Acid-base chemistry of high-elevation streams in the great smoky mountains

Cook, Robert B.; Elwood, Jerry W.; Turner, Ralph R.; Bogle, Mary Anna; Mulholland, Patrick J.; Palumbo, Anthony V.

doi:10.1007/bf01257133

Cited by 28 publications

(21 citation statements)

References 46 publications

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“…Seasonal trends were observed for nitrate concentrations, where greater baseflow nitrate concentrations occurred during the winter. Cook et al (1994) observed similar nitrate seasonality and attributed the increased winter export to lower vegetation uptake, greater deposition, and rates of organic decomposition and nitrification exceeding plant requirements. The increased nitrate concentrations during the dormant season have potential to contribute to stream acidification, as observed at Site M2 during two winter storms.…”

Section: Discussionsupporting

confidence: 51%

“…Other studies outside the southern Appalachian region found OA to significantly contribute to acidification episodes using dissolved organic carbon (DOC) measurements as a surrogate for OA (Hyer et al 1995;Wellington and Driscoll 2004). Cook et al (1994) found increased DOC during stormflows in the GRSM, and suggested OA flushed from the riparian zone could be responsible for pH depressions during certain episodes. Several baseflow and stormflow samples were analyzed for DOC concentration and found to be between 1.5 and 4.5 mg/L with higher concentrations occurring for the stormflow samples compared to the baseflow samples (Fig.…”

Section: Discussionmentioning

confidence: 97%

“…This is particularly true in the Great Smoky Mountains (GRSM) which receives high rates of atmospheric deposition of acids typical to rates found throughout the Appalachian region of the US (Shubzda et al 1995;Baumgardner et al 2003;NADP 2006). Episodic acidification was first observed in GRSM headwater streams in 1985 by Cook et al (1994), where they found that pH dropped one unit to 4.8 and ANC declined to −48 μeq/L during episodes. In general, the GRSM is particularly susceptible to acid storm events because of its low buffering capacity.…”

mentioning

confidence: 96%

“…Subsurface hydrologic flow paths vary from shallow to deep during episodes depending on hillslope steepness, soil horizon structure, and antecedent moisture, which greatly influence ion transport in watersheds (Potter et al 1988;Cook et al 1994;Lawrence 2002).…”

mentioning

confidence: 99%

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Characterizing Episodic Stream Acidity During Stormflows in the Great Smoky Mountains National Park

Deyton

Schwartz

Robinson

et al. 2008

Water Air Soil Pollut

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Episodic acidification of surface waters has been observed in the Great Smoky MountainsNational Park, similar to other forested watersheds with base-poor bedrock in the eastern US receiving acids from atmospheric deposition. Three remote, forested, high-elevation streams were selected in the Little Pigeon River watershed for study; two of which brook trout have extirpated, and believed to have resulted from severe acidity during stormflows. This research characterized stream chemistry during episodes in order to better understand potential factors that contribute to rapid drops in pH and acid neutralizing capacity (ANC) during stormflows. Autosamplers initialized by sondes, collected samples during storm events for analysis of pH, ANC, cations, and anions over a 15-month period. ANC and pH depressions, and increased concentrations in sulfate, nitrate, and organic acids were observed for all storms at each study site. ANC contribution analysis indicated sulfate was the strongest contributor to ANC depressions, but nitrate, cation dilution, and organic acids were also significant in some cases. Acidic deposition appears to be the primary source of episodic acidification, supported also by the finding that larger stormflows preceded by long, dry periods resulted in significantly larger pH depressions. It appears stream acidification episodes may be driven by acid deposition. However, this study documents the variability of several ion contributors to observed stormflow ANC depressions illustrating the spatial and temporal complexity of watershed processes that influence this phenomenon.

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Section: Discussionsupporting

confidence: 51%

Section: Discussionmentioning

confidence: 97%

mentioning

confidence: 96%

mentioning

confidence: 99%

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Characterizing Episodic Stream Acidity During Stormflows in the Great Smoky Mountains National Park

Deyton

Schwartz

Robinson

et al. 2008

Water Air Soil Pollut

View full text Add to dashboard Cite

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“…It has been known for decades that atmospheric deposition of SO 4 2− and NO 3 − from coal-fired power plants, vehicles, and other sources can cause stream acidification in Appalachian regions with base-poor bedrock (Driscoll et al 1980;Herlihy et al 1991;Wigington et al 1996). Stream acidification in the GRSM was initially observed in the 1980s by Johnson and Lindberg (1992) and Cook et al (1994). During this period, acidic deposition was characterized at the Noland Divide Watershed (NDW) in the GRSM as part of the Integrated Forest Study (IFS), a North American and European program to examine its effects on forest nutrient cycles (Lindberg and Lovett 1992).…”

