Abiotic synthesis of organic molecules from minerals containing traces of dissolved H2O,CO2 and N2 part II: Experimental data

Even though a given mineral, for instance olivine, may contain only traces of dissolved H₂O, CO₂ and N₂ the gases which evolve from its surface during heating comprise (a) highly reduced molecules such as H₂, CH₄, C_mH_n and more complex hydrocarbons, HCN and other N-bearing compounds (b) oxidized species in various degrees of oxidation from formaldehyde and CO to oxygen. These gases evolve sequentially besides H₂O, CO₂ and possibly N₂, their relative amounts being controlled by experimental parameters such as the rate of heating. Preliminary indications of amino acids have been obtained by liquid extraction. The chemical complexity is a consequence of radical reactions between different solute species in the surface and the bulk of the mineral grains. Data for synthetic MgO and for mantle-derived olivine are presented.     

Synthesis of biomolecules from N2, CO,and H2O by electric discharge

A model primitive gas containing a mixture of N₂, CO and water vapor over a water pool (300 mL, 37 °C) was subjected to electric discharges. The discharge vessel (7 L in volume) was equipped with a CO₂ absorber (The CO₂ being formed during the discharge), thus simulating possible absorption of CO₂ in the primitive ocean. The vessel also has a cold trap ( –15 °C), which protects the primary products against the further decomposition in the discharge phase by enabling these products to adhere to the trap. Since the partial pressures of CO and N₂ decreased at rates of 1.5–1.7 cmHg day^–1 and 0.1–0.2 cmHg day^–1, respectively, the gases were added at regular intervals. The solution was analyzed at regular intervals for HCN, HCHO and urea, and maximum concentrations of about 50, 2, and 140 mM were observed. The discharge phase was continued for 6 months. In the solution, glycine (5.6% yield based on the carbon), glycylglycine (0.64%), orotic acid (0.004%) and small amounts of the other amino acids were found.     

Annual emissions of dissolved CO2, CH4, and N2O in the subsurface drainage from three cropping systems

Indirect emission of nitrous oxide (N₂O), associated with nitrogen (N) leaching and runoff from agricultural lands is a major source of atmospheric N₂O. Recent studies have shown that carbon dioxide (CO₂) and methane (CH₄) are also emitted via these pathways. We measured the concentrations of three dissolved greenhouse gases (GHGs) in the subsurface drainage from field lysimeter that had a shallow groundwater table. Aboveground fluxes of CH₄ and N₂O were monitored using an automated closed‐chamber system. The annual total emissions of dissolved and aboveground GHGs were compared among three cropping systems; paddy rice, soybean and wheat, and upland rice. The annual drainage in the paddy rice, the soybean and wheat, and the upland rice plots was 1435, 782, and 1010 mm yr^?1, respectively. Dissolved CO₂ emissions were highest in the paddy rice plots, and were equivalent to 1.05–1.16% of the carbon storage in the topsoil. Dissolved CH₄ emissions were also higher in the paddy rice plots, but were only 0.03–0.05% of the aboveground emissions. Dissolved N₂O emissions were highest in the upland rice plots, where leached N was greatest due to small crop biomass. In the soybean and wheat plots, large crop biomass, due to double cropping, decreased the drainage volume, and thus decreased dissolved GHG emissions. Dissolved N₂O emissions from both the soybean and wheat plots and the upland rice plots were equivalent to 50.3–67.3% of the aboveground emissions. The results indicate that crop type and rotation are important factors in determining dissolved GHG emissions in the drainage from a crop field.     

