X射线衍射分析长期钾素盈亏对土壤含钾类矿物的影响

利用1991年—2013年国家紫色土肥力与肥料效益监测站长期定位试验的土壤样品,采用X射线衍射(XRD)光谱分析技术,研究了22年长期钾素投入亏缺和盈余处理中性紫色土壤钾素含量及含钾类矿物的演变特征。XRD图谱分析发现,长期钾素亏缺处理导致土壤云母、钾长石等含钾类原生矿物加速风化,表现为连续施肥22年<连续施肥12年<原始土壤,同时促进了蒙脱石的形成;长期钾素盈余处理土壤云母、钾长石等原生矿物风化程度虽得到有效缓解,但较原始土壤相比仍有明显风化。土壤含钾类粘土矿物的演变与原生矿物变化相似,长期钾素亏缺导致土壤粘粒中伊利石发生了明显崩解,且随着施肥年限的增加,粘粒中伊利石的含量随之减少,长期钾素盈余处理明显缓解了伊利石的风化进程;但是无论是钾素亏缺或盈余处理都出现土壤中伊利石的风化崩解,同时伴随蒙脱石等膨胀型矿物的形成,现有的钾素盈余水平也不能阻止土壤含钾类矿物的风化崩解。另外,长期钾素亏缺导致土壤中速效钾和缓效钾含量逐年降低,22年分别降低62.0%和37.4%;而钾素盈余处理提高了土壤速效钾含量,但缓效钾呈现下降趋势;土壤伊利石的风化程度和土壤缓效钾的演变趋势相吻合。表明中性紫色土壤中伊利石是土壤缓效钾的主要来源,长期钾素亏缺会造成土壤钾素枯竭和含钾类矿物的加速风化崩解,降低土壤供钾能力。     

紫金山金铜矿明矾石的红外光谱及XRD特征

通过红外光谱(IR)和X射线粉晶衍射(XRD)对紫金山金铜矿中火山机构的不同部位、不同形态明矾石的组成物相、结构特征进行了研究。实验结果表明,该矿中明矾石的红外光谱吸收峰沿北西向成矿带从火山口向外有逐渐减弱的趋势;明矾石的(006)和(004)晶面发育程度及晶胞参数大小显示从火山口沿北西向成矿带均有逐渐增加的趋势。结合电子探针分析结果,进一步得出该矿中明矾石的红外光谱及XRD特征主要与火山机构中不同部位明矾石中钾的含量有关,火山口附近温度较高,有利于钠对钾的类质同象替换,具有较高含量的钠,钾含量相对较低,而远离火山口温度较低,不利于钠对钾的类质同象替换,钠含量较低,钾含量相对较高。     

微波消解/ICP-MS法检测八种梨果实中主要矿质元素含量

采用ICP-MS法测定了八种梨果实中的钠、钾、钙、镁、锌、铜、铁、锰、硼等元素的含量。不同品种梨果实中主要元素组成基本相同, 但各种元素的含量存在一定的差异。其中,钾的含量最高, 其次是镁、钙、钠等元素。采用欧盟果蔬汁工业协会(AIJN)提供的果汁质量评价参考范围作参照标准,梨果实中钾、镁和钙元素含量高于该标准,钠元素含量低于该标准,其余元素含量均接近于该标准的规定。     

不同产地的螺旋藻粉中元素含量分析

采用X射线荧光光谱分析法(XRF)测定了5个不同产地的螺旋藻粉中钾、钠、钙、镁、铁、锌、锰等元素的含量。螺旋藻含有丰富的人体所必需的矿质元素,不同产地的螺旋藻粉的主要元素谱基本相同,但各种元素的含量存在一定的差异。钾的含量最高,平均为5.00%,钠含量为0.352%,平均钠/钾比为0.070。探讨了钾、钠/钾比与螺旋藻的医疗保健作用的关系,较低的钠/钾比有利于高血压患者恢复健康。所用测定方法具有简便、快捷、准确、灵敏度高、适用元素多和含量范围广等特点。研究结果为提高螺旋藻矿质元素的品质以及进一步开发利用螺旋藻提供了新的科学依据。     

加入法测钨铼丝中的钾

钨铼丝中随微量钾的增加，材料的可塑性增加，使产品经贸耐用，但钾的含量大于１５０μｇ．ｇ＾－１时，其材料硬度过高，成形困难而难于加工，一般钨铼丝中微量钾的测定采用直接法，因基体产生基体效应而使结果超差。作者拟定了用过氧化氢分解样品，稀释后加标准钾溶液。在氯化镧存在下，用乙炔火焰原子吸收仪测其吸光度，作曲线计算样品中钾的含量。此方法快速方便，结果准确，消除了基体效应。     

