Remote air pollution measurement

The availability of high energy tunable laser sources has extended the possibilities for remote air pollution measurement. This paper presents a discussion and comparison of the Raman method, the resonance and fluorescence backscatter method, long path absorption methods and the differential absorption method. A comparison of the above remote detection methods shows that the absorption methods offer the most sensitivity at the least required transmitted energy. Topographical absorption provides the advantage of a single ended measurement, and differential absorption offers the additional advantage of a fully depth resolved absorption measurement. Recent experimental results confirming the range and sensitivity of the methods are presented. Future widespread use of remote pollution monitoring will probably be limited to the infra-red to interact with molecular spectral bands and to meet eye safety requirements.     

Pulsed power corona discharges for air pollution control

Successful introduction of pulsed corona for industrial purposes very much depends on the reliability of high-voltage and pulsed power technology and on the efficiency of energy transfer. In addition, it is of the utmost importance that adequate electromagnetic compatibility (EMC) is achieved between the high-voltage pulse source and the surrounding equipment. Pulsed corona is generated in a pilot unit that produces narrow 50 MW pulses at 1000 pps (net average corona power 1.5 kW). The pilot unit can run continuously for use in industrial applications such as cleaning of gases (100 m³/h) containing NO or volatile organic compounds (VOCs) or fluids (e.g., waste water). Simultaneous removal of NO and ethylene to obtain clean CO₂ from the exhaust of a combustion engine was tested at an industrial site. Various chemical processes, such as removal of toluene or styrene from an airflow are tested in the laboratory. We developed a model to analyze the conversion of these pollutants. To examine the discharges in the reactor we use current, voltage, and E-field sensors as well as a fast charge-coupled device (CCD) camera. Detailed energy input measurements are compared with CCD movies to investigate the efficiency of different streamer phases. EMC techniques incorporated in the pilot unit are based on the successful concept of constructing a low transfer impedance between common mode currents induced by pulsed power and differential mode voltages in signal lines and external main lines     

The mechanism of detection of air pollution by an ionization chamber

The mechanism of detection of chemical vapors in air by an ionization chamber supplied by DC and AC voltage has been described. The theoretical explanation is based on numerical solutions of the differential equations of the cylindrical ionization chamber. The current of the ionization chamber operating in the AC regime has two components: a conductive component, caused by the ions drifts, and a capacitive component, caused by the distortion of the electric field. The ionization chamber operating in the DC regime has only the first component; hence the AC supplied chamber has larger response than the DC supplied chamber.     

Ultrafast MRI of the fetus: an increasingly important tool in prenatal diagnosis of congenital anomalies

Objective

To demonstrate the additional utility of ultrafast magnetic resonance imaging (MRI) of the fetus in the evaluation of sonographically detected or equivocal fetal congenital anomalies.

Material and Methods

Twenty five pregnant women with ultrasound detected fetal congenital anomalies underwent ultrafast fetal MRI.

Results

MRI findings altered the diagnosis of two cases of giant arachnoid cyst and sizable interhemispheric cyst associated with agenesis of the corpus callosum. MRI added additional findings of occult spinal diastematomyelia in two out of four cases of Chiari/meningocele malformation. MRI revealed impaired sulcation and unilateral cleft palate in suspected case of Walker-Warburg syndrome. In the remaining 18 cases MRI confirmed the diagnosis of Meckel–Gruber syndrome in three cases, hydronephrosis in six cases, cerebral ventriculomegaly in five cases, isolated omphalocele in three cases and findings suggestive of aneuploidy in the last case.

Conclusion

Ultrasound is the screening method of choice for evaluation of the fetus. Ultrafast MRI is a complementary adjunctive modality with excellent tissue contrast that can image the fetus in multiple planes and add information in sonographically detected or equivocal congenital anomalies that may be significant to establish definitive accurate diagnosis and hence adequate management and counseling.     

Spectral characteristics of wind and air pollution data in an industrial area

Summary A comparison is made between the spectral features of sulfur dioxide concentration and zonal and meridional components of wind speed over a highly industrialized area situated on the coast. The paper focuses on the characteristic times of the meso-synoptic scale. Diurnal and longer period oscillations were identified. Variations of ground-level SO₂ concentrations are attributed to local sea-breeze circulation and to the synoptic weather period of wind speed.     

