Impact of Acid Compounds

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Impact of Acid Compounds On Forested Ecosystems
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Copper Hill, Tennessee
Photograph used by permission from the Copper
Hill Museum, Ducktown, Tennessee
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Copper Hill, Tennessee

• Open pit smelting and harvesting of trees to make
  charcoal devastated the valley. The refining of
  copper released high concentrations of sulfur
  dioxide and sulfuric acid in the air.

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Impacts to Lichens

• Gymnoderma lineare is an endangered species.
• Chemical analysis of the tissue revealed the
  dying colonies have a higher sulfur content than
  healthy colonies.

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Shining Rock Wilderness
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Types of Fine Particles
Data from Shining Rock IMPROVE site as noted
in WinHaze software program.
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Effect of Sulfates
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Shining Rock Wilderness
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By 2010 vehicle use will grow 70 and electricity
use 50. By 2040 vehicle use will grow 170 and
electricity 100.
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1990 Clean Air Act Amendments
Annual Mean Wet Sulfate Deposition1989 through
1991
Annual Mean Wet Sulfate Deposition2001 through
2003
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Nutrient Cycling

• Bases such as Ca2, Mg2, K are essential for
  vegetation growth.
• Bases are return to the soil when falling leaves
  and woody material are decomposed.
• Bases originate from weathered rocks and
  windblown dust.
• In the soil bases maintain an ionic balance by
  attaching to negatively charged soil particles.

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Nutrient Cycling
Acid particles deposited from the atmosphere come
in contact with the vegetation and soils.
Chemical reactions will occur before the soil
water is transported to a stream or lake.
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Nutrient Cycling
Sulfuric acid deposited from the atmosphere will
separate into hydrogen ions (H) and a sulfate
particle in the soil. The hydrogen ions will
partially displace the bases. Furthermore, soils
in the southeast are known to retain sulfates.
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Nutrient Cycling
Sulfates move into the soil solution. In order
to maintain an ionic balance an equivalent amount
of positive charged ions (bases) will adhere to
the sulfates.
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Nutrient Cycling
High levels of acid deposition result in an
increase in H ion which results in a pH decrease
of the soil.
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Nutrient Cycling
If the pH decreases below 4.5 then Al3 will
become mobile. Al3 enters the roots more easily
than other bases which results in a nutrient
deficiency. The deficiency is compounded
because Al3 kills the fine roots so even less
bases are absorbed.
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Nutrient Cycling
Soils that have become severely acidified will
have increased H ion and Al3 in the soil
solution, which in large quantities are toxic to
stream and lake aquatic biota.
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Areas at Risk

• Geology (lithology) influences the amount of
  bases available in the soil.
• Elevation higher elevations have lower
  microbial activity, have shallower soils, and
  have more cloud deposition.
• Sulfur present in the rocks being weathered to
  form the soils and/or being retained by the soils
  as it is deposited from the atmosphere.
• Overstory conifer types are more acidic.

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Stream Water Chemistry

• One measure of stream health (and the health of
  the watershed) is the acid neutralizing capacity
  (ANC).
• ANC Sum Bases Sum Acids
• Bases calcium, potassium, magnesium and sodium
• Acids sulfate, nitrate, and cloride

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Stream Classification for Trout Populations
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Synoptic Survey - ANC Results
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Episodic Acidification
Storm
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Population Estimates - Mean
1 National Stream Survey results
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Sensitive Geology
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MAGIC Sites (N66)
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Historical ANC Trend
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Historical ANC Trend
Percentages are expressed as the percent of the
modeled streams (n66) that were simulated to
have ANC below the target level in the selected
year.
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ANC Trend Linville Gorge
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Critical Load

• The quantitative estimate of an exposure to
  one or more pollutants below which significant
  harmful effects on specified sensitive elements
  of the environment do not occur according to
  present knowledge. (Nilsson and Grennfelt 1988)
• Critical loads can be developed for any
  pollutants.

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Critical Load Development
Critical loads are defined for specific
indicators and effects.
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Attain a Stream ANC 20 by 2100 for Linville
Gorge Wilderness
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Setting Target Loads
Note for some sites we may not be able to
achieve the desired ANC within a specified time
period. Utilized the Model of Acidification of
Groundwater in Catchments (MAGIC) model.
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Estimating The Critical Load From A Water Sample
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Symptoms of Nutrient Deficiency
Spruce and beech suffering from magnesium or
potassium deficiency can develop a yellowing of
the older foliage Typically, the yellowing trees
will be scattered through out the forest stand.
Managed forest in the Central Black Forest in
Germany. Taken from Forest Decline
Cause-Effect Research in the United States of
North America and Federal Republic of Germany
(1988).
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Mitigation
Taken from Effects of Acid Deposition on the
Forests of Europe And North America (1990).
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