Section: Introductionmentioning

confidence: 95%

Long-Term Effects of Acidic Deposition on Water Quality in a High-Elevation Great Smoky Mountains National Park Watershed: Use of an Ion Input–Output Budget

Cai

Schwartz

Robinson

et al. 2009

Water Air Soil Pollut

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Impacts from acidic deposition on stream water quality in the Great Smoky Mountains National Park (GRSM) have long been reported; however, a better understanding of the biogeochemical processes that regulate stream acidification is needed for resource management. Water quality monitoring of Noland Divide Watershed (NDW), a high-elevation watershed in the GRSM, was used to generate an ion input-output budget in order to evaluate what processes have influenced stream pH and acid neutralizing capacity (ANC) over the long term. NDW was equipped with wet deposition, throughfall, soil lysimeters, and stream collection stations, and monitoring began in 1991 and continues to the present. Using data from 1991 to 2006, this study found annual deposition fluxes of SO 4 2− and NO 3 − averaged 1,735 and 863 eq ha −1 year −1 , respectively. Data indicated that 61% of the net SO 4 2− entering the watershed was retained, suggesting soil adsorption dominates as a biogeochemical process. Although net SO 4 2− retention was observed, SO 4 2− appeared to move rapidly through NDW during large precipitation events causing stream acidification, as evidenced by significant inverse correlations between biweekly throughfall SO 4 2− flux and stream event pH and ANC. Nitrogen uptake by forest vegetation and nitrification play key roles in regulating NO 3 − export to the stream as observed by 32% retention of net inorganic nitrogen, and 96% of NH 4 + input was converted to NO 3 − in the uppermost soil horizon. Net export of base cations (Ca 2+ , Mg 2+ , Na + ) is observed and apparently moderates stream acidification. In contrast, 71% of net K + input was retained, which is likely due to forest vegetation uptake. Net export of Ca 2+ was 867 eq ha −1 year −1 compared to net throughfall of 790 eq ha −1 year −1 . Long-term cation depletion from the NDW soils could limit recovery potential in stream water quality. Findings from this NDW study suggest that future stream acidification conditions in high-elevation GRSM watersheds are dependent on interrelated biogeochemical processes and precipitation patterns, illustrating the need to better understanding potential impacts of climate variability on stream water quality.

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Critical loads and exceedances for nitrogen and sulfur atmospheric deposition in Great Smoky Mountains National Park, United States

et al. 2016

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Abstract. Acid deposition has impacted sensitive streams, reducing the amount of habitat available for fish survival in the Great Smoky Mountains National Park (GRSM) and portions of the surrounding Southern Appalachian Mountains by decreasing pH and acid neutralizing capacity (ANC) and mobilizing aluminum dissolved from soil. Land managers need to understand whether streams can recover from the elevated acid deposition and sustain the healthy aquatic biota, and if so, how long it would take to achieve this condition. We used a dynamic biogeochemical model, PnET-BGC, to evaluate past, current, and potential future changes in soil and water chemistry of watersheds of the GRSM in response to the projected changes in acid deposition. The model was parameterized with soil, vegetation, and stream observations for 30 stream watersheds in the GRSM. Using model results, the level of atmospheric deposition (known as a "critical load") above which harmful ecosystem effects (defined here as modeled stream ANC below a defined target) occur was determined for the 30 study watersheds. In spite of the recent marked decreases in atmospheric sulfur and nitrate deposition, our results suggest that stream recovery has been limited and delayed due to the high sulfate adsorption capacity of soils in the park resulting in a long lag time for recovery of soil chemistry to occur. Model simulations suggest that over the long term, increases in modeled stream ANC per unit decrease in NH 4 + deposition are greater than unit decreases in SO 4 2− or NO 3 − deposition, due to high SO 4 2− adsorption capacity and the limited N retention of the watersheds. Watershed simulations were used to extrapolate the critical load results to 387 monitored stream sites throughout the park and depict the spatial pattern of atmospheric deposition exceedances. These types of model simulations inform park managers on the amount of air quality improvement needed to meet the stream restoration goals.

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Acid-base chemistry of high-elevation streams in the great smoky mountains

Cited by 28 publications

References 46 publications

Characterizing Episodic Stream Acidity During Stormflows in the Great Smoky Mountains National Park

Characterizing Episodic Stream Acidity During Stormflows in the Great Smoky Mountains National Park

Long-Term Effects of Acidic Deposition on Water Quality in a High-Elevation Great Smoky Mountains National Park Watershed: Use of an Ion Input–Output Budget

Critical loads and exceedances for nitrogen and sulfur atmospheric deposition in Great Smoky Mountains National Park, United States

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