The various conditions of pyrolysis method have been developed for separation and determination of both organic and elemental carbon contents in airborne particulate matter because of its facility and simplicity. The following several conditions for pyrolysis were studied. (1) (in inert gas) Organic carbon ≤ 650 °C < Elemental carbon (in the presence of Oxygen) (2) (in inert gas) Organic carbon ≤ 450 °C < Elemental carbon (in the presence of Oxygen) (3) (in inert gas) Organic carbon ≤ 400 °C < Elemental carbon (in the presence of Oxygen) (4) (in air) Organic carbon ≤ 350 °C < Elemental carbon (in air) (5) (in air) Organic carbon ≤ 300 °C < Elemental carbon (in air) These conditions of pyrolysis method were applied to airborne particulate matter at Tsukuba, Pepperbush (NIES CRM No. 1) and Vehicle Exhaust Emission particulates (NIES CRM No. 8). Consequently, it was found that the pyrolysis method in inert gas (item (1)(2)(3)) has a tendency to overestimate elemental carbon content in samples because of carbonization during the removing procedure of organic carbon. On the other hand, strict control is required for the pyrolysis conditions in air (item (4)(5)) because of the quick ashing of the samples. In conclusion, the pyrolysis method in helium carrier gas at heating temperature of 500 °C and heating period of 10 minutes is recommended for separation of carbonaceous content in airborne particulate matter.
Collection performance of an electret filter, which carries permanent electric charges on its fibers, was studied experimentally. The filter, made of polypropylene, is 4 mm in thickness. Fibers are cylindrical of 33 μm in diameter. Experiments were carried out at the filtration velocity of 28 and 40 cm/s. Collection efficiency of the electret filter is high when it is clean but decreases as smoke particles are loaded. The collection efficiency of a single electret fiber is ten times greater than that of a conventional filter. The charge density of the fiber, and the relationship between collection efficiency and pressure drop in the filter are also discussed.
Angular distributions of light scattered by aerosols (phase function) and the aerosol size distributions were simultaneously measured by a polar-nephelometer and two kinds of particle size analyzers, the electrical aerosol analyzer (WAA) and the optical particle counters (OPC) , respectively. Twelve phase functions were compared with those constructed by the measured size distributions using the assumed complex indices of refraction. Then, most likelihood values of the complex index of refraction and the synthesized size distribution were estimated using the least square method. The dependence of the size distributions by the OPC on the complex index of refraction were investigated in order to infer the real size distributions. As a result : 1) It is possible to estimate the most likelihood value of the complex index of refraction. In this period, the mean values of the complex index of refraction, m=mr-mi·i, were estimated to be 1.5l to 1.54 for mr and 0.012 to 0.026 for mi. But, in order to obtain the optically effective complex index of refraction consistent with the real size distribution, it might be necessary to assume the complex indices of refraction respective to each mode of the bimodal distributions. 2) The size distribution for r < 0.158 μm by the WAA can describe well the optical phenomena by aerosols under usually hazy conditions. Aerosol particles within this reliable range have a share in only about 40 % of the total extinction (or scattering) coefficient. The size distribution for 0.158 < r < 0.5 μm, however, seems to have a large error optically. 3)The OPC has to precisely discriminate the particle size at least because of the optically high response of its distribution shape, and moreover to count the exact number density. It is important to examine carefully the contribution of the size distribution for the unknown regions, r < 0.15 μm apparently, and the effect of the complex index of refraction to optical informations when estimating them using the size distribution only by the OPC.