Dynamics of dissolved O2, CO2, CH4, and N2O in a tropical coastal swamp in southern Thailand

We studied the distribution of dissolved O₂, CO₂, CH₄, and N₂O in a coastal swamp system in Thailand with the goal to characterize the dynamics of these gases within the system. The gas concentrations varied spatially and seasonally in both surface and ground waters. The entire system was a strong sourcefor CO₂ and CH₄, and a possible sink for atmospheric N₂O. Seasonal variation in precipitation primarily regulated the redox conditions in the system. However, distributions of CO₂, CH₄, and N₂O in the river that received swamp waters were not always in agreement with redox conditions indicated by dissolvedO₂ concentrations. Sulfate production through pyriteoxidation occurred in the swamp with thin peat layerunder aerobic conditions and was reflected by elevatedSO ₄ ^2– /Cl^– in the river water. When SO ₄ ^2– /Cl^– was high, CO₂ and CH₄ concentrations decreased, whereas the N₂O concentration increased. The excess SO ₄ ^2– in the river water was thus identified as a potential indicator for gas dynamics in this coastal swamp system.     

Continuous mass spectrometric measurement of dissolved H2, O2, and CO2 during chemolithoautotrophic growth of Alcaligenes eutrophus strain H 16

Summary Polarographic oxygen electrodes, a mass spectrometer with a membrane inlet system, and a redox electrode were used to measure dissolved H₂, O₂, and CO₂ continuously during chemolithoautotrophic cultivation of Alcaligenes eutrophus H 16. A mass spectrometer is a versatile instrument for measuring dissolved gases. Its dynamic characteristics are comparable to conventional sterilizable oxygen electrodes. A redox electrode combined with an oxygen electrode is a simple but somewhat limited sensor to measure dissolved H₂.Symbols and Abbreviations a Empirical constant [Eq. (1)] - b Empirical constant [Eq. (1)] - c Concentration - D Diffusion coefficient - E Redox potential direct electrode measurement - F Flow velocity - I Signal from amis spectrometer - k_La Volumetric transport coefficient - k_Lá Apparent volumetric transport coefficient - Q_max Maximal specific gas uptake rate - q Mean value of ratios of apparent k_Lá-values of two gases - q_F Ratio of diffusion coefficients - q_S Square root of ratio of diffusion coefficients - S Limiting substrate concentration - t Time - v Velocity - X Cell dry mass concentration - DSM Deutsche Sammlung für Mikroorganismen, Göttingen, F.R.G. - IL Polarographic electrode, Instrumentation Laboratories, SpA., Milan, Italy - WTW Polarographic electrode, Wissenschaftlich-Technische Werkstätten, Weilheim, FRG - MS Mass spectrometer - PHB Poly--hydroxybutyric acid Presented at the 1st European Congress on Biotechnology; Interlaken, Switzerland September 25–29, 1978     

Coupling dissolved organic carbon,CO2 and productivity in boreal lakes

相似文献   

Prebiotic synthesis in atmospheres containing CH4, CO,and CO2

The prebiotic synthesis of organic compounds using a spark discharge on various simulated primitive earth atmospheres at 25 degrees C has been studied. Methane mixtures contained H2 + CH4 + H2O + N2 + NH3 with H2/CH4 molar ratios from 0 to 4 and pNH3 = 0.1 torr. A similar set of experiments without added NH3 was performed. The yields of amino acids (1.2 to 4.7% based on the carbon) are approximately independent of the H2/CH4 ratio and whether NH3 was present, and a wide variety of amino acids are obtained. Mixtures of H2 + CO + H2O + N2 and H2 + CO2 + H2O + N2, with and without added NH3, all gave about 2% yields of amino acids at H2/CO and H2/CO2 ratios of 2 to 4. For a H2/CO2 ratio of 0, the yield of amino acids is extremely low (10(-3)%). Glycine is almost the only amino acid produced from CO and CO2 model atmospheres. These results show that the maximum yield is about the same for the three carbon sources at high H2/carbon ratios, but that CH4 is superior at low H2/carbon ratios. In addition, CH4 gives a much greater variety of amino acids than either CO or CO2. If it is assumed that an abundance of amino acids more complex than glycine was required for the origin of life, then these results indicate the requirement for CH4 in the primitive atmosphere.     

