Possible Sampling Artifact in Real Time Particle Size Distributions Related to Sampling Rate

Figures & data

FIG. 1 Aliasing caused by instrument sampling rate slower than the signal. The sampling rate is three times slower than the signal.

FIG. 2 Ultrafine particle number concentrations and size distributions when MAP was parked at roadside on 7 October 2004. (a) Concentrations (cm^{− 3}) of 10.8, 22.1, 29.4, and 52.3 nm particles. (b) Number size distributions at specific times (marked as A, B, C, and D). (c) Time-averaged and synthesized spectra for the period 14:45:00–14:45:29. (d) Time-averaged and synthesized spectra for the period 14:45:30–14:45:59.

FIG. 3 Ultrafine particle number concentrations and size distributions when MAP was traveling on road on 7 October 2004. (a) Concentrations (cm^{− 3}) of 10.8, 22.1, 29.4, and 52.3 nm particles. (b) Number size distributions at specific times (marked as A, B, C and D). (c) Time-averaged and synthesized spectra for the period 11:28:00–11:28:29. (d) Time-averaged and synthesized spectra for the period 11:28:30–11:28:59.

FIG. 4 Ultrafine particle number concentrations and size distributions in Tseung Kwan O Tunnel on 7 October 2004. (a) Concentrations (cm^{− 3}) of 10.8, 22.1, 29.4, and 52.3 nm particles. (b) Number size distributions at specific times (marked as A, B, C, D, and E). (c) Time-averaged and synthesized spectra for the period 16:34:00–16:34:29. (d) Time-averaged and synthesized spectra for the period 16:34:30–16:34:59.

FIG. 5 Synthesized size distributions based on MAP 1-s roadside data, 7 October 2004. (a) and (b) 3s, (c) 6s.

FIG. 6 Synthesized size distributions based on MAP 1-s tunnel data, 7 October 2004. (a) and (b) 3s, (c) 6s.