Final Report: Linking Watershed-Scale Indicators of Changes in Atmospheric Deposition to Regional Response patterns

EPA Grant Number: R825762
Title: Linking Watershed-Scale Indicators of Changes in Atmospheric Deposition to Regional Response patterns
Investigators: Kahl, Jeffrey , Ballard, S. , Cosby, Bernard , Fernandez, Ivan , Ludwig, P. , Mageean, Deirdre , Norton, Sharon , Rustad, Lindsey
Institution: University of Maine
EPA Project Officer: Hiscock, Michael
Project Period: September 1, 1997 through August 31, 2000 (Extended to September 30, 2001)
Project Amount: $623,395
RFA: Water and Watersheds Research (1997) RFA Text |  Recipients Lists
Research Category: Water , Water and Watersheds

Objective:

The main objectives of this research project were to: (1) address the status, trends, and relationships involved in the response to ambient acidic deposition in high-elevation lakes, and the response to experimental acidification at the Bear Brook Watershed in Maine; and (2) develop the findings of this research in a format that facilitates its use by policymakers, to help them make decisions guided by the appropriate scientific information.

Component II was designed to link the scientific and technical aspects of the research (Component I) to the practical needs of decision-makers and resource managers. In practice, the demand for the output of Component II was determined to be low by the target audiences: state agencies, environmental nongovernmental organizations (NGOs), and the forest products industry. In Year 3, we changed direction with the approval of our Environmental Protection Agency (EPA) Project Officer, and in addition to the original objectives, we evaluated the predicted comparative response of lakes in Maine compared to those in the Adirondack region of New York, both of which are populations shown to be impacted by acidic deposition.

This research project was part of a program addressing scientific and societal needs by investigating the processes and indicators of response and recovery at the Bear Brook Watershed in Maine (BBWM) and in high-elevation lakes in Maine (HELM). Information from this project was used in the 2002 EPA assessment of the 1990 Clean Air Act Amendments (CAAA) to ascertain trends in ecological response, and to determine the effectiveness of the CAAA in influencing these trends. Therefore, this research had direct influence on future policy and legislation as Congress prepares to debate the re-authorization of the Clean Air Act.

Summary/Accomplishments (Outputs/Outcomes):

Anthropogenic Acidity in Atmospheric Deposition. NOx and SOx emissions from combustion of fossil fuels react with water in the atmosphere to produce "acid rain," containing small amounts of nitric and sulfuric acids. This acidity (and the resulting sulfate and nitrate) may travel hundreds or thousands of miles before being deposited as dryfall or wet deposition. Maine receives precipitation that ranges in mean annual pH from 4.6 to 4.7. This pH range is believed to be at least twice as acidic as in prehistoric time.

Goals of the Clean Air Act Amendments. The 1990 Clean Air Act Amendments set target reductions for sulfur emissions from industrial sources as a means of reducing the acidity in deposition (nitrogen reductions are not yet required by the CAAA). The intended effect of the reductions in precipitation acidity was to decrease the acidity of acidic and low alkalinity waters and thereby improve their biological condition.

Acid-Base Status of Surface Waters in Maine. Approximately 100 clearwater Maine lakes are estimated to be acidic based on surveys conducted by EPA and the University of Maine. Many more lakes and streams have low buffering capacity and are considered "sensitive" to acidification, and some of these have been at least somewhat acidified in the past 150 years. Most of the acidic lakes are found in two subpopulations: 90 high-elevation lakes (located above 600 meters) and 150 seepage lakes (located in sand and gravel deposits). These groups of "canary" lakes are ideal for trend monitoring because of the: (1) availability of long-term data, (2) hydrologic sensitivity to acidification, and (3) general lack of major local human disturbances in their watersheds. The high-elevation lakes, in particular, have been acidified by atmospheric deposition to an extent similar to the lakes in the Adirondack region of NY. The responses of high-elevation lakes to ambient levels of acidic deposition were compared to the response of experimental levels of acidic deposition at the BBWM.

There has been no population-wide acid-base recovery in the high-elevation lakes, despite substantial declines in sulfate concentrations in precipitation and lakewater. This unexpected result suggests that further reductions in sulfur or nitrogen deposition may be necessary for recovery in these lakes. Moreover, conductance (a measure of total ion concentration) in these lakes declined by an average of 8 percent in the past decade. Calcium has declined an average of 10 percent. The increasingly dilute character of lakes by itself means that while no population-wide acid-base recovery is evident, there appears to be a population-wide increase in the vulnerability of these lakes to environmental stressors, such as acidic deposition.

