^29Si,^27Al Magic—Angle—Spinning Nuclear Magnetic Resonance（MAS NMR） Studies of Kaolinite and Its Thermal Transformation Products

²⁷Al,²⁹Si MAS NMR studies of kaolinite and its thermal transformation products show that in the kaolinite-mullite reaction series there is an extensive segregation of Al₂O₃ and SiO₂ and the reaction of Al₂O₃ with SiO₂ to form mullite is the main path of mullite formation. At about 850° C, the peak intensity of A1(V) reaches its maximum and with the further rise of temperature the A1(V) signal completely disappears. At about 950°C, γ-Al₂O₃ accounts for about 71% of the material phases containing Al atoms. In the series there is no obvious presence of Al-Si spinel. The²⁷Al and²⁹Si MAS NMR spectra show that there is an obvious difference between the temperature points for Al-O₂(OH)₄ octahedral sheet collapsing and Si-O₄ tetrahedral sheet breaking down.     

Modelling the OH stretch envelope shape and temperature effects in infrared spectra of hydrous silica and silicate glasses

Simple model calculations show that the reversible temperature effects reported for broad OH-stretching bands in infrared spectra of silica, aluminosilicate, and similar glasses can be explained, in essentials, by homogeneous thermal broadening of the ν(OH) envelope constituents and a decrease in intensity with increasing temperature taking place uniformly across the band. This means that these effects are reasonably consistent with the temperature behaviour of narrow ν(OH) bands of crystalline OH-bearing minerals. These findings leave little room for the previously agreed interpretation in terms of a change in hydrogen-bonding strength, although the dependence of integrated intensity on temperature still remains to be understood. Received: 16 April 1999 / Accepted: 4 April 2000     

Technical Note Reactive silica and strength of fly ashes

The use of fly ash in geotechnical engineering depends greatly on its pozzolanic reactivity. Though many factors influence the reactivity of fly ash it is well recognized that reactive silica and lime content play a major role. A new, accurate and reliable method for the determination of reactive silica content of fly ash has been established. The reactive silica content, obtained as acid soluble silica in about 2 to 3 N hydrochloric acid, is found to correlate well with unconfined compressive strength of fly ashes. The reactive silica content of fly ash is also important in the stabilization of soils using fly ash. © Rapid Science Ltd. 1998     

Rapid formation of rock varnish and other rock coatings on slag deposits near Fontana,California

Manganiferous rock varnish, silica glaze and iron skins have formed on 20- to 40-year-old slag piles near Fontana, southern California. Rapid rock-varnish formation is associated with an unidentified cocci bacterium that grows rapidly in culturing experiments, combined with the likelihood that Mn-rich solutions flow over slag surfaces. A new model is proposed for the formation of silica glaze, involving soluble Al-Si complexes and the nature of wetting films. Iron skins occur where runoff is concentrated, and where iron bacteria grow. Observations indicate: (i) substrate can be important in supplying Mn, as well as maintaining a stable surface and channelling runoff to microspots where varnish grows; (ii) ignorance of boundary layer pH/Eh conditions makes chemical-physical models of varnish formation speculative; (iii) the balance between cementation of recently nucleated varnishes and erosional shear stresses is poorly understood, but is probably an important limiting factor on varnish growth rates; and (iv) there must be at least two steps in biotic varnishing-accretion of Mn-Fe in casts, followed by cementation of clays by either in situ cast residue or Mn-Fe remobilized from casts. Varnish accretion may be limited by the rate at which both steps occur. Rapid development of readily distinguishable manganiferous rock varnishes at this post-1952 site highlights the danger of speculation on the ages of landforms based solely on the appearance of rock-varnish coatings.     

二氧化硅溶解度方程和地温计

对地表至下地壳和上地幔温压条件下二氧化硅溶解度实验研究的进展进行了综述，并给出了石英和非晶质ＳｉＯ２在纯水和盐水溶液中的溶解度定量方程，介绍了估算地热库温度的ＳｉＯ２地质温度计。     

黄河下游营养盐浓度、入海通量月变化及“人造洪峰”的影响

于2009年至2011年在黄河下游采集溶解及颗粒态营养盐样品,分析了黄河下游各形态营养盐的浓度变化及营养盐入海通量,结果表明各形态氮的浓度多呈丰水期低、枯水期高,溶解无机氮是溶解态氮的主要存在形式;受黄河高悬浮颗粒物含量的影响,磷以颗粒态占绝对优势,而溶解态磷以溶解无机磷为主要存在形态;生物硅的含量平均约占硅酸盐与生物硅之和的20％,硅的浓度丰水期高于枯水期.颗粒态磷与生物硅的含量与悬浮颗粒物含量呈正相关.营养盐的组成具有高氮磷比、高硅磷比、低硅氮比的特点.近年来黄河下游溶解无机氮浓度显著升高而溶解无机磷变化不大,硅酸盐的浓度有所下降.黄河下游水沙通量、营养盐入海通量有明显的季节变化,丰水期占全年总入海通量的42％～84％.调水调沙期间,各营养盐的浓度和组成均有明显变化,氮的浓度、DIN/PO4-P下降,磷与硅的浓度、SiO3-Si/DIN、SiO3-Si/PO4-P升高,颗粒态营养盐的比例明显增加.短期内大量水沙及营养盐入海通量对黄河口及渤海生态系统产生重要影响.     

