ICP-AES测定邻苯二甲酸氢钾-氢氧化钠作用下土壤中重金属全量及形态分析

空白土壤作为质量控制样品,采用邻苯二甲酸氢钾-氢氧化钠进行处理土壤样品为对照,用HNO₃-HF-HClO₄混酸对土壤样品进行消化,运用等离子体发射光谱仪(ICP-AES)测定了提取处理后土壤样品中Mo, Pb, As, Hg, Cr, Cd, Zn, Cu, Ni的全量以及酸可提取态、氧化物结合态、有机结合态三种化学形态的含量。获知不同pH的邻苯二甲酸氢钾-氢氧化钠缓冲溶液对土壤中重金属全量及形态转化作用的影响。结果表明：除Pb和Zn外,投加不同pH邻苯二甲酸氢钾-氢氧化钠缓冲溶液对土壤中重金属全量的消解和测定有促进作用。邻苯二甲酸氢钾-氢氧化钠缓冲溶液对土壤中Cr, Cu, Hg, Pb的酸可提取态、对土壤中As, Hg, Pb, Zn的氧化结合态、对土壤中As和Hg的有机结合态的转化有促进作用。在pH 5.8时,Cu和Hg的酸可提取态的含量最大值分别为2.180和0.632 mg·kg-1;在pH 6.2时,Pb的氧化结合态的含量最大值为27.792 mg·kg-1;在pH 6.0时,Hg的有机结合态含量最大值为4.715 mg·kg-1。     

重金属团簇(M2Te)3(M=Au, Ag, Cu)赝势从头算研究

使用相对论和非相对论赝势,在HF和MP2理论水平上研究了重金属混合/掺杂团簇(M2Te)3(M=Au, Ag, Cu) 的几何构型和稳定性.结果显示,团簇存在具有D3h,C2v和C3v对称性的三种稳定异构体,并且各异构体之间能量相差很小.电子相关效应对M-M键长的修正十分显著,而对M-Te键长和Te-M-Te键角的修正非常小.相对论效应使所有键长变短、Te-M-Te键角变大.两种效应都提高振动频率、降低能量,使团簇结构变得更加紧凑,使多聚物趋于更加稳定.     

ICP-OES法测定穿心莲药材中6种重金属元素溶出特性的研究

以电感耦合等离子体发射光谱法(ICP-OES)同时测定了中药穿心莲中的As,Ba,Cd,Cr,Cu,Pb等6种重金属元素,方法相对标准偏差2.1%~4.6%,回收率92.0%~103.2%,灵敏度高、简单、准确可靠。考察了采用热回流提取、浸泡提取、超声辅助提取等不同提取方法和提取溶剂时,上述6种元素的溶出情况。结果表明,实验所用穿心莲药材中Ba的含量最高,其次为Cu和Cr,而As,Pb,Cd在药材中含量相对较低。随着提取溶剂中乙醇含量升高,Ba的溶出减少,而Cu、Cr的溶出增加,Cd在酸性溶液中溶出最多;提取方法则以冷浸法溶出重金属元素最少,使用纯水和碱水的热回流提取重金属元素溶出相对较多。以上差异可能与这些元素在药材中的存在形态有关。     