At BBWM, the response of the reference stream reflected the dilution response in the high-elevation lakes, although magnified. The decline in base cations was stronger, and thus there was significant acidification, despite a large decline in sulfate concentrations. Nitrate also declined substantially. The experimental watershed responded to increased nitrogen and sulfur loading that is intended to induce the changes caused by acidic deposition, and is revealing different short- and long-term responses after more than a decade of experimentation. Ultimately, these findings are setting up the ideal recovery experiment for the treated watershed in future years. The treated watershed showed an increase of leaching of the base cations for several years, but then the concentrations began to decline, paralleling the base cation decline evident in the reference watershed. It is not known if this is due to impoverishment in the soils caused by the enhanced deposition loading, or due to another response related to the decline of base cations in waters throughout the Northeast. There is clear evidence for a difference in soil exchangeable base cation pools between watersheds that is comparable in mass to the excess base cation mass exported in the treated stream, compared to the reference.

Soils as Predictors of Surface Water Acid-Base Status. Soils were sampled along transects in 20 of the HELM population of lakes to evaluate potential relationships between soil chemical properties and lake chemistry. In addition, at the BBWM, intensive soil studies were conducted in both the reference and treated watersheds. For the larger population of HELM lakes, few strong correlations were evident between mean soil chemistries and lake chemistry. This is in part a result of the relatively narrow range of soil types encountered in these high elevation ecosystems. Base cation and aluminum soil properties were the best correlated to lake chemistries, suggesting a relatively direct linkage between soil exchangeable cation processes and acid-base status of associated surface waters. Although the population of lakes studied for soil relationships was sorted based on lake NO3 concentrations, no relationship was evident for the nitrogen properties studied. This supports the notion that linkages between N deposition and changes in surface water chemistry as well as ecosystem function are complex and often long-term processes that are poorly understood. At the BBWM study site, there was clear evidence of the long-term additions of N and S to the treated watershed when compared to the reference watershed for both cation chemistry and nitrogen. However, the clearest differences between watersheds attributable to the treatments were, once again, in soil base cation and aluminum properties.

Predicted Responses During Recovery. The Tracking Analysis Framework (TAF) model was developed during the National Acid Precipitation Assessment Program in the 1980s. TAF integrates aspects of emissions, atmospheric transport, and effects on lake and soil acidity, fish biology, the economics of recreational fishing, human health, and visibility. The effects of deposition on lake water chemistry in TAF are modeled with a reduced-form of the Model of Acidification of Groundwater in Catchments (MAGIC).

There was greater variation in the predictions of acid neutralizing capacity (ANC) and calcium from the 100 MAGIC runs for the Adirondack lakes than the HELM lakes. In contrast, the fit of the reduced form models to the MAGIC output was better for the Adirondacks with respect to ANC and similar for both sets of lakes for calcium. For the HELM lakes, TAF underpredicted the ANC values of several lakes with low ANC values and overpredicted ANC for a number of lakes with high ANC values.

Predicted ANC values increased from 2000 to 2030 under all four future deposition scenarios, with a range of 1.9 to 35.7 µeq/L. The recovery of some lakes under the modest deposition reduction already falls in this range. Although predicted calcium concentrations generally decreased across all HELM lakes between 2000 and 2030, the differences in the two years were relatively small and ranged from -0.1 to -10.8 µeq/L. This range is less than already observed in many lakes. Both aquatic aluminum concentrations and soil base saturation generally decreased over the 30-year period.

Complications for "Trend" Assessment. Declines in atmospheric deposition of sulfate have led directly and rapidly to widespread declines in sulfate concentrations in Maine surface waters, similar to the response in the rest of the northeastern United States. This response is one measure of the intended recovery in surface waters, and marks a success of the CAAA and efforts by industry in reducing SO2 emissions. However, the anticipated recovery (decrease) in acidity corresponding to the decline in sulfate has been minimal at best. Based on results that include assessment of soil chemistry at BBWM and in a subset of high-elevation lakes, there are at least four factors that are important in understanding the recovery, or lack of recovery, in surface waters:

· Declining surface water concentrations of base cations (e.g., calcium, magnesium) have offset the decline in sulfate, resulting in a lack of recovery in acidity. In some cases, acidification has accompanied the decline in sulfate during the 1990s. The cause and effect of the relationship between base cations and sulfate must be better understood as part of long-term monitoring of surface waters.

· Climate change and climate variability may obscure trends in surface water chemistry, or may even counteract the effects of decreased deposition (e.g., by inducing a decline in base cations to offset a decline in sulfate).

