Delivery of Complex Organic Compounds from Evolved Stars to the Solar System

Stars in the late stages of evolution are able to synthesize complex organic compounds with aromatic and aliphatic structures over very short time scales. These compounds are ejected into the interstellar medium and distributed throughout the Galaxy. The structures of these compounds are similar to the insoluble organic matter found in meteorites. In this paper, we discuss to what extent stellar organics has enriched the primordial Solar System and possibly the early Earth.     

Influence of soil organic matter decomposition on arbuscular mycorrhizal fungi in terms of asymbiotic hyphal growth and root colonization

Soil organic matter is known to influence arbuscular mycorrhizal (AM) fungi, but limited information is available on the chemical components in the organic matter causing these effects. We studied the influence of decomposing organic matter (pure cellulose and alfalfa shoot and root material) on AM fungi after 30, 100, and 300 days of decomposition in nonsterile soil with and without addition of mineral N and P. Decomposing organic matter affected maize root length colonized by the AM fungus Glomus claroideum in a similar manner as other plant growth parameters. Colonized root length was slightly increased by both nitrogen and phosphorus application and plant materials, but not by application of cellulose. In vitro hyphal growth of Glomus intraradices was increased by soil extracts from the treatments with all types of organic materials independently of mineral N and P application. Pyrolysis of soil samples from the different decomposition treatments revealed in total 266 recognizable organic compounds and in vitro hyphal growth of G. intraradices in soil extract positively correlated with 33 of these compounds. The strongest correlation was found with 3,4,5-trimethoxybenzoic acid methyl ester. This compound is a typical product of pyrolysis of phenolic compounds produced by angiosperm woody plants, but in our experiment, it was produced mainly from cellulose by some components of the soil microflora. In conclusion, our results indicate that mycelia of AM fungi are influenced by organic matter decomposition both via compounds released during the decomposition process and also by secondary metabolites produced by microorganisms involved in organic matter decomposition.     

Evolution of soil organic matter changes using pyrolysis and metabolic indices: a comparison between organic and mineral fertilization

The aim of this study was to evaluate chemical and biochemical changes of organic matter in fertilized (ammonium nitrate) and amended (vermicompost and manure) soils using pyrolysis and metabolic indices. The metabolic potential [dehydrogenase (DH-ase)/water soluble organic carbon (WSOC)], the metabolic quotient (qCO2) and the microbial quotient (Cmic:Corg) were calculated as indices of soil organic matter evolution. Pyrolysis-gas chromatography (Py-GC) was used to study structural changes in the organic matter. Carbon forms and microbial biomass have been measured by dichromate oxidation and fumigation-extraction methods, respectively. Dehydrogenase activity has been tested using INT (p-Iodonitrotetrazolium violet) as substrate. The results showed that organic amendment increased soil microbial biomass and its activity which were strictly related to pyrolytic mineralization and humification indices (N/O, B/E3). Mineral fertilization caused a greater alteration of native soil organic matter than the organic amendments, in that a high release of WSOC and relatively large amounts of aliphatic pyrolytic products, were observed. Therefore, the pyrolysis and metabolic indices provided similar and complementary information on soil organic matter changes after mineral and organic fertilization.     

Confined-pyrolysis as an experimental method for hydrothermal organic synthesis

A closed pyrolysis system has been developed as a tool for studying the reactions of organic compounds under extreme hydrothermal conditions. Small high pressure stainless steel vessels in which the ratio of sediment or sample to water has been adjusted to eliminate the headspace at peak experimental conditions confines the organic components to the bulk solid matrix and eliminates the partitioning of the organic compounds away from the inorganic components during the experiment. Confined pyrolysis experiments were performed to simulate thermally driven catagenetic changes in sedimentary organic matter using a solids to water ratio of 3.4 to 1. The extent of alteration was measured by monitoring the steroid and triterpenoid biomarkers and polycyclic aromatic hydrocarbon distributions. These pyrolysis experiments duplicated the hydrothermal transformations observed in nature. Molecular probe experiments using alkadienes, alkenes and alkanes in H₂O and D₂O elucidated the isomerization and hydrogenation reactions of aliphatic compounds and the competing oxidative reactions occurring under hydrothermal conditions. This confined pyrolysis technique is being applied to test experiments on organic synthesis of relevance to chemical evolution for the origin of life.     

