Production, Preservation and Degradation of Organic Matter

Killops, S. D.; Killops, Vanessa

doi:10.1002/9781118697214.ch3

Cited by 6 publications

(8 citation statements)

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“…These diverse compounds may have originated from progressive OM decomposition 4 and accumulation of organic compounds resistant to microbial degradation, such as those highly unsaturated and aromatic compounds. 71 Plant colonization tended to reduce the abundance of those middle-weighted molecular mass DOM (Figure S1), compared with those without plant colonization, which was consistent with the lower M/Z w value in DOM of plant-colonized tailings (Table 1). This may be due to the rhizosphere priming effects, which stimulated further microbial decomposition of macromolecules into small molecules.…”

Section: Resultsmentioning

confidence: 93%

“…These changes suggested that the OM amendment coupled with microbial activities in the tailings significantly increased the DOM chemodiversity, exhibiting an increased representation of higher unsaturation and aromatic groups, as well as carboxyl-rich alicyclic compounds, compared to the control. These diverse compounds may have originated from progressive OM decomposition and accumulation of organic compounds resistant to microbial degradation, such as those highly unsaturated and aromatic compounds …”

Section: Resultsmentioning

confidence: 99%

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Chemodiversity of Dissolved Organic Matter and Its Molecular Changes Driven by Rhizosphere Activities in Fe Ore Tailings Undergoing Eco-Engineered Pedogenesis

You

Boughton

et al. 2021

Environ. Sci. Technol.

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Dissolved organic matter (DOM) plays an important role in soil structure and biogeochemical function development, which are fundamental for the eco-engineering of tailings-soil formation to underpin sustainable tailings rehabilitation. In the present study, we have characterized the DOM composition and its molecular changes in an alkaline Fe ore tailing primed with organic matter (OM) amendment and plant colonization. The results demonstrated that microbial OM decomposition dramatically increased DOM richness and average molecular weight, as well as its degree of unsaturation, aromaticity, and oxidation in the tailings. Plant colonization drove molecular shifts of DOM by depleting the unsaturated compounds with a high value of nominal oxidation state of carbon (NOSC), such as tannin-like and carboxyl-rich polycyclic-like compounds. This may be partially related to their sequestration by secondary Fe–Si minerals formed from rhizosphere-driven mineral weathering. Furthermore, the molecular shifts of DOM may have also resulted from plant-regulated microbial community changes, which further influenced DOM molecules through microbial–DOM interactions. These findings contribute to the understanding of DOM biogeochemistry and ecofunctionality in the tailings during early pedogenesis driven by OM input and pioneer plant/microbial colonization, providing an important basis for the development of strategies and technologies toward the eco-engineering of tailings-soil formation.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Chemodiversity of Dissolved Organic Matter and Its Molecular Changes Driven by Rhizosphere Activities in Fe Ore Tailings Undergoing Eco-Engineered Pedogenesis

You

Boughton

et al. 2021

Environ. Sci. Technol.

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“…lipids, sugars, proteins), geopolymers (e.g. humic substances) and bio-monomers related, or not, to microbial degradation (Killops and Killops, 2004, Lee et al, 2004, Meyers and Ishiwatari, 1993and Wakeham and Lee, 1989. The organic compounds present in natural waters are generally derived from photosynthetic processes, with the exception of deep-sea extreme environments, such as submarine hydrothermal systems and methane seeps, where organic biomass can be produced by chemosynthesis.…”

