Mass Concentration Of Suspended Particles Research Articles

Comprehensive hygienic assessment of the dust factor in the asbestos cement manufacturing industry

Objective: to conduct comprehensive hygienic studies of the dust factor in the asbestos cement manufacturing industry and to determine the presence of a relationship between the content level of respirable fibres and the mass concentration of suspended particles in order to actualize the methodology of the assessment of the air of a working area containing mineral fibrous aerosols. Materials and methods. The mass concentrations of dust and the content level of respirable fibres in the air of the working area and the morphological characteristics of dust aerosol were analyzed. Results. The content of dust in the air of the working area in terms of the mass measurements of suspended particles does not exceed the hygienic standards and ranges from 0.20 ± 0.004 mg/m 3 to 1.47 ± 0.085 mg/m 3 , and the content level of respirable fibres is from 0.20 ± 0.044 f/cm 3 to 1.13 ± 0.204 f/cm 3 . The presence of a positive correlation of moderate strength between the content level of respirable fibres and the mass concentration of suspended particles has been found. Conclusion. The microscopy of the preparations of dust samples makes it possible to determine a morphological picture which is characteristic for various stages of the technological process. There is a positive correlation of moderate strength between the content level of respirable fibres in the air of the working area and the concentration of suspended particles. However, the obtained patterns of dependence are capable of accounting up to 49.3 % of the variations of respirable fibres on the basis of the mass concentration of suspended particles, which does not make it possible to use them for the conversion of the values.

State and prospects for development of measurements of aerosol particle concentration, as well as air ions

The author highlighted the problems in Russia associated with the metrological support of measurements of the mass concentration of suspended particles of RM-10, RM-2.5, RM-1 fractions, as well as the number concentration of medium and heavy air ions.

A critical review of in vitro dosimetry for engineered nanomaterials.

A major obstacle in the development of accurate cellular models for investigating nanobio interactions in vitro is determination of physiologically relevant measures of dose. Comparison of biological responses to nanoparticle exposure typically relies on administered dose metrics such as mass concentration of suspended particles, rather than the effective dose of particles that actually comes in contact with the cells over the time of exposure. Adoption of recently developed dosimetric methodologies will facilitate determination of effective dose delivered to cells in vitro, thereby improving the accuracy and reliability of in vitro screening data, validation of in vitro with in vivo data, and comparison across multiple datasets for the large variety of nanomaterials currently in the market.

Extraordinary High Microwave Absorption Cross Section of Ultralong Carbon Nanotubes

The microwave-induced heating of nanoparticles has been actively studied in pursuit of more efficient microwave absorbers. Here we systematically investigated the microwave absorption cross section of conductive particles (Al), magnetic particles (Fe3O4), and carbon nanotubes with different lengths. The particles were suspended in silicone oil and irradiated with a microwave at 2.45 GHz using a single-mode microwave reactor. The experimentally measured heating rate was analytically modeled based on the modified Lambert–Beer law to obtain the microwave absorption cross section per mass. The microwave-induced heating rate was primarily dependent on optical absorbance, which is proportional to the mass concentration of suspended particles. Under the similar optical absorbance, longer nanotubes provided greater microwave absorption cross section which could be described by the short dipole antenna theory. The microwave absorption cross section of 5 mm long multiwalled carbon nanotubes was ∼4080 times greater ...

Progress in Development of Russian National Measurement Standards in the Field of Mass Concentration Measurement of Suspended Particles

