scholarly journals Seasonal hydrology and permafrost disturbance impacts on dissolved organic matter composition in High Arctic headwater catchments

2017 ◽  
Vol 3 (2) ◽  
pp. 378-405 ◽  
Author(s):  
J. Fouché ◽  
M. J. Lafrenière ◽  
K. Rutherford ◽  
S. Lamoureux
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Active Layer ◽  
Climate Change Impacts ◽  
High Arctic ◽  
Low Molecular Weight ◽  
Headwater Catchments ◽  
Precipitation Regimes ◽  
Spring Freshet

Arctic landscapes are experiencing intense warming and modification of precipitation regimes with climate change. Permafrost disturbances and climate change impacts on hydrology of Arctic watersheds are likely to modify the quantity and composition of exported dissolved organic matter (DOM). In July 2007, intense rainfall and active layer thickening caused widespread active layer detachments at Cape Bounty, Melville Island (Canada). This study investigates the impacts of seasonal hydrology and permafrost disturbance on DOM composition exported from High Arctic headwater catchments. In 2012, streams were sampled from three disturbed catchments and one undisturbed catchment. The composition of DOM was characterized using absorbance and fluorescence spectroscopy. DOM was mostly exported during the spring freshet. Throughout this period, the undisturbed catchment exported humified DOM with high humic-like fluorescence that likely originated from runoff through shallow organic rich soil. In contrast, DOM exported from disturbed catchments was fresher, less humified with a high proportion of low molecular weight humic acid. We demonstrate that disturbed catchments delivered likely more labile DOM derived from either thawed permafrost or enhanced microbial activity. If this labile DOM comes from an ancient pool, as indicated by other studies at this site, disturbances may strengthen the permafrost carbon feedback on climate change.

Differences in Riverine and Pond Water Dissolved Organic Matter Composition and Sources in Canadian High Arctic Watersheds Affected by Active Layer Detachments

2018 ◽  
Vol 52 (3) ◽  
pp. 1062-1071 ◽  
Author(s):  
Jun-Jian Wang ◽  
Melissa J. Lafrenière ◽  
Scott F. Lamoureux ◽  
André J. Simpson ◽  
Yves Gélinas ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Active Layer ◽  
Pond Water ◽  
High Arctic ◽  
Canadian High Arctic ◽  
Organic Matter Composition

scholarly journals Canadian permafrost stores large pools of ammonium and optically distinct dissolved organic matter

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Fouché ◽  
C. T. Christiansen ◽  
M. J. Lafrenière ◽  
P. Grogan ◽  
S. F. Lamoureux
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Optical Properties ◽  
Chemical Composition ◽  
Dissolved Organic Matter ◽  
Active Layer ◽  
Low Molecular Weight ◽  
Permafrost Degradation ◽  
Soil Cores ◽  
Cryogenic Processes

Abstract Permafrost degradation may lead to mobilization of carbon and nutrients and enhance microbial processing rates of previously frozen organic matter. Although the pool size and chemical composition of dissolved organic matter (DOM) are fundamental determinants of the carbon cycle in Arctic watersheds, its source within the seasonally thawing active layer and the underlying permafrost remains largely uncharacterized. Here, we used 25 soil cores that extended down into the permafrost from nine sites across Arctic Canada to quantify dissolved organic carbon (DOC) and nitrogen stocks, and to characterize DOM optical properties. Organic permafrost stores 5–7 times more DOC and ammonium than the active layer and mineral permafrost. Furthermore, the permafrost layers contain substantial low molecular weight DOM with low aromaticity suggesting high biodegradability. We conclude that soil organic matter stoichiometry and cryogenic processes determine permafrost DOM chemistry, and that thawing will mobilize large amounts of labile DOC and ammonium into Arctic watersheds.

scholarly journals DOM degradation by light and microbes along the Yukon River-coastal ocean continuum

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Brice K. Grunert ◽  
Maria Tzortziou ◽  
Patrick Neale ◽  
Alana Menendez ◽  
Peter Hernes
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Salinity Gradient ◽  
Coastal Ocean ◽  
Interactive Effects ◽  
The Arctic ◽  
Yukon River ◽  
Spring Freshet ◽  
Dom Composition

AbstractThe Arctic is experiencing rapid warming, resulting in fundamental shifts in hydrologic connectivity and carbon cycling. Dissolved organic matter (DOM) is a significant component of the Arctic and global carbon cycle, and significant perturbations to DOM cycling are expected with Arctic warming. The impact of photochemical and microbial degradation, and their interactive effects, on DOM composition and remineralization have been documented in Arctic soils and rivers. However, the role of microbes, sunlight and their interactions on Arctic DOM alteration and remineralization in the coastal ocean has not been considered, particularly during the spring freshet when DOM loads are high, photoexposure can be quite limited and residence time within river networks is low. Here, we collected DOM samples along a salinity gradient in the Yukon River delta, plume and coastal ocean during peak river discharge immediately after spring freshet and explored the role of UV exposure, microbial transformations and interactive effects on DOM quantity and composition. Our results show: (1) photochemical alteration of DOM significantly shifts processing pathways of terrestrial DOM, including increasing relative humification of DOM by microbes by > 10%; (2) microbes produce humic-like material that is not optically distinguishable from terrestrial humics; and (3) size-fractionation of the microbial community indicates a size-dependent role for DOM remineralization and humification of DOM observed through modeled PARAFAC components of fluorescent DOM, either through direct or community effects. Field observations indicate apparent conservative mixing along the salinity gradient; however, changing photochemical and microbial alteration of DOM with increasing salinity indicate changing DOM composition likely due to microbial activity. Finally, our findings show potential for rapid transformation of DOM in the coastal ocean from photochemical and microbial alteration, with microbes responsible for the majority of dissolved organic matter remineralization.