基于模糊识别的苹果花期冠层钾素含量高光谱估测

依据2008年和2009年2年在栖霞试验区利用地物光谱仪ASD FieldSpec3测定的苹果花期冠层高光谱和实验室内测定的钾素含量数据,以冠层高光谱反射率及其11变换形式与钾素含量分别进行相关分析,以相关系数最大者为自变量,采用模糊识别算法,建立钾素含量估测模型;以2008年的检验样本对模型进行检验,并利用2009的独立试验数据对模型进行验证。结果表明,原始光谱反射率(R)及其倒数(1/R)、对数(lgR)、平方根(R1/2)与钾素含量的相关性较差,但它们的一阶微分和二阶微分与钾素含量之间的相关性明显增强;建立的钾素含量估测模型=11.344 5h+1.309 7的相关系数r为0.985 1,总均方根差RMSE为0.355 7,F统计量为3 085.6;24个检验样本实测值与估测值的平均相对误差为9.8%,估测精度为90.2%;2009年试验验证精度达到了83.3%。表明模型用于苹果花期冠层钾素含量的估测具有较高的稳定性,模型精度能满足生产上对苹果钾素含量估测的要求。     

低本底伽马能谱测量在沉积岩分类判别中的应用及其影响因素探讨

沉积岩中放射性元素铀、钍、钾的含量主要取决于岩石中泥质的含量,而泥质含量的高低是判别沉积岩类别的主要依据,因此,可以将铀、钍、钾的比活度或含量值作为判别沉积岩岩类的量化指标。利用低本底伽马能谱法测量岩石样品中铀、钍、钾的比活度或含量,可以快速、准确地进行岩类判别。由于放射性测量受样品几何形状、样品质量及其所含水分含量变化的影响,因此岩类判别的准确性会受到影响。通过理论探讨和实验验证,发现各待测核素特征峰计数率值与样品质量成线性关系, 且不同的能量区域、不同的岩性,线性关系系数与趋势拟合程度都是不同的;当样品的水分含量不超过10%(取样时,岩屑水分不超过10%)时,对测量结果的影响很小(变化值均在一倍均方差以内),因此,水分含量对低本底伽马能谱法判别沉积岩岩类的准确性不产生显著的影响,一般可以不予考虑。对陕西定边某油气勘查区钻孔岩屑样品进行判别试验,对实测数据进行质量校正后,利用铀、钍、钾道的“归一化”计数率值(即单位质量的计数率)只能粗略地划分不同沉积岩的大类,再以铀、钍、钾特征峰的合峰计数率建立综合判别模式,能够对岩类进行进一步细分,且判别准确度达到75%以上。     

英平顽痹消和英平顽痹通中钾钠钙镁的分析

用原子吸收法测定4种英平顽痹消和1种英平顽痹通中钾、钠、钙、镁的含量。该类药物中钾、钠、钙、镁的含量均较丰富；本结果为探讨该类药物中宏量元素与疗效的关系提供了有用数据。     

基于ICP-MS法的苹果酒发酵过程矿质元素的动态分析

利用电感耦合等离子质谱仪(ICP-MS)测定苹果酒发酵的不同时期主要矿质元素含量,分析在苹果酒发酵过程中主要矿质元素的吸收和释放的动态变化。结果表明：发酵液中含有的主要矿质元素有钾、钠、钙、镁、铁、锰、铜、锌、锶、硼等十种,其中钾元素的含量最高,在苹果汁中达到1 853.83 mg·L-1,经过发酵后的含量为1 654.38 mg·L-1。在发酵过程中,各种矿质元素的含量处于不断的动态变化之中,整体看来,在发酵进行72～120 h以及144～216 h,大部分矿质元素的含量变化波动较大;尤其在发酵进行到192 h,大部分矿质元素的含量都达到峰值或谷值,其中铁和锌元素的含量达到峰值,钾、钠、钙、镁、锰、硼六种元素的含量达到谷值。但在随后发酵结束前的24 h内,矿质元素的含量又剧烈反弹。经过发酵过程后,钾、镁、铜、锌、硼等元素的含量显著降低,钠、钙、锰、铁、锶等元素含量变化不显著。对十种元素进行相关性分析,结果表明钙元素和锰元素之间的相关性最高,pearson相关系数达到0.924。试验结果为调控酿酒过程,控制产品质量提供了理论依据。     