Land use and season affect fluxes of CO2, CH4, CO,N2O,H2 and isotopic source signatures in Panama: evidence from nocturnal boundary layer profiles

Conversion of tropical rainforests to pastures and plantations is associated with changes in soil properties and biogeochemical cycling, with implications for carbon cycling and trace gas fluxes. The stable isotopic composition of ecosystem respiration (δ¹³C_R and δ¹⁸O_R) is used in inversion models to quantify regional patterns of CO₂ sources and sinks, but models are limited by sparse measurements in tropical regions. We measured soil respiration rates, concentrations of CO₂, CH₄, CO, N₂O and H₂ and the isotopic composition of CO₂, CH₄ and H₂ at four heights in the nocturnal boundary layer (NBL) above three common land‐use types in central Panama, during dry and rainy seasons. Soil respiration rates were lowest in Plantation (average 3.4 μmol m^?2 s^?1), highest in Pasture (8.3 μmol m^?2 s^?1) and intermediate in Rainforest (5.2 μmol m^?2 s^?1). δ¹³C_R closely reflected land use and increased during the dry season where C₃ vegetation was present. δ¹⁸O_R did not differ by land use but was lower during the rainy than the dry season. CO₂ was correlated with other species in approximately half of the NBL profiles, allowing us to estimate trace gas fluxes that were generally within the range of literature values. The Rainforest soil was a sink for CH₄ but emissions were observed in Pasture and Plantation, especially during the wet season. N₂O emissions were higher in Pasture and Plantation than Rainforest, contrary to expectations. Soil H₂ uptake was highest in Rainforest and was not observable in Pasture and Plantation during the wet season. We observed soil CO uptake during the dry season and emissions during the wet season across land‐use types. This study demonstrated that strong impacts of land‐use change on soil–atmosphere trace gas exchange can be detected in the NBL, and provides useful observational constraints for top‐down and bottom‐up biogeochemistry models.     

Dormancy and impotency of cocklebur seeds I. CO2, C2H4 O2 and high temperature

High O₂ tensions, CO₄, C₂H₄ and high temperatures were effectivenot only in breaking the dormancy of cocklebur (Xanthium pennsylvanicumWallr.) seeds but also in increasing the germination potentialof the nondormant but small seeds. There were few qualitativedifferences in response to these factors between the dormantand impotent seeds. Unlike CO₂, however, enriched O₂ and C₂H₄were stimulative even at the low temperature of 13°C. Germination induced by CO₂, C₂H₄ and high temperature treatmentswas lowered when endogenously evolved C₂H₄ or CO₂ was removed,whereas the effect of O₂ enrichment was not affected by theirremoval. CO₂ and high temperatures remarkably stimulated C₂H₄production, whereas O₂ enrichment had no such effect. C₂H₄ productivity was lower in the dormant than non-dormantseeds, suggesting that the after-ripening is characterized byincreasing C₂H₄ production. (Received August 20, 1974; )     

Drainage increases CO2 and N2O emissions from tropical peat soils

Tropical peatlands are vital ecosystems that play an important role in global carbon storage and cycles. Current estimates of greenhouse gases from these peatlands are uncertain as emissions vary with environmental conditions. This study provides the first comprehensive analysis of managed and natural tropical peatland GHG fluxes: heterotrophic (i.e. soil respiration without roots), total CO₂ respiration rates, CH₄ and N₂O fluxes. The study documents studies that measure GHG fluxes from the soil (n = 372) from various land uses, groundwater levels and environmental conditions. We found that total soil respiration was larger in managed peat ecosystems (median = 52.3 Mg CO₂ ha^?1 year^?1) than in natural forest (median = 35.9 Mg CO₂ ha^?1 year^?1). Groundwater level had a stronger effect on soil CO₂ emission than land use. Every 100 mm drop of groundwater level caused an increase of 5.1 and 3.7 Mg CO₂ ha^?1 year^?1 for plantation and cropping land use, respectively. Where groundwater is deep (≥0.5 m), heterotrophic respiration constituted 84% of the total emissions. N₂O emissions were significantly larger at deeper groundwater levels, where every drop in 100 mm of groundwater level resulted in an exponential emission increase (exp(0.7) kg N ha^?1 year^?1). Deeper groundwater levels induced high N₂O emissions, which constitute about 15% of total GHG emissions. CH₄ emissions were large where groundwater is shallow; however, they were substantially smaller than other GHG emissions. When compared to temperate and boreal peatland soils, tropical peatlands had, on average, double the CO₂ emissions. Surprisingly, the CO₂ emission rates in tropical peatlands were in the same magnitude as tropical mineral soils. This comprehensive analysis provides a great understanding of the GHG dynamics within tropical peat soils that can be used as a guide for policymakers to create suitable programmes to manage the sustainability of peatlands effectively.     

