Acidic Depositions in Wyoming
Recent reports indicate that two-thirds of the United States and
one-half of Canada receive acidic depositions. Commonly referred to
as "acid rain", acidic depositions have been defined as precipitation
that has a pH level less than 5.65, the theoretical natural acidity
level of distilled water in equilibrium with atmospheric carbon
dioxide. Acidic depositions can include rain, sleet, snow, fog, dew,
dry particles, and gases. The major causes of acidity in acidic
depositions are sulfates, nitrates, and possibly organic anions.
Chemical analyses indicate that petroleum and coal burning, and ore
smelting may all be important emission sources for these chemicals in
While not currently perceived as a problem in Wyoming, acidic
depositions have been found in this State and others in the Rocky
Mountain Region. And, industrial developments are planned in the
region (e.g., gas sweetening plants near the Overthrust Belt of
southwestern Wyoming) that will have atmospheric emissions of
potentially acid forming chemicals. Consequently, concerns about
potential adverse impacts from acidic depositions in Wyoming are
increasing. The following report is a result of requests from the
Wyoming Game and Fish Department and the Wyoming Environmental Quality
Council to the Wyoming Water Research Center for information and
advice useful in addressing these concerns.
Acidic depositions have been suggested to produce adverse effects
upon a number of resources. In this document are reviewed the current
state of the scientific knowledge for the known effects of acidic
depositions on soils, Crops, forests, surface-water quality, aquatic
organisms, human health, and cultural materials. Overall, the most
significant effects have been suggested to occur in poorly buffered
Although no actual effects have been observed in the State, a
number of general conclusions can be made about the possible effects
by acidic depositions on the resources of Wyoming.
- Soils - Within the non-mountainous regions of Wyoming,
natural conditions have created alkaline soils generally
considered as insensitive to acidic depositions.
Potentially sensitive soils would be limited to thin, poorly
buffered soils present on slowly-weathered bedrock, such as
granite. These areas are generally confined to higher
elevations in some mountain ranges.
- Crops - Since virtually all crops in Wyoming are grown in
relatively arid areas thar have insensitive alkaline soils,
acidic depositions should have no adverse effects. Such
depositions, in fact, may produce fertilizing effects.
- Forests - Forest tree spedes which have been suggested to
be potentially sensitive to acidic depositions in the
northeastern United States also grow in Wyoming. These
species include spruce, firs, and pines. There are no data,
however, demonstrating whether Wyoming forests are
potentially sensitive to acidic depositions.
- Surface-water quality - While few data are generally
available, enough exist to indicate that some high mountain
areas contain a relatively high proportion of lakes
potentially sensitive to acidic depositions. Such lakes
have alkalinity levels less than 200 µeq/l. For example,
one data set indicates that about 70 percent of the lakes
over 9,000 feet elevation in the Wind River Range may be
potentially sensitive to acid inputs. Because of natural
characteristics, lakes and streams at lower elevations and
in non-mountainous regions are generally well buffered and
are, therefore, considered insensitive to any probable
future inputs of acidic depositions. It should be
emphasized, however, that present acidic deposition rates in
Wyoming do not appear to pose a threat to Wyoming surface
- Aquatic organisms - Wyoming lakes and streams that are
potentially sensitive to acidification by acidic depositions
contain many aquatic species potentially sensitive to
acidity. If these waters were to become acidic (pH levels
below 6.0), many of these species would be adversely
affected. Depending on the degree of acidification, some
species populations could become locally extinct. However,
acidic deposition rates would have to be many times greater
than currently reported for the State before these affects
would be likely to occur.
- Human health - While potential adverse effects to human
health from acidic depositions have been hypothesized,
actual effects have not been documented for any human
population. Therefore, although the potential may exist for
acidic depositions to cause health effects in Wyoming, the
possibility of such effects developing is unknown and
probably very small.
- Cultural materials - Cultural materials exist in Wyoming
that are potentially sensitive to acidic depositions, but
these materials are primarily located in the more populated,
non-mountainous, relatively arid regions of the State.
Therefore, potentially adverse effects from future acidic
depositions in Wyoming will likely have little detectable
effects on most cultural materials of concern.
In this review a number of research needs were identified as
valuable in helping to understand the possible significance of acidic
depositions in Wyoming. Lists of environmental monitoring and
research projects were then presented that could help supply needed
information. From these, various projects we·e recommended for a
Wyoming sponsored monitoring and research program to investigate
acidic depositions. Considerations involved in selection of the
projects included probability of impacts, information gaps, data
applicability, feasibility of completion, and costs.
The suggested monitoring and research program addresses five
general areas viewed as important to an overall State sponsored
- It must be determined whether acidity levels in atmospheric
depositions are great enough to potentially cause future
- Sources emitting potentially acid forming chemicals, both
in-state and out-of-state, must be identified and quantified
to help in determining where controls may be needed and
where downwind resources may be impacted.
- Potentially sensitive natural and cultural resources must be
identified to determine the location and the extent of
resources potentially at risk from acidic depositions.
- To definitively determine whether acidic depositions
adversely impact any resource requires establishment of a
monitoring and research program to determine possible trends
of change for these resources and actual cause(s) of these
- As a result of efforts under the above four categories,
additional actions will be defined that can help to evaluate
potential effects of and mitigations and management measures
for acidic depositions in Wyoming.
In relation to these five areas, nine monitoring and research
projects are suggested:
- Compile and evaluate existing atmospheric deposition data.
- Monitor present atmospheric depositions.
- Inventory emission sources.
- Develop instate/out-of-state source budgets for acids in
- Develop inventories of resources at potential risk, based on
- Select study sites for long-term collection of monitoring
and baseline environmental data.
- Monitor for long-term changes in surface water quality and
- Monitor for short-term changes in surface water quality
following snowmelts and major rainfalls.
- Conduct soil surveys in watersheds surrounding the long-term
Of these, many can readily be completed using existing data, and
several can be rapidly undertaken with Federal funding.
Due to the widespread concern about possible impacts from acidic
depositions, many groups and individuals have potential interests and
involvements in a State sponsored monitoring and research program.
These potentially include 21 organizations in the Executive Branch of
State government, 10 Standing Committees in the State Legislative
Branch, over 25 Federal organizations, and a variety of industrial
groups, environmental and conservation organizations, plus other
miscellaneous groups. The possible interests and involvements of
these organizations and individuals are briefly discussed.
It is concluded that. acidic depositions pose an unique
environmental problem. Assessing the significance of the potential
impacts to Wyoming will require an extensive state-wide monitoring and
research program, coordinated by a single authority. Only through the
cooperation among many State and Federal agencies, and a selection of
other interested groups and individuals, can the present or future
impacts from acidic depositions in Wyoming be accurately assessed.
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