The Effects of Acid Rain on Vermont's Forests

Abstract

Forest ecosystems are a cornerstone in the foundation of Vermont's rural landscapes. The health of Vermont's forests plays a major role in the economic, social and ecologically stability of Vermont. The forests provide Vermont with wildlife habitat, biological diversity, forestry jobs, numerous recreational opportunities, and a beautiful landscape.Vermont’s economic longevity depends on the health of Vermont’s forests for tourism especially in the fall, recreational opportunities with majestic landscapes, Agriforestry products such as timber and maple syrup. Vermont takes pride in its heritage of being a landscape that is economically based on recreation, tourism, agriculture, and forestry products. It is essential to maintain these values so future generations are able to enjoy the beauty of Vermont's rural landscapes.

Emission of pollutants from the combustion of fossil fuels are attacking the forest health in Vermont. The Midwest states of theUnited States use fossil fuels for many industrial and commercial applications. The pollutants that are emitted in the Midwest rise into the atmosphere and are carried to Vermont through the atmospheric circulatory patterns of North America. The long range transport of these constituents has forced many northeastern states and Canadian provinces to take strategic actions to combat the effects of acidic deposition on forest ecosystems. The Acid Rain Action Plan of 1998 was developed by The Committee on the Environment of The Conference of New England and Eastern Canadian Premiers. The goal of the conference committee was to work on regional problems such as acid rain and mercury.

What is Acid Precipitation?
Figure 2. pH Scale, Hubbard Brook Research Foundation ( HBRF, 2002)

The pH Scale: 1 is acidic, 7 is neutral, and 12 is alkali

The pH scale measures the hydrogen ion concentration using a logarithmic scale; normal rainwater has a pH of 5.5 because of many natural sources such as volcanoes that release natural emissions of carbon dioxide which increase the hydrogen ion concentration of the rainwater. Rainwater that is below 5.5 is considered acidic. The hydrogen ion concentration in rainwater is further increased when overwhelming amounts of anthropogenic emissions that are added to the atmosphere.

"The pH scale measures how acidic or basic a substance is. It ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic, and a pH greater than 7 is basic. Each whole pH value below 7 is ten times more acidic than the next higher value. For example, a pH of 4 is ten times more acidic than a pH of 5 and 100 times (10 times 10) more acidic than a pH of 6. The same holds true for pH values above 7, each of which is ten times more alkaline (another way to say basic) than the next lower whole value. For example, a pH of 10 is ten times more alkaline than a pH of 9" (EPA 2002c).

The Clean Air Act

In 1970 the Clean Air Act Amendments were passed and substantially increased the federal authority and responsibilities of controlling air pollution.(Powell, 1998) The 1977 amendments added a "mid-course" correction to the law. Congress later ex paned regulatory requirements for stationary and mobile sources in 1990 addressing problems like acid rain and toxic pollutants. The Clean Air Act is an extensive and detailed set of laws that addresses the problems associated with air pollution. The requirements listed in the Clean Air Act are established by the federal government (by the Environmental Protection Agency (EPA)) and properly administered by the state. The Clean Air Act has three general categories of regulatory programs designed to limit air pollution.

1) National Ambient Air Quality Standards: National uniform minimum standards for common air pollutants which endanger public health or welfare and which are derived from numerous and diverse sources. These standards are minimum standards and no state can be less stringent.However, states can impose stricter standards.

2) State Implementation Plans: Specifies to the EPA how states plan to achieve and maintain their air quality standards that are no less stringent than the National Ambient Air Quality Standards.

3)Best Available Control Technology: Nationally uniform requirements for new stationary sources of air pollutants. New Stationary sources of air pollutants are forced to install technology-forcing equipment that is the best available control technology for limiting emissions based on the volume of pollutants which can be emitted per unit of plant input or output (Powell, 1998)

The Clean Air Act has significantly decreased the emissions of sulfur oxides, carbon monoxide, and volatile organic compounds since the early 1970’s. However nitrogen oxide emissions in the United States has been steadily increasing since the 1940’s. Nitrogen oxides are the only air pollutant that has persistently increased through the Clean Air Act. One of the reasons believed for the ever increasing nitrogen oxides emissions is that total amount of automobile emissions has increased.