A method to estimate net community metabolism from profiles of dissolved O2 and N2

A method to estimate net community metabolism (NCM) in natural waters using vertical profiles of water temperature, salinity, dissolved O₂, gas tension, and calculated dissolved N₂ is presented. The method utilizes the disparate biological activity of dissolved O₂ and N₂ to estimate metabolism at different depths in the water column. For well-mixed surface waters, N₂ saturation levels are assumed to be the result of a quasi steady state balance of net warming or cooling and air–water gas exchange. Dissolved O₂ levels are assumed to maintain a similar balance, subject to net biological activity, and NCM is then calculated based on the difference between N₂ and O₂ saturation levels and the estimated timescale required to equilibrate the layer with the atmosphere. For deeper stratified layers of water that warmed after layer formation in isolation from the atmosphere, the temperature at formation is calculated using the measured N₂ concentration and an assumed N₂ saturation level of 100% at formation. By assuming that initial N₂ and O₂ saturation levels were equal, the initial O₂ concentration is calculated based on solubility relationships. NCM of the deeper waters is then estimated based on this information and knowledge of the general seasonal heating cycle of the waters. Daily mean water temperature and dissolved gas levels are used in the calculations. The method was assessed using profile measurements collected at Long Pond, Plymouth, Massachusetts, USA, on 23 August 2002. Oxygen was supersaturated relative to N₂ by approximately 4% in the 0–6 m deep epilimnion, and undersaturated relative to N₂ by approximately 7% in the stratified water at 9 m depth. The estimated 4-day average NCM for the epilimnion was 140 ± 70 mgC m⁻²day⁻¹. For waters at 9 m depth, the temperature at formation was calculated to be 6.58 °C, and the estimated 100-day average NCM was −2.5 ± 0.6 mgC m⁻³ day⁻¹. An independent estimate of −4.6 ± 0.9 mgC m⁻³ day⁻¹ was derived from the measured O₂ decline at 9 m depth over the same period of 2003.     

Isolation of deuterated histones from yeast grown on media dissolved in 2H2O

We have succeeded in growing Saccharomyces cerevisiae (baker's yeast) on media containing ²H₂O and isolating the core histones highly deuterated in the non-exchangeable positions. The deuterated histones obtained here are of great value for their possible widespread use for structural studies of chromatin.     

N2O emissions from agricultural lands: a synthesis of simulation approaches

Nitrous oxide (N₂O) is primarily produced by the microbially-mediated nitrification and denitrification processes in soils. It is influenced by a suite of climate (i.e. temperature and rainfall) and soil (physical and chemical) variables, interacting soil and plant nitrogen (N) transformations (either competing or supplying substrates) as well as land management practices. It is not surprising that N₂O emissions are highly variable both spatially and temporally. Computer simulation models, which can integrate all of these variables, are required for the complex task of providing quantitative determinations of N₂O emissions. Numerous simulation models have been developed to predict N₂O production. Each model has its own philosophy in constructing simulation components as well as performance strengths. The models range from those that attempt to comprehensively simulate all soil processes to more empirical approaches requiring minimal input data. These N₂O simulation models can be classified into three categories: laboratory, field and regional/global levels. Process-based field-scale N₂O simulation models, which simulate whole agroecosystems and can be used to develop N₂O mitigation measures, are the most widely used. The current challenge is how to scale up the relatively more robust field-scale model to catchment, regional and national scales. This paper reviews the development history, main construction components, strengths, limitations and applications of N₂O emissions models, which have been published in the literature. The three scale levels are considered and the current knowledge gaps and challenges in modelling N₂O emissions from soils are discussed.     

