Waterlogging and soil reduction affect the amount and apparent molecular weight distribution of dissolved organic matter in wetland soil: a laboratory study

Soil Research ◽  
2018 ◽  
Vol 56 (1) ◽  
pp. 28 ◽  
Author(s):  
Asmaa Rouwane ◽  
Malgorzata Grybos ◽  
Isabelle Bourven ◽  
Marion Rabiet ◽  
Gilles Guibaud
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Humic Substances ◽  
Apparent Molecular Weight ◽  
Redox Condition ◽  
Redox Conditions ◽  
Wetland Soil ◽  
Soil Redox ◽  
Reducing Conditions

The release of dissolved organic matter (DOM) from wetland soils is an important pathway for the input of organic compounds into adjacent aquatic environments. In the present study we investigated, under controlled laboratory conditions, the quantity and quality of DOM released from a wetland soil subject to waterlogging and reducing conditions. Three soil redox conditions (oxic, moderately reducing and advanced reducing) were distinguished based on nitrate, ferrous ions and sulfate concentrations in soil solution. Under each redox condition, the quantity (dissolved organic carbon (DOC), humic substances and peptides plus proteins (P-PN) and quality (aromaticity; specific ultraviolet absorbance at 254 nm (SUVA254nm)) and apparent molecular weight (aMW) distribution) of DOM were investigated. The results showed that soil redox condition affects the amount and properties of mobilised DOM. The rate of DOM release and SUVA254 values were highest during the transition from oxic to moderately reducing conditions, whereas both stabilised during progression to advanced reducing conditions. In addition, the mobilised DOM is expected to be more reactive because of an increase in polar substituents in aromatic structures between oxic and moderately reducing conditions. During the development of moderately reducing conditions, dissolved humic substances increased significantly, whereas their aMW distribution (between 500 and 6000 ) remained constant for each of the three different redox conditions. In contrast, the quantity of dissolved P-PN remained low and steady under the three redox conditions, whereas the aMW distribution of protein-like and microbial by-product-like compounds decreased during the development of reducing conditions (aMW of compounds between 100 and >100 000).

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.

Ferric Chloride Coagulation for Removal of Dissolved Organic Matter and Trihalomethane Precursors

1993 ◽  
Vol 27 (11) ◽  
pp. 113-121 ◽  
Author(s):  
A. Amirtharajah ◽  
K. E. Dennett ◽  
Anne Studstill
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Humic Substances ◽  
Ferric Chloride ◽  
Fast Atom Bombardment ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Before And After

Ferric chloride coagulation of two types of natural dissolved organic matter was studied. The molecular weight distribution of Suwannee River humic substances currently used as an international standard was characterized using fast atom bombardment mass spectrometry (FABMS). The molecular weight distributions were characterized before and after coagulation. Ferric chloride dosage and pH domains on the iron coaglation diagrams were developed for removal of these humic substances and for determination of the resulting trihalomethane formation potentials (THMFP) of the treated water. The results indicate that it is possible to maximize the removal of dissolved organic matter and minimize trihalomethanes by coagulation only under very specific conditions of pH and ferric chloride dosage.

Role of microbial reducing activity in antimony and arsenic release from an unpolluted wetland soil: a lab scale study using sodium azide as a microbial inhibiting agent

2016 ◽  
Vol 13 (6) ◽  
pp. 945 ◽  
Author(s):  
Asmaa Rouwane ◽  
Marion Rabiet ◽  
Isabelle Bourven ◽  
Malgorzata Grybos ◽  
Lucie Mallet ◽  
...  
Keyword(s):  
Organic Matter ◽  
Sodium Azide ◽  
Apparent Molecular Weight ◽  
Wetland Soil ◽  
Soil Microbial ◽  
Reducing Conditions ◽  
Key Factor ◽  
Reducing Activity ◽  
The Given

