Refractory Organic Material Research Articles

Variations in [formula omitted] ratios in recent marine sediments: evidence for a fossil organic component

The value of the pre-bomb 129 I/ 127 I ratio in the hydrosphere is important for the use of this isotope system for dating and tracing purposes. In order to determine this value and to examine spatial variability, 129 I/ 127 I ratios were measured in 25 sediment samples from five cores taken at geographically distinct coastal areas. The results indicate a pre-anthropogenic 129 I/ 127 I ratio of 1500×10 −15, in good agreement with values derived from previous sediment and groundwater studies. Results from shallow sediments show that the layer of bioturbation is dominated by the addition of anthropogenic 129 I . The good agreement between results for this layer from different cores supports the understanding that marine iodine is isotopically homogeneous and associated with organic material which is actively remineralized at the sediment–water interface. Lower ratios (down to 354×10 −15, corresponding to an age of 32.5 Ma) and larger variations than expected were found in sections of the cores below the layer of bioturbation. These observations can be explained by the presence of refractory fossil organic material, transported by rivers to the sediments from uplifted, continental shales. The results suggest that marine iodine is present in two forms, a labile component which is isotopically homogeneous, and a refractory component which is associated with kerogen (or other fossil organic compounds) whose 129 I/ 127 I ratio reflects the age of these compounds. 129 I/ 127 I ratios can be used to identify and date fossil organic material in Recent sediments, the presence of which can alter the assumptions underlying models of the global carbon cycle.

Production and transport of long-chain alkenones and alkyl alkenoates in a sea water column in the northwestern Pacific off central Japan

Abstract Sinking particles collected from year-long time-series sediment traps at 1674, 4180, 5687 and 8688 m depths, the underlying bottom sediment at 9200 m depth, and suspended particles from surface and subsurface waters in the northwestern North Pacific off Japan were analyzed for long-chain alkenones and alkyl alkenoates (A&A) which are derived mainly from Gephyrocapsacean algae, especially Emiliania huxleyi and Gephyrocapsa oceanica. Alkenone temperature records in sediment trap samples at 1674 m were almost similar to observed sea surface temperatures (SST) with a time delay of one half to one full month. However, alkenone temperatures in trap samples were about slightly lower than measured SST in late spring to early fall. The lowering might be caused by formation of the seasonal thermocline. Nevertheless, these temperature drops observed in trap samples were smaller than those actually observed in a subsurface layer off central Japan. Vertical profiles of A&A concentrations and alkenone temperatures in suspended particles collected from the subsurface waters in early fall indicated that these compounds were produced mostly in a surface mixed layer above the depth of the chlorophyll maximum even in warm seasons. These results suggested that alkenone temperatures strongly reflected SST rather than the temperatures of thermocline waters in these study areas even in such a warm season. Pronounced maxima in A&A fluxes found in sediment trap samples at 1674 m in late spring to summer showed that A&A productions were highest during the periods of spring bloom, according to a time delay between alkenone temperatures and observed SST. Seasonal patterns of alkenone records in trap samples at 4180 and 5687 m could also preserve SST signals well, suggesting that A&A in deep sea waters were mainly derived from primary products in the surface layer. A&A fluxes tended to decrease with water depth, and the ratios of A&A to particulate organic carbon (POC) rapidly decreased in underlying bottom sediment. This clearly indicates that A&A were decomposed and diluted by other refractory organic materials in either the water column or the sediment–water interface. However, A&A compositions were consistently uniform between the trap samples and the underlying bottom sediments, so that A&A could not qualitatively alter during early diagenetic processes.

Ion irradiation: Its relevance to the evolution of complex organics in the outer solar system

Ion irradiation of carbon containing ices produces several effects among which the formation of complex molecules and even refractory organic materials whose spectral color and molecular complexity both depend on the amount of deposited energy. Here results from laboratory experiments are summarized. Their relevance for the formation and evolution of simple molecules and complex organic materials on planetary bodies in the external Solar System is outlined.

Vibrational spectroscopy of ion-irradiated frozen butane

In this paper we present a detailed experimental study of the evolution of frozen butane (10 K) before, during and after irradiation with 3 keV He ion beams. Because of irradiation, different molecular species are formed, among which a refractory organic material that, upon further irradiation, evolves towards an amorphous carbon. The techniques used for the analysis are “in situ” infrared (IR) and Raman spectroscopy. The results may have relevance in astrophysics: the produced refractory residues are in fact good analogs of the organic mantles on interstellar grains and of the organics found in carbonaceous meteorites such as Orgueil and Murchison.

