Ion Mass Balances and Seasonal Fluxes from Four Acidic Brownwater Streams in Nova Scotia

Freedman, Bill; Clair, Ta

doi:10.1139/f87-066

Cited by 40 publications

(16 citation statements)

References 13 publications

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“…Due to the high binding constants of free ferric iron with organic substances, concentrations of Fe in freshwater are generally positively correlated with DOM. Previous reports on Mn concentration in lakes and rivers also reveal an inverse correlation between pH and Mn concentrations (Dickson 1980;Underwood et al 1986;Freedman and Clair 1987). Historically, Cu has been one of the most intensively studied trace metals.…”

Section: Introductionmentioning

confidence: 94%

Watershed land use as a determinant of metal concentrations in freshwater systems

Das

Nordin

2009

Environ Geochem Health

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Concentrations of Fe, Mn, Cu, dissolved organic matter (DOM), and pH were synthesized from 30 publications to determine the factors regulating concentrations and behavior of metals in freshwater systems. Results from the review suggest that contrasting watershed land use can directly (erosion and runoff) and indirectly (in-lake processes including metal-DOM-pH interactions) affect the metal concentrations in freshwater systems. Among the watershed land uses considered here, concentrations of Fe, Mn, and Cu were observed in the following order: arctic lakes < forested < agricultural < urbanized < mined. A drastic difference in mean metal concentrations has been observed when undisturbed or low impact watersheds (arctic and forested) were changed by agricultural, urban, and mining developments. Relationships between metal concentrations and pH revealed that metals precipitate at high pH (pH > 5). Additionally, at pH < 5, metal concentrations were significantly correlated with DOM due to metal-DOM complexation. High ratios of metal: DOM occur only at low DOM concentrations. Collectively, two general conclusions can be drawn from this review. First, lakes, rivers, and streams with urbanized watersheds are the most susceptible to increased concentrations of metals. Secondly, these results also suggest that regardless of high or low DOM in the water column, pH would affect metal concentrations in freshwater systems. Nonetheless, free metal ions would be higher in freshwater systems with acidic water and low DOM.

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Section: Introductionmentioning

confidence: 94%

Watershed land use as a determinant of metal concentrations in freshwater systems

Das

Nordin

2009

Environ Geochem Health

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“…Gran titration alkalinity values are often negative in MR and MPB, with annual averages of 0.0 mEq l j1 at both sites [10]. Specific conductance is also low in each stream (20 mS cm j1 ), reflecting the low dissolved ion loads.…”

Section: Study Area and Field Methodsmentioning

confidence: 98%

Testing the MAGIC acid rain model in highly organic, low-conductivity waters using multiple calibrations

Dennis

Clair

Cosby

2005

Environ Model Assess

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Accurate predictions of acid precipitation effects on water resources are important in order to allow a better understanding of various pollution control strategy outcomes. Dynamic geochemical models have been developed to address this need, but have to be tested under a variety of environmental conditions to provide confidence in their predictions. The most commonly used aquatic acidification model in North America and Europe is the model of acidification of groundwater in catchments (MAGIC). Though extensively used, MAGIC has never been tested in catchments with extremely low ionic strength water and high in natural organic acids (NOAs) from wetlands, two conditions which are common in large parts of Canada. We calibrated the model for two catchments located in Nova Scotia, Canada, which had some of the most dilute freshwaters reported in the literature and very high NOA. We also evaluated the variability inherent in calibration data sets by using five separate data sets collected over a 15-year period at the same sites. We show good model simulations for the main cations and anions in catchment waters. However, modeling pH is more difficult in the highly organic waters and requires modification to the acid dissociation constants. Calculated acid neutralization capacity can also be more difficult to model due to the low ion content making small errors more important. In theory, multiple calibrations of a model at a same site should produce identical hindcasts and predictions. In reality, the multiple calibrations produced a series of similar, but not identical outcomes which give a probable range of past values and future outcomes. We feel that this practical approach to validation is a useful addition to the arsenal of model testing tools.