Environmental contextAntimony and arsenic are toxic elements occurring naturally in the environment. We found that arsenic release to water from an unpolluted wetland soil is related to microbial reducing activity only, whereas antimony can still be released when this activity is inhibited, suggesting the involvement of additional processes. The findings show that microbial/non-microbial mechanisms control arsenic and antimony release and can thereby impact water quality at wetland outlets. AbstractIn wetland soils, the mobility of geogenic metal(loid)s is usually associated with direct or indirect microbial-induced processes (solubilisation of mineral and organic components, pH induced desorption, competition effects, dissimilatory reduction). To identify the role of microbial reducing activity in As and Sb release, we conducted two series of soil incubations (sodium azide-treated (NaN3-T) and non-treated (NT)) in closed batches for 36 days. During the incubation period, we monitored the evolution of dissolved As, Sb, Mn, FeII, organic carbon (DOC), humic substances (HS) and proteins (PN) with their apparent molecular weight distribution (aMW) as well as pH, reduction potential (Eh) and alkalinity. Results showed that the release of As and Sb occurred when microbially reducing conditions prevailed (NT soil Eh ~0mV and FeII>40mg L–1) and was inhibited for As in the absence of microbial reducing activity (NaN3-T soil; Eh>250mV and Fe<1mg L–1). In contrast, Sb behaved differently since its release was only slowed down when microbially reducing conditions were inhibited. We concluded that soil microbial reducing activity fully controls the release of As and to a lesser extent that of Sb when NaN3 is used as a microbial inhibiting agent. Since Sb release and dissolved organic matter (DOM) solubilisation (NaN3-induced artefact) occurred simultaneously in the absence of microbially reducing conditions, we concluded that organic matter could be one key factor controlling Sb mobilisation in the given conditions, which is not the case for As.

scholarly journals Characterization of Soil Organic Matter Individual Fractions (Fulvic Acids, Humic Acids, and Humins) by Spectroscopic and Electrochemical Techniques in Agricultural Soils

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1067
Author(s):  
Aleksandra Ukalska-Jaruga ◽  
Romualda Bejger ◽  
Guillaume Debaene ◽  
Bożena Smreczak
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Humic Substances ◽  
Humic Acids ◽  
Agricultural Soils ◽  
Fulvic Acids ◽  
Sorption Properties ◽  
Aliphatic Chains

The objective of this paper was to investigate the molecular characterization of soil organic matter fractions (humic substances (HS): fulvic acids-FAs, humic acids-HAs, and humins-HNs), which are the most reactive soil components. A wide spectrum of spectroscopic (UV–VIS and VIS–nearIR), as well as electrochemical (zeta potential, particle size diameter, and polydispersity index), methods were applied to find the relevant differences in the behavior, formation, composition, and sorption properties of HS fractions derived from various soils. Soil material (n = 30) used for the study were sampled from the surface layer (0–30 cm) of agricultural soils. FAs and HAs were isolated by sequential extraction in alkaline and acidic solutions, according to the International Humic Substances Society method, while HNs was determined in the soil residue (after FAs and HAs extraction) by mineral fraction digestion using a 0.1M HCL/0.3M HF mixture and DMSO. Our study showed that significant differences in the molecular structures of FAs, Has, and HNs occurred. Optical analysis confirmed the lower molecular weight of FAs with high amount of lignin-like compounds and the higher weighted aliphatic–aromatic structure of HAs. The HNs were characterized by a very pronounced and strong condensed structure associated with the highest molecular weight. HAs and HNs molecules exhibited an abundance of acidic, phenolic, and amine functional groups at the aromatic ring and aliphatic chains, while FAs mainly showed the presence of methyl, methylene, ethenyl, and carboxyl reactive groups. HS was characterized by high polydispersity related with their structure. FAs were characterized by ellipsoidal shape as being associated to the long aliphatic chains, while HAs and HNs revealed a smaller particle diameter and a more spherical shape caused by the higher intermolecular forcing between the particles. The observed trends directly indicate that individual HS fractions differ in behavior, formation, composition, and sorption properties, which reflects their binding potential to other molecules depending on soil properties resulting from their type. The determined properties of individual HS fractions are presented as averaged characteristics over the examined soils with different physico-chemical properties.

Sign in / Sign up

Export Citation Format

Share Document