Mie scattering techniques for air pollution measurement with lasers

Lidar (laser radar) techniques of remotely observing atmospheric particulates have obvious relevance to air pollution. After briefly noting the capability of lidar in a semiquantitative role for monitoring spatial and temporal variations of particulate concentration attention is directed to the problems of evaluating lidar observations quantitatively in terms of such physically meaningful parameters as the turbidity, opacity or particulate mass concentration of smoke plumes or the ambient atmosphere. Solutions based on Mie scattering theory are illustrated with examples from (1) hazy atmospheres (2) smoke plumes and (3) controlled aerosols in a test chamber. While noting that the role of lidar in research applications in air pollution is well established, its routine operational use is seen to be dependent upon further experimental and technological development. Its potential for monitoring ambient air quality and emission sources is stressed.     

Application of mobile vehicle lidar for urban air pollution monitoring

A mobile vehicle lidar system has been developed and applied to detect urban air quality. On September 21 and22, 2015, particulate matter observation with mobile vehicle lidar was carried out in the Binhai New Area of Tianjin. Combined with the latitude and longitude information acquired by a GPS, the three-dimensional distribution of the aerosol extinction coefficient was presented in the experimental area. Furthermore, the source,distribution, and the transportation path of the aerosols in the area were investigated based on lidar data, local meteorological data, and backward trajectory analysis. The results show that mobile vehicle lidar can detect the atmospheric aerosols and reflect the stereoscopic distribution properties of aerosols. The potential of this vehicle lidar system provides a new scientific basis for the study of the source, distribution, and transportation of atmospheric particles.     

Field evaluation of an electrostatic PM10 mass monitor used for continuous ambient particulate air pollution measurements

The aim of this paper is to evaluate field values based on electrostatic charge technique of a PM10 mass monitor used for continuous measuring of ambient particulate air pollution. The PM10 mass monitor included electrostatic PM10 mass monitor (EPMM) and wireless monitor systems. In this study, the performance of the EPMM was simultaneously evaluated with a commercially available tapered element oscillating microbalance (TEOM) for measurements at ambient condition. The data of the sensor was connected to the internet through a GSM connection to a public cellular network. The monitoring data of ambient PM was collected and compared for both EPMM and TEOM by measuring at Chiang Mai City Hall during May 1st – 31st, 2015. The two different instruments showed good results that were highly correlated. The comparison between the EPMM and TEOM data values resulted in R² of 0.8352 and 0.9697, and a slope of 0.8401 and 0.9087 for 1-h and 24-h, respectively. In addition, it was found that the relative humidity played an important role in PM10 mass concentration and its electrical properties of the EPMM. Particularly the EPMM proved its advantages in measuring and detecting PM10 particulate air pollution for mass concentrations in the range from 0 to 500 μg/m³.     

Physical aspects of radiometric monitoring of air pollution

We analyze the main physical approximations of radiometric monitoring of minor gas components (MGC) in the atmosphere in the millimeter wave range. Theoretical spectra of atmospheric obsorptions are obtained for the lower layers allowing for some MGCs for contents exceeding one-time limiting permissible concentrations. Conclusions are drawn on the diagnostic conditions for some MGCs using their thermal radio emission in the microwave range. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 6, pp. 722–732, June, 1997.     

Spontaneous Raman scattering: a useful tool for investigating the afterglow of nanosecond scale discharges in air

Nanosecond scale discharges are considered an interesting way for assisting combustion by enhancing either flame stabilization or ignition. Better understanding of energy deposit and radical species production processes is still required under pressure conditions normally encountered in combustion. The purpose of the present paper is to show that spontaneous Raman scattering, seldom used to investigate nanosecond pulsed discharges, is a useful measurement method for investigating the energy deposit of these discharges. The advantage of spontaneous Raman scattering is described by analyzing N₂ and O₂ spectra during the post-discharge of a filamentary nanosecond air discharge under atmospheric pressure, using phase-locked average spectra. The main advantages of spontaneous Raman scattering measurements are that they allow line-wise probing of different species with the same experimental setup and the determination of vibrational distribution by comparison with theoretical modeling over a wide range of vibrational levels (from v=0 to v=20 for N₂). The model proposed takes into account the high level of vibrational excitation and the strong non-equilibrium observed, allowing the characterization of the vibrational relaxation over the complete post-discharge duration. Although the rotational structure is not resolved, the rotational temperature and thus translational temperature are determined with a moderate uncertainty for T above 500 K.     

