碱式氯化镁和氧化镁晶须的制备与表征

以活性氧化镁和氯化镁为原料在水热条件下合成了碱式氯化镁晶须。碱式氯化镁晶须热解后形貌保持得很好,得到氧化镁晶须。制得的晶须长度在200μm左右,直径约0.5μm。采用X射线衍射仪、扫描电镜、热重分析仪表征碱式氯化镁和氧化镁晶须,探讨了各个工艺条件对产物的影响。实验结果表明,碱式氯化镁晶须的最佳工艺条件为:反应时间8~12 h,搅拌速率初始在500 r.min-1左右,120 min时调为1 000 r.min-1,氧化镁与氯化镁的物质的量之比0.10~0.15,氯化镁溶液的浓度4.0 mol.L-1以上,反应温度150~200℃,反应釜的填充度50%~80%。在此条件下制得了形貌良好的碱式氯化镁晶须。     

Variation of infrared absorption spectra in the system Bi2Al4−x Fe x O9 (x = 0–4), structurally related to mullite

The crystal structure of Bi₂Al_4−x Fe _x O₉ compounds (x = 0–4) has striking similarities with the crystal structure of mullite. A complete substitution of Al by Fe³⁺ in both octahedral and tetrahedral sites is a particular structural feature. The infrared (IR) spectra of the Bi₂M₄O₉ compounds (M = Al, Fe³⁺) are characterised by three band groups with band maxima in the 900–800, 800–600 and 600–400 cm⁻¹ region. Based on the spectroscopic results obtained from mullite-type phases, the present study focuses on the composition-dependent analysis of the 900–800 cm⁻¹ band group, which is assigned to Al(Fe³⁺)–O stretching vibrations of the corner-sharing MO₄ tetrahedra. The Bi₂Al₄O₉ and Bi₂Fe₄O₉ endmembers display single bands with maxima centred at 922 and 812 cm⁻¹, respectively. Intermediate Bi₂Al_4−x Fe _x O₉ compounds exhibit a distinct splitting into three relatively sharp bands, which is interpreted in terms of ordering effects within the tetrahedral pairs. Thereby the high-energy component band of the band triplet relates to Al–O–Al conjunctions and the low-energy component band to Fe–O–Fe conjunctions. The intermediate band is assigned to stretching vibrations of Al–O–Fe or Fe–O–Al configurations of the corner-sharing tetrahedral pairs. Bands in the 800–600 cm⁻¹ range are assigned to low-energy stretching vibrations of the MO₄ tetrahedra and to M–O–M bending vibrations of the tetrahedral pairs. Absorptions in the 600–400 cm⁻¹ range are essentially determined by M–O stretching modes of the M cations in octahedral coordination.     

三烷基氧膦纤维素富集－感耦等离子体质谱法测定地质样品中钨钼锡

研究了三烷基氧膦（ＴＲＰＯ）纤维素色层分离富集痕量元素Ｗ、Ｍｏ和Ｓｎ的条件，根据吸附与洗脱实验中的现象初步探讨了ＴＲＰＯ与Ｗ、Ｍｏ、Ｓｎ的反应机理。以Ｒｈ为内标采用感耦等离子体质谱法进行测定。标准加入回收率为９８％～１０１％；Ｗ、Ｍｏ、Ｓｎ的测定下限分别为０．０２、０．０１、０．１μｈ／ｇ；重复取样测定的ＲＳＤ（ｎ＝１５）均小于１０％。经对地球化学标准物质分析，结果与推荐值相符。     

From surface acidity to surface reactivity; inhibition of oxide dissolution

Paul Schindler's early work on the acid-base chemistry of oxides was instrumental for the development of the concept of surface complexation. This approach has not only been important in establishing a theory on the adsorption of metal ions and ligands as a function of pH and solution variables, but has become essential in establishing surface speciation (coordinative structural and electronic arrangement at the solidwater interface) which in turn determines surface reactivity. The factors that affect dissolution of Fe(III) (hydr)oxides and inhibition of dissolution are discussed. A few examples for the inhibition of reductive and ligand-promoted dissolution by binuclear complexes of oxoanions (phosphate, borate) and of protonpromoted dissolution by Cr(III) are given.     

