Aerosol sources

The paper summerizes the experimental data on the equilibrium factor, F, the free fraction, fp, the attachment rate to the room air aerosol, X, the recoil factor,, and the plateout rates of the free, qf, and the attached, q3, radon daughters, determined in eight rooms of different houses. In each room several measurements were carried out at different times, with different aerosol sources (cigarette smoke, stove heating etc.) and under low (v<0.3 It1) and moderate (0.3[Pg.288]

The mean value of the equilibrium factor F measured in houses without aerosol sources was 0.3 t 0.1 and increased up to 0.3 by additional aerosol particles in the room air. The fraction of the free radon daughters had values between fp = 0.06-0.13 with a mean value near 0.1. Only additional aerosol sources led to a decrease of f - values below 0.05. 

The rooms without aerosol sources and low ventilation rate (v<0.3 hf1 ) had low aerosol concentrations (2 103 - 104 cm-3) due to the small influence of the higher aerosol concentrations outdoors (aerosols by traffic and combustions) (Table la). In this case the aerosol in the room air was aged by coagulation and plateout and had less condensation nuclei of smaller sizes (d<100 nm). Rooms with a moderate ventilation show higher particle concentrations ((1-5) 10 cm 3) (Table Ila). With aerosol sources in a room (Table III) the aerosol concentrations can increase to 5 105 particles/cm3. The relative error of the measured particle concentration is in the order of 15% primary determined by the uncertainties of the absolute calibrations of the condensation nuclei counter. 

The equilibrium factor F in low ventilated rooms without aerosol sources varied between 0.2 and 0.4 (Table la) with an average value near 0.30 a similar value as reported by Keller and Folkert, 1983, and by Wicke and Porstendorfer, 1982. In rooms with additional aerosol sources an average F-value between 0.4 and 0.5 was obtained (Table III). An error of about 20 % can be estimated for the equilibrium factor. 

The free fraction of the radon daughters f measured in rooms with lo i/ ventilation and no aerosol sources shows values between 0.06 - 0.15 (Table lb) with a mean value near 0.10. In this case the values of the attachment rates X range between 20 hr and 40 hr. The fp-values < 0.05 were obtained in rooms with aerosol sources, which always had values of the attachment rate > 100 It1 (Table III). 

The results of these measurements show that the fraction of the free radon daughters in rooms with low and moderate ventilation and without any aerosol sources are higher (fp = 0.06 - 0.15) than proposed in literature (Jacobi and Eisfeld, 1980 ICRP 32, 1981 NEA, 1983). A mean value of 10 % (fp = 0.1) was determined. Only additional aerosol sources in a room such as cigarette smoke, cooking, candle light or stove heating led to a decrease of the fp-value below 0.05. 

Table III. The aerosol particle concentration (Z), the equilibrium factor (F), the free fraction (fp), the attachment parameters (X,B,d), the plateout rates (qf, qa) and the recoil factor (ri), obtained in lowly ventilated rooms with aerosol sources.

The mean value of the equilibrium factor F in houses i/as 0.3 0.1 without aerosol sources and can increase up to 0.3 with cigarette smoke in the room air. 

Then the unattached fraction was calculated in each measurement and was found to be between. 05 and. 15 without aerosol sources in the room and below. 05 in the presence of aerosol sources. The effective dose equivalent was computed with the Jacobi-Eisfeld model and with the James-Birchall model and was more related to the radon concentration than to the equilibrium equivalent radon concentration. On the basis of our analysis a constant conversion factor per unit radon concentration of 5.6 (nSv/h)/(Bq/m ) or 50 (ySv/y)/(Bq/m3) was estimated. 

Our analysis shows that the unattached fraction in the domestic environment is between. 05 and. 15 without any aerosol sources in the room and can decrease below. 05 in the presence of aerosol sources. These values are much larger than assumed by James (1984) (fp-3%) and by the NEA-report (1983) (fp=2%). However the few experimental results reported in the literature agree with our findings. Bruno (1983) found an unattached fraction of. 07 and Reineking (1985), Shimo (1984) and Duggan (1969) measured about. 10. The last two results are calculated by means of the room model from the reported unattached Po-218 concentrations. 

A comparison of the aerosol sources listed in Tables III and IV suggests that the second distribution listed in Table III having a d of 0.39 wn corresponds to the second distribution listed in Table IV and represents aerosols arising from coagulation and condensation. Similarly, distribution 5 in Table III apparently coincides with the third seunple of aerosols listed by Whitby and Cantrell as arising from natural and man-made sources. It is conceivable that the first distribution listed in Table III corresponds to the first source listed in Table IV. This statement cannot be made with certainty, however, since the resolution of the SEN technique used was not high enough. 

Hopke, P.K. The Application of Factor Analysis to Urban Aerosol Source Resolution, ACS SYMPOSIUM SERIES, No. 167, 1981. 

The Application of Factor Analysis to Urban Aerosol Source Resolution... 

Among these techniques are various forms of a statistical method called factor analysis. Several forms of factor analysis have been applied to the problem of aerosol source resolution. These different forms provide several different frameworks in which to examine aerosol composition data and Interpret it in terms of source contributions. 

After the number of factors have been determined, it is necessary to interpret the factors as physically real sources. For the applications of this approach to aerosol source identification (4,6-10), the reduced size matrix of eigenvectors was rotated in such a way as to maximize the number of values that are zero or unity. This rotation criterion, called "simple structure" is described in the appendix of reference 4. 

Gatz, D. F. Identification of Aerosol Sources in the St. Louis Area Using Factor Analysis, J. Appl. Met., 1978, 1, 600. 

Secondary , in Chemical Composition of the Atmospheric Aerosol Source/Air Quality Relationships, E.S. Macias and P.K. Hopke, Eds., A.C.S. Symposium Series, 1981. 

Review of the Chemical Receptor Model of Aerosol Source Apportionment... 

There are two general types of aerosol source apportionment methods dispersion models and receptor models. Receptor models are divided into microscopic methods and chemical methods. Chemical mass balance, principal component factor analysis, target transformation factor analysis, etc. are all based on the same mathematical model and simply represent different approaches to solution of the fundamental receptor model equation. All require conservation of mass, as well as source composition information for qualitative analysis and a mass balance for a quantitative analysis. Each interpretive approach to the receptor model yields unique information useful in establishing the credibility of a study s final results. Source apportionment sutdies using the receptor model should include interpretation of the chemical data set by both multivariate methods. 

Urban aerosols are complicated systems composed of material from many different sources. Achieving cost-effective air particle reductions in airsheds not meeting national ambient air quality standards requires identification of major aerosol sources and quantitative determination of their contribution to particle concentrations. Quantitative source Impact assesment, however, requires either calculation of a source s impact from fundamental meteorological principles using source oriented dispersion models, or resolving source contributions with receptor models based on the measurement of characteristic chemical and physical aerosol features. Q)... 

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