LANDSAT images of urban air pollution in stable meteorological conditions

Summary This paper deals with the city of Milan and its province, a highly inhabited area located in the Po Valley (North Italy), where stable atmosphere and prolonged inversions are frequent, especially during the domestic heating season (from October to March). In fact anticyclonic conditions in Northern Italy easily lead to temperature inversions of about (300÷400) m and give rise to the ?heat island? effect in the area. It follows that temperature is higher in the city than in the countryside, reaching its maximum value in the centre of the town and decreasing towards the suburbs; consequently this system can become highly stable and trap pollutants in a closed dome up to very critical values. Two LANDSAT images were examined, together with the ground-level pollution data recorded by the Public Health Office network; the first one was representative of a typical highly polluted day in Milan in winterly stable meteorological condition, while the second one, taken in a windy and scarcely polluted day, gave a thermal reference map. Relations between ground-level SO₂ concentrations and thermal radiant power measured by LANDSAT TM band 6 were investigated. The results showed a significant correlation between radiance and concentrations, and the sign of this statistical index came out negative. The authors think that this is due to the simultaneous presence in the atmosphere of Milan of SO₂, dust, aerosol and particles of various size which decrease the transparency of the atmosphere in thermal band.     

Tunable infra-red lasers and their applications to air pollution measurements

This paper describes a number of tunable infra-red lasers and techniques employing them for the detection and monitoring of gaseous air pollutants. Recent progress in the development of lasers that can be matched to characteristic infra-red absorption or emission lines of certain pollutants suggest wide potential application for sensitive specific monitoring. Examples to be described include highly-specific point-sampling,in situ source monitoring, ambient air monitoring, resonance fluorescence, and remote heterodyne detection.This work was supported by the Environmental Protection Agency.     

空气的绝热指数γ的大气压修正

通过讨论分析指出:空气的绝热指数随海拔的升高而减小,随气压的降低而降低.从而为学生实验测定空气的比热容比提供一个参考.     

Electron microscopy of nanoemulsions: an essential tool for characterisation and stability assessment

The characterisation of pharmaceutical formulations by microscopic techniques is essential to obtain reliable data about the actual morphology of the system. Since the size range of colloidal drug delivery systems has long ago reached the lower end of the nanometer scale, classical light microscopy has been replaced by electron microscopy techniques which provide sufficient resolution for the visualisation of nano-sized structures. Indeed, the superior resolution and methodological versatility of electron microscopy has rendered this technique an indispensable tool for the analysis of nanoemulsions. Microscopic analysis of these lipid-based drug delivery systems with particle sizes in the lower submicron range provides critical information about the size, shape and internal structure of the emulsion droplets. Moreover, surfactant aggregates such as liposomes or multilamellar structures which remain unnoticed during particle size measurements can be detected in this fashion. This review provides a brief overview about both transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques which have been employed to characterise nanoemulsions. Of special interest are sophisticated cryo techniques of sample preparation for both TEM and SEM which deliver high-quality images of nanoemulsions in their natural state. An overview about the instrumentation and sample preparation for all presented methods is given. Important practical aspects, sources of error and common artefacts as well as recent methodological advances are discussed. Selected examples of electron microscopic studies of nanoemulsions are presented to illustrate the potential of this technique to reveal detailed and specific information.     

Solid-state NMR as an analytical tool: quantitative aspects

Analytical methods based on solid-state NMR are becoming increasingly popular. However, these flourishing activities bring up the issue of how accurately NMR can assess an analyte proportion in a solid sample. The use of a chemical intensity reference for this purpose is a natural but often unsuitable choice, due to sample stability or preciousness. We propose here a protocol to perform quantitative measurements in solid-state NMR, by calibration of the circuit response through a low-power pulse injected during the acquisition (the so-called ERETIC method). Although this method has been in use for some time in liquid-phase and in vivo NMR, we point out here some peculiarities and useful applications typical of solids. Namely, the temperature dependence of the signal intensity imposes care in the application to MAS experiments.     

Laser remote sensing and photoacoustic spectrometry applied in air pollution investigation

We have applied two spectroscopic techniques in order to investigate air pollution dispersion in real and simulated atmosphere: the Titan–Sapphire laser technique based on differential absorption lidar (DIAL), and CO₂ laser photoacoustic spectrometry (LPS). A set of spatial NO₂ measurements was performed over a highway outside a city and in an urban street canyon with extensive traffic. Qualitative agreement was found between the results obtained by DIAL and by physical modeling based on LPS measurements in a wind tunnel.