Water chemistry and dissolved organic carbon trends in lakes from Canada’s Atlantic Provinces: no recovery from acidification measured after 25 years of lake monitoring

We analyzed chemistry trends for 66 Atlantic Canada lakes using data collected from 1983 to 2007, as well as from 1990 to 2007 and 2000 to 2007 for the original 66 and a further 25 lakes that were later added to the network. Though receiving the lowest acid deposition in eastern North America, the region’s waters are seriously affected by acid rain because of poorly buffering soils and bedrock. Earlier work had shown that despite large decreases in sulfate deposition, lake pH and calculated acid neutralization capacity (ANCc) had not increased as they had elsewhere in North America and Europe. Despite a 50% decrease in acid deposition, a further 10 years of lake chemistry data showed a regional increase in ANCc only at the beginning of the sampling period but no increase since the early 1990s. There were also no increases in pH and base cations in the region’s lakes. We show a regional increase in Gran titration ANC (ANCG) from 2000 to the present, which we ascribe to increases in dissolved organic carbon that is probably due to a regional increase in annual air temperatures.

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Ionic aluminium concentrations exceed thresholds for aquatic health in Nova Scotian rivers, even during conditions of high dissolved organic carbon and low flow

Hydrology and Earth System Sciences ◽

10.5194/hess-24-4763-2020 ◽

2020 ◽

Vol 24 (10) ◽

pp. 4763-4775 ◽

Cited By ~ 1

Author(s):

Shannon M. Sterling ◽

Sarah MacLeod ◽

Lobke Rotteveel ◽

Kristin Hart ◽

Thomas A. Clair ◽

...

Keyword(s):

Nova Scotia ◽

North America ◽

Organic Carbon ◽

Atlantic Salmon ◽

Dissolved Organic Carbon ◽

Acid Deposition ◽

Linear Mixed Model ◽

Aquatic Organisms ◽

Base Flow ◽

Low Flow

Abstract. Acid deposition released large amounts of aluminium into streams and lakes during the last century in northern Europe and eastern North America. Elevated aluminium concentrations caused major environmental concern due to aluminium's toxicity to terrestrial and aquatic organisms and led to the extirpation of wild Atlantic salmon populations. Air pollution reduction legislation that began in the 1990s in North America and Europe successfully reduced acid deposition, and the aluminium problem was widely considered solved. However, accumulating evidence indicates that freshwater systems still show delays in recovery from acidification, with poorly understood implications for aluminium concentrations. Here, we investigate spatial and temporal patterns of labile cationic forms of aluminium (Ali) from 2015 to 2018 in 10 catchments in Nova Scotia, Canada; this region was one of the hardest hit by acid deposition, although it was not considered to have an aluminium problem due to its high dissolved organic carbon (DOC) concentrations that were expected to reduce Ali concentrations. Surprisingly, our results show the widespread and frequent occurrences of Ali concentrations that exceed toxic thresholds in all sampled rivers despite high DOC concentrations. Generalized linear mixed model results reveal that DOC, instead of being inversely related to Ali, is the strongest predictor (positive) of Ali concentrations, suggesting that the recruitment properties of DOC in soils outweigh its protective properties in streams. Lastly, we find that, contrary to the common conceptualization that high Ali levels are associated with storm flow, high Ali concentrations are found during base flow. Our results demonstrate that elevated Ali concentrations in Nova Scotia continue to pose a threat to aquatic organisms, such as the biologically, economically, and culturally significant Atlantic salmon (Salmo salar).

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Assessing the nonconservative fluvial fluxes of dissolved organic carbon in North America

Journal of Geophysical Research Atmospheres ◽

10.1029/2011jg001820 ◽

2012 ◽

Vol 117 (G1) ◽

Cited By ~ 43

Author(s):

Ronny Lauerwald ◽

Jens Hartmann ◽

Wolfgang Ludwig ◽

Nils Moosdorf

Keyword(s):

North America ◽

Organic Carbon ◽

Dissolved Organic Carbon

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Increased Iron-Carbon Interactions Under Long-Term Acid Deposition Enhance Soil Organic Carbon Sequestration in A Tropical Forest in Southern China

10.21203/rs.3.rs-570953/v1 ◽

2021 ◽

Author(s):

Jingwen Chen ◽

Yuanliu Hu ◽

Steven J. Hall ◽

Dafeng Hui ◽

Jianling Li ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Tropical Forest ◽