基于Py-GC-MS/MS技术的高寒草原土壤有机质不同组分指纹特征研究

采用热裂解气相色谱质谱联用(Py-GC-MS/MS)技术来研究高寒草原土壤有机质5个密度组分之间的指纹差异。对150种热解产物进行定性定量分析,并将其根据相似的化学性质分为:烷基类化合物、芳烃及多环芳烃、木质素、酚类物质、多糖、含氮化合物及几丁质。研究结果表明:在高寒草原土壤中,F1(密度为小于1.6g/cm~3)组分主要为植物碎屑,虽然该组份在整体土壤中质量含量较少(0.13%)但其有机质含量相对较高(5.7%),该组份中含有较多的木质素及长链烷基类化合物(主要来源于植物),且随着密度的增加,此类化合物的含量逐渐减少。F2(密度为1.6—1.8g/cm~3)、F3(密度为1.8—2.0g/cm~3)及F4(密度为2.0—2.25g/cm~3)3个组分化学性质相似,其有机化合物的含量在密度组分中呈现增加或减少的过渡状态。F5(密度大于2.25g/cm~3)组分是该土壤的主要组成部分,其质量含量高达98%,该组份中的微生物指纹信息(微生物来源的多糖及含氮化合物)均高于前4个组分。同时,芳烃及多环芳烃这类难降解的物质随着密度的增大逐渐累积,在F5组分中富集。     

Supernovae, neutron stars and biomolecular chirality

Recent theoretical and experimental investigations of the origin of biomolecular chirality are reviewed briefly. Biotic and abiotic theories are evaluated critically with the conclusion that asymmetric photochemical processes with circulary polarized light (CPL), particularly asymmetric photolyses, constitute the most viable mechanisms. Solar CPL sources appear too weak and random to be effective. We suggest an alternative CPL source, namely, the synchrotron radiation from the neutron star remnants of supernova explosions. This could asymmetrically process racemic compounds in the organic mantles of the dust grains in interstellar clouds, and the resulting chiral molecules could be transferred to Earth by cold accretion as the solar system periodically traverses these interstellar clouds.     

Transformation of buffalo manure by composting or vermicomposting to rehabilitate degraded tropical soils

The addition of composted buffalo manure may lead to qualitative and quantitative improvement of the organic matter content of degraded tropical agricultural soils in Northern Vietnam. The objectives of this study were to follow the biochemical changes occurring during composting of buffalo manure with and without earthworms during 3 months and to study the effect of the end products (compost and vermicompost) on soil biochemical parameters and plant growth after two months of incubation under controlled conditions in an open pot experiment. Our conceptual approach included characterisation of organic matter of the two composts before and after addition to soil by elemental, isotopic analysis and analytical pyrolysis and comparison with conventional fertilisation. We also analysed for lignin content and composition.Our results showed that composting in the presence of earthworms led to stronger transformation of buffalo manure than regular composting. Vermicompost was enriched in N-containing compounds and depleted in polysaccharides. It further contained stronger modified lignin compared to regular compost. In the bulk soil, the amendment of compost and vermicompost led to significant modification of the soil organic matter after 2 months of exposure to natural weather conditions. The lignin component of SOM was unaffected whatever the origin of the organic amendment. Compost and vermicompost amendments both enhanced aggregation and increased the amount of organic matter in water stable aggregates. However, vermicompost is preferable to compost due to its beneficial effect on plant growth, while having similar positive effects on quantity and quality of SOM.     