应用元素分析仪测定铅锌矿中的高含量硫

目前对铅锌矿中高含量硫的测定主要采用传统的重量法和容量法,但由于铅锌矿基体复杂,干扰较多,造成操作步骤繁琐;而采用湿法仪器分析又受制于样品的前处理等问题使得测定结果的准确度较差。本文建立了应用元素分析仪测定铅锌矿中的高含量硫(1.0%~32.0%)的分析方法。将样品磨制成粒度小于0.075 mm的粉末,样品制备时加入高纯二氧化硅作为稀释剂以降低铅锌矿的含硫量,仪器测量时加入线状氧化铜作为添加剂以提高硫的氧化效果,优先选用与实际测定样品相同性质的铅锌矿国家标准物质GBW07287(硫的标准值为10.76%)建立标准曲线以减小基体效应。方法精密度(RSD,n=12)小于1%,实际样品分析的测定值与重量法的相对误差小于1%。本方法比化学分析方法的操作简单,几乎没有干扰;比湿法仪器分析方法的样品前处理步骤少,待测元素硫的损失少,测定结果可靠度高。     

海洋沉积物32 Si测年方法研究

天然32Si是宇宙射线成因的,随着降水进入湖泊或海洋,被硅质生物摄取后最终存在于生物硅中。32Si来源单一,生产速率相对恒定,半衰期为150 a,可测年的时间尺度为100~1 000 a,是该时间尺度最合适的测年核素,填补了百年到千年时间尺度测年方法的空白。本文建立了海洋沉积物32Si的测量方法,主要步骤为:（1）样品前处理;（2）生物硅的分离与纯化;（3）生物硅样品中磷的分离与纯化;（4）32P的制样与β计数测量。全程通过硅钼蓝和磷钼蓝分光光度法监测实验过程硅和磷的损失情况,对南沙海域采集的沉积物岩心进行研究,得到南沙海域沉积物岩心32Si的平均活度为16.60 mBq/kg,范围值为8.39~33.34 mBq/kg;32Si在SiO₂中的平均比活度为0.356 Bq/kg,32Si的核素丰度平均值为1.29×10-16（32Si/SiO₂）;根据岩心32Si活度估算得深水区（水深1 335~1 537 m）和浅水区（121~141 m）岩心的沉积速率分别为0.106 cm/a、0.191 cm/a;根据32Si活度计算32Si的平均沉降通量为2.14×10-6 Bq/（cm2·a）,与参考文献的结果较为吻合。     

北极新奥尔松地区土壤中生物硅含量及形态特征

硅循环与碳循环密切相关,生物硅作为硅的重要载体,在全球硅循环中占有十分重要的地位。目前,人们对陆地生态系统的硅循环做了大量研究,但对极地地区硅的研究却极为少见。利用中国第五次北极考察获得的土壤与植物样品,对北极新奥尔松地区中国黄河站站基表层土壤中生物硅的含量及土壤和植被中生物硅(主要为植硅体)的形态进行了初步研究。主要结论为:北极新奥尔松地区中国黄河站站基附近表层土壤中颗粒有机碳的含量为1.00—69.3 mg·g-1,平均值为13.7 mg·g-1;颗粒有机氮含量为0.11—9.84 mg·g-1,平均值为1.43 mg·g-1;可溶态硅含量为3.90—26.3μg·g-1,平均值为10.7μg·g-1;生物硅含量为5.60—9.97 mg·g-1,平均值为7.56 mg·g-1,且其含量与土壤颗粒态有机碳和颗粒有机氮呈正相关关系,表明三者具有相似来源。北极表层土壤生物硅比温带、热带地区生物硅含量要高。植物样品中植硅体形态以帽形、圆形、平滑棒形、齿形、刺棒形和哑铃形等形态为主,大小在10—100μm之间。土壤样品中的植硅体主要来源于植物,形态分别为平滑棒形、刺棒形、圆形、哑铃形、鞍形、尖形和帽形,另外硅藻也是北极土壤中生物硅的组成部分,其中裸露土壤中藻类(羽纹纲硅藻)占生物硅的多数(93.3%)。对比发现,有植被覆盖的土壤中,土壤有机碳、可溶出态硅、生物硅含量和植硅体形态丰富度往往比无植被覆盖或寡植被区土壤高,这表明尽管该地区植被稀少,但植物生长对该地区土壤硅循环存在显著影响,值得进一步关注。     

长江口几种优势桡足类对微型浮游动物的摄食研究

利用现场海水培养实验,结合浮游动物网样数据,研究长江口邻近海域几种优势桡足类(中华哲水蚤、背针胸刺水蚤、太平洋纺锤水蚤和精致真刺水蚤)对微型浮游动物的摄食影响。结果表明,精致真刺水蚤虽然属于肉食性种类,但几乎不摄食微型浮游动物;其余三种杂食性桡足类中华哲水蚤、背针胸刺水蚤和太平洋纺锤水蚤对微型浮游动物(纤毛虫+异养甲藻)的摄食率分别为0.66、0.09和0.59μg C/(ind·d),分别占其日总摄食量的29%、24%和37%。其中,异养甲藻在初始生物量和对桡足类饵料贡献上分别占整个微型浮游动物的30%和28%,是微型浮游动物中一个重要的组成类群。中华哲水蚤对微型浮游动物的摄食率与初始食物浓度有显著的正相关关系,并且对体长20μm纤毛虫的清滤率要明显高于对体长20μm的纤毛虫(P0.01)的清滤率,表明其偏好摄食较大个体的食物。通过Chesson选择性指数显示,尽管微型浮游动物在生物量上远小于浮游植物,但桡足类能优先选择摄食微型浮游动物;进一步结合网采浮游动物数据,获得各站三种优势桡足类丰度平均占桡足类总丰度的77%,但它们对微型浮游动物现存生物量的摄食压力仅为0.8%,表明桡足类对微型浮游动物群落的下行控制作用并不明显,仍有大部分微型浮游动物生物量未通过摄食途径进入到桡足类群落中。