Effects of Silver Nanoparticles on Denitrification and Associated N2O Release in Estuarine and Marine Sediments

Silver nanoparticles(AgNPs)have been widely used in medicine and consumer products.And it enters the river in dif-ferent ways,then finally converges to the ocean through the estuary.AgNPs polution can affect NO₂?and N₂O production by denitri-fiers in aquatic system.The effects of AgNPs on denitrification activity,nitrogen transformation and nitrous oxide(N₂O)emission were investigated in Dagu River Estuary(DRE)and Jiaozhou Bay(JZB).The results showed that the potential denitrification activity(PDA),NO₃?and NO₂?reduction rates decreased with an increase of AgNPs concentration in DRE and JZB.However,the N₂O ac-cumulation was significantly increased at AgNPs concentrations above 5 mg kg^?1in both areas,and the accumulation rate was greater in estuary than in bay(P<0.05).Moreover,the total bacterial count showed a slightly increasing trend with an increase of AgNPs concentration(P>0.05)in DRE and JZB.Importantly,the relative abundance of narG,nirS and nosZ gene in two areas decreased with the increase of AgNPs concentration,and the negative effect of AgNPs varied in order:nosZ>nirS>narG,inferring that the expression of denitrifying related genes could be significantly and differently inhibited by AgNPs addition.Thus,this study demon-strated that the inhibitory effect of AgNPs on different denitrification process,which may lead to the increase of inorganic nitrogen accumulation and N₂O realease.This study provides a scientific basis for the further studies of AgNPs on the ecological impact mechanism and environmental effects of offshore sedimentary environment.     

中国小麦和玉米农田N2O减排措施及潜力

旱作农田是N₂O的主要排放源,削减其N₂O排放有助于整体降低农田温室气体排放。运用整合分析(Meta-analysis)的方法,研究了不同农业管理措施对中国小麦和玉米农田N₂O排放的影响,并估算了各减排措施的减排潜力。结果表明：添加抑制剂可显著减少小麦和玉米农田N₂O排放36%~46%,并增加作物产量;施氮量减少30%以内,可削减N₂O排放10%~18%,且对产量无明显影响;施用缓(控)释肥和秸秆还田能显著减少小麦田N₂O排放,但对玉米田的减排效果并不显著。在不同的减排措施下,中国小麦和玉米农田N₂O减排潜力分别为9.29~13.90 Gg N₂O-N/生长季和10.53~23.19 Gg N₂O-N/生长季。河南、山东、河北和安徽省小麦田减排潜力最大,占全国小麦田N₂O减排潜力的53%;黑龙江、吉林、山东、河北和河南省玉米田减排潜力最大,约占全国玉米田N₂O减排潜力的50%。     

关于镜铁矿综合回收利用的试验研究

为了充分利用矿区内大量的镜铁矿资源,在原有工艺和试验研究的基础上,采用弱磁-强磁（两段）-摇床-分级工艺流程,在最终磨矿细度为-0.075 mm为95.10%的条件下,可得到产率29.46%、品位68.19%、回收率58.98%的综合铁精矿,及产率12.73%、品位68.89%、回收率25.75%的云母氧化铁产品,获得了良好的技术指标.     

Petrology and Fe–Ti oxide reequilibration of the 1991 Mount Unzen mixed magma

A dacitic magma (64.5 wt.% SiO₂), a mixture of phenocryst-rich rhyodacite and an aphyric mafic magma, was erupted during the recent 1991–1995 Mount Unzen eruptive cycle. The experimental and analytical results of this study reveal additional details about conditions in the premixing and postmixing magmas, and the nature of the mixing process. The preeruption rhyodacitic magma was at a temperature of 790±20°C according to Fe–Ti oxide phenocryst cores, and at a depth of 6 to 7 km (160 MPa) according to Al-in-hornblende geobarometry. The mafic magma that mixed with the rhyodacite is found as andesitic (54 to 62 wt.% SiO₂) enclaves in the erupted magma and was essentially aphyric when intruded. Phase equilibria indicate that an aphyric andesite at 160 MPa is >1030°C (H₂O-saturated) and possibly as high as 1130°C (2 wt.% H₂O). The composition of the rhyodacite which was mixed with the andesite is estimated to lie between 67 and 69 wt.% SiO₂. Using these compositions and temperatures, the temperature of the Unzen magma after mixing is estimated to be at least 850° to 870°C. The groundmass Fe–Ti oxide microphenocrysts and those in pargasite-bearing reaction zones around biotite phenocrysts both give 890±20°C temperatures; the oxide–oxide contacts give temperatures of 910±20°C. The 900±30°C postmixing temperatures are consistent with phase-equilibria experiments which show that the magma was not above 930°C at 160 MPa. Our Fe–Ti oxide reequilibration experiments suggest that the mixing of the two magmas began within a few weeks of the eruption, which is a shorter time than is calculated using available diffusion data. There is also evidence that some mixing took place much closer to the time of extrusion based on the presence of unrimmed biotite phenocrysts in the magma.