Changes in dissolved lignin-derived phenols, neutral sugars, uronic acids, and amino sugars with depth in forested Haplic Arenosols and Rendzic Leptosols

A major part of the dissolved organic matter produced in the organic layers of forest ecosystems and leached into the mineral soil is retained by the upper subsoil horizons. The retention is selective and thus dissolved organic matter in the subsoils has different composition than dissolved organic matter leached from the forest floor. Here we report on changes in the composition of dissolved organic matter with soil depth based on C-to-N ratios, XAD-8 fractionation, wet-chemical analyses (lignin-derived CuO oxidation products, hydrolysable sugars and amino sugars) and liquid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy. Dissolved organic matter was sampled directly beneath the forest floor using tension-free lysimeters and at 90cm depth by suction cups in Haplic Arenosols under Scots pine (Pinus sylvestris L.) and Rendzic Leptosols under European beech (Fagus sylvatica L.) forest. At both sites, the concentrations of dissolved organic carbon (DOC) decreased but not as strongly as reported for deeply weathered soils. The decrease in DOC was accompanied by strong changes in the composition of dissolved organic matter. The proportion of the XAD-8-adsorbable (hydrophobic) fraction, carboxyl and aromatic C, and the concentrations of lignin-derived phenols decreased whereas the concentrations of sugars, amino sugars, and nitrogen remained either constant or increased. A general feature of the compositional changes within the tested compound classes was that the ratios of neutral to acidic compounds increased with depth. These results indicate that during the transport of dissolved organic matter through the soils, oxidatively degraded lignin-derived compounds were preferentially retained while potentially labile material high in nitrogen and carbohydrates tended to remain dissolved. Despite the studied soils' small capacity to sorb organic matter, the preferential retention of potentially refractory and acidic compounds suggests sorption by the mineral soil matrix rather than biodegradation to govern the retention of dissolved organic matter even in soils with a low sorption capacity.     

Release of dissolved organic matter by photosynthesizing algae in Lake Kinneret,Israel*

The incorporation of inorganic carbon in particulate and dissolved organic matter by natural populations of photosynthesizing algae has been studied in Lake Kinneret, Israel, from August 1972 to December 1973. The release of dissolved organic material was directly related to the rates of particulate productivity. However, the percentage of extracellular release (PER) of dissolved organic compounds showed an inverse relationship with chlorophyll a concentrations. Mean PER values (for the trophogenic layer) over the experimental period were 3·7%, and were lowest during the exponential growth phase of the annual dinoflagellate bloom (mean PER = 1·9%). Highest PER were measured in deep, light-limited samples (mean = 31·7%; s.d.· 21·9%). In a dense metalimnic layer of photosynthetic sulphur bacteria (Chlorobium phaeobacterioides), PER was not as extremely high as has been reported for a similar layer in Lake Wadolek, Poland. Although the amounts of dissolved organic matter released by phytoplankton in Lake Kinneret were low, they may have significance as growth modulators and as substrates for heterotrophic organism.     

Organic compounds in re-circulated leachates of aerobic biological treated municipal solid waste

Biodegradation of organic matter is required to reduce the potential of municipal solid waste for producing gaseous emissions and leaching contaminants. Therefore, we studied leachates of an aerobic-treated waste from municipal solids and a sewage sludge mixture that were re-circulated to decrease the concentration of biodegradable organic matter in laboratory-scale reactors. After 12 months, the total organic C and biological and chemical oxygen demands were reduced, indicating the biodegradation of organic compounds in the leachates. Curie-point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis-field ionization mass spectrometry (Py-FIMS) revealed that phenols, alkylaromatic compounds, N-containing compounds and carbohydrates were the predominate compounds in the leachates and solid waste. Leachate re-circulation led to a higher thermal stability of the residual organic matter as indicated by temperature-resolved Py-FIMS. Admixture of sewage sludge to solid waste was less effective in removing organic compounds from the leachates. It resulted in drastic higher and more bio-resistant loads of organic matter in the leachates and revealed increased proportions of alkylaromatic compounds. The biodegradation of organic matter in leachates, re-circulated through municipal solid waste, offers the potential for improved aerobic waste treatments and should be investigated on a larger scale.     

