Atmospheric deposition to forests

Conference · Sat Jan 01 04:00:00 EST 1983

OSTI ID:5579590

Lovett, G M

The processes of wet and dry deposition in forests are described with special reference to the northeastern United States and to chemical species important in acidic deposition. For wet deposition, it is noted that background or natural pH values are probably in the range of 5 to 7, but current pH values over most of the eastern United States are less than 4.6. Both meteorological and chemical factors influence the acidity of precipitation. The best long-term data record for the northeastern United States (that of the Hubbard Brook Experimental Forest in central New Hampshire) indicates no significant trend in rainfall acidity in the period of record (1964 to 1980), but the data do indicate that nitric acid has increased in importance relative to sulfuric acid in its contribution to that acidity. Deposition decreases along a southwest to northeast transect through the northeastern states. Deposition to high-elevation ecosystems is severalfold higher than deposition to nearby lowland ecosystems because of increased rain and snowfall, the effect of cloud water deposition, and possibly increased dry deposition. Theory and the few measurements available suggest particle deposition to be important for alkaline materials, such as soil dust, and gaseous deposition to be important for H/sup +/, N, and S. The importance of dry deposition relative to wet deposition increases with increasing proximity to pollution source areas. The forest canopy influences atmospheric deposition to the forest floor by taking up or releasing nutrients and strong acidity, releasing weak acidity, and trapping dry depositions. 60 references, 2 figures.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 5579590
• Report Number(s): CONF-8308115-2; ON: DE84003384
• Country of Publication: United States
• Language: English

Related Subjects

500200* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACID RAIN
ATMOSPHERIC PRECIPITATIONS
DEPOSITION
FORESTS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
NITRIC ACID
PARTICLES
PH VALUE
RAIN
SULFURIC ACID
TOPOGRAPHY