New England States and Eastern Canadian Premiers Actions to minimize Acidic Deposition

Acid Rain Action Plan of 1997-1998, New England Governors and Eastern Canadian Premiers

The Acid Rain Action Plan is an international strategic plan to minimize emissions of mercury and acidic deposition in the Northeast region of North America. The Acid Rain Action Plan is a “comprehensive and coordinated plan for further reducing emissions of sulfur dioxide and oxides of nitrogen which contribute to th e problem of long range transport of air pollutants acid deposition…(NEG,ECP, 1998).” The plan also includes a research and monitoring agenda, which targe ts the goal of this of regional data analysis to better understand the impacts of regional deposition and the process of current air pollution control programs. The basis of action for The New England Governors and The Eastern Canadian Premiers was that watersheds and forests of “particularly high elevation forests, in the northeastern United States and Eastern Canada are especially sensitive to the effects of acid deposition due to the predominance of thin poorly buffered soils throughout the region. While significant reduction of sulfur emissions have taken place in the region and across North America, resulting in significant reductions in wet deposition levels, remaining emissions of both sulfur and nitrogen compounds, particularly those generated in the Midwestern U.S. and central Canada, continue to negatively impact this region (NEG,ECP, 1998).”

The Acid Rain Partnership, Data Without Borders, 2001 Progress Report, Commitee on the Environmnet of the Confernce of New England Governors and Eastern Canadian Premiers.

The 2001 progress report data without borders shows the combined efforts of the United States and Canada to minimize acidic deposition. This report does go into more detail about the specific goals of the committee. One of the committee's goals is to introduce a system of real-time data for emissions and acidic deposition in North America. So that they can better understand the causes and effects of acidic deposition. Combined with the goal of emissions reductions, the committee is devoted to reduceing the amount of acidic deposition that falls on northeastern North America.

Formation of Acid Rain

Fossil fuels such as coal, oil, and natural gas are combusted to provide energy for transportation, home heating, commercial manufacturing, utility plants, smelting plants and various industrial processes. When fossil fuels are combusted for energy needs, the combustion produces by-products such as volatile organic compounds, sulfur dioxides and nitrogen oxides. When these compounds are emitted into the atmosphere they mix with water molecules in clouds and form sulfuric, carbonic, and nitric acid compounds. The moisture of the cloud along with the sulfuric, carbonic and nitric acids begins to condense and acidic rain, snow, or fog precipitates out of the atmosphere. The precipitation then falls to the earth's surfaces at an increased level of acidity due to the added constituents. The increased acidity of the wet deposition, inhibits growth rates by making forest ecosystems more susceptible to the effects of climatic extremes, droughts, and pest infestation (HBRF,2002).

Figure 4. Sources of Acidic Precipitation, Environmnetal Protection Agency (EPA 2002a)

Figure 4. represents the sources of acidic precipitation; particulate matter and wet deposition are both natural and anthropogenic sources. Both natural and anthropogenic emissions cause acidic precipitation.

Acid Deposition: "The process by which acidic particles, gases, and precipitation leave the atmosphere. More commonly referred to as acid rain, acid deposition has two components: wet and dry deposition." (EPA 2002b)

Dry Deposition: "The settling of gases and particles out of the atmosphere. Dry deposition is a component of acid deposition, more commonly referred to as acid rain." (EPA 2002b)

Wet Deposition: "The process by which chemicals are removed from the atmosphere and deposited on the Earth's surface via rain, sleet, snow, cloudwater, and fog." (EPA 2002b)

Vermont Acid Precipitation Monitoring Program sites are used to measure pollution constituents in the air. These sites are monitoring sites that collect air pollution data and are use as indicators to measure the progress of the Clean Air Act Amendments. The picture on the left portrays the typical method used for sampling of the pH of precipitation.

Figure 5.Mt. Mansfield deposition pH, Vermont Monitoring Cooperative (VMC, 2000)

The Vermont Acid Precipitation Monitoring Program is a branch of the Vermont Monitoring Cooperative which has been tracking the acidic deposition that has fallen at Mt. Mansfield site from 06/06/80 to 12/31/00 and at the Underhill station from 06/07/83 to 12/31/00. The Mt. Mansfield and Underhill monitoring station's data indicate that acidic deposition has decreased over the past two decades. The trend-lines for the Mt. Mansfield and Underhill monitoring stations indicate that the pH of precipitation at these two sites has increased. This means that the pH of the precipitation has increased towards a more neutral level. Figures 5. and 6.

Figure 6. Underhill deposition pH, Vermont Monitoring Cooperative (VMC,2000)

Morrisville acid deposition data indicates that acidic deposition over the past two decades has increased. The trend line for the Morrisville pH precipitation data indicates that the pH of the precipitation has decreased. This means that the pH of the Morrisville precipitation has become more acidic over time.

