微量金属物证的扫描电镜/X射线能谱检验

金属物证是常见物证,在各类案件中都可能碰到,尤以盗窃案中为最多.作案使用的工具例如改锥、钳子、钢锯、以及配制钥匙等都会在现场造成微量金属的转移.传统的检验方法是用肉眼或光学显微镜进行痕迹比对.但扫描电镜具有光学显微镜所无法相比的优势,尤其对于粗糙样品,扫描电镜的数值孔径α一般在10-2～10-3,其景深（D=200/aM）比光学显微镜要大几十到上百倍.扫描电镜更大的优势还在于观察痕迹形态的同时能对痕迹表面的附着物进行成份分析.大量的实验研究表明,物体相互受力形成痕迹的同时,总伴随着物质的相互转移。

柴油机排气颗粒中有机组分的分离方法及微量金属的测定

采用柱层析和化学方法将柴油机颗粒有机可溶成分按化学和物理性质分为有机碱、有机酸、脂肪类有机物、芳烃化合物、中极性有机物、高极性有机物 6大类 ,并测定这些有机物质的百分组成及回收率 .同时 ,使用等离子发射光谱法 (ICP- AMS)分析了颗粒中金属物质的种类及相应的含量 。

^(210)Pb Chronology and Trace Metal Geochemistry in the Intertidal Sediment of Qinjiang River Estuary, China

Historical records of metal inputs were studied by using a sediment core collected from a sand-rich mudflat in the Qinjiang River estuary, China. 210Pb chronology was used to reconstruct the fluxes of Hg, Cu, Pb, Zn, Cd, Cr and As to the core site during the last 86 years. Based on the constant initial concentration model, the sedimentation rates are 1.18 cm year-1 in the top 30 cm sandy layer and 0.92 cm year-1 in the muddy bottom layer. To compensate for grain-size and mineralogy effects on metal concentra-tions, aluminum was used as the normalizing element. The enrichment factors (EF) indicate that the natural inputs had prevailed up to the early 1980s. After this period, the intensity of human activities has resulted in continual increasing trend of metals towards the surface. Recent sediment samples from the Qinjiang River estuary are found moderately enriched by Cd (EF>1.5) and slightly enriched by other metals (EF<1.5). Considering that the drainage area of the Qinjiang River is mostly agricultural land, the increased Cd may be due to the usage of fertilizers and pesticides in agricultural activities and the combustion of fossil fuels.

Distribution and pollution assessment of trace metals in seawater and sediment in Laizhou Bay

Selected trace metals （Pb, Cd, Cu, Hg） and arsenic in seawater and surface sediments of Laizhou Bay were determined, to evaluate their spatial distribution, pollution risk and potential ecological risk. Concentrations of the elements were 0.56-2.07, 0.14-0.38, 12.70-18.40, 0.014-0.094, and 1.13- 2.37 μg/L in the seawater and 8.94-32.2, 0.18-0.67, 4.51-30.5, 0.006-0.058, and 5.75-15.3 mg/kg in sediments for Pb, Cd, Cu, Hg and As, respectively. High concentrations of the trace metals and arsenic in seawater and surface sediments were generally observed near the fiver estuary. The pollution risk result of the elements showed that Cu was the prominent trace metal pollutant in seawater, followed by Hg, Pb, Cd and As. The metal complex pollution index in seawater was at a medium level. The most important trace metal pollutant in sediments was Cd, followed by As, Cu, Pb, and Hg. Our pollution assessment suggests that trace metal pollution in Laizhou Bay sediments was at a low level. The potential ecological risk was also low in surface sediment.

The Analysis of Trace Metals in Bottom Mud of the Weihe River by Atomic Absorption Spectrometry

[Objective] This study was conducted to investigate the contents of trace metal ions in Youhe sediment in the Youhe reach of the Yellow River. [Method] Under certain experimental conditions, the contents of trace metal ions in the Weihe River sediment were mainly analyzed by atomic absorption spectrometry, including the contents of Zn, Cu, Mg and Mn. [Result] The Mn content in the bottom mud was 469.5 μg/g, which was the highest, followed by the Zn content of 111.0 μg/g and the Mg content of 99.0 μg/g, and the Cu content was the lowest, of 8.30μg/g. [Conclusion] This method is simple and rapid with higher accuracy.

Trace Metals （Cu, Pb, Zn, Mn, Mo, As） Analysis as a Base for Environmental Studies in Argentina

In Argentina, at Central Andes Eastside, Cumbres Calchaquies, Aconquija Range and Ambato Block constitute a mountain chain that erects about 5,000 masl. Its geological story reveals morphotectonic and magmatic processes are similar to the Pampean Ranges at which they belong to, giving origin to mineralized areas. Geochemical concentrations of trace metals （Cu, Pb, Zn, Mn, Mo, As） in stream sediments are related to the geology and mineral manifestations of the area. Geochemical high average concentration of Cu, Pb and Mo are observed in all ranges. It highlights the presence of As in Cumbres Calchaquies-Aconquija Range and Zn, Mn in the mountains of Aconquija Range-Ambato Block. It was determined that Cu-Zn-Mn complex is adsorbed or precipitated most frequently by Mn oxides. Complex Pb-Zn, Mn-As, Mo-As and Pb-Mo are absorbed by other agents （clay; oxides of Mn, Fe, AI; organic matter）.