· Continued atmospheric loading of nitrogen may be influencing the acid-base status of watersheds in undetermined ways. Concentrations of nitrogen in deposition are now equivalent to sulfur in the northeastern United States, due to the decline in sulfur emissions. Concentrations of nitrate have remained at 1980s levels in the high-elevation lakes and some streams at Acadia National Park, but overall there has been a regional decline in nitrate in surface waters during the 1990s. If nitrate had not declined, additional waters may have acidified. The role of nitrogen in acidification and recovery may be the most difficult to understand because of the many complex geochemical and biological mechanisms involved, including the potentially long-term nature of their mechanisms of change.

· Increases in dissolved organic carbon in most lake populations may have contributed natural organic acidity to surface waters, further complicating our interpretation of the response to the CAAA. This factor is an important long-term research question that is not well understood. Documentation of the response of watersheds to changes in atmospheric deposition may take longer than the timeframe of available data, or the onset of recovery may have a lag time. This uncertainty can only be resolved with long-term data.

Information Dissemination. This research project indicates that the efforts to enhance the interactions between stakeholders and scientists must be guided by three considerations that relate to the culture of the stakeholders: (1) the needs and values of the stakeholders; (2) the political climate in which they operate; and (3) an understanding of how they assimilate information into their decision making. These factors vary across groups, and thus, different models are needed to disseminate information for different cultures. Given the limited resources, it is therefore essential to choose where and how to focus efforts to disseminate information and engage stakeholders. For example, the forest products industry stakeholders were satisfied with the present level of communication with scientists, in part because their short-range outlook based on corporate quarterly reporting was not concerned with long-term potential impacts from acidic deposition. In contrast, government and environmental NGOs were interested in using scientific information directly, and they also were interested in understanding the economic and human impacts of watershed-level effects.