Dense molecular shocks and accretion onto protostellar disks

We have examined the physical and chemical processes which accompany the propagation of a J-type shock through molecular astrophysical gas of density 10(exp 7.5) - 10(exp 12) H nuclei per cu cm. Our study is primarily relevant to the high-density accretion shocks which are associated with the supersonic infall of material during the collapse of a molecular cloud core to form a protostar. We have carried out a general parameter study to determine the characteristic infrared emission spectrum of dense molecular shocks and the extent of grain destruction within such shocks as a function of relevant shock parameters. Accretion shocks with mass accretion rates approximately greater than 10(exp -5) solar masses per y are plausible sources of the CO v = 2-0 vibrational band emission observed in many protostars, at least for sources of moderate CO v = 2-0 luminosity (approximately less than few x 10(exp 23) W). Rovibrational emissions from H2O and OH are also predicted to be luminous in dense molecular accretion shocks. Vaporization is the dominant mechanism of grain destruction within dense molecular shocks, leading to the efficient removal of those grains which are heated to their vaporization temperature by the combined effects of radiative heating, drag heating, and thermal heating by the hot postshock gas. The criteria for grain vaporization are obtained for grains composed of several different materials: metallic iron, silicate, troilite, refractory organic materials, volatile organic materials, and water ice.

Abiotic transformation of labile protein to refractory protein in sea water

Abstract In order to determine if organic matter dissolved in sea water may undergo abiotic alterations that make it resistant to microbial degradation, the protein ribulose 1,5-bisphosphate carboxylase (RuBPcase) was abiotically aged in sterile sea water and then exposed to natural bacterial assemblages. Rates of protein assimilation decreased when protein was aged as little as 6 h; protein aged for 40 days was degraded 4-fold more slowly than non-aged protein. Abiotic modification rates, calculated from decreases in degradation rate with increasing aging time, were highest during the initial day of aging (0.8–4.8 d−1) and then decreased to 0.03 d−1. No aging effect was observed in organic-free sea water, indicating that organic-organic interactions produced the refractory protein. Amino acids from the protein were fully recovered after acid hydrolysis, indicating that the decreased lability was not caused by acid-stable molecular changes to the protein. Abiotic complexation of labile organic compounds with existing DOM may be a critical first step in the formation of refractory organic materials.

Distribution and composition of particulate organic matter in the Ross Sea (Antarctica)

The biochemical composition and spatial distribution of particulate organic matter (POM) were studied in the Ross Sea (Antarctica) in summer 1989 to assess the quantitative role of organic carbon fractions in the cycling of organic matter in the water column. Large differences in chemical composition were observed between surface and deep layers. The results indicated that, despite large geographical differences, POM was quite homogeneous, of phytoplankton origin and mostly detrital. Different ratios were used to investigate the changes in biochemical composition of particulate organic matter in relation to the ice-melting: C∶N (organic carbon∶organic nitrogen ratio) and C-POM∶POC (sum of carbohydrate, protein and lipid carbon∶total organic carbon ratio) were used to analyse the percentage of refractory organic material. PPRT∶PCHO (protein∶carbohydrate ratio) were used to establish POM “age” and RNA∶DNA ratios as a relative measure of particulate activity; POC∶Chl a and N-PPRT∶Chl a ratios were used to estimate the autotrophic contribution to the suspended particulate organic matter. Despite its low caloric value (5.3 Kcal g POM−1), an high caloric content in the photic layer (1.6 Kcal m−3 of POM and 2.5 Kcal m−3 of POC) was found thus indicating that a large amount of food was available to higher trophic levels.

Past sedimentary organic matter accumulation and degradation controlled by productivity

CHANGES in bottom-water oxygen concentration are commonly invoked to account for past changes in sedimentary organic carbon accumulation, as organic matter is more readily preserved in anoxic conditions1–5. On the other hand, upper-water productivity has been shown to be the main controlling factor for accumulation of organic matter in modern sediments6,7. It is therefore important to understand whether productivity significantly influenced accumulation patterns in the past, for example during the formation of petroleum source rocks. Here we present a study of a 150-Myr-old sequence containing short-term cycles in organic carbon content from the Kimmeridge Clay formation in Northern England. The lack of bioturbation and the fine-scale laminations throughout this section demonstrate that the sequence was deposited under continuously anoxic bottom-water conditions, so that oxic excursions cannot account for the cyclic accumulation pattern. We show that in this cycle, increased planktonic productivity appears to have caused both increased sedimentary accumulation of refractory organic material, and increased anaerobic degradation of metobolizable organic material. Thus, upper-water productivity should be considered as an important factor in controlling past as well as present accumulation patterns.

