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consistent with Joachim et al. ( I ) , who reported that in most dust storms particles measured under similar conditions &re in the range of 1-20 ym. The mean diameter obtained from the AMM and CNC data during the dust storm increased from 0.1 hm on a typical day to 0.8 ym under some storm conditions. Although the AMM-CNC method can only provide an indication of the actual mean particle diameter, our experimental evidence suggests that a significant fraction of the desert aerosol is in the submicron range. The mean diameter obtained from the EASA measurements also increased under storm conditions, but only up to 0.25 ym. While the D , (EASA) value ignores the contribution of large particles to the mean diameter, it also suggests that a substantial fraction of the desert particles are in the submicron range. The mean particle diameter size of
I
Figure 6. Diurnal variation in mean particle diameter obtained by EASA (asterisks)and by the AMM-CNC method (circles).
particle diameter during a typical dust storm, is more consistent with our experimental data. Acknowledgment
D,(AMM/CNC) = ( ~ V T / [ T ( C N C ) ] ) ~ ' ~
(8)
A continuous presentation of mean particle diameter as estimated by both methods for a period of 3 consecutive days is presented in Figure 6. The comparison between the results from the two methods is rather interesting. Throughout most of the day, with the exception of the late night hours, the agreement between the two methods is reasonable to good. However, during the late night hours and also during dust storms, no correlation between the diameter calculated from the EASA data and the AMM-CNC data could be found. While the EASA data suggested that the mean particle diameter is always in the range of 0.06-0.15 pm, the AMM-CNC methods estimated that during late night hours D , is usually from 0.2 to 0.4 ym and in some cases even higher. This discrepancy is thought to be the result of the late-night formation of large particles due to coagulation. Some of the Iarge particles were too large to be measured by the submicron size analyzer, and their contribution to the mean diameter has not been take into account. It should also be noted that the accuracy of the late-night measurements is reduced simply because of low concentration of particulates in the air. Dust Storms. On several occasions during this study, a moderate dust-storm episode occurred. During such an episode, the T S P concentration increased from an average 30min daily maximum of 80 pg/m3 to more than 2000 pg/m3 for a period of several hours. The automatic dust monitor was not ready for such episodes, which requires a much shorter sampling time, and in many cases the information obtained was incomplete. From the partial information, which proved to be valid, it was found that the large fraction of the particle mass (from 40% to 80%)was in the respirable range. This is
We thank Mr. M. Turner, the head of the Municipal Environmental Protection Unit, for his long and hard effort of initiating the Air Quality Control program in this city, Mr. B. Malenky for his technical assistance, and Mr. A. Conway for his assistance in preparing this manuscript for press. Literature Cited (I) Joachim, J. H.; Alexander, M.; Ashbel, D. J. Appl. Meteorol. 1973, 12, 792. (2) Ganor, E. Ph.D. Dissertation, The Hebrew University, Jerusalem, Israel, 1975. (3) Aerosol Technology Committee, ATHA Guide for Respirable Mass Sampling. A m . Znd. Hyg. Assoc. J . 1970,31, 133. (4) Fuchs, N. A. "Mechanism of Aerosols"; Pergamon Press: New York, 1964; p 27. (5) Husar, R. B.; Whitby, K. T.; Lin, B. Y. H. J. Collord Interface Sci. 1972,39, 177. (6) Parker, R. D.; Buzzard, G. H.; Dzubay, T. G.; Bell, J. P. Atmos. Environ. 1977,11,617. (7) Cahill, T. A.; Ashbaugh, L. L.; Barone, J. B.; Elder, R. A.; Feeney, P. J.; Flocchini, R. G.; Goodart, C.; Shadoan, D. J.; Wolfe, G. W. J . Air Pollut Control Assoc. 1977,27,675. (8) Bullin, J. A.; Moe, R. D.; Miculka, J. P. "The Measurements and Analysis of Resuspended Dust from Roadways in Texas"; College Station, TX, 1979, Texas Transportation Institute Research report 528-IF. (9) Baum, E. J.; Pitter, R. L. "The Impact of Emission from Transportation Sources on Air Quality's Atmospheric Aerosol"; State of Oregon, Highway Division, Air Quality Study 5149-621-10,1976. (10) Whitby, K. T.; Husar, R. B.; Lin, B. H. Y. J. Colloid Interface Sci. 1972,39, 177. (11) Corn, M. "Air Pollution"; Stern, A. C., Ed.; Academic Press: New York, 1976; Chapter 3. Received for review August 1, 1980. Revised manuscript received March 23,1981. Accepted J u l y 17,1981. This work was supported by resources from the Municipality of Jerusalem for which we are grateful.
Correction 1980, Volume 14 Yoshiaki Ishizu: General Equation for the Estimation of Indoor Pollution. Page 1255. The last term of eq 9 should be
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