Processes determining cloudwater composition: Inferences from field measurements

Conference · Mon Sep 01 04:00:00 EDT 1986

OSTI ID:6907785

Daum, P H

Mechanisms considered for the composition of cloudwater include: (1) nucleation scavenging of aerosol; (2) scavenging of soluble gases; and (3) reactive scavenging of less soluble gases. The efficiency of aerosol scavenging by nucleation was examined by use of a variety of physical and chemical techniques. The data are consistent with essentially complete (>90%) scavenging of both particle mass and sulfate by cloudwater. Similarly, comparisons of interstitial HNO/sub 3/ and cloudwater nitrate concentrations are consistent with essentially complete scavenging of nitric acid by cloud droplets. Studies of reactive scavenging focussed on the aqueous phase reactions of SO/sub 2/ with H/sub 2/O/sub 2/ and O/sub 3/. Measurements suggest that the O/sub 3//SO/sub 2/ reaction is slow with respect to cloud lifetimes; the H/sub 2/O/sub 2//SO/sub 2/ reaction appears to be rapid for representative atmospheric conditions. H/sub 2/O/sub 2/ concentrations ranged from less than 0.1 ..mu..M to 100 ..mu..M; equivalent gas phase concentrations from aqueous phase concentrations, cloud liquid water content, and H/sub 2/O/sub 2/ solubility typically ranged from less than 0.05 ppB and 1 ppB during the summer, and less than 0.05 ppB during winter. A strong negative correlation between H/sub 2/O/sub 2/ and interstitial SO/sub 2/ concentrations is consistent with the rapid and quantitative in-cloud reaction of SO/sub 2/ with H/sub 2/O/sub 2/ in which either these species acts as the limiting reagent. Low level stratus clouds in winter exhibited high concentrations of interstitial SO/sub 2/ and very low concentrations of cloudwater H/sub 2/O/sub 2/. No direct evidence for in-cloud oxidation of NO or NO/sub 2/ to HNO/sub 3/ was found.

• Research Organization: Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6907785
• Report Number(s): BNL-38800; CONF-8609193-2; ON: DE87001463
• Country of Publication: United States
• Language: English

Related Subjects

500200* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACIDIFICATION
ATMOSPHERIC CHEMISTRY
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMISTRY
CLOUDS
FLUIDS
GASES
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
MATHEMATICAL MODELS
NAPAP
NITROGEN COMPOUNDS
NITROGEN OXIDES
OXIDES
OXYGEN COMPOUNDS
OZONE
PARTICLES
PARTICULATES
PEROXIDES
PRECIPITATION SCAVENGING
SEPARATION PROCESSES
SULFUR COMPOUNDS
SULFUR DIOXIDE
SULFUR OXIDES