Figure 7. Morrisville deposition pH, Vermont Monitoring Cooperative (VMC, 2000)

Soil pH Data

Figure 8. Johnson State College, Bio 255 Fundamentals of Ecology, Fall 2001

In the fall of 2001 a line intersect survey was preformed by the Biology 255 Fundamentals of Ecology class at Johnson State College. This data reflects the current soil pH of these study sites. Most of the soils in this region seem to be well buffered. The data suggests that most of the study areas have a soil pH ranging from 6 to 7 in these regions.

United States Emission Trends

Figure 9. United States Emission Trends, Environmental Protection Agency, (EPA, 2002d)

From the time period of 1940-1970 volatile organic compounds (VOC) and sulfur oxides emissions had steadily increased and in 1970 peaked. Since the Clean Air Act Amendments of 1970, the emissions trend of these constituents has significantly decreased. Nitrogen oxides are the only constituent that has had an increase in emission short tons in the last decade.

Figure 10. United States Carbon Monoxide Trends, Environmental Protection Agency, (EPA, 2002d)

Carbon monoxide emission of the United States have decreased due to the progress of the Clean Air Act in the early 1970’s From the time period of 1970 to 1990 national carbon monoxide emissions have significantly decreased. And in the last decade variable shifts in national carbon monoxide emissions indicates that this pollutant has been minimized to levels that existed pre 1950.

Why does New England receive acidic precipitation?

The Northeastern United States has acidic deposition for several reasons. Emissions from smelting operations and utilities plants in most states east of the Mississippi are significant contributors to the Northeast air quality problems. Figure 11. National sulfur dioxide emissions from utilities represents how much pollution was emitted from these states in 1980, 1990, 1996, and 1997. Comparatively the eastern United States has the highest levels of sulfur dioxide emissions from utilities plants.

Figure 11. Sulfur Dioxide Emissions from Utlities Plants, Environmental Protection Agency (EPA, 1999).

The sulfur dioxide and other emissions are carried by prevailing wind patterns that blow across the United States in an easterly fashion. The Tropical Air stream and the Pacific Air stream (figure 12) transport emissions to the Northeast from source regions in the midwest United States.

Figure 12. North American Airstreams,

New England Governors and Eastern Canadian Premiers. (ENGECP,2001)

Figure 13.National pH deposition 1996, National Atmospheric Deposition Program/National Trends Network, 1996 (NADP/NTN,1996)

Figures 13. 1996 and 14. 1997 represents the average pH of rainfall for each National Atmospheric Deposition Program site. The Northeast received much higher levels of acidic deposition than the rest of the nation. The Northeast's poor air quality is directly related to the Midwest states.

Figure 14.National pH deposition 1997, National Atmospheric Deposition Program/National Trends Network, 1997 (NADP/NTN,1997)

The Affects of Acidic Precipitation on Forest Ecosystems

Figure 15. Acid Deposition Effects On Trees, Hubbard Brook Research Fundation, (HBRF, 2002)
Current research at the Hubbard Brook research forests in New Hampshire and Pennsylvania have demonstrated that acid rain is a significant problem to forest ecosystems. National sulfur dioxide, volitile organic compounds, and carbon dioxide have declined as a result of the Clean Air Act however, nitrogen oxide emissions have increased figures 9 and 10. The Hubbard Brook Foundation has concluded that acid deposition has "altered, and continues to alters soils in a number of ways:"(HBRF, 2002)

This is a list prepared by the (EPA 2001) of things that individuals can do to use less energy.

"Individuals can contribute directly by conserving energy, since energy production causes the largest portion of the acid deposition problem. For example, you can:

TAKE ACTION NOW

Choose from two prewritten letters available at the link below to send to a Vermont Representative about current air quality legislation.

"TAKE ACTION NOW" Write to a Vermont Representative

Summary

Acidic deposition in Vermont is a major problem among forest ecosystems. Forest ecosystems loss their resilience and become more vulnerable to infestation, droughts, and climatic stresses when exposed to precipitation that is below normal.

The Clean Air Act has had significant success in lowering national emissions of carbon monoxide, sulfur dioxide and volatile organic compounds. Nitrogen oxides on the other hand have steadily increased since the establishment of the Clean Air Act. The Vermont Monitoring Cooperative data indicates that the acidic deposition that falls on Mt. Mansfield and Underhill has decreased. While Morrisville data indicates that acidic deposition at this site has increased.

