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Title: Low hygroscopicity of ambient fresh carbonaceous aerosols from pyrotechnics smoke

Pyrotechnics (fireworks) displays are common for many cultures worldwide, with Independence Day celebrations occurring annually on July 4th as the most notable in the U.S. Given an episodic nature, fireworks aerosol properties are poorly characterized. Here we report observations of optical properties of fresh smoke emissions from Independence Day fireworks smoke sampled at Los Alamos National Laboratory, New Mexico U.S.A. on 4–5 July 2016. Aerosol optical properties were measured with a photoacoustic extinctiometer (PAX, DMT, Inc., Model 870 nm) at low RH < 30% and a humidity controlled nephelometry system (Ecotech, Inc., 450 nm Aurora). ‘Dry’ light scattering coefficient (σsp) increased from background < 15 Mm –1 reaching 120 Mm –1 (450 nm) as a 2-min event peak, while the absorption coefficient increased from background of 0.5–4.4 Mm –1 (870 nm). The event peak occurred at 00:35 on 5 July 2016, ~3 h after local fireworks events, and decreased to background by 04:00 on 5 July 2016, showing well mixed aerosol properties. A notable result is that the aerosol hygroscopic response, as characterized by the ratio of wet to dry light scattering or f(RH = 85%), declined to 1.02 at the peak fireworks influence from a background ~1.7. Strong wavelengthmore » dependence of light scattering with Ångström exponent ~2.2 throughout the event showed a size distribution dominated by sub-micrometer particles. Likewise, single scattering albedo at 870 nm remained constant throughout the event with ω = 0.86 ± 0.03, indicating light absorbing carbon, though not dominant, was mixed with organic carbon. Subsequent laboratory testing with ground-level sparklers showed that pyrotechnics smoke can generate a strong hygroscopic response, however. As confirmed with chemical analysis, the chemistry of the fireworks was key to defining the hygroscopic response. As a result, sparkler smoke was dominated by salt species such as hygroscopic potassium chloride while it lacked the black powder explosives in aerial fireworks that contribute organic and elemental carbon to its non-hygroscopic smoke.« less
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [3] ; ORCiD logo [3]
  1. New Mexico Institute of Mining and Technology, Socorro, NM (United States)
  2. New Mexico Institute of Mining and Technology, Socorro, NM (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-17-25199
Journal ID: ISSN 1352-2310
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Atmospheric Environment (1994)
Additional Journal Information:
Journal Name: Atmospheric Environment (1994); Journal Volume: 178; Journal Issue: C; Journal ID: ISSN 1352-2310
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Workforce Development for Teachers and Scientists (WDTS) (SC-27); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Earth Sciences; Aerosols; Pyrotechnics; Air Quality; Smoke; Hygroscopicity; Health; Climate; Fireworks smoke; Ultrafine particles; Fine mode aerosols; Carbonaceous aerosols; Photoacoustic extinctiometer (PAX); Nephelometer
OSTI Identifier:
1419756