TY - JOUR
T1 - On the sensitivity of particle size to relative humidity for Los Angeles aerosols
AU - McMurry, Peter H.
AU - Stolzenburg, Mark R.
PY - 1989
Y1 - 1989
N2 - A TDMA system (Tandem Differential Mobility Analyzer; Rader D.J. and McMurry P.H. J. Aerosol Sci. 17, 771-787, 1986) was used to measure the sensitivity of particle size to relative humidity for monodisperse Los Angeles aerosols. Measurements were made at Claremont, CA on 13 days between 19 June and 3 September 1987, in conjunction with the Southern California Air Quality Study (SCAQS). The particle sizes that were studied ranged from 0.05 μm to 0.5 μm diameter at ambient relative humidity (typically 45-65%). The data provide clear evidence that these atmospheric aerosols were externally mixed. Monodisperse ambient aerosols were often found to split into nonhygroscopic (no water uptake) and hygroscopic portions when humidified. An average of 30% of the particles in the 0.2-0.5 μm range were nonhygroscopic. However, the proportion of the particles that was nonhygroscopic varied considerably from day to day and was, on occasion, as high as 70-80% of the particles. There was no clear evidence for nonhygroscopic 0.05 μm particles, but the data are not definitive on this point. The data also show that for the hydrophilic aerosol fraction, the larger particles (0.4-0.5 μm) grew more when humidified than did smaller particles (0.05-0.2 μm). As relative humidities were increased from 50% to 90%, particle diameters grew by average factors of 1.46 ±0.02 (for 0.5 μm particles), 1.49 ± 0.08 (0.4 μm), 1.19 ± 0.08 (0.2 μm) and 1.12 ± 0.05 (0.05 μm). Similarly, when particles were dried from 50% RH to 6-10% RH, particle diameters changed by factors ranging from 0.94 ± 0.03 (0.5 μm) to 0.98 ± 0.01 (0.05 μm).
AB - A TDMA system (Tandem Differential Mobility Analyzer; Rader D.J. and McMurry P.H. J. Aerosol Sci. 17, 771-787, 1986) was used to measure the sensitivity of particle size to relative humidity for monodisperse Los Angeles aerosols. Measurements were made at Claremont, CA on 13 days between 19 June and 3 September 1987, in conjunction with the Southern California Air Quality Study (SCAQS). The particle sizes that were studied ranged from 0.05 μm to 0.5 μm diameter at ambient relative humidity (typically 45-65%). The data provide clear evidence that these atmospheric aerosols were externally mixed. Monodisperse ambient aerosols were often found to split into nonhygroscopic (no water uptake) and hygroscopic portions when humidified. An average of 30% of the particles in the 0.2-0.5 μm range were nonhygroscopic. However, the proportion of the particles that was nonhygroscopic varied considerably from day to day and was, on occasion, as high as 70-80% of the particles. There was no clear evidence for nonhygroscopic 0.05 μm particles, but the data are not definitive on this point. The data also show that for the hydrophilic aerosol fraction, the larger particles (0.4-0.5 μm) grew more when humidified than did smaller particles (0.05-0.2 μm). As relative humidities were increased from 50% to 90%, particle diameters grew by average factors of 1.46 ±0.02 (for 0.5 μm particles), 1.49 ± 0.08 (0.4 μm), 1.19 ± 0.08 (0.2 μm) and 1.12 ± 0.05 (0.05 μm). Similarly, when particles were dried from 50% RH to 6-10% RH, particle diameters changed by factors ranging from 0.94 ± 0.03 (0.5 μm) to 0.98 ± 0.01 (0.05 μm).
KW - CCN
KW - Hygroscopic aerosols
KW - activation
KW - aerosol water content
KW - condensation
KW - externally mixed aerosols
KW - hydrophobic aerosols
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U2 - 10.1016/0004-6981(89)90593-3
DO - 10.1016/0004-6981(89)90593-3
M3 - Article
AN - SCOPUS:0024476659
SN - 0004-6981
VL - 23
SP - 497
EP - 507
JO - Atmospheric Environment (1967)
JF - Atmospheric Environment (1967)
IS - 2
ER -