Assessing the efficiency of urban waste biocomposting by analytical pyrolysis (Py-GC/MS)

Analytical pyrolysis (Py-GC/MS) was used to study complex composting processes. The technique was first validated for reproducibility and finally applied to assess the efficiency of a microbial bio-accelerator product (CBB) in composting organic residues with different composition. Fresh lignocellulosic and urban wastes were treated with CBB and the composting kinetics studied to investigate the transformations undergone in the course of biocomposting. Our findings demonstrate that these changes, as well as the efficiency of CBB, can be monitored through the molecular characterization of the released pyrolysis products. The CBB bacterial product effectively seems to favour composting accelerating the process and shorten composting time. Analytical pyrolysis was informative in assessing to which extent compost transformation reached an acceptable stabilization point. The technique could be also developed into a semi-quantitative tool to monitor changes of main organic matter components (polysaccharides, proteins, lignin, lipids, etc.) as composting proceeds.     

Thermal conversion of elephant grass (Pennisetum purpureum Schum) to bio-gas, bio-oil and charcoal

Elephant grass is an abundant, fast growing plant with significant potential as a renewable energy source and for conversion to higher calorific value fuels. This work investigates thermal conversion of elephant grass to bio-gas, bio-oil and charcoal under two heating rates of 10 and 50 degrees C/min. The energy required to pyrolyse elephant grass was evaluated using computer aided thermal analysis technique, while composition of the resultant bio-gas and bio-oil products were monitored with gas chromatographic and mass spectroscopic techniques. At 500 degrees C, the bio-gas compounds consisted primarily of CO(2) and CO with small amounts of methane and higher hydrocarbon compounds. The heat of combustion of the bio-gas compounds was estimated to be 3.7-7.4 times higher than the heat required to pyrolyse elephant grass under both heating rates, which confirms that the pyrolysis process can be self-maintained. Faster heating rate was found to increase the amount of liquid products by 10%, while charcoal yields remained almost the same at 30%. The bio-oil mainly consisted of organic acids, phthalate esters, benzene compounds and amides. The amount of organic acids and benzene compounds were significantly reduced at 50 degrees C/min, while the yields of phthalate esters and naphthalene compounds increased. The difference in bio-oil composition with increased heating rate is believed to be associated with the reduction of the secondary reactions of pyrolysis, which are more pronounced under lower heating rate.     

Digestive efficiency of the Hoatzin, Opisthocomus hoazin: a folivorous bird with foregut fermentation

The Hoatzin Opisthocomus hoazin is the only known bird with a well-developed foregut plant fermentation system; most fermentation takes place in the crop and caudal oesophagus. To test Hoatzin digestive efficiency, balance (total collection) trials with captive Hoatzins were made using two experimental diets of different composition and fibre content. Dry matter (DM) intakes were similar for the diets (mean = 62.8 g DM/kg body mass/ day). Average DM, organic matter and nitrogen digestibilities were not significantly different between diets, with average values of 72.9%, 75.0% and 78.3%, respectively. In vitro organic matter digestibilities by cow ruminal inoculum were very similar to organic matter digestibilities in live Hoatzins for both diets. Fibre digestibility was among the highest recorded for herbivorous birds. Cellulose and acid detergent fibre digestibilities were 58.8% and 52.7%, respectively. Neutral detergent fibre (NDF) digestibility differed among diets—the higher the NDF content of the diet, the higher the NDF digestibility. The NDF digestibilities were 37.9% and 70.9% for the two diets with NDF concentrations of 32.4% and 37.3%, respectively. Differences in NDF digestibility can be attributed to the different concentrations of hemicellulose in the experimental diets. The high overall digestibility by captive Hoatzins is higher than values previously reported for other avian herbivores but similar to those of foregut-fermenting mammals on similar diets. The unique digestive strategy of the Hoatzin maximizes digestion of cell wall and cell contents. The high digestive efficiency in the Hoatzin is not predicted by allometric models of fibre digestion as a function of body mass. Other nutritional benefits, such as detoxification of plant secondary compounds and microbial synthesis of essential amino acids and vitamins, may explain the evolution of foregut fermentation in this avian folivore.     