Journal Articles on this Report : 18 Displayed | Download in RIS Format

Other project views: All 84 publications 27 publications in selected types All 20 journal articles
Type Citation Project Document Sources
Journal Article Aber J, McDowell W, Nadelhoffer K, Magill A, Bernston G, Kamakea M, McNulty S, Currie W, Rustad L, Fernandez I. Nitrogen saturation in temperate forest ecosystems: hypotheses revisited. BioScience 1998;48(11):921-934. R825762 (Final)
  • Abstract: JSTOR
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  • Journal Article Campbell JL, Hornbeck JW, Mitchell MJ, Adams MB, Castro MS, Driscoll CT, Kahl JS, Kochenderfer JN, Likens GE, Lynch JA, Murdoch PS, Nelson SJ, Shanley JB. Input-output budgets of inorganic nitrogen for 24 forest watersheds in the Northeastern United States: a review. Water, Air, and Soil Pollution 2004;151(1-4):373-396. R825762 (Final)
  • Abstract: SpringerLink
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  • Journal Article Fernandez I, Rustad L, David M, Nadelhoffer K, Mitchell M. Mineral soil and solution responses to experimental N and S enrichment at the Bear Brook Watershed in Maine. Environmental Monitoring and Assessment 1999;55(1):165-185. R825762 (1999)
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  • Abstract: SpringerLink
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  • Journal Article Fernandez IJ, Simmons JA, Briggs RD. Indices of forest floor nitrogen status along a climate gradient in Maine, USA. Forest Ecology and Management 2000;134(1-3):177-187. R825762 (Final)
  • Full-text: Science Direct
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  • Abstract: Science Direct
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  • Other: Science Direct
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  • Journal Article Kahl J, Norton S, Fernandez I, Rustad L, Handley M. Nitrogen and sulfur input-output budgets in the experimental and reference watersheds, Bear Brook Watershed in Maine. Environmental Monitoring and Assessment 1999;55(1):113-131. R825762 (1999)
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  • Abstract: SpringerLink
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  • Journal Article Mason CF, Norton SA, Fernandez IJ, Katz LE. Deconstruction of the chemical effects of road salt on stream water chemistry. Journal of Environmental Quality 1999;28(1):82-91. R825762 (Final)
  • Abstract: JEQ
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  • Journal Article Norton SA, Cosby BJ, Fernandez IJ, Kahl JS, Church MR. Long-term and seasonal variations in CO2: linkages to catchment alkalinity generation. Hydrology and Earth System Sciences 2001;5(1):83-91. R825762 (Final)
  • Full-text: HESS PDF
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  • Abstract: HESS
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  • Journal Article Norton S, Kahl J, Fernandez I. Altered soil-soil water interactions inferred from stream water chemistry at an artificially acidified watershed at Bear Brook Watershed, Maine USA. Environmental Monitoring and Assessment 1999;55(1):97-111. R825762 (1999)
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  • Abstract: SpringerLink
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  • Journal Article Norton S, Kahl J, Fernandez I, Haines T, Rustad L, Nodvin S, Scofield J, Strickland T, Erickson H, Wigington Jr. P, Lee J. The Bear Brook Watershed, Maine (BBWM), USA. Environmental Monitoring and Assessment 1999;55(1):7-51. R825762 (1999)
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  • Abstract: SpringerLink
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  • Journal Article Parker JL, Fernandez IJ, Rustad LE, Norton SA. Effects of nitrogen enrichment, wildfire, and harvesting on forest-soil carbon and nitrogen. Soil Science Society of America Journal 2001;65(4):1248-1255. R825762 (Final)
  • Full-text: SSSAJ
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  • Abstract: SSSAJ
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  • Other: SSSAJ PDF
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  • Journal Article Parker JL, Fernandez IJ, Rustad LE, Norton SA. Soil organic matter fractions in experimental forested watersheds. Water, Air, and Soil Pollution 2002;138(1-4):101-121. R825762 (Final)
  • Abstract: SpringerLink
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  • Journal Article Pellerin BA, Fenandez IJ, Norton SA, Kahl JS. Soil aluminum distribution in the near-stream zone at the Bear Brook Watershed in Maine. Water, Air, and Soil Pollution 2002;134(1-4):189-204. R825762 (Final)
  • Abstract: SpringerLink
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  • Journal Article Roy S, Norton S, Fernandez I, Kahl J. Linkages of P and Al export at high discharge at the Bear Brook Watershed in Maine. Environmental Monitoring and Assessment 1999;55(1):133-147. R825762 (1999)
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  • Abstract: SpringerLink
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  • Journal Article Stoddard JL, Driscoll CT, Kahl JS, Kellogg JH. A regional analysis of lake acidification trends for the Northeastern U.S., 1982-1994. Environmental Monitoring and Assessment 1998;51(1-2):399-413. R825762 (Final)
  • Abstract: SpringerLink
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  • Journal Article Stoddard JL, Driscoll CT, Kahl JS, Kellogg JH. Can site-specific trends be extrapolated to a region? An acidification example for the northeast. Ecological Applications 1998;8(2):288-299. R825762 (Final)
  • Abstract: ESA
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  • Journal Article Stoddard JL, Jeffries DS,Lukewille A, Clair TA, Dillon PJ, Driscoll CT, Forsius M, Johannessen M, Kahl JS, Kellogg JH, Kemp A, Mannio J, Monteith DT, Murdoch PS, Patrick S, Rebsdorf A, Skjelkvale BL, Stainton MP, Traaen T, van Dam H, Webster KE, Wieting J, Wllander A. Regional trends in aquatic recovery from acidification in North America and Europe. Nature 1999;401(6753):575-578. R825762 (Final)
  • Abstract: Nature
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  • Journal Article Wang Z, Fernandez I. Soil type and forest vegetation influences on forest floor nitrogen dynamics at the Bear Brook Watershed in Maine (BBWM). Environmental Monitoring and Assessment 1999;55(1):221-234. R825762 (1999)
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  • Abstract: SpringerLink
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  • Journal Article White G, Fernandez I, Wiersma B. Impacts of ammonium sulfate treatment on the foliar chemistry of forest trees at the Bear Brook Watershed in Maine. Environmental Monitoring and Assessment 1999;55(1):235-250. R825762 (1999)
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  • Abstract: SpringerLink
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  • Supplemental Keywords:

    watersheds, acid deposition, ecological effects, acid rain, public policy, northeast, EPA Region 1., RFA, Scientific Discipline, Geographic Area, Water, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Nutrients, Water & Watershed, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Ecological Effects - Environmental Exposure & Risk, Air Deposition, Ecological Risk Assessment, Ecology and Ecosystems, Watersheds, Ecological Indicators, atmospheric processes, risk assessment, ecosystem modeling, hydrological stability, acidification, geochemical modeling, atmospheric deposits, nutrient stress, aquatic ecosystems, forests, regional response patterns, water quality, nitrate loss, spatial and temporal patterns, Maine (ME), ecosystem stress, acid rain

    Relevant Websites:

    http://www.umaine.edu/DrSoils/bbwm/bbwm.html Exit

    Progress and Final Reports:

    Original Abstract
  • 1998
  • 1999 Progress Report
  • 2000 Progress Report
  • 2001