Microbial Oxidation of Organic Matter of Histosols

1980 ◽  
pp. 169-201 ◽  
Author(s):  
Robert L. Tate
Keyword(s):  
Organic Matter ◽  
Microbial Oxidation

scholarly journals Cryptic Cycling of Complexes Containing Fe(III) and Organic Matter by Phototrophic Fe(II)-Oxidizing Bacteria

2019 ◽  
Vol 85 (8) ◽  
Author(s):  
Chao Peng ◽  
Casey Bryce ◽  
Anneli Sundman ◽  
Andreas Kappler
Keyword(s):  
Organic Matter ◽  
Anoxygenic Phototrophic Bacteria ◽  
Aquatic Environments ◽  
Photic Zone ◽  
Iron Cycling ◽  
Microbial Oxidation ◽  
Photochemical Reduction ◽  
Content Type ◽  
Dissolved Iron ◽  
New Type

ABSTRACTFe-organic matter (Fe-OM) complexes are abundant in the environment and, due to their mobility, reactivity, and bioavailability, play a significant role in the biogeochemical Fe cycle. In photic zones of aquatic environments, Fe-OM complexes can potentially be reduced and oxidized, and thus cycled, by light-dependent processes, including abiotic photoreduction of Fe(III)-OM complexes and microbial oxidation of Fe(II)-OM complexes, by anoxygenic phototrophic bacteria. This could lead to a cryptic iron cycle in which continuous oxidation and rereduction of Fe could result in a low and steady-state Fe(II) concentration despite rapid Fe turnover. However, the coupling of these processes has never been demonstrated experimentally. In this study, we grew a model anoxygenic phototrophic Fe(II) oxidizer,Rhodobacter ferrooxidansSW2, with either citrate, Fe(II)-citrate, or Fe(III)-citrate. We found that strain SW2 was capable of reoxidizing Fe(II)-citrate produced by photochemical reduction of Fe(III)-citrate, which kept the dissolved Fe(II)-citrate concentration at low (<10 μM) and stable concentrations, with a concomitant increase in cell numbers. Cell suspension incubations with strain SW2 showed that it can also oxidize Fe(II)-EDTA, Fe(II)-humic acid, and Fe(II)-fulvic acid complexes. This work demonstrates the potential for active cryptic Fe cycling in the photic zone of anoxic aquatic environments, despite low measurable Fe(II) concentrations which are controlled by the rate of microbial Fe(II) oxidation and the identity of the Fe-OM complexes.IMPORTANCEIron cycling, including reduction of Fe(III) and oxidation of Fe(II), involves the formation, transformation, and dissolution of minerals and dissolved iron-organic matter compounds. It has been shown previously that Fe can be cycled so rapidly that no measurable changes in Fe(II) and Fe(III) concentrations occur, leading to a so-called cryptic cycle. Cryptic Fe cycles have been shown to be driven either abiotically by a combination of photochemical reduction of Fe(III)-OM complexes and reoxidation of Fe(II) by O2, or microbially by a combination of Fe(III)-reducing and Fe(II)-oxidizing bacteria. Our study demonstrates a new type of light-driven cryptic Fe cycle that is relevant for the photic zone of aquatic habitats involving abiotic photochemical reduction of Fe(III)-OM complexes and microbial phototrophic Fe(II) oxidation. This new type of cryptic Fe cycle has important implications for biogeochemical cycling of iron, carbon, nutrients, and heavy metals and can also influence the composition and activity of microbial communities.

scholarly journals Allochthonous sources of iodine and organic carbon in an eastern Ontario aquifer

2019 ◽  
Vol 56 (3) ◽  
pp. 209-222 ◽  
Author(s):  
Alexander J. Lemieux ◽  
Stewart M. Hamilton ◽  
Ian D. Clark
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Principal Component ◽  
Marine Phytoplankton ◽  
Pore Waters ◽  
Microbial Oxidation ◽  
Glacial Sediments ◽  
Decomposition Of Organic Matter ◽  
Eastern Ontario ◽  
Bedrock Aquifer

Regional geochemical characterization of groundwaters in a bedrock aquifer in the Ottawa – St. Lawrence Lowlands of eastern Ontario has identified an iodine (I) anomaly, with values regularly exceeding 150 μg/L and a maximum observed concentration of 10 812 μg/L. The spatial distribution, enrichment mechanisms, and sources of I and organic matter were investigated using geochemical and isotopic data. High-I groundwaters (>150 μg/L) are prevalent in Na–Cl-type groundwaters at low bedrock elevations in areas overlain by thick layers of glacial sediments. I is thought to be linked to massive muds in the glacial sediments overlying the aquifer, deposited during the postglacial incursion of the Champlain Sea 12–10 ka BP. Principal component analysis of I and 18 other chemical parameters revealed correlations among I, salinity, and indicators of microbial oxidation of organic matter, suggesting that the intrusion of saline pore waters affected by decomposition of organic matter such as marine phytoplankton in the massive muds is the dominant process controlling I enrichment in groundwater. 129I/127I ratios in the pre-modern waters vary between near-marine values of 460 × 10−14 and 5 × 10−14, demonstrating that older allochthonous I derived from the surrounding Paleozoic sedimentary terrain also contributed to the I pool in the Champlain Sea basin. 14C ages and δ13C signatures for dissolved organic carbon in groundwater and disseminated organic carbon within the glaciomarine muds highlight an allochthonous source of terrestrial organic carbon predating the Champlain Sea incursion, likely transported via glacial meltwaters in tandem with I to the Champlain Sea basin.

scholarly journals Physicochemical changes in pyrogenic organic matter (biochar) after 15 months field-aging

2014 ◽  
Vol 6 (1) ◽  
pp. 731-760 ◽  
Author(s):  
A. Mukherjee ◽  
A. R. Zimmerman ◽  
R. Hamdan ◽  
W. T. Cooper
Keyword(s):  
Organic Matter ◽  
Crop Yields ◽  
Physicochemical Characteristics ◽  
Exchange Capacity ◽  
Interactive Effects ◽  
Microbial Oxidation ◽  
Sem Images ◽  
Physicochemical Changes ◽  
Pyrogenic Organic Matter ◽  
Over Time

Abstract. Predicting the effects of pyrogenic organic matter (OM) addition (either natural or intentional as in the case of biochar amendment) on soil chemistry and crop yields has been hampered by a lack of understanding of how pyrogenic OM evolves in the environment over time. This work compared the physicochemical characteristics of newly-made and 15 month field-aged biochars and biochar-soil mixtures. After aging, biochars made by pyrolysis of wood and grass at 250, 400 and 650 °C exhibited 5-fold increases in cation exchange capacity (CEC), on average, appearance of anion exchange capacity (AEC) and significant decreases in pH, ash content and nanopore surface area. Cross polarization 13C-NMR analyses indicated relative increases in O-containing functional groups including substituted aryl, carboxyl and carbonyl C, likely via abiotic and microbial oxidation and losses of O-alkyl groups, likely via leaching. Similar chemical trends were observed for soil-biochar mixtures suggesting the same biochar aging processes occurred in the soil environment. However, there was evidence for a major role of soil OM-microbe-biochar interaction during aging. Field-aging of soil with biochar resulted in large increases in C and N content (up to 124 and 143%, respectively) and exchange capacity (up to 43%) beyond that calculated by the weighted addition of the properties of biochar and soil aged separately. These beneficial interactive effects varied greatly with soil and biochar type. Scanning electronic microscopy (SEM) images of biochar particles, both aged alone and with soil, showed colonization by microbes and widespread surficial deposits that were likely OM. Thus, sorption of both microbially-produced and soil OM are likely processes that enhanced biochar aging. Among the important implications of these findings are that biochar's full beneficial effects on soil properties only occur over time and proper assignment of C sequestration credits to biochar users will require consideration of soil-biochar interactions.

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