LIBS结合单变量定标法对土壤中铅元素含量检测

重金属污染一直影响着人们的健康生活,如镉,铅和铜等的污染,故而土壤重金属的快速检测和如何预防,一直受各国学者关注和研究。传统土壤重金属检测方法（如原子吸收光谱法、X荧光光谱法等）样品预处理复杂,分析成本较高,易形成样品的二次污染,不能满足快速分析的要求。激光诱导击穿光谱（LIBS）是一种典型的原子发射光谱,它是基于分析物质中原子和离子受激发而发射的特征谱线信息,进而研究物质成分的分析方法。LIBS技术能够快速检测任何状态（固、液和气态）物质元素的成分和含量,被看作是未来化学检测和快速绿色分析领域的新兴技术。LIBS技术具有对样本简单预处理（或不需要处理）、多元素同步分析、远距离测量、适用性广等优势,被广泛用于生活生产的各个领域,已成为近年来国内外学者广泛关注和研究的热点之一。在农业信息快速感知的大背景下,以激光诱导击穿光谱技术为技术手段,以土壤重金属铅元素为研究对象,运用理论分析和数学建模相结合,建立了多种基于单变量定标曲线的土壤重金属铅检测模型,并进行了模型验证。自制15个已知的铅元素浓度梯度的谱线土壤样本,在获取了土壤LIBS数据之后,对其进行预处理对比,建立了基于谱峰强度、谱峰积分、洛伦兹拟合强度三种定标曲线模型,对土壤中铅元素含量进行定量分析,得出基于三种定标曲线模型对土壤中铅元素含量的预测决定系数R2分别为0.918 0,0.910 1和0.914 3,三种定标曲线分析方法的预测结果都较好,说明了LIBS结合单变量定标曲线法对土壤中铅含量的检测可靠性高。最后选取部分样本数据进行验证,结果较好。研究结果为研发便携式农田土壤污染物检测技术与装备提供技术支撑,也为农田精准管理和科学施肥奠定基础。     

Diffusion of gases across lipid membranes with OmpA channel: a molecular dynamics study

Molecular transport across biological membranes occurs in a range of important chemical and biological processes. The biological membrane can usually be modelled as a phospholipid bilayer, but to correctly represent biological transport, the embedded transmembrane proteins must also be included. In previous molecular simulation studies on transport of small gas molecules in dipalmitoylphosphatidylcholine (DPPC) bilayer membrane, a coarse-grained model was used to provide direct insight into collective phenomena in biological membranes. Coarse graining allowed investigation of longer time and length scales by reducing the degrees of freedom and employing suitable potentials. In this work, membranes that include transmembrane proteins are modelled. This allows one to compare the molecular transport across a lipid membrane with and without the assistance of transmembrane channels. Outer membrane protein A (OmpA) – a porin from Escherichia coli with a small pore size – was chosen in this study because its detailed structure is known, it has high stability and is known to form a nonspecific diffusion channel that permits the penetration of various solutes. In this work the pore characteristics and interaction between lipid and protein were investigated and transport of water and other small gas molecules within the channel were studied. The MD simulation results obtained are compared with previous simulation results and available experimental data. The results obtained from this study will lead to better understanding of protein functionality and advance the development of biochips and drug delivery systems.     

Application of SSNTDs to investigations of radiation accident after-effects

Track methods and devices used for studies conducted after radiation accidents are considered. Solid State Nuclear Track Detectors (SSNTDs) are applied for measurements of contamination in soil, water, biological and other objects of alpha-emitting radionuclides, as well as for estimation of neutron doses by means accident dosimeters. Known radiation accidents (Chernobyl a.o.) and potential emergencies (sunken submarine “Komsomolets”, nuclear reactors) are discussed. Some result of SSNTD application at after-accident period are presented.     

乌鲁木齐市安宁渠区蔬菜中重金属的分布特征研究

对乌鲁木齐市郊安宁渠区在土壤调查的基础上，又进行了蔬菜中的重金属调查．并对蔬菜进行了污染评价．结果标明：土壤的环境元素组合与蔬菜的不同．土壤和蔬菜的重金属聚类分析结果也不同．按食品卫生标准进行评价，蔬菜中Cd、Pb的超标率最高，大白菜的超标率比四季豆和长豇豆更高．长豇豆对重金属的富集系数相对较小．     

Relationship between paddy soil adhesion to steel and to rubber

Forty-three pairs of samples concerning adhesion of paddy soil to steel and to rubber are used to identify the relationship between these two groups of variables. Results show that there is no significant difference between them, implying that they are roughly equal to each other in engineering practice.     