Even though the pH of the Underhill and Mt. Mansfield stations has decreased over the last twenty years, the actual pH of the average precipitation is acidic. Natural rain water has a pH of 5.5 because volcanoes naturally emit carbon dioxide into the atmosphere. The carbon dioxide emissions causes carbonic acids to form and lower the pH of the precipitation. In recent years the pH of these two stations was close to 4.5. The Morrisville station has seen decreases in the pH of precipitation, meaning that the precipitation has become more acidic over time. The pH of the precipitation at the Morrisville station is close to 4.5 as well.

These acidic precipitation conditions cause soils to become acidified. Acidic deposition causes calcium, magnesium and aluminum to leached from soils. The soils then are able to accumulate nitrogen and sulfur compounds from the acidified precipitation. Acid deposition continues to effect forest ecosystems because aluminum toxic. The aluminum is taken up by the tree's root and it affects growth rates and resilience. These conditions cause spruce trees and sugar maple to be defoliated.

Acid rain significantly impacts forest ecosystems in Vermont. The acid rain makes them more acceptable to environmental stresses. It is apparent that acid rain currently influences Vermont's forest ecosystems and will influence them for many years to come. Poorly buffered soils in this region have caused chronic acidification of this regions soils. Meaning that they are saturated with acidic solutions and they will not stablize untill the acid deposition in the notheast United States decrease considerably

References:

Committee on the Environment of the Conference of New England Governors and Eastern Canadian Premiers. (ENGECP,2001), 2001, The Acid Rain Partnership, Data Without Borders Retrieved from the World Wide Web on 24 Mar 2002. from http://www.cmp.ca/DataWoBorders.pdf

Environmental Protection Agency (EPA), 2002a. Environmental Issues, Acid Rain, Sources of Acid Precipitation. Retrieved from the World Wide Web on 28 Jan 2002. from http://www.epa.gov/airmarkets/acidrain/index.html

Environmental Protection Agency (EPA), 2002b. Definitions, Acid Rain. Retrieved from the World Wide Web on 30 Jan 2002. from http://www.epa.gov/airmarkets/glossary.html

Environmental Protection Agency (EPA), 2002c. What is pH?. Retrieved from the World Wide Web on 5 Feb 2002. from http://www.epa.gov/airmarkets/acidrain/ph.html

Environmental Protection Agency (EPA), 2001. What Society can do about Acid Rain.Retrieved from the World Wide Web on 13 Feb 2002. from www.epa.gov.airmarkets/acidrain/society/

Environmental Protection Agency (EPA), 2002d. National Emission Inventory, Air Pollutant Emission Trends. Retrieved from the World Wide Web on 12 Mar 2002 from http://www.epa.gov/ttn/chief/trends/

Environmental Protection Agency (EPA), 1999. Progress Report on the EPA Acid Rain Program. Retrieved from the World Wide Web on Mar 15 2002 from http://www.epa.gov/airmarkt/progress/arpreport/acidrainprogress.pdf

H ubbard Brook Research Foundation (HBRF), 2002. Acid Rain Revisted, Advances in scientific understanding since the passage of the 1970 and 1990 Clean Air Act Amendments. Retrieved from the World Wide Web on 4 Feb 2002. from http://www.hbrook.sr.unh.edu/hbfound/report.pdf

National Atmospheric Deposition Program/National Trends Network, (NADP/NTN), 1996, Hydrogen Ion Concentration as pH From Measurements Made At The central Analytical Lab, 1996 Retrieved from the World Wide Web on 24 Mar 2002. from http://nadp.sws.uiuc.edu/isopleths/maps1997/phlab.gif

National Atmospheric Deposition Program/National Trends Network, (NADP/NTN), 1997, Hydrogen Ion Concentration as pH From Measurements Made At The central Analytical Lab, 1997 Retrieved from the World Wide Web on 24 Mar 2002. from http://nadp.sws.uiuc.edu/isopleths/maps1997/phlab.gif

National Forest Health Monitoring Program, (NFHMP), Vermont, 2000 Forest Health Highlights. Retrieved from the World Wide Web on 25 Mar 2002 from http://na.fs.fed.us/spfo/fhm/fhh/fhh-00/vt/vt_00.pdf

New England Governors and Eastern Candian Premiers, (ENG,ECP), 1998, Acid Rain Action Plan.Retrieved from the World Wide Web on 25 Mar 2002 from www.cmp.ca/neg/reports/acid-e.htm

Powell,Frona M., 1998, Law and the Environment, West Educational Publishing Company, USA. 245-246

Vermont Monitoring Cooperative (VMC),Vermont Acid Precipitation Monitoring Program. Retrieved from the World Wide Web on 12 Mar 2002 from http://vmc.snr.uvm.edu/subproj.asp?ID=11.

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