Aerosol Mass Concentration Measurements Research Articles

A closure study of aerosol mass concentration measurements: comparison of values obtained with filters and by direct measurements of mass distributions

We compare measurements of aerosol mass concentrations obtained gravimetrically using Teflon coated glass fiber filters and by integrating mass distributions measured with the differential mobility analyzer–aerosol particle mass analyzer (DMA–APM) technique (Aerosol Sci. Technol. 36 (2002) 227). The DMA–APM technique measures the distribution of particle mass as a function of mobility size for particles of arbitrary shape and composition (Relationship between particle mass and mobility, and between aerodynamic and mobility size distributions for diesel exhaust particles, Environ. Sci. Technol., 2003). Because DMA–APM measurements are made on particles suspended in the air, data are not affected by volatilization or adsorption that can affect the accuracy of the filter measurements. We show that the average ratio of the filter to DMA–APM mass concentrations for laboratory-generated dioctyl sebacate (DOS) and sodium chloride (NaCl) aerosols is 1.14±0.28, and they are well correlated ( R 2>0.97). For diesel exhaust aerosols from an engine operating at 75% load, the two techniques agreed well with the average ratio of 0.98±0.20. When the engine was operated at a low (10%) load, mass concentrations measured with the filter were 2.13±0.54 times higher than values measured with the DMA–APM. We believe that the higher filter loading may be due to the adsorption of condensable vapors, which are emitted at higher rates under low engine load conditions. Measurements in which the condensable organics were removed with a catalytic stripper show much better agreement between the filter and DMA–APM, which support the hypothesis that vapor adsorption leads to artificially high filter data for low-load measurements. We conclude that the DMA–APM technique can be used to evaluate the accuracy of filter samples that may be affected by sampling artifacts, and to measure mass distributions with high time resolution for sub-0.5 μm aerosols.

Aerosol mass concentration measurement in calm air during sampler characterisation

Aerosol mass concentration measurement in calm air during sampler characterisation

Continuous method for pulverized coal combustion emission mass monitoring

A method for pulverized coal combustion aerosol mass concentration measurements with a dilution system and tapered element oscillating microbalance (TEOM) is introduced. The TEOM microbalance method gives continuous information about mass concentration variations in a minute scale time resolution. Particle upper size limit is chosen with a cyclone.

Technical note The effects of the harmattan dust on air conductivity and visibility at Ibadan, Nigeria

Measurements of aerosol mass concentration M, air conductivity λ and visibility V were made during part of the Harmattan season of 1978–79; the mean values for January—a peak Harmattan month—being 293 μg m −3, 3.9 × 10 −14 (Ωm) −1 and 8.8 m, respectively. Relations are obtained between M and λ, and M and V for the locality; the later being M( μg m −3) = 1600 V −0.62( km).

A comparison of techniques for automatic aerosol mass concentration measurement

Mass concentrations of atmospheric aerosols measured by an integrating nephelometer and a piezo electric quartz crystal particle mass monitor have been compared in detail. The results were evaluated relative to a filtration method as standard and the three techniques were found to be equivalent to within ±25 μ/ 3 over the range 30–200 μ/m 3. The advantages and disadvantages of these instruments for medium term (daily) averages and short term peak concentration measurements are discussed. Differing responses of the methods to small and large particles revealed a sampling error related to wind velocity. A drop in sampled mass concentration by up to a factor of two due to wind speeds up to 9 m/sec was observed.