Multivariate regulation of soil CO2 and N2O pulse emissions from agricultural soils

Climate and land‐use models project increasing occurrence of high temperature and water deficit in both agricultural production systems and terrestrial ecosystems. Episodic soil wetting and subsequent drying may increase the occurrence and magnitude of pulsed biogeochemical activity, affecting carbon (C) and nitrogen (N) cycles and influencing greenhouse gas (GHG) emissions. In this study, we provide the first data to explore the responses of carbon dioxide (CO₂) and nitrous oxide (N₂O) fluxes to (i) temperature, (ii) soil water content as percent water holding capacity (%WHC), (iii) substrate availability throughout, and (iv) multiple soil drying and rewetting (DW) events. Each of these factors and their interactions exerted effects on GHG emissions over a range of four (CO₂) and six (N₂O) orders of magnitude. Maximal CO₂ and N₂O fluxes were observed in environments combining intermediate %WHC, elevated temperature, and sufficient substrate availability. Amendments of C and N and their interactions significantly affected CO₂ and N₂O fluxes and altered their temperature sensitivities (Q₁₀) over successive DW cycles. C amendments significantly enhanced CO₂ flux, reduced N₂O flux, and decreased the Q₁₀ of both. N amendments had no effect on CO₂ flux and increased N₂O flux, while significantly depressing the Q₁₀ for CO₂, and having no effect on the Q₁₀ for N₂O. The dynamics across DW cycles could be attributed to changes in soil microbial communities as the different responses to wetting events in specific group of microorganisms, to the altered substrate availabilities, or to both. The complex interactions among parameters influencing trace gas fluxes should be incorporated into next generation earth system models to improve estimation of GHG emissions.     

Influence of elevated CO2 and nitrogen nutrition on rice plant growth,soil microbial biomass,dissolved organic carbon and dissolved CH4

Rice (Oryza sativa) was grown in six sunlit, semi-closed growth chambers for two seasons at 350 L L^–1 (ambient) and 650 L L^–1 (elevated) CO₂ and different levels of nitrogen (N) supplement. The objective of this research was to study the influence of CO₂ enrichment and N nutrition on rice plant growth, soil microbial biomass, dissolved organic carbon (DOC) and dissolved CH₄. Elevated CO₂ concentration ([CO₂]) demonstrated a wide range of enhancement to both above- and below-ground plant biomass, in particular to stems and roots (for roots when N was not limiting) in the mid-season (80 days after transplanting) and stems/ears at the final harvest, depending on season and the level of N supplement. Elevated [CO₂] significantly increased microbial biomass carbon in the surface 5 cm soil when N (90 kg ha^–1) was in sufficient supply. Low N supplement (30 kg ha^–1) limited the enhancement of root growth by elevated [CO₂], leading consequently to diminished response of soil microbial biomass carbon to CO₂ enrichment. The concentration of dissolved CH₄ (as well as soil DOC, but to a lesser degree) was observed to be positively related to elevated [CO₂], especially at high rate of N application (120 kg ha^–1) or at 10 cm depth (versus 5 cm depth) in the later half of the growing season (at 80 kg N ha^–1). Root senescence in the late season complicated the assessment of the effect of elevated [CO₂] on root growth and soil organic carbon turnover and thus caution should be taken when interpreting respective high CO₂ results.     

Sediment-water fluxes of dissolved inorganic carbon, O2, nutrients, and N2 from the hypoxic region of the Louisiana continental shelf