Degradation of medium-chain-length polyhydroxyalkanoates in tropical forest and mangrove soils

Bacterial polyhydroxyalkanoates (PHAs) are perceived to be a suitable alternative to petrochemical plastics because they have similar material properties, are environmentally degradable, and are produced from renewable resources. In this study, the in situ degradation of medium-chain-length PHA (PHA_MCL) films in tropical forest and mangrove soils was assessed. The PHA_MCL was produced by Pseudomonas putida PGA1 using saponified palm kernel oil (SPKO) as the carbon source. After 112 d of burial, there was 16.7% reduction in gross weight of the films buried in acidic forest soil (FS), 3.0% in the ones buried in alkaline forest soil by the side of a stream (FSst) and 4.5% in those buried in mangrove soil (MS). There was a slight decrease in molecular weight for the films buried in FS but not for the films buried in FSst and in MS. However, no changes were observed for the melting temperature, glass transition temperature, monomer compositions, structure, and functional group analyses of the films from any of the burial sites during the test period. This means that the integral properties of the films were maintained during that period and degradation was by surface erosion. Scanning electron microscopy of the films from the three sites revealed holes on the film surfaces which could be attributed to attack by microorganisms and bigger organisms such as detritivores. For comparison purposes, films of polyhydroxybutyrate (PHB), a short-chain-length PHA, and polyethylene (PE) were buried together with the PHA_MCL films in all three sites. The PHB films disintegrated completely in MS and lost 73.5% of their initial weight in FSst, but only 4.6% in FS suggesting that water movement played a major role in breaking up the brittle PHB films. The PE films did not register any weight loss in any of the test sites.     

土壤中SeO_3~（2－）和SeO_4~（2－）的提取及其离子色谱分析

本文研究了土壤中ＳｅＯ和ＳｅＯ的提取并成功地用离子色谱进行分析。方法灵敏、简便，可用于土壤中微量ＳｅＯ和ＳｅＯ的同时测定，取５ｇ于土样，其检测限分别为４０和５０ｎｇ／ｇ。     

Coarse‐Grained Simulations of Model Polymer Nanofibres

We describe the development of a coarse‐grained (CG) force field for nylon‐6 (polycaprolactam) and its application to the simulation of the structure and macromolecular dynamics within cylindrical fibres formed by this polymer, having diameters in the 14–28 nm range. Our CG model is based on the MARTINI force field for the non‐bonded interactions and on Boltzmann‐inverted gas‐phase atomistic simulations for intramolecular stretching and bending energies. The simulations are carried out on infinite, isolated nanofibres at temperatures of 300, 400 and 500 K, with different starting configurations. Starting from ordered chain‐extended configurations, we simulate the melting of the polymer in the nanofibres and, after cooling back to room temperature, its re‐crystallization in a chain‐folded lamellar configuration. This agrees with experimental observations on electrospun nylon‐6 nanofibres and demonstrated the suitability of the approach for the simulation of these systems. The effect of nanoscale confinement on the structure and dynamics of the polymer chains is extensively discussed.

     

Speciation of arsenic by ion chromatography inductively coupled plasma mass spectrometry using ammonium eluents

A method based on ion chromatography (IC) and inductively coupled plasma MS (ICP-MS) was developed for the speciation of arsenic in water and soil extracts. An anion-exchange column (G3154A/101) was used to separate As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) with excellent resolution. Various ammonium salts, including NH4H2PO4, (NH4)2HPO4, (NH4)2CO3, and NH4HCO3, were examined as eluents to reduce matrix interference from chloride and to solve clogging problems. The best arsenic speciation was obtained within 9 min with excellent resolution and without interference from high chloride concentrations using an eluent containing 7.5 mM (NH4)2HPO4 at pH 7.9. The detection limits for the target arsenic species ranged from 0.1 to 0.4 microg/L with direct injection of sample without matrix elimination. The proposed method was effectively demonstrated by determining arsenic species in contaminated waters and soils of Bangladesh.     

Identification and spectra–structure determination of soil minerals: Raman study supported by IR spectroscopy and X‐ray powder diffraction

Raman and IR spectroscopy were used for the characterization of several minerals in morphologically similar vertisol sequences from Kiževak (Serbia). It helped us to establish the surface layer transition going from calcic vertisols (containing gypsum and calcite) to calcimagnesic vertisols (containing aragonite, magnesium‐calcite and dolomite) derived from peridotite and serpentinite. The observed band positions are found to be solely characteristic for each carbonate mineral and are used to discuss the main structural features of carbonates and sulfates present in the studied soil. It was found that the dolomite, calcite and aragonite concretions are present in the deepest layer of the soil, whereas the gypsum is found in the topsoil. The identification was confirmed of the carbonates having calcite and aragonite structure, and the representative from the sulfate group (gypsum) was confirmed by X‐ray powder diffraction. Copyright © 2009 John Wiley & Sons, Ltd.