Stated references for ensuring traceability of chemical measurements for long-term environmental monitoring

Traceability is now considered to be a key concept in chemical and biological measurement sciences. While this concept is increasingly used in many areas, it is still prone to misunderstandings with respect to more ‘classical' terms such as e.g. accuracy. Traceability implies that measurement data are linked to stated references through an unbroken chain of comparisons, all with stated uncertainties. What does the word ‘stated references' mean when it is applied to complex environmental analysis? This paper discusses how traceability can be conceived in the context of environmental monitoring, in particular the various stated references (documented standards, reference materials, environmental specimens) to which chemical environmental data may be linked to.     

Human hair as a marker of pollution by chemical elements emitted by a thermoelectric power plant

A preliminary study was undertaken to assess the risk posed to the environment and health of residents by trace elements released by fuel combustion in the thermoelectric power plant of Pian de’ Gangani (Montalto di Castro, Latium, Italy). In this context, analysis of human hair can be considered as an advantageous approach to monitor the exposure of population to the adverse effects of the power plant, which is now fully operative. To this purpose 92 healthy children (aged 9–10 years) were selected from two primary schools of Montalto di Castro and Pescia Romana. The young age of the donors guarantees that the effects of cosmetic treatment and occupational exposure on the representativeness of data are minimized. Hair samples were collected, washed and digested as prescribed by already well-established procedures. Inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were employed for the determination of the trace and minor elements of interest (As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, P, Pb, Sb, Se, Tl, V and Zn). The entire analytical procedure was checked for both measurement precision and accuracy by using the Certified Reference Material BCR No. 397 Human Hair. The mean values obtained were (in μg g⁻¹): As, 0.159±0.044; Ca, 393±187; Cd, 0.047±0.055; Co, 0.040±0.038; Cr, 0.704±0.208; Cu, 12.0±10.3; Fe, 12.1±10.8; Mg, 40.6±27.7; Mn, 0.383±0.296; Ni, 0.868±1.331; P, 141±138; Pb, 1.64±1.63; Sb, 0.041±0.058; Se, 0.430±0.135; Tl, 0.001±0.001; V, 0.185±0.158; and Zn, 177±173. These experimental figures can be assumed to be the baseline values prior to the full operation of the power plant. Within the next 4–5 years it is planned to conduct a similar study with a new group of subjects, comparable for age, sex, style of life and exposure mode, to the present ones so as to detect possible trends in the bioaccumulation of the above elements.     

Catalytic decomposition of CFC-12 on solid acids SO_4~(2-)M_xO_y (M = Zr, Ti, Sn, Fe, Al)

The catalytic decomposition of dichlorodifluoromethane (CFC-12) in the presence of water vapor on a series of SO42- -promoted solid acids was investigated. CFC-12 was decomposed completely on SO42-/ZrO2, SO42-/TiO2, SO42-/SnO2, SO42-/Fe2O3 and SO42-/Al2O3 at 265℃, 270℃, 325℃, 350℃ and 325℃, respectively, and the selectivity to by-products was ne-gleclable. Obvious deactivation was found on SO42-/ZrO2 and SO42-/Al2O3 during several hours on stream, while the catalytic activity was maintained on SO42-/TiO2, SO42-/SnO2 and SO42-/Fe2O3 for 240 h on stream.     

Termination impedance of open-ended cylindrical tubes at high sound pressure levelImpédance terminale d'un tuyau cylindrique ouvert à fort niveau sonore

The study deals with nonlinear acoustical effects localised at the open-end of a cylindrical tube. The termination impedance is measured using a two microphone method. Due to the separation of the acoustic flow at the pipe end, the real part of the termination impedance depends on the volume velocity at the open end. It is shown that the radius of curvature of the edges of the open end of the tube has a crucial influence on the amplitude of the nonlinear losses. Several regimes are shown for the low radii of curvature. To cite this article: M. Atig et al., C. R. Mecanique 332 (2004).     

Miniaturized instrumentation for field applications: general considerations for environmental sensor networks

Various aspects of chemical instrument miniaturizing are explored. The limitations imposed by scaling laws are discussed, and the influences of system dynamics on chemical and physical behaviour of molecules in microsystems are presented. The complexity of chemical systems, as defined by intra- and intermolecular forces, influencing minimum device dimensions is illustrated for solution and gas-phase species. The basic concepts for environmental sensor networks are presented for a hypothetical system.     

环境工程专业生产实习的改革与实践

生产实习是环境工程专业实践教学环节中的一个重要组成部分,是学生接触环境工程专业领域生产实际的重要手段。针对目前生产实习的现状和存在的典型问题,提出六条改革和实践的措施,将理论与生产实践相联系,初见成效。     

户外居住环境设计研究

中国的城市正在以前所未有的速度发生着翻天覆地的变化,昨日辉煌迷人的旧住区今天却成为了时代的落伍者,整片整片的新居住区拔地而起。在不同的时代,人类有不同的生活理想和生活方式,经过一代代的历史沉淀,形成不同的居住文化。时至今日,传统难以为继,在居住环境方面我们的做法往往是先排房子,后作环境,这就带来了一系列问题：户外环境千篇一律、人文特色与户外环境活力丧失、缺少了地域特色等等。因此需要我们认真去研究,寻找一条出路。     

环境水样中有机污染物前处理方法的研究进展

综述了环境水样中有机污染物前处理方法的研究进展情况,重点介绍了液液萃取、固相萃取、液相微萃取、固相微萃取和液相分散型微萃取技术5种前处理方法的一些基本情况及其优缺点。     

陕西省经济发展与环境污染的计量模型研究

根据陕西省1989～2008年统计年鉴中相关经济和环境数据,建立了人均GDP与典型环境指标工业三废、工业二氧化硫以及烟尘排放量的计量模型,并对其变化原因进行了分析.结果表明,陕西省经济发展与环境污染的计量模型中,并未出现典型的"倒U"型曲线模型,而是各有其特点,烟尘排放量与工业废气排放量都没有出现转折趋势,工业固废排放量几乎呈现直线式上升,工业废水和工业二氧化硫的污染已经有所好转,但趋势还不太稳定,文章最后提出了一些建议.     

Spontaneous emission of NMR signals in hyperpolarized proton spin systems

Hyperpolarization of nuclear spins is gaining increasing interest as a tool for improving the signal-to-noise ratio of NMR and MRI. While in principle, hyperpolarized samples are amenable to the same or similar experiments as are used in conventional NMR, the large spin polarization may give rise to unexpected effects. Here, spontaneous emission of signal was observed from proton spin systems, which were hyperpolarized to negative spin temperature by dynamic nuclear polarization (DNP). An unexpected feature of these emissions is that, without any radio-frequency excitation, multiple beats arise that cannot be explained by the Bloch equations with radiation damping. However, we show that a simple modification to these equations, which takes into account an additional supply of hyperpolarized magnetization from a reservoir outside of the active detection region, can phenomenologically describe the observed signal. The observed effect demonstrates that even well-known mechanisms of spin evolution can give rise to unexpected effects when working with hyperpolarized samples, which may need to be addressed through the development of new experimental techniques.