Ion irradiation experiments relevant to cometary physics

During their stay in the Oort cloud (4.6 × 109 years), comets are subject to the flux of galactic cosmic rays. Experimental results on the chemical and physical changes induced by ion and electron irradiation of relevant materials have been recently reviewed with a view to their relevance for cometary astrophysics. In particular, the ability of ion irradiation of simple carbon‐containing ices to produce complex refractory organic materials has been discussed. Here we discuss further experiments carried out in our laboratory whose results are relevant to cometary physics. Experiments on targets much thicker than the penetration range of irradiating ions give support to the hypothesis that the ion‐produced cometary organic crust can “survive” gas ejection from deeper layers and be as old as the comet itself. A study of IR and Raman spectra obtained “in situ” before, during, and after irradiation of frozen benzene has clarified the processes producing, after long enough exposures, a tridimensional network of aromatic molecules linked together by linear chains. We call this material ion‐produced hydrogenated amorphous carbon. Other experimental data demonstrate the transition from crystalline to amorphous water ice induced by ion irradiation at temperatures between 10 and 100 K. Thus the observation of amorphous ice cannot be considered, as it has been up to now, a definitive proof of its formation and permanence at low T.

Ion concentrations in interstitial water as indicators for phosphorus release processes and reactions

Sediment composition and interstitial water concentrations of soluble reactive phosphorus (SRP), dissolved iron, ammonia nitrogen and dissolved organic carbon and pH were monitored at five sampling stations in the shallow Lake Loosdrecht (The Netherlands). The differences in concentrations between the sediments were much larger than the differences in overall sediment composition. The concentrations of SRP and ammonia were strongly correlated, the ratio between them was close to that predicted from a mineralization model. Possibly, the high concentrations of refractory organic material in the sediments affect the availability of iron. The pore water was calculated to be frequently supersaturated with respect to vivianite. This, however, did not seem to affect the phosphate concentrations in the pore water.

Irradiation Effects on Comets and Cometary Debris

AbstractFor the last 10 years, many experimental results have been obtained on the chemical and physical changes induced by ion and electron irradiation of materials relevant to comets. Those results are reviewed here, together with their physical interpretation and their relevance for cometary astrophysics. Cometary material is, from the time of its origin, altered by the large amount of energy deposited by energetic ions. Four phases of the irradiation history are considered: the pre-cometary phase, during which interstellar dust is bombarded by cosmic-ray ions; the accretion phase, during which comets are built up, possibly in an environment rich in fast ions (T-Tau phase); the cometary phase, during which the outer layers of the comets are irradiated by galactic ions in the Oort cloud; and the post-cometary phase, during which dust, lost from the comet, is bombarded by solar ions.The relevant applications of laboratory results are reviewed. In particular, the ability of ion irradiation of simple carbon-containing ices to produce complex refractory organic materials is discussed. In the Oort cloud, this process can occur several meters into the surface, so that the buildup of a stable organic crust may occur. A comparison of ion irradiation at various stages is also made with other models for the production of organics.

Preparation of Ultrapure Potassium Peroxydisulfate

Abstract Peroxydisulfate salts are effective oxidants for refractory organic material, including humic substances, but their usefulness in trace metal determinations is limited by the presence of impurities in commercial preparations. Peroxydisulfates were synthesized chemically and electrolytically, and assayed accurately in admixture with side products and starting materials. Even without elaborate environmental controls, the non-electrochemical route was adapted readily to the preparation of potassium Peroxydisulfate containing < 6ngg−1 of Zn, and < 3ngg−1 of Cu and Pb. A key step in the synthesis was the purification of H2O2 by fractional recrystallization.

Analytical methods for the direct determination of inorganic and organic species: Seasonal changes of iron, sulfur, and pedogenic and aquogenic organic constituents in the eurotrophic Lake Bret, Switzerland

The behavior of elements and organic compounds is determined by the properties of their chemical forms. Analytical methods are needed that provide information not only about total concentrations of elements and organic compounds but also about the identities and concentrations of their species. Approaches for the determination of species distributions are outlined. A combination of methods (differential pulse polarography, colorimetry, flame atomic absorption spectrometry, absorbance measurements, fluorescence measurements, cathodic sweep voltammetry