Characterization of cloud-water and precipitation chemistry and deposition at elevated sites in central and southern California

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:7018087

Collett, Jr, J L

The chemical composition of cloudwater samples collected in the Sierra Nevada Mountains of central California between 1985 and 1988 was dominated by NH{sub 4}{sup +}, NO{sub 3}{sup {minus}}, and SO{sub 4}{sup 2{minus}}. The balance between these three species usually was responsible for determining the cloudwater pH. The composition of cloudwater in Sequoia National Park is determined primarily by the concentrations of precursor aerosol and soluble gases. Park aerosol concentrations were observed to increase during the approach of a cold front. Over 265 hours of cloud interception were observed, during a one-year period of continuous monitoring, at 1860 m elevation in Sequoia National Park. Most interception was observed at elevations above 1500 m produced during the passage of convective clouds, associated with cold fronts, across the Sierra. Deposition of pollutants, including acid,s to the forest canopy at the elevations above 1500 m was estimated to be significant, relative to inputs from precipitation and dry deposition. Cloudwater interception may, in fact, be the dominant deposition mechanism for NH{sub 4}{sup +} and NO{sub 3}{sup {minus}}, particularly for isolated trees or ridgetop canopies where wind speeds are higher and cloudy air parcels can impact directly on foliar surfaces. A precipitation study, conducted in the South Coast Air Basin surrounding Los Angeles during the winter of 1987, illustrated the rapid scavenging of pollutants from the air column by falling raindrops. Results of a comparison of N(V) and S(VI) deposition during an extended precipitation event with the atmospheric loading of these species over the basin prior to the event suggested that both species were produced in the atmosphere during the rainstorm. Evidence was seen for in-cloud production of SO{sub 4}{sup 2{minus}}, but not NO{sub 3}{sup {minus}}.

• Research Organization: California Inst. of Tech., Pasadena, CA (USA)
• OSTI ID: 7018087
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
01 COAL, LIGNITE, AND PEAT
CLOUDS
CHEMICAL COMPOSITION
ACID RAIN
AEROSOLS
AMMONIUM COMPOUNDS
ATMOSPHERIC CHEMISTRY
CALIFORNIA
CANOPIES
DEPOSITION
LEAVES
METEOROLOGY
MONITORING
MOUNTAINS
NATURE RESERVES
NITRATES
PH VALUE
SCAVENGING
SULFATES
TREES
WASHOUT
ATMOSPHERIC PRECIPITATIONS
CHEMISTRY
COLLOIDS
DISPERSIONS
FEDERAL REGION IX
NITROGEN COMPOUNDS
NORTH AMERICA
OXYGEN COMPOUNDS
PLANTS
PRECIPITATION SCAVENGING
RAIN
RESOURCES
SEPARATION PROCESSES
SOLS
SULFUR COMPOUNDS
USA
540120* - Environment
Atmospheric- Chemicals Monitoring & Transport- (1990-)
010900 - Coal
Lignite
& Peat- Environmental Aspects