Mechanisms and rates of atmospheric deposition of selected trace elements and sulfate to a deciduous forest watershed. [Roles of dry and wet deposition concentrations measured in Walker Branch Watershed]

Technical Report · Fri Jun 01 04:00:00 EDT 1979

DOI:https://doi.org/10.2172/5997611· OSTI ID:5997611

Lindberg, S. E.; Harriss, R. C.; Turner, R. R.; Shriner, D. S.; Huff, D. D.

The critical links between anthropogenic emissions to the atmosphere and their effects on ecosystems are the mechanisms and rates of atmospheric deposition. The atmospheric input of several trace elements and sulfate to a deciduous forest canopy is quantified and the major mechanisms of deposition are determined. The study area was Walker Branch Watershed (WBW) in eastern Tennessee. The presence of a significant quantity of fly ash and dispersed soil particles on upward-facing leaf and flat surfaces suggested sedimentation to be a major mechanism of dry deposition to upper canopy elements. The agreement for deposition rates measured to inert, flat surfaces and to leaves was good for Cd, SO/sub 4//sup =/, Zn, and Mn but poor for Pb. The precipitation concentrations of H/sup +/, Pb, Mn, and SO/sub 4//sup =/ reached maximum values during the summer months. About 90% of the wet deposition of Pb and SO/sub 4//sup =/ was attributed to scavenging by in-cloud processes while for Cd and Mn, removal by in-cloud scavenging accounted for 60 to 70% of the deposition. The interception of incoming rain by the forest canopy resulted in a net increase in the concentrations of Cd, Mn, Pb, Zn, and SO/sub 4//sup =/ but a net decrease in the concentration of H/sup +/. The source of these elements in the forest canopy was primarily dry deposited aerosols for Pb, primarily internal plant leaching for Mn, Cd, and Zn, and an approximately equal combination of the two for SO/sub 4//sup =/. Significant fractions of the total annual elemental flux to the forest floor in a representative chestnut oak stand were attributable to external sources for Pb (99%), Zn (44%), Cd (42%), SO/sub 4//sup =/ (39%), and Mn (14%), the remainder being related to internal element cycling mechanisms. On an annual scale the dry deposition process constituted a significant fraction of the total atmospheric input. (ERB)

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 5997611
• Report Number(s): ORNL/TM-6674
• Country of Publication: United States
• Language: English

Related Subjects

500200* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
AIR POLLUTION
ATMOSPHERIC PRECIPITATIONS
CADMIUM
CONTAMINATION
DATA
DATA FORMS
DEPOSITION
EARTH ATMOSPHERE
ELEMENTS
ENVIRONMENTAL TRANSPORT
EXPERIMENTAL DATA
FORESTS
GRAPHS
INFORMATION
ISOLATED VALUES
LEAD
MANGANESE
MASS TRANSFER
METALS
MINERAL CYCLING
MONITORING
NORTH AMERICA
NUMERICAL DATA
OXYGEN COMPOUNDS
POLLUTION
SEASONAL VARIATIONS
SOUTHEAST REGION
SULFATES
SULFUR COMPOUNDS
TENNESSEE
TRACE AMOUNTS
TRANSITION ELEMENTS
USA
VARIATIONS
WATERSHEDS
ZINC