Section: Organic Matter In Sedimentsmentioning

confidence: 99%

Rare earth elements and neodymium isotopes in sedimentary organic matter

Freslon

Bayon

Toucanne

et al. 2014

Geochimica et Cosmochimica Acta

129

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International audienceWe report rare earth element (REE) and neodymium (Nd) isotope data for the organic fraction of sediments collected from various depositional environments, i.e. rivers (n=25), estuaries (n=18), open-ocean settings (n=15), and cold seeps (n=12). Sedimentary organic matter (SOM) was extracted using a mixed hydrogen peroxide/nitric acid solution (20%-H2O2-0.02M-HNO3), after removal of carbonate and oxy-hydroxide phases with dilute hydrochloric acid (0.25M-HCl). A series of experimental tests indicate that extraction of sedimentary organic compounds using H2O2 may be complicated occasionally by partial dissolution of sulphide minerals and residual carbonates. However, this contamination is expected to be minor for REE because measured concentrations in H2O2 leachates are about two-orders of magnitude higher than in the above mentioned phases.The mean REE concentrations determined in the H2O2 leachates for samples from rivers, estuaries, coastal seas and open-ocean settings yield relatively similar levels, with σREE=109±86ppm (mean±s; n=58). The organic fractions leached from cold seep sediments display even higher concentration levels (285±150ppm; mean±s; n=12). The H2O2 leachates for most sediments exhibit remarkably similar shale-normalized REE patterns, all characterized by a mid-REE enrichment compared to the other REE. This suggests that the distribution of REE in leached sedimentary organic phases is controlled primarily by biogeochemical processes, rather than by the composition of the source from which they derive (e.g. pore, river or sea-water).The Nd isotopic compositions for organic phases leached from river sediments are very similar to those for the corresponding detrital fractions. In contrast, the SOM extracted from marine sediments display εNd values that typically range between the εNd signatures for terrestrial organic matter (inferred from the analysis of the sedimentary detrital fractions) and marine organic matter (inferred from the analysis of local surface seawater). A notable exception is the case of organic matter (OM) fractions leached from cold seep sediment samples, which sometimes exhibit εNd values markedly different from both terrigenous and surface seawater signatures. This suggests that a significant fraction of organic compounds in these sediments may be derived from chemosynthetic processes, recycling pore water REE characterized by a distinct isotopic composition.Overall, our results confirm that organic matter probably plays an important role in the oceanic REE budget, through direct scavenging and remineralization within the water column. Both the high REE abundances and the shape of shale-normalized patterns for leached SOM also suggest that OM degradation in sub-surface marine sediments during early diagenesis could control, to a large extent, the distribution of REE in pore waters. Benthic fluxes of organic-bound REE could hence substantially contribute to the exchange processes between particulates and seawater that take place at ocean margins. Neodymium ...

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“…Inconsistencies in OM degradation patterns between deep and shallow sites (Fig. 8) can be ascribed to the varying intensity of microbial activities in the sediment column, as sedimentary OM is primarily consumed by bacteria during diverse metabolic interactions (Killops & Killops 2004). Despite the difference in degradation patterns, sediments from all the sampling sites consistently show the importance of aquatic proteins and carbohydrates decomposition in the upper 15 cm with subsequent lipids decomposition in the deeper sediment.…”

Section: Sedimentary Organic Matter Degradationmentioning

confidence: 99%

Post-depositional alteration of stable isotope signals by preferential degradation of algae-derived organic matter in reservoir sediments

Liu¹,

Wendt‐Potthoff

Barth

et al. 2021

Preprint

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Post-depositional degradation of organic matter (OM) in freshwater sediments is crucial for driving the biogeochemical dynamics and influencing the consequential carbon burial. This process also often causes diagenetic alterations on paleoenvironmental proxies. Yet, mechanisms behind the degradation of sedimentary OM and the depth-related variations in stable isotope ratios can only be explained in part. Degradation of sedimentary OM in two drinking water reservoirs with contrasting trophic states (eutrophic versus mesotrophic) and catchment land-use (agriculture versus forestry) were studied with a combination of typical chemical treatments to group sedimentary organic matter into four different biochemical fractions, i.e., carbohydrates, proteins, lignins and lipids. Our results show that the degradation of sedimentary OM was mainly driven by preferential degradation of aquatic proteins and carbohydrates. In a subsequent step, lipids seemed to be degraded. This process entails more pronounced reduction of sedimentary OM and associated depth variations in δ13C and δ15N in the eutrophic reservoir of agricultural catchment, when compared to the mesotrophic reservoir with a forest dominated catchment. Moreover, changes in the relative proportions of biochemical components in sedimentary OM have more pronounced impact on δ15N isotope values relative to the ones of δ13C. Our findings also suggest that algae-derived OM is primarily responsible for the post-depositional alterations of elemental and isotopic compositions of sedimentary OM. This may be of importance for estimates of carbon sinks in lakes and reservoirs.

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Production, Preservation and Degradation of Organic Matter

Cited by 6 publications

References 0 publications

Chemodiversity of Dissolved Organic Matter and Its Molecular Changes Driven by Rhizosphere Activities in Fe Ore Tailings Undergoing Eco-Engineered Pedogenesis

Chemodiversity of Dissolved Organic Matter and Its Molecular Changes Driven by Rhizosphere Activities in Fe Ore Tailings Undergoing Eco-Engineered Pedogenesis

Rare earth elements and neodymium isotopes in sedimentary organic matter

Post-depositional alteration of stable isotope signals by preferential degradation of algae-derived organic matter in reservoir sediments

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