures of trioctahedral micas, the ellipsoids of cationic sites are uniaxial positive, elongated parallel toc ^*. In hendricksite, this is observed only for the two zinc-free sites (T and A; in the octahedra M(1) and M(2), which contain zinc, the ellipsoids are approximately uniaxial negative, flattened parallel toa, which is a unique situation.Zinc which habitually favours the tetrahedral coordinations with oxygen, enters the octahedra only, i.e. the chemically anisotropic sites, in hendricksite. The strong polarizability of Zn²⁺ is proposed to explain this behaviour.An examination of the behaviour of Zn²⁺ in other compounds shows that this situation is general, zinc favours chemically anisotropic sites and specially those adjacent to OH or H₂O.

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Affinement de la structure cristalline de la hendricksite, mica trioctaédrique potassique riche en Zn et Mn; une contribution à la connaissance cristallochimique des minéraux zincifères

Résumé On a affiné par moindres carrés la structure de la hendricksite, mica trioctaédrique de type biotite, caractérisé par une teneur élevée en Zn²⁺ et Mn²⁺. La formule structurale de ce mica est: (K_0m89Na_0,10Ba_0,04)(Mg_1,57Zn_0,54Mn _0,40 ²⁺ Fe _0,25 ²⁺ Al_0,07Ti_0,07Cr_0,01)(Si_2,92Al_1,08)O₁₀(OH)₂. Le groupe spatial estC2/m et les paramètres de la maille:a=5,340(2) Å,b=9,254(2) Å,c=10,235(3) Å, =100,07(2)°; le volume de la maille estV=497,98 ų. Le résidu final non-pondéré estR=0,072. Les distances cation-anion moyennes dans les polyèdres sont les suivantes: T–O=1,659 Å, M(1)–O=2,093 Å, M(2)–O=2,088 Å, A–O_long=3,316 Å et A–O_court=3,004 Å où A désigne le cation alcalin. L'angle de rotation tétraédrique, =6,7°, est très semblable à celui de la phlogopite. L'analyse des densités électroniques, des dimensions et distorsions des polyèdres montre que Zn²⁺ est exclusivement en coordinance octaédrique et qu'il n'y a pas d'ordre entre les cations hexacoordonnés. On présente une comparaison des caractères structuraux de la hendricksite avec ceux des deux principaux pôles des biotites, la phlogopite et l'annite.L'effet de la forte covalence de la liaison Zn–O est particulièrement visible sur les dimensions et orientations des ellipsoides d'agitation thermique des deux sites octaédriques, sites zincifères. Dans toutes les structures de micas trioctaédriques publiées, les ellipsoides des sites cationiques sont uniaxes positifs, allongés parallèlement àc ^*, ce qui s' observe effectivement dans les deux sites non-zincifères (T et A) de la hendricksite, par contre, dans les octaèdres M(1) et M(2), qui contiennent le zinc, les ellipsoides sont approximativement uniaxes négatifs, applatis parallèlement àa, ce qui est une situation unique.Le zinc, qui se fixe généralement en sites tétraédriques dans les structures de type oxyde, occupe les sites octaédriques, c'est-à-dire les sites chimiquement anisotropes dans la hendricksite. La forte polarisabilité de Zn²⁺ est proposée pour expliquer ce comportement.Un examen du comportement de Zn²⁺ dans d'autres phases montre que cette situation est tout à fait générale, le zinc privilégiant les sites chimiquement anisotropes et en particulier ceux adjacents à OH où H₂O.

     

Human influence upon sedimentation in Llangorse Lake,Wales

Palaeolimnological studies at Llangorse Lake, Wales, constitute part of the British contribution to IGCP Project 158 (The Palaeohydrology of the Temperate Zone in the Last 15000 Years). The lake has been adopted as the Reference Site for the South Wales region under Subproject 158B (Lake and Mire Environments) and is located in the Reference Area for Britain: the Severn Basin. Results of biological, physical, and multielement chemical analyses on a 12.35 m Livingstone core are presented and compared with previous analyses on short Mackereth cores taken from two troughs in the lake basin. Human impact upon post-glacial sedimentation is assessed with reference to sediment chemistry, physical properties, and sedimentation rates, based on relative pollen, ¹⁴C, and ²¹⁰Pb dating. Vegetational history of the catchment is inferred from a pollen diagram for a section of the core from c. 8 to 6.75 m depth in which evidence for human impact is first apparent. Water content, loss on ignition, and carbonate content are presented for the whole core; density, water content, loss on ignition, carbonates, and elemental analyses of P, Ca, Mg, K, Ti, Al, Fe, and Mn for the interval 6 75 and 8.25 m depth. Sedimentation rates were low during Boreal and Atlantic times (c. 9000- 5000 BP), rose significantly from the time of the elm decline (estimated at 5000 BP) and increased further at c. 1800 BP when nekron muds were succeeded by deposition of silty clay. Inferred rates of erosion of soils from the catchment are discussed and related to sediment chemistry.