光谱法分析研究新疆瓜果微量元素含量

利用原子吸收法和原子发射法对新疆十一类瓜果八种微量元素进行检测,并与中国生物标准进行比较分析。 结果发现,新疆和田地区苹果含锌66.75 mg·kg-1、含钾819.2 mg·kg-1、含锰4.657 mg·kg-1,大枣含锶8.62 mg·kg-1;新疆库尔勒地区石榴含钾687 mg·kg-1;新疆哈密地区大枣锰、锌、锶、钙、铁、镍和钾七种微量元素含量均高出各相应的中国生物标准;在十一类瓜果中铜元素含量均低于中国生物标准;八种微量元素含量平均值在新疆库尔勒石榴、新疆和田苹果、新疆哈密大枣中表现很高（分别为91.82, 121.5, 275.3 mg·kg-1）;在新疆五家渠种植的西瓜中八种微量元素表现出果皮中平均含量（54.19 mg·kg-1)是瓤中平均含量(48.69 mg·kg-1)的1.11倍。其研究结果对新疆瓜果营养成分研究提供科学的基础数据。     

Measurement and kinetics of elemental and atomic potassium release from a burning biomass pellet

Combining polarizing-filtered planar laser-induced fluorescence (PLIF) with simultaneous laser absorption, quantitative laser-induced breakdown spectroscopy (LIBS) and two-color pyrometry, the potassium release during the combustion of biomass fuels (corn straw and poplar) has been investigated. The temporal release profiles of volatile atomic potassium and potassium compounds from a corn straw show a single peak. The woody biomass, poplar, produces a dual-maxima distribution for potassium and potassium compounds. For both biomass samples, the highest concentrations of released atomic potassium and potassium compounds occur in the devolatilization stage. The mass ratios between volatile atomic potassium and potassium compounds in the corn straw and poplar cases are 0.77% and 0.79%, respectively. These values agree well with chemical equilibrium predictions that 0.68% of total potassium will be in atomic form. A two-step kinetic model of potassium release has been developed, which gives better predictions during the devolatilization stage than the existing single-step model. Finally, a map of potassium transformation processes during combustion is developed. Starting with inorganic and organic potassium, there are eight proposed transformation pathways including five proposed release pathways that occur during the combustion. The pathways describe the transformation of potassium between the fuel volatile matter, char, and ash. Potassium release during the devolatilization stage is due to pyrolysis and evaporation; during the char burnout stage, potassium release is due to char oxidation and decomposition; and during the ash cooking stage, potassium release is caused by reactions between the ash and H₂O in the co-flow.     

钾扩散耦合引起的心脏中螺旋波的变化

在某些情况下, 心肌细胞外的钾离子浓度是变化的, 钾离子的横向扩散会导致细胞外钾离子的聚集和产生钾扩散耦合, 用考虑钾扩散耦合的Luo-Rudy相I心脏模型研究了钾扩散耦合对螺旋波动力学的影响. 数值模拟结果表明: 当钾扩散耦合比较强时, 钾扩散耦合使细胞外钾离子浓度先升高, 然后做规则振荡, 导致螺旋波做无规则漫游; 观察到螺旋波的波臂宽度和频率随钾扩散耦合的强度增大而减小, 这样, 当钾扩散耦合足够强时, 钾扩散耦合可以消除螺旋波和时空混沌. 关键词： 钾扩散耦合 螺旋波 时空混沌     

A comparison of ion scattering spectra and molecular dynamics simulations at the surface of silicate glasses

Molecular dynamics simulations are correlated with experimental ion scattering spectra to elucidate the surface structure and composition of fused silica and potassium trisilicate glass. The ion scattering spectra and molecular dynamics simulations both show that the oxygen atoms dominate the surface monolayer of fused silica. The ion scattering spectra of fracture surfaces of potassium trisilicate glass show a large potassium signal with little scattering signal from the oxygen or silicon atoms indicating a predominance of potassium in the surface monolayer. This local enrichment of potassium in the surface monolayer is due to their shielding of the charged silicate tetrahedra at the surface. This is also consistent with the simulations.     