Dust in the universe: Implications for terrestrial prebiotic chemistry

In the present review we analyze the available literature on the distribution of dust in the Universe, methods of its observation and determination of the chemical composition, and the roles for terrestrial prebiotic chemistry. The most plausible natural sources of dust on the Earth in the prebiotic era are sedimentation of interplanetary dust, meteoritic and cometary impacts, volcanic eruptions, and soil microparticulates; the interplanetary medium being among the most powerful supplier of the dust matter. Two fundamental roles of dust particles for the origins of life are considered: (1) catalytic formation of prebiotic compounds; and (2) delivery of organic matter to the Earth by space dust particles. Due to the fact that there is only approximate information on the chemical composition and properties of interstellar, circumstellar, and major part of interplanetary dust, even the simulating experiments are difficult to perform. Until these gaps are filled, it seems reasonable to focus efforts of the scientists dealing with dust-driven catalytic formation of prebiotically important compounds on the volcanic and meteoritic/cometary impact environments.     

Organic matter in meteorites.

Some primitive meteorites are carbon-rich objects containing a variety of organic molecules that constitute a valuable record of organic chemical evolution in the universe prior to the appearance of microorganisms. Families of compounds include hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, amino acids, amines, amides, heterocycles, phosphonic acids, sulfonic acids, sugar-related compounds and poorly defined high-molecular weight macromolecules. A variety of environments are required in order to explain this organic inventory, including interstellar processes, gas-grain reactions operating in the solar nebula, and hydrothermal alteration of parent bodies. Most likely, substantial amounts of such organic materials were delivered to the Earth via a late accretion, thereby providing organic compounds important for the emergence of life itself, or that served as a feedstock for further chemical evolution. This review discusses the organic content of primitive meteorites and their relevance to the build up of biomolecules.     

Photochemical conversions of lower aldehydes in aqueous solutions and in fog

One of the possible paths of abiogenic synthesis of biologically important compounds on primordial Earth, as well as under extraterrestrial conditions, might have been the photochemical conversions of polyatomic organic molecule detected at present in the interstellar medium and in cosmic bodies. The important contribution from lower aldehydes is emphasized. Experimental results show that amino acids, peptide-like compounds, N-heterocyclic compounds, etc., are formed by UV irradiation (254 nm) of aqueous solutions either of formaldehyde, or of acetaldehyde with ammonium nitrate. UV-irradiated fog of the same composition yields aminoacids, mostly glycine.     

Preservation of overmature,ancient, sedimentary organic matter in carbonate concretions during outcrop weathering

Concretions are preferentially cemented zones within sediments and sedimentary rocks. Cementation can result from relatively early diagenetic processes that include degradation of sedimentary organic compounds or methane as indicated by significantly ¹³C‐depleted or enriched carbon isotope compositions. As minerals fill pore space, reduced permeability may promote preservation of sediment components from degradation during subsequent diagenesis, burial heating and outcrop weathering. Discrete and macroscopic organic remains, macro and microfossils, magnetic grains, and sedimentary structures can be preferentially preserved within concretions. Here, Cretaceous carbonate concretions of the Holz Shale are shown to contain relatively high carbonate‐free total organic carbon (TOC) contents (up to ~18.5 wt%) compared to the surrounding host rock (with <2.1 wt%). TOC increases with total inorganic carbon (TIC) content, a metric of the degree of cementation. Pyrite contents within concretions generally correlate with organic carbon contents. Concretion carbonate carbon isotope compositions (δ¹³C_carb) range from ?22.5 to ?3.4‰ (VPDB) and do not correlate strongly with TOC. Organic carbon isotope compositions (δ¹³C_org) of concretions and host rock are similar. Thermal maturity data indicate that both host and concretion organic matter are overmature and have evolved beyond the oil window maturity stage. Although the organic matter in general has experienced significant oxidative weathering, concretion interiors exhibit lower oxygen indices relative to the host. These results suggest that carbonate concretions can preferentially preserve overmature, ancient, sedimentary organic matter during outcrop weathering, despite evidence for organic matter degradation genetic mechanisms. As a result, concretions may provide an optimal proxy target for characterization of more primary organic carbon concentrations and chemical compositions. In addition, these findings indicate that concretions can promote delayed oxidative weathering of organic carbon in outcrop and therefore impact local chemical cycling.     

