A Technique for Rapid Estimation of the Charge Distribution of Submicron Aerosols under Atmospheric Conditions

Figures & data

FIG. 1 Schematic diagram of parallel DMA system used to measure the aerosol mobility and size distributions in the estimation of the aerosol charge distribution. Example measurements of indoor air with negative ionizer.

FIG. 2 Measured mobility distribution (DMA-2, single cycle) of indoor air with negative ionizer compared to fitted mobility distribution (calculated from DMA-1 measurement and different charge distributions).

FIG. 3 Charge distribution of 200 nm particles for different measurement environments.

FIG. 4 Total number of negatively charged particles (10.5–1100 nm) measured with DMA-1 versus that measured with DMA-2 for different atmospheric environments.

FIG. 5 Hour-averaged measured mobility distribution (DMA-2) compared to fitted mobility distribution for ambient indoor air. (Error bars shown are of the standard deviation of the single cycle measurements.)

FIG. 6 Hour-averaged measured mobility distribution (DMA-2) compared to fitted mobility distribution for negative ionizer. (Error bars shown are of the standard deviation of the single cycle measurements.)

FIG. 7 Hour-averaged measured mobility distribution (DMA-2) compared to fitted mobility distribution for measurements made at ground level downwind of a HV overhead powerline. (Error bars shown are of the standard deviation of the single cycle measurements.)

TABLE 1 Correlation parameters of the total number of negatively charged particles (10.5–1100 nm) measured with (DMA-1) and without neutralization (DMA-2) for single cycle measurements made in the 3 environments investigated

	DMA-1 / DMA-2 correlation
Measurement	N	Linear regression line	R ^2
Lab	1207	N −neut = 1.10N −meas – 33	0.991
Lab with ionizer	129	N −neut = 3.75N −meas – 45	0.919
Powerline	40	N −neut = 0.48N −meas + 37	0.887

FIG. 8 Variation of 1/x before, during, and after the use of a negative ionizer.

TABLE 2 Asymmetry ratios and correlation coefficients for different time resolutions for a 1 h period under ambient indoor conditions and with the use of a negative room ionizer

	Indoor ambient		Indoor with ionizer
	(01:00 to 02:00)		(10:30 to 11:30)
Time resolution	Average x	R ^2	Average x	R ^2
1 h	0.896	0.995	0.0128	0.992
30 min	0.898	0.994	0.0124	0.992
15 min	0.900	0.992	0.0136	0.992
6 min	0.900	0.991	0.0123	0.992
3 min	0.901	0.986	0.0122	0.989