Effect of the cesium and potassium doping of multiwalled carbon nanotubes grown in an electrical arc on their emission characteristics

The effect of cesium and potassium atoms deposited onto multiwalled carbon nanotubes grown in an electrical arc on their emission characteristics was studied. The current–voltage characteristics of the field electron emission of specimens with cesium or potassium doped multiwalled carbon nanotubes of this type were revealed to retain their linear character in the Fowler–Nordheim coordinates within several orders of magnitude of change in the emission current. The deposition of cesium and potassium atoms was shown to lead to a considerable increase in the emission current and a decrease in the work function φ of studied emitters with multiwalled nanotubes. The work function was established to decrease to φ ~ 3.1 eV at an optimal thickness of coating with cesium atoms and to φ ~ 2.9 eV in the case of doping with potassium atoms. Cesium and potassium deposition conditions optimal for the attainment of a maximum emission current were found.

     

SIMS study of the interaction of CO and O2 with K adsorbed on Au

SIMS was used to study the adsorption of potassium on a gold foil, and the interaction of O₂ and CO with potassium monolayers and submonolayers. The SIMS K⁺ signal decreased with increasing coverage of K in a manner which can be attributed to work function changes. Oxygen interacts readily with potassium monolayers and submonolayers. No evidence for the adsorption of CO on chemisorbed potassium was obtained. The results are compared with coadsorption studies on substrates other than gold.     

Thermal diffusion of potassium on the modified iron surface

The diffusion of potassium on the polycrystalline iron surface modified by adsorbed oxygen and nitrogen has been studied by means of AES. The migration of potassium atoms has been observed independently on the constitution of the iron surface in the temperature range between 300 and 450 °C. The final concentration of potassium on the iron surface increases with temperature from 300 to 400 °C, irrespective of what atoms accompany potassium on the surface. At 450 °C, the final level of potassium concentration is decreased. The profiles of the concentration on the surface along the line crossing the source of potassium were also acquired. Applying the diffusion model of finite source, the diffusion coefficient of potassium for oxygen-covered and nitrogen-covered surfaces were evaluated.     

WOx phase growth on SiO2/Si by decomposition of tungsten hexacarbonyl: Influence of potassium on supported tungsten oxide phases

Synchrotron based photoemission spectroscopy was used to study the adsorption of tungsten hexacarbonyl on SiO₂ surfaces modified by potassium. Results were compared with the ones obtained when no potassium was present. Experiments using W4f and Si2p intensities variations show that, at 140 K, the tungsten hexacarbonyl growth proceeds via a simultaneous multilayer mode for the two kinds of surfaces but with differences in compositions of growing layers. Indeed, it is evidenced that, even at cryogenic temperatures, the presence of potassium induces decomposition of a significant part of tungsten hexacarbonyl molecules through a strong interaction between tungsten and potassium atoms in opposition to potassium-free surface cases where W(CO)₆ molecules are simply physisorbed. Additional irradiation of adsorbed molecules with photons coming from 0-order synchrotron radiation, subsequent going back to room temperature and additional thermal treatments up to about 700 K were then used to induce further decomposition of the adsorbed precursor. It allows as well to get rid of carbon and, finally, to stabilize different W-based species on the surface. The state of tungsten remaining on the surface is then strongly influenced by presence of potassium. When potassium is present, highly oxidized tungsten species are observed, whereas reduced species are mainly detected for potassium-free surfaces. Moreover, as diffusion of potassium is revealed during formation of tungsten phase, one should guess that potassium plays a crucial role in tungsten oxidation mechanism.     

烟草中钾的连续流动分析方法研究

本文研究了用ALLIANCE自动分析仪测定烟草中钾,选择了最佳仪器分析条件和样品报样条件,并与传统的四苯硼钠重量法作了对比,在此基础上建立了一种连续测定草中钾的方法,为准确快速地测定烟草中的钾提供了保证。     

SIMS investigation of the Si(111) oxidation promoted by potassium overlayers

The removal of the potassium is a critical issue in the Si oxidation promoted by potassium overlayers. The effects of the morphology of the potassium and SiO₂ overlayers on the potassium desorption process have been investigated using a very sensitive technique: SIMS. For a uniform potassium overlayer (monolayer, simultaneous oxygen/potassium adsorption or multilayers exposed to low O₂ pressure) there is no evidence of a significant amount of potassium left after its desorption. However, under specific conditions: potassium multilayers exposed to high O₂ pressure (in which SiO₂ islands were observed using SEM), there is a significant amount of potassium left under the surface after the desorption attempt. These effects of the overlayer morphologies allow us to explain some reported contradictory results.