Alteration and Stability of Complex Macromolecular Amino Acid Precursors in Hydrothermal Environments

Origins of Life and Evolution of Biospheres - The early Solar System comprised a broad area of abiotically created organic compounds, including interstellar organics which were integrated into...     

Evidence for organic synthesis in high temperature aqueous media — Facts and prognosis

Hydrothermal systems are common along the active tectonic areas of the earth. Potential sites being studied for organic matter alteration and possible organic synthesis are spreading ridges, off-axis systems, back-arc activity, hot spots, volcanism, and subduction. Organic matter alteration, primarily reductive and generally from immature organic detritus, occurs in these high temperature and rapid fluid flow hydrothermal regimes. Hot circulating water (temperature range — warm to >400 °C) is responsible for these molecular alterations, expuslion and migration. Compounds that are obviously synthesized are minor components because they are generally masked by the pyrolysis products formed from contemporary natural organic precursors. Heterocyclic sulfur compounds have been identified in high temperature zones and hydrothermal petroleums of the Guaymas Basin vent systems. They can be interpreted as being synthesized from formaldehyde and sulfur or HS _x ^– in the hydrothermal fluids.Other products from potential synthesis reactions have not yet been found in the natural systems but are expected based on known industrial processes and inferences from experimental simulation data. Various industrial processes have been reviewed and are of relevance to hydrothermal synthesis of organic compounds. The reactivity of organic compounds in hot water (200–350 °C) has been studied in autoclaves, and supercritical water as a medium for chemistry has also been evaluated. This high temperature aqueous organic chemistry and the strong reducing conditions of the natural systems suggest this as an important route to produce organic compounds on the primitive earth. Thus a better understanding of the potential syntheses of organic compounds in hydrothermal systems will require investigations of the chemistry of condensation, autocatalysis, catalysis and hydrolysis reactions in aqueous mineral buffered systems over a range of temperatures from warm to >400 °C.Presented in part at the International Society for the Study of the Origin of Life Meeting, Barcelona, Spain, July 1993.     

Decomposition of soil organic matter from boreal black spruce forest: environmental and chemical controls

Black spruce forests are a dominant covertype in the boreal forest region, and they inhabit landscapes that span a wide range of hydrologic and thermal conditions. These forests often have large stores of soil organic carbon. Recent increases in temperature at northern latitudes may be stimulating decomposition rates of this soil carbon. It is unclear, however, how changes in environmental conditions influence decomposition in these systems, and if substrate controls of decomposition vary with hydrologic and thermal regime. We addressed these issues by investigating the effects of temperature, moisture, and organic matter chemical characteristics on decomposition of fibric soil horizons from three black spruce forest sites. The sites varied in drainage and permafrost, and included a “Well Drained” site where permafrost was absent, and “Moderately well Drained” and “Poorly Drained” sites where permafrost was present at about 0.5 m depth. Samples collected from each site were incubated at five different moisture contents (2, 25, 50, 75, and 100% saturation) and two different temperatures (10°C and 20°C) in a full factorial design for two months. Organic matter chemistry was analyzed using pyrolysis gas chromatography-mass spectrometry prior to incubation, and after incubation on soils held at 20°C, 50% saturation. Mean cumulative mineralization, normalized to initial carbon content, ranged from 0.2% to 4.7%, and was dependent on temperature, moisture, and site. The effect of temperature on mineralization was significantly influenced by moisture content, as mineralization was greatest at 20°C and 50–75% saturation. While the relative effects of temperature and moisture were similar for all soils, mineralization rates were significantly greater for samples from the “Well Drained” site compared to the other sites. Variations in the relative abundances of polysaccharide-derivatives and compounds of undetermined source (such as toluene, phenol, 4-methyl phenol, and several unidentifiable compounds) could account for approximately 44% of the variation in mineralization across all sites under ideal temperature and moisture conditions. Based on our results, changes in temperature and moisture likely have similar, additive effects on in situ soil organic matter (SOM) decomposition across a wide range of black spruce forest systems, while variations in SOM chemistry can lead to significant differences in decomposition rates within and among forest sites.