Globally, hypoxic areas (<63?mmol O₂ m^?3) in coastal waters are increasing in number and spatial extent. One of the largest coastal hypoxic regions has been observed during the summer in the bottom-water of the Louisiana continental shelf. The shelf receives the sediments, organic matter, and nutrients exported from the Mississippi River watershed, and much of this material is ultimately deposited to the sea floor. Hence, quantifying the rates of sediment-water dissolved inorganic carbon (DIC), oxygen (O₂), and nutrient fluxes is important for understanding how these processes relate to the development and maintenance of hypoxia. In this study, the sediment-water fluxes of DIC, O₂, nutrients, and N₂ (denitrification) were measured on the Louisiana shelf during six cruises from 2005 to 2007. On each cruise, three to four sites were occupied in or directly adjacent to the region of the shelf that experiences hypoxia. DIC fluxes, a proxy for total sediment respiration, ranged from 7.9 to 21.4?mmol?m^?2 day^?1 but did not vary significantly either spatially or as a function of bottom-water O₂ concentration. Overall, sediment respiration and nutrient flux rates were small in comparison to water-column respiration and phytoplankton nutrient demand. Nitrate fluxes were correlated with bottom-water O₂ concentrations (r?=?0.69), and there was evidence that decreasing O₂ concentrations inhibited coupled nitrification-denitrification. Denitrification rates averaged 1.4?mmol?N?m^?2 day^?1. Scaled to the area of the shelf, the denitrification sink represented approximately 39% of the N load from the Mississippi River watershed. The sediment-water fluxes reported from this study add substantial information on the spatial and temporal patterns in carbon, O₂, and nutrient cycling available for the Louisiana continental shelf and, thus, improve the understanding of this system.     

间作对旱地CO2和N2O排放影响的研究进展

农田温室气体排放是近年来科学界的研究热点,采用合适的种植模式是减少农田温室气体排放的有效途径之一.本文综述了作物间作对旱地土壤CO₂和N₂O排放的影响及机理.合理间作能够提高土壤有机碳(SOC)含量、促进不同作物秸秆向SOC转化、降低SOC矿化速率,从而减少CO₂排放.禾本科与豆科作物间作能够在维持作物产量的情况下,减少化学氮肥投入、土壤有效氮残留及还田秸秆产生的无机氮,降低N₂O排放.间作作物的互作、田间小气候环境的改善也是影响土壤温室气体排放的重要因素.今后,要增加土壤温室气体监测时长并对影响因子进行综合、全面的分析,尤其是从分子水平探究间作模式下土壤微生物对温室气体产生过程的作用机理,为构建环境友好型农业模式提供科学依据.     

Winter production of CO2 and N2O from alpine tundra: environmental controls and relationship to inter-system C and N fluxes

Fluxes of CO₂ and N₂O were measured from both natural and experimentally augmented snowpacks during the winters of 1993 and 1994 on Niwot Ridge in the Colorado Front Range. Consistent snow cover insulated the soil surface from extreme air temperatures and allowed heterotrophic activity to continue through much of the winter. In contrast, soil remained frozen at sites with inconsistent snow cover and production did not begin until snowmelt. Fluxes were measured when soil temperatures under the snow ranged from –5°C to 0°C, but there was no significant relationship between flux for either gas and temperature within this range. While early developing snowpacks resulted in warmer minimum soil temperatures allowing production to continue for most of the winter, the highest CO₂ fluxes were recorded at sites which experienced a hard freeze before a consistent snowpack developed. Consequently, the seasonal flux of CO₂ –C from snow covered soils was related both to the severity of freeze and the duration of snow cover. Over-winter CO₂ –C loss ranged from 0.3 g C m⁻² season⁻¹ at sites characterized by inconsistent snow cover to 25.7 g C m⁻² season⁻¹ at sites that experienced a hard freeze followed by an extended period of snow cover. In contrast to the pattern observed with C loss, a hard freeze early in the winter did not result in greater N₂O–N loss. Both mean daily N₂O fluxes and the total over-winter N₂O–N loss were related to the length of time soils were covered by a consistent snowpack. Over-winter N₂O–N loss ranged from less 0.23 mg N m⁻² from the latest developing, short duration snowpacks to 16.90 mg N m⁻² from sites with early snow cover. These data suggest that over-winter heterotrophic activity in snow-covered soil has the potential to mineralize from less than 1% to greater than 25% of the carbon fixed in ANPP, while over-winter N₂O fluxes range from less than half to an order of magnitude higher than growing season fluxes. The variability in these fluxes suggests that small changes in climate which affect the timing of seasonal snow cover may have a large effect on C and N cycling in these environments. Received: 5 April 1996 / Accepted: 25 November 1996