外源一氧化氮对镉胁迫下番茄幼苗叶绿体保护作用的光谱学分析

镉（Cd）是重要的重金属污染源，一氧化氮（NO）是近年来发现的一种普遍存在于生物界的信使分子，研究表明其参与了植物对Cd胁迫的应答反应调控。文章用硝普纳（SNP）作为NO供体，向番茄幼苗喷洒100mol·L^-1SNP1d后加入50mol·L^-1Cd处理7d，取完全展开叶片，提取叶绿体进行光谱学研究，分别测定了叶绿体室温吸收光谱、叶绿体低温荧光光谱和DCPIP电子传递效率等指标，研究外源NO缓解Cd对叶绿体毒性的影响。结果发现，CA对叶绿素a、叶绿素b和类胡萝b素含量都有不同程度的降低，NO处理缓解了CA的影响，使叶绿体室温吸收光谱的吸收率提高；CA导致686nm处峰（PSII）偏移4nrn，峰值降低33％，734nm处峰值降低23％，外源NO缓解了Cd对光合系统的影响，使得叶绿体低温荧光光谱在686和734nm的峰值分别仅下降17％和100o；以DCPIP为人工电子受体，Cd处理的叶绿体中DCPIP还原速率较慢，光合电子传递（H2O→DCPIP）速率降低1．5倍，外源NO处理显著缓解了Cd对电子传递链的抑制，使其光合电子传递速率恢复到对照的水平。该研究可为NO处理增强植物对Cd胁迫的抗性提供理论依据。     

Physics of sinking and selection of plankton cell size

Gravitational sinking in the water column is known to affect size composition of planktonic communities. One important driver toward the reduction of plankton size is the fact that larger cells tend to sink faster below the euphotic layer. In this work, we discuss the role of gravitational sinking in driving cell size selection, showing that the outcome of phytoplankton competition is determined by the dependence of sinking velocity on cell size, shape, and on the temporal variability associated with turbulence. This opens a question on whether regional modulations of the turbulence intensity could affect size distribution of planktonic communities.     

Study of the parameters affecting the binding of metals in solution by Chlorella vulgaris

The ability of Chlorella vulgaris to accumulate heavy metals in solution (Mn, Cr, Ni, Zn and Cu) was investigated. Various parameters (algal biomass, pH and contact time of the algae with the sample) have been studied. Nine mg of algal biomass, pH 8 and 15 min of contact time, with 1 ppm of each metal, were the optimized conditions. At pH 8, the optimum value to rise the maximum binding, a fraction of metals in solution precipitates forming hydroxides. Combining both processes, a chemical–biological system for the removing of metals at ppb levels from the environment is obtained. The simultaneous determination of these five metals was performed by capillary electrophoresis (CE) with a UV/Vis detector.     

Thermodynamic properties of CeCu6-xAux: Fermi-liquid vs. non-Fermi-liquid behaviour

We report on a detailed comparison of the thermodynamic properties of the heavy-fermion system CeCu₆ which can be described as a Fermi liquid at low temperatures T < 0.1 K, and CeCu_5.9Au_0.1 where strong deviations from the Fermi-liquid behaviour were found previously in the T dependence of the specific heat C, magnetization M and electrical resistivity p. The specific heat, magnetization and elastic constants are investigated in a large range of magnetic fields, corroborating the idea that the non-Fermi-liquid behaviour arises from low-lying spin excitations. For the elastic constants, a striking linear T dependence is found for CeCu_5.9Au_0.1 in contrast to the T² Fermi-liquid behaviour of CeCu₆.     

Asymptotics of the Interband Light Absorption Coefficient near the Band Edge for an Alloy-Type Model

We find the asymptotics of the interband light absorption coefficient of an alloy-type model in the case when the ground-state energies of the electron and the hole Hamiltonians are finite.     

Self consistent modified extended Hückel (SC-MEH) calculations on heavy metal systems. I. Platinum(II) tetragonal planar complexes with and without relativistic effects

The Self Consistent Modified Extended Hückel molecular orbital method had been applied to several square planar complexes of platinum (II). Calculations including both the limited 5d, 6s, 6p and extended 5s, 5p, 5d, 6s, 6p starting bases for platinum were made. It is shown that in PtCl ₄ ^2– both the nuclear quadrupole moment and minimum total energy vs. bond distance are calculated to be in good agreement with experiment, only with the extended platinum AO basis.Specific inclusion of relativistic parameters via a pseudo-relativistic approximation are shown to have a significant effect on the energy molecular energy levels, however no meaningful rationalization can be made without the simultaneous inclusion of ligand field parameters as well.Supported in part by a grant made available through the Cancer Association of Greater New Orleans. Use of the facilities of the Computer Research Center of the University of New Orleans is gratefully acknowledged.