scholarly journals Size-Based Characterization of Freshwater Dissolved Organic Matter finds Similarities within a Water Body Type across Different Canadian Ecozones

2020 ◽  
Author(s):  
Pieter J. K. Aukes ◽  
Sherry L. Schiff ◽  
Jason J. Venkiteswaran ◽  
Richard J. Elgood ◽  
John Spoelstra
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Size Exclusion Chromatography ◽  
Water Body ◽  
Size Exclusion ◽  
List Type ◽  
Body Type ◽  
Wide Range ◽  
Exclusion Chromatography ◽  
Dom Composition

ABSTRACTDissolved Organic Matter (DOM) represents a mixture of organic molecules that vary due to different source materials and degree of processing. Characterizing how DOM composition evolves along the aquatic continuum can be difficult. Using a size-exclusion chromatography technique (LC-OCD), we assessed the variability in DOM composition from both surface and groundwaters across a number of Canadian ecozones (mean annual temperature spanning −10 to +6 C). A wide range in DOM concentration was found from 0.2 to 120 mg C/L. Proportions of different size-based groupings across ecozones were variable, yet similarities between specific water-body types, regardless of location, suggest commonality in the processes dictating DOM composition. A PCA identified 70% of the variation in LC-OCD derived DOM compositions could be explained by the water-body type. We find that DOM composition within a specific water-body type is similar regardless of the differences in climate or surrounding vegetation where the sample originated from.HighlightsSize-exclusion chromatography (using LC-OCD) is a fast and effective tool to quantify differences in DOM composition across different environmentsProportions of biopolymers and low molecular weight fractions can distinguish between surface and groundwater DOMSimilar water-body types have comparable DOM size compositions across ecozones that range in annual air temperatures from –10 to 6ºC

Measuring dissolved organic matter in estuarine and marine waters: size-exclusion chromatography with various detection methods

2018 ◽  
Vol 15 (7) ◽  
pp. 436 ◽  
Author(s):  
Gabriel Dulaquais ◽  
Johann Breitenstein ◽  
Matthieu Waeles ◽  
Rémi Marsac ◽  
Ricardo Riso
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Humic Substances ◽  
Size Exclusion Chromatography ◽  
Size Exclusion ◽  
Marine Waters ◽  
Wide Range ◽  
Exclusion Chromatography

Environmental contextDissolved organic matter (DOM), a key parameter in aquatic biogeochemistry, is difficult to characterise owing to its variable composition and structure. We report a chromatographic method with carbon, nitrogen and absorbance detection able to record the size distribution of DOM and changes in its composition. The method could be used to identify additional sources to river or coastal waters as well as monitoring the DOM size/reactivity continuum in open oceans. AbstractWe studied the performance and limitations of size-exclusion chromatography with organic carbon, ultraviolet and organic nitrogen detectors (SEC-OCD-UVD-OND) for characterising dissolved organic matter (DOM) in estuarine and marine waters. We identified a strong salt effect on dissolved organic carbon (DOC) determination; however, calibration gave good results at salinity levels close to those of the sample analysed (ΔS ± 2 psu (practical salinity units)), with limited matrix effects, enabling an accurate measurement of DOC, as demonstrated by an intercalibration exercise. The repeatability, reproducibility and limit of detection (3 ppb for both carbon and nitrogen) for the three detectors demonstrated the robustness of the method for a wide range of natural waters, including carbon-rich freshwaters and deep seawaters with low carbon content (6000 ppb-C to 300 ppb-C). Deeper analysis of the SEC demonstrated that proteins and polysaccharides are partly fractionated within the column, and that terrestrial humic substances, isolated on a XAD-8 resin, can also be eluted in both fractions associated with biopolymers and low-molecular-weight neutrals. Application of the method to the study of DOM along a macrotidal estuary that was influenced by agricultural activities revealed significant changes in its composition despite a conservative DOC distribution. Distinct origins and qualities of high-molecular-weight (>500 kDa) organic compounds were identified for riverine and marine end-members. A new diagram to track changes in DOM lability is proposed to complete the humic-substances diagram.

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