Aerodisperse system (ambient aerosol) is a dynamic system, thus its physical and chemical properties change continuously in the atmosphere. In addition to the changing characteristic of atmospheric aerosols, their accurate and precise measurements are a challenging task because these measurements depend on several parameters for which the traceable standards/calibration are essentially required. In Russia, the traceability for these measurements is provided in accordance with the recommendations of the Russian national regulatory standard “State hierarchy scheme for the instruments deployed for the measurements of the disperse parameters of aerosols, suspensions and powdered materials.” The State primary standard for the units of disperse parameters of aerosols, suspensions and powdered materials (GET-163) and the State primary special standard for the unit of mass concentration of particles in aerodispersed media (GET-164) are placed at the top of the hierarchy scheme. This paper describes the State primary special standard GET-164 and the specificity of ensuring the traceability in disseminating the unit realized by this primary special standard to working measurement instruments. Methods used to generate aerodispersed media with desired properties are validated and the problem for achieving the highest accuracy in the measurements related to the primary special standard GET-164 is discussed. The SI unit of mass concentration of particulate matter is disseminated from the State primary special standard GET-164 to the working instruments through a set of working standards. The methods, which are used to generate aerodispersed media in disseminating the unit of mass concentration, provided for carrying out investigations and calibration of measurement instruments over a wide range of the mass concentration of suspended particles of different disperse composition. The main ways of improving the standard facilities in the field of measurements of the mass concentration of suspended particles are (i) related to the improvement of the method used to measure concentrations by means of a beta-ray analyzer-comparator (included in the composition of the State primary special standard GET-164) by reducing the uncertainty of the approximation of the conversion characteristics and (ii) due to implementation of methods providing for accurately controlled dilution of aerosols to extend the ranges in which the mass concentration values of suspended particles are reproduced. In order to develop a procedure for international comparisons of such standards, the corresponding investigations of the State primary special standard GET-164 were carried out.

The study of Central Taiwan particles concentration variations during earthquake period

Ambient particle concentration was taken on the traffic sampling site over the Chung-Chi Road over the bridge (CCROB) in front of Hungkuang Institute of Technology (HKIT). The sampling time was from August 1999 to December 1999. During the sampling period, Taiwan's biggest earthquake in more than a century registered 7.3 on the Richter scale (Taiwan Chi-Chi Earthquake). Besides, there are more than 20,000 aftershocks following the Taiwan Chi-Chi Earthquake within 3 months. Thus, the mass concentration of particles with aerodynamic diameters smaller than 2.5 μm (PM 2.5) and PM 2.5–10 was also collected then compared with the total mass concentration of suspended particles (TSP) in this study. The average TSP, PM 2.5–10, and PM 2.5 concentrations are 106, 24.6, and 58.0 μg/m 3, respectively, after the Taiwan Chi-Chi Earthquake. The average TSP concentrations before and after Taiwan Chi-Chi Earthquake were 69.6 and 127 μg/m 3, respectively. In addition, statistical analysis of the PM 10 data from this study and EPA in 1999 yielded a T statistic of 0.147, which is smaller than t (0.975,18)=2.101. It is indicated that there was no significant difference. So, the PM 10 concentrations measured after Taiwan Chi-Chi Earthquake in this study were also greater than those data previously obtained from Taiwan EPA in the same region of this area. The relationships between TSP, PM 10, PM 2.5–10, and PM 2.5 particle concentrations and wind speed ( R 2) are .77, .59, .58, .58, respectively. And the ratios of PM 2.5/PM 2.5–10, PM 2.5/PM 10, and PM 10/TSP are 221%, 67.2%, 58.0%, respectively. The average ratios of PM 2.5/PM 2.5–10 and PM 2.5/PM 10 increase by about 120% and 17%. It indicated that the fine-particles concentration increases compared to the coarse-particles concentration after 921 Taiwan Chi-Chi Earthquake. And the proposed reasons are that local motor vehicle emissions combined the fine particles transported from the Chi-Chi epicenter. More importantly, the wind direction was mainly blown from southeastern part. These two main factors enhance the fine-particles concentration in this area.

Piezoelectric microbalance for monitoring the mass concentration of suspended particles

Preliminary experiments prove the feasibility of a piezoelectric microbalance for measuring the mass concentration of suspended particles. The piezoelectric microbalance consists of a vibrating piezoelectric crystal driven by a standard oscillator circuit. The crystal oscillates with very high stability at its resonant mechanical frequency. A collector, such as an impactor or an electrostatic precipitator, deposits the suspended particles onto the electrode surface of the vibrating crystal. The resonant frequency shifts downward linearly with the added mass of the particles. Frequency is monitored with a standard digital counter. The time rate of change of the frequency is proportional to the mass concentration of ambient suspended particles. Experimental and theoretical mass sensitivities (for example, 5.5 Hz μg −1) are identical. Experiments demonstrate the high sensitivity and time resolution of the instrument. With an electrostatic-precipitator collector sampling at 1 1. min −1 the total mass concentration of suspended atmospheric particles (say, 100 μg m −3) is measured to within ±5 per cent in only 41 s. Experiments with an impactor collector show the diurnal variation of the mass concentration of suspended indoor particles, showing decay in the evening and a steep rise during working hours.