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“…Clair et al (2001a), using daily and weekly sampling data from three streams in southwestern NS, showed that several low pH episodes lasting from days in small streams to weeks in larger rivers, can occur in regional water courses. Wigington et al (1992) showed that the sharpest pH episode ever reported in the literature was from the Mersey River in Nova Scotia (Freedman and Clair 1987) with a 3.2 pH unit decline in the early 1980s. This low value has not been remeasured, though occasional values of 4.0 are measured during snowmelt episodes in this region.…”

Section: Short-term Episodesmentioning

confidence: 99%

“…Nevertheless, NO 3 -is rarely found above analytical detection levels in non-agricultural or non-urban waters, so that it usually has no influence in acidifying waters though it can occasionally be measured during snowmelt events in the winter and spring. However, receiving forest catchments seem to absorb and process most of the deposited N (Freedman and Clair 1987;Yanni et al 2000a) and because of this, we were unable to develop an NO 3 -distribution map for the region.…”

Section: Sulfate and Nitrogen In Atlantic Canada Watersmentioning

confidence: 99%

Freshwater acidification research in Atlantic Canada: a review of results and predictions for the future

et al. 2007

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Atlantic Canada receives the lowest acid deposition amounts in eastern North America, but has some of the most acidic surface waters on the continent, due to the low buffering provided by regional bedrock and wetlands that produce natural organic acids. Southwestern and eastern parts of Nova Scotia combine poor buffering, high organic acidity, and higher acid deposition, to produce extremely low surface water pH and acid neutralization capacity (ANC) values. Although sulfate deposition is decreasing, concurrent reductions in dissolved base cations, as well as the acid-base characteristics of natural organic acids, are not allowing the recovery of ANC or surface water pH. Spring-time acid pulses occur in Atlantic Canada, though these have been reduced in severity with decreases in winter acid deposition, while autumnal low pH pulses caused by organic acids are a regular occurence in Nova Scotia and must be separated from mineral acidity pulses. Geochemical modeling using both critical load and dynamic approaches, nevertheless predict improvements in the water chemistry of Nova Scotia lakes within the next 20 years. However, re-establishment of pre-acidification water chemistry in most of its lakes will require greater reductions in S emissions than are currently planned in Canada and the United States.Résumé : La côte Atlantique du Canada reçoit les plus faibles dépositions de pluies acides du nord-est Américain, mais possède les eaux de surface les plus acides du continent, dues au faible pouvoir tampon de la roche mère et aux terres humides qui génèrent naturellement des substances organiques acides. Le sud-ouest et l'est de la Nouvelle-É cosse combinent une haute acidité organique et la plus importante déposition acide, ce qui engendre des eaux de surface qui engendre des pH de l'eau de surface et des capacités de neutralisation de l'acide (ANC) extrêmement faibles. Bien que la déposition des sulfates soit à la baisse, une réduction simultanée des cations basiques, ainsi que les caractéristiques acide-base des acides organiques naturels, ne permettent pas la récupération de l'ANC ou du pH des eaux de surface. Des poussées printanières d'acidité surviennent sur la côte Atlantique du Canada, bien que la sévérité de celles-ci ait été réduite avec une diminution des précipitations acides hivernales, alors que les poussées de forte acidité automnales causées par les acides organiques reviennent régulièrement en Nouvelle-É cosse, et doivent être distinguées des poussées d'acidité minérale. Le modelage géochimique, à l'aide des approches dynamique et de charge critique, prédisent néanmoins des améliorations de la chimie de l'eau des lacs en Nouvelle-É cosse, au cours des 20 prochaines années. Cependant, le retour à la chimie de l'eau d'avant l'acidification nécessitera des réductions plus élevées des émissions de S que celles couramment envisagées, au Canada et aux Etats-Unis.Mots-clés : côte Atlantique du Canada, acidification, eau douce, carbone organique total, acidité organique.[Traduit par la Rédaction]

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Ion Mass Balances and Seasonal Fluxes from Four Acidic Brownwater Streams in Nova Scotia

Cited by 40 publications

References 13 publications

Watershed land use as a determinant of metal concentrations in freshwater systems

Watershed land use as a determinant of metal concentrations in freshwater systems

Testing the MAGIC acid rain model in highly organic, low-conductivity waters using multiple calibrations

Freshwater acidification research in Atlantic Canada: a review of results and predictions for the future

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