Modeling and Optimization of Relocation of Some Heavy Metals and Micro-nutrients in the Argan Trees

This work constitutes a contribution to the study of the physical-chemical performance of some heavy metals and micro-nutrients in the Argan trees. The samples are harvested from small Argan trees, three samples （soil, wood, leaves） per tree. The content of various heavy metals and micro-nutrient in aerial parts （leaves, wood and soil） were analyzed in the Argan tree by the method of ICP-ES. The results of analysis of data for the chemical variables were measured for several trees at different measurement times, do not affect the dispersion of the data. The use of chemometrics has allowed us to interpret the results obtained especially those related to the characterization of heavy metals and micro-nutrient after calibration by variable regression of these results in order to get an overall estimate of the optimal content, and to follow changes in the methods of treatment. The results of the characteristics of Argan trees have been treated using the statistical method of Principal Component Analysis （MFA）, The MFA was used to analyze the three groups simultaneously. These groups are fairly similar.

Carbon Paste Electrodes for the Analysis of Some Agricultural Pollutants and Trace Metals

The present work is concerned with the voltammetric application of unmodified tricresyl phosphate carbon paste electrode （TCP-CPE） and in situ bismuth-film modified tricresyl phosphate-based carbon paste electrode （BiF-TCP-CPE）. The TCP-CPE was examined with the main objective of using it for the differential pulse voltammetric analysis of some neonicotinoid insecticides in aqueous Britton-Robinson buffer solution pH 7.0 as supporting electrolyte. After comparing the performance of the TCP-CPE with that of silicone oil carbon paste electrode, quantitative analysis of imidacloprid, thiamethoxam and clothianidin was performed in model solutions and real samples （river water and commercial insecticide formulations）. The in situ prepared BiF-TCP-CPE was tested for a simultaneous detection of selected heavy metal ions （Cd^2＋ and Pb^2＋） at a μg/dm^3 concentration level, using square wave anodic stripping voltammetric technique. The influence of different electrochemical pretreatments of the working electrode on the bismuth deposition and analyte signals were investigated. Film formation was studied at untreated, pre-cathodized and pre-anodized TCP-CPEs in the acetic buffer solution pH 4.6, containing 1 μg/cm^3 Bi （III）.

Trace Metals in PM_(2.5):A Story beyond Border

In a lab of the CAS Institute of Process Engineering（IPE）in Beijing,Winifred Uduak Anake,a visiting woman scientist from Covenant University.Nigeria was dashing to finish testing the 100 plus samples she collected from her home country.＂1 am trying to find out the type and amount of hazardous trace metals bound to the tiny particles trapped on the filters,＂she explained：＂out of worries about their possible threat to human health.＂Before concluding her three-month stay she needed to complete examining the morphology of the particles,total trace metals,

Grain Size and Metallic Trace Element Contents in Sediments of Kemaman Coast, Terengganu, Malaysia, South China Sea

A total of 43 sediment samples were collected at Kemaman coast, Terengganu, by using Smith Mclntyre grab. These sediments were analyzed to determine the grain size, sediment texture and metallic trace elements. Lazer diffraction method using PSA （particle size analyzer） was used to determine the grain size and sediment texture. Teflon bomb was used to digest the sediments for metallic trace elements concentration. Results showed that the study area was dominated with sand particles （60.5%） followed by loamy sand （20.9%）, sandy clay （16.3%） and silt loam （2.3%）. On the other hand, the average concentrations of each metallic trace elements were 0.12 pg/g for Cd; 36.6 lag/g for Cr; 9.51 pg/g for Cu; 11.6 ~tg/g for N： 41.5 ~tg/g for Zn and 29.3/ag/g for Pb. Based on the results, it was found out that coarse sediments showed lower levels of metallic trace elements and higher levels in fine sediments. In addition, enrichment factor was calculated to assess the pollution status of the study area. Based on the calculation, the enrichment of metallic trace elements ranked in the following order： Pb 〉 Cd 〉 Zn 〉 Cu 〉 Ni 〉 Cr. The significant enrichment of Pb and moderate enrichment of Cd and Zn indicated that there are anthropogenic inputs while the rest of the metals can be considered from natural sources although there are effects of anthropogenic inputs in some sampling location.

Soil calcium content as the driving factor for vegetative structure and soil microbial function diverging across a fire chronosequence of the boreal forests in northeast China

The role of biophysical variables in constructing community structure changes with the time since fire.The major objective of this study is to verify the transition stage and its underlying variables for the postfire forest and soil microbial function in the boreal forested area of China.A 50-year fire chronosequence was presented,and biomass of forbs,shrubs and woody plants was separately weighted to assess their contribution to the whole community with the year since fire(YSF).Simultaneously,soil biophysical properties were measured for stands in different time periods after fire.Soil microbial functions,i.e.growth efficiency(GE)and carbon use efficiency(CUE),were calculated based on ecoenzymatic and soil nutrient stoichiometry.In terms of vegetative structure,forbs’proportion decreased from 75%to 1.5%,but the proportion of woody plants increased from 0.04%to 70%across this fire chronosequence.GE and CUE of soil microorganisms averaged 0.242 and 0.236 and were significantly higher in 9,15 and 31 YSF than in 2 and 3 YSF.Soil metal content was significantly increased at the late stage of this fire chronosequence,and soil calcium content showed a positive correlation with woody plant biomass and a negative correlation with soil microbial function.Overall,the present work highlights that the time period of 15 and 31 YSF is a hallmark stage for aboveground vegetative structure and soil microbial function to change in different trends and that the calcium content may partly account for these two divergent trajectories.