scholarly journals Active layer slope disturbances affect seasonality and composition of dissolved nitrogen export from High Arctic headwater catchments

2017 ◽  
Vol 3 (2) ◽  
pp. 429-450 ◽  
Author(s):  
Melissa J. Lafrenière ◽  
Nicole L. Louiseize ◽  
Scott F. Lamoureux
Keyword(s):  
Active Layer ◽  
High Arctic ◽  
Rainfall Runoff ◽  
Headwater Catchments ◽  
Dissolved Nitrogen ◽  
Total Dissolved Nitrogen ◽  
Nitrate Export ◽  
Limiting Nutrient ◽  
Seasonal Discharge ◽  
The Impact

This study investigates the impacts of active layer detachments (ALDs) on nitrogen in seasonal runoff from High Arctic hillslope catchments. We examined dissolved nitrogen in runoff from an undisturbed catchment (Goose (GS)) and one that was disturbed (Ptarmigan (PT)) by ALDs, prior to disturbance (2007) and 5 years after disturbance (2012). The seasonal dynamics of nitrogen species concentrations and fluxes were similar in both catchments in 2007, but the mean seasonal nitrate concentration and mass flux from the disturbed catchment were on the order of 30 times higher relative to the undisturbed catchment in 2012. Stormflow yielded 45% and 60% of the 2012 total dissolved nitrogen flux in GS and PT, respectively, although rainfall runoff provided less than 25% of seasonal discharge. Results support that through the combined effects of increased disturbance and rainfall, climate change stands to significantly enhance the export of nitrate from High Arctic watersheds. This study highlights that the increase in the delivery of nitrate from disturbance is especially pronounced late in the season when downstream productivity and the biological demand for this often limiting nutrient are high. Our results also demonstrate that the impact of ALDs on nitrate export can persist more than 5 years following disturbance.

Photoformation of Low-Molecular-Weight Organic Acids from Brown Water Dissolved Organic Matter

2003 ◽  
Vol 37 (18) ◽  
pp. 4190-4198 ◽  
Author(s):  
Thomas Brinkmann ◽  
Philip Hörsch ◽  
Daniel Sartorius ◽  
Fritz H. Frimmel
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Organic Acids ◽  
Low Molecular Weight

Effects of dissolved organic matter on sorption of benzotriazole to soil

2020 ◽  
Author(s):  
Lin Wu ◽  
Jin’e Dai ◽  
Erping Bi
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Organic Contaminants ◽  
Low Molecular Weight ◽  
Sorption Equilibrium ◽  
Solution Ph ◽  
Environmental Behaviors ◽  
Unsaturated Zones ◽  
Molecular Weight Fractions

<p>Dissolved organic matter (DOM) plays an important role in affecting the environmental behaviors of organic contaminants. Effects of two representative DOMs (dissolved humic acid (HA) and tannic acid (TA)) on sorption of benzotriazole (BTA) to a reference soil were investigated by batch experiments. The results indicated that TA had stronger sorption to soil than HA (initial solution pH=6.0±0.1). This is because that TA contains more carboxylic and phenolic groups than those of HA. In the solution with DOM, the enhanced sorption of BTA was caused by cumulative sorption resulting from sorbed DOM. Hydrogen bonding was proposed as the main binding mechanism between BTA and the sorbed DOM. When the solution pH at sorption equilibrium increased from 6.5 to 10.5, the electrostatic repulsion inhibited the sorption of BTA in solution with/without HA. In addition, less hydrogren bonds made the effect of HA in promoting BTA sorption decrease when solution pH changed from 6.5 to 10.5. Higher molecular weight fractions of HA could be preferentially sorbed by the soil, its enhancement on BTA sorption was more obvious than that of the low molecular weight fractions. These findings are conducive to a better understanding of environmental behaviors of BTA as well as other organic compounds with similar structure in the unsaturated zones.</p>

scholarly journals Photomineralization of terrigenous dissolved organic matter in Arctic coastal waters from 1979 to 2003: Interannual variability and implications of climate change

2006 ◽  
Vol 20 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Simon Bélanger ◽  
Huixiang Xie ◽  
Nickolay Krotkov ◽  
Pierre Larouche ◽  
Warwick F. Vincent ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Interannual Variability ◽  
Coastal Waters
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