Acid Deposition ◽

Southern China ◽

Base Cations ◽

Tropical Soils ◽

C Sequestration ◽

Ph Sensitive ◽

Soil C

Abstract Atmospheric acid deposition remains a widespread problem that may influence the protection of carbon (C) in soil by altering organo-mineral interactions. However, the impacts of additional acidity on organo-mineral interactions and soil C sequestration in naturally acidic tropical soils with a high content of reactive iron (Fe) phases have not been well studied. Here we sampled a nearly 10-yr field experiment with a gradient of acidity treatments (0, 9.6, 32, 96 mol H+ ha− 1 yr− 1 as nitric acid + sulfuric acid) to examine how acidification alters organo-mineral interactions and soil organic carbon (SOC) pools in a tropical forest in southern China. As expected, soil acidification significantly enhanced the leaching of base cations (e.g., Ca2+), and it also altered the solubility and composition of Fe and Al phases. The acidity treatments converted more crystalline Fe (oxyhydr)oxides to short-range-ordered phases, resulting in a large increase in Fe-bound C vs. a relatively small decrease in Ca-bound C. Overall, the acidity treatments increased the mineral-associated C stock to 32.5–36.4 Mg C ha− 1 vs. 28.8 Mg C ha− 1 in the control, accounting for 71–83% of the observed increase in total SOC stock. These findings highlight the importance of pH-sensitive geochemical changes and the key roles of Fe in regulating the response of SOC to further inputs of acid deposition even in highly weathered and naturally acidic soils. The magnitude of SOC changes observed here indicates the importance of including pH-sensitive geochemistry in Earth system models to predict ecosystem C budgets under future acid deposition scenarios.

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Modelling the effects of climate on long-term patterns of dissolved organic carbon concentrations in the surface waters of a boreal catchment

Hydrology and Earth System Sciences ◽

10.5194/hess-12-437-2008 ◽

2008 ◽

Vol 12 (2) ◽

pp. 437-447 ◽

Cited By ~ 26

Author(s):

M. N. Futter ◽

M. Starr ◽

M. Forsius ◽

M. Holmberg

Keyword(s):

Surface Water ◽

Organic Carbon ◽

Dissolved Organic Carbon ◽

Surface Waters ◽

Organic Soils ◽

Catchment Scale ◽

Changing Climate ◽

Recovery From Acidification ◽

Carbon Concentrations ◽

Process Based Models

Abstract. Dissolved organic carbon concentrations ([DOC]) in surface waters are increasing in many regions of Europe and North America. These increases are likely driven by a combination of changing climate, recovery from acidification and change in severity of winter storms in coastal areas. INCA-C, a process-based model of climate effects on surface water [DOC], was used to explore the mechanisms by which changing climate controls seasonal to inter-annual patterns of [DOC] in the lake and outflow stream of a small Finnish catchment between 1990 and 2003. Both production in the catchment and mineralization in the lake controlled [DOC] in the lake. Concentrations in the catchment outflow were controlled by rates of DOC production in the surrounding organic soils. The INCA-C simulation results were compared to those obtained using artificial neural networks (ANN). In general, "black box" ANN models provide better fits to observed data but process-based models can identify the mechanism responsible for the observed pattern. A statistically significant increase was observed in both INCA-C modelled and measured annual average [DOC] in the lake. This suggests that some of the observed increase in surface water [DOC] is caused by climate-related processes operating in the lake and catchment. However, a full understanding of surface water [DOC] dynamics can only come from catchment-scale process-based models linking the effects of changing climate and deposition on aquatic and terrestrial environments.

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Holocene ice wedge formation in the Eureka Sound Lowlands, high Arctic Canada

Quaternary Research ◽

10.1017/qua.2020.126 ◽

2021 ◽

pp. 1-13

Author(s):

Kethra Campbell-Heaton ◽

Denis Lacelle ◽

David Fisher ◽

Wayne Pollard

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Numerical Simulations ◽

High Arctic ◽

Desert Environment ◽

Peat Accumulation ◽

Polar Desert ◽

Molar Ratios ◽

Air Temperatures ◽

Ice Wedge

Abstract Ice wedges are ubiquitous periglacial features in permafrost terrain. This study investigates the timing of ice wedge formation in the Fosheim Peninsula (Ellesmere and Axel Heiberg Islands). In this region, ice wedge polygons occupy ~50% of the landscape, the majority occurring below the marine limit in the Eureka Sound Lowlands. Numerical simulations suggest that ice wedges may crack to depths of 2.7–3.6 m following a rapid cooling of the ground over mean winter surface temperatures of −18°C to −38°C, corresponding to the depth of ice wedges in the region. The dissolved organic carbon (DOC)/Cl molar ratios suggest that the DOC in the ice wedges is sourced from snowmelt and not from leaching of the active layer. Based on 32 14CDOC measurements from 15 ice wedges, the wedges were likely developing between 9000–2500 cal yr BP. This interval also corresponds to the period of peat accumulation in the region, a proxy of increased moisture. Considering that winter air temperatures remained favorable for ice wedge growth throughout the Holocene, the timing of ice wedge formation reflects changes in snowfall. Overall, this study provides the first reconstruction of ice wedge formation from a high Arctic polar desert environment.

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Drivers of Dissolved Organic Carbon Mobilization From Forested Headwater Catchments: A Multi Scaled Approach

Frontiers in Water ◽

10.3389/frwa.2021.578608 ◽

2021 ◽

Vol 3 ◽

Author(s):

Thomas Adler ◽

Kristen L. Underwood ◽

Donna M. Rizzo ◽

Adrian Harpold ◽

Gary Sterle ◽

...

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Acid Deposition ◽

Iterative Process ◽

Catchment Scale ◽

Regional Patterns ◽

Headwater Catchments ◽

Catchment Characteristics ◽

Pattern Approach

Understanding and predicting catchment responses to a regional disturbance is difficult because catchments are spatially heterogeneous systems that exhibit unique moderating characteristics. Changes in precipitation composition in the Northeastern U.S. is one prominent example, where reduction in wet and dry deposition is hypothesized to have caused increased dissolved organic carbon (DOC) export from many northern hemisphere forested catchments; however, findings from different locations contradict each other. Using shifts in acid deposition as a test case, we illustrate an iterative “process and pattern” approach to investigate the role of catchment characteristics in modulating the steam DOC response. We use a novel dataset that integrates regional and catchment-scale atmospheric deposition data, catchment characteristics and co-located stream Q and stream chemistry data. We use these data to investigate opportunities and limitations of a pattern-to-process approach where we explore regional patterns of reduced acid deposition, catchment characteristics and stream DOC response and specific soil processes at select locations. For pattern investigation, we quantify long-term trends of flow-adjusted DOC concentrations in stream water, along with wet deposition trends in sulfate, for USGS headwater catchments using Seasonal Kendall tests and then compare trend results to catchment attributes. Our investigation of climatic, topographic, and hydrologic catchment attributes vs. directionality of DOC trends suggests soil depth and catchment connectivity as possible modulating factors for DOC concentrations. This informed our process-to-pattern investigation, in which we experimentally simulated increased and decreased acid deposition on soil cores from catchments of contrasting long-term DOC response [Sleepers River Research Watershed (SRRW) for long-term increases in DOC and the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) for long-term decreases in DOC]. SRRW soils generally released more DOC than SSHCZO soils and losses into recovery solutions were higher. Scanning electron microscope imaging indicates a significant DOC contribution from destabilizing soil aggregates mostly from hydrologically disconnected landscape positions. Results from this work illustrate the value of an iterative process and pattern approach to understand catchment-scale response to regional disturbance and suggest opportunities for further investigations.

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Long-term patterns in dissolved organic carbon, major elements and trace metals in boreal headwater catchments: trends, mechanisms and heterogeneity

Biogeosciences ◽

10.5194/bg-10-2315-2013 ◽

2013 ◽

Vol 10 (4) ◽

pp. 2315-2330 ◽

Cited By ~ 61

Author(s):

S. K. Oni ◽

M. N. Futter ◽

K. Bishop ◽

S. J. Köhler ◽

M. Ottosson-Löfvenius ◽

...

Keyword(s):

Water Quality ◽

Trace Metals ◽

Organic Carbon ◽

Dissolved Organic Carbon ◽

Temporal Trends ◽

Monotonic Increase ◽

Surface Water Hydrology ◽

Organic Carbon Concentration ◽

Recovery From Acidification

Abstract. The boreal landscape is a complex, spatio-temporally varying mosaic of forest and mire landscape elements that control surface water hydrology and chemistry. Here, we assess long-term water quality time series from three nested headwater streams draining upland forest (C2), peat/mire (C4) and mixed (C7) (forest and mire) catchments. Acid deposition in this region is low and is further declining. Temporal trends in weather and runoff (1981–2008), dissolved organic carbon concentration [DOC] (1993–2010) and other water quality parameters (1987–2011) were assessed. There was no significant annual trend in precipitation or runoff. However, runoff increased in March and declined in May. This suggested an earlier snowmelt regime in recent years. Significant monotonic increasing trends in air temperature and length of growing season suggested a decrease in snowfall and less spring runoff. Stream [DOC] was positively correlated with some trace metals (copper, iron and zinc) and negatively with several other chemical parameters (e.g. sulfate, conductivity, calcium). Both sulfate and conductivity showed declining trends, while a significant increase was observed in pH during winter and spring. Calcium and magnesium showed monotonic decreasing trends. The declining trajectories of stream base cation and sulfate concentrations during other times of the year were not accompanied by changes in pH and alkalinity. These results indicate subtle effects of recovery from acidification. Water temperature increased significantly both annually and in most months. A simultaneous monotonic increase in iron (Fe) and [DOC] in autumn suggests co-transport of Fe-DOC in the form of organometallic complexes. A monotonic increase in UV absorbance in most months without co-occurring changes in DOC trend suggests a shift in DOC quality to a more humic-rich type. The observed increase in soil solution [DOC] and subtle trends in stream [DOC] suggest that climate rather than recovery from acidification is the dominant driver of DOC trends in the Svartberget catchment.

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