Bonds In Organic Matter Research Articles

PHYTOPLANKTON PRIMARY PRODUCTIVITY

Primary productivity is an important integral parameter describing energy potential of aquatic organisms’ vital activity. Primary productivity determines the quality of water environment, its self- purifying capacity – from the Global Ocean to various continental ecosystems (Odum 1953, Williams et al. 2002, Bott et al. 2006, Kuehl and Troelstrup 2013).
 Primary productivity is a bioenergy process transforming the solar energy into the energy of chemical bonds in organic matter, newly synthesized by the autotrophic link. The autotrophic link is mainly formed by algae from different ecological groups (phytoplankton, phytobenthos, phytoperiphyton) and higher aquatic plants.
 As any process of energy production and transition, primary production in aquatic ecosystems is regulated by the laws of thermodynamics: the first law – the Lomonosov-Lavoisier law, the second law – the entropy law (Odum 1953). It is necessary to state clearly, that green plants do not transform the total amount of the Sun’s radiant energy, but only a part of it, within the spectral range between 480 and 720 nm (within the wavelength band of photosynthetically active radiation).A simplified equation describing the primary production process can be represented as follows:Proceeding from the above equation, primary productivity may be considered equivalent to (analogous to) the photosynthesis intensity.
 There is a range of various methods for estimating PP: according to algal cell number, according to nutrient dynamic in water, according to diurnal dynamics of dissolved oxygen, according to chlorophyll a content, light-and-dark bottle method in oxygen or radiocarbon modification. With consideration taken of these methods’ advantages and disadvantages, researchers will be able to obtain the most reliable and unbiased primary productivity data.

Integrated catalytic hydroconversion of three crop stalks to valuable oxygenated organic chemicals

Two flexible regulation systems were designed and used for the integrated catalytic hydroconversion (CHC) of lignocellulose to valuable oxygenated organic chemicals. Under the dual constraints of initial H2 pressure (IHP) and temperature, three crop stalks can be almost completely degraded over a hydrothermally stable Ru/La(OH)3 in one-pot, while the synergetic transfer of active hydrogen effectively promotes the cleavage of >C-O- bridged bonds in organic matter with highly complex structures during this period. As a result, abundant >Cal-O- (>32%) and >C=O (>24%) derived platform chemicals such as alkanols, cyclanols, carboxylic acids, and esters were obtained at high IHP and low temperature. Correspondingly, various >Car-O- (>50%) and >C=O (>30%) derived platform chemicals such as phenols, alkoxy-substituted phenols, ketones, and carboxylic acids dominated the derived bio-oils at low IHP and high temperature. The designed selective CHC strategies have the characteristics of convergent conversion to the two major derivative chemical demand directions. Therefore, these two atom-economic and effective degradation approaches are conducive to obtaining abundant functional small molecules, which can be further converted to various downstream platform products.

New Insights into the Primary Reaction Products of Naomaohu Coal via Breaking Weak Bonds with Supercritical Ethanolysis

Coal is an important energy source in the world, and its chemical structure is the basis of its application, especially for its pyrolysis and liquefaction. Supercritical ethanolysis is a type of chemical extraction that can effectively depolymerize some weak bonds in organic matter. In this work, new insights into the primary products of Naomaohu coal were studied with supercritical ethanolysis. The non-covalent and weak covalent bonds (such as ether and ester bonds) in the coal were broken to yield small molecular compounds (SMCs) with a conversion of 70.3% (dry and ash-free basis) at 370 °C. SMCs, including esters, alcohols, aldehydes, ethers, ketones, hydrocarbons (aromatic and aliphatic hydrocarbons), acids, phenols, and heteroatom compounds, were identified quantitively through gas chromatography/mass spectrometry. Fourier transform infrared spectroscopy and 13C nuclear magnetic resonance were used to characterize the structure of the coal and its ethanolysis residues. The structure characteristic of...

Hydrogenation of organic matter as a terminal electron sink sustains high CO2:CH4 production ratios during anaerobic decomposition

Once inorganic electron acceptors are depleted, organic matter in anoxic environments decomposes by hydrolysis, fermentation, and methanogenesis, requiring syntrophic interactions between microorganisms to achieve energetic favorability. In this classic anaerobic food chain, methanogenesis represents the terminal electron accepting (TEA) process, ultimately producing equimolar CO2 and CH4 for each molecule of organic matter degraded. However, CO2:CH4 production in Sphagnum-derived, mineral-poor, cellulosic peat often substantially exceeds this 1:1 ratio, even in the absence of measureable inorganic TEAs. Since the oxidation state of C in both cellulose-derived organic matter and acetate is 0, and CO2 has an oxidation state of +4, if CH4 (oxidation state −4) is not produced in equal ratio, then some other compound(s) must balance CO2 production by receiving 4 electrons. Here we present evidence for ubiquitous hydrogenation of diverse unsaturated compounds that appear to serve as organic TEAs in peat, thereby providing the necessary electron balance to sustain CO2:CH4>1. While organic electron acceptors have previously been proposed to drive microbial respiration of organic matter through the reversible reduction of quinone moieties, the hydrogenation mechanism that we propose, by contrast, reduces CC double bonds in organic matter thereby serving as (1) a terminal electron sink, (2) a mechanism for degrading complex unsaturated organic molecules, (3) a potential mechanism to regenerate electron-accepting quinones, and, in some cases, (4) a means to alleviate the toxicity of unsaturated aromatic acids. This mechanism for CO2 generation without concomitant CH4 production has the potential to regulate the global warming potential of peatlands by elevating CO2:CH4 production ratios.

Occurrence of particle‐bound polysulfides and significance of their reaction with organic matters in marine sediments

Inorganic polysulfides (Sn2−, where n > 1) contribute to the incorporation of sulfur into organic matter in reducing sediments, especially when conditions exist for partial oxidation of sulfide. Inorganic polysulfides have been assumed previously to exist only in the aqueous phase. Our results suggest that a significant fraction of inorganic polysulfides is bound to the particulate‐phase of sediments and can react with carbon‐carbon unsaturated bonds in organic matter, thereby attaching it to the particulate phase through polysulfide linkages. This mechanism may affect the bioavailability of the reactive organic matter in sediments and hence may play an important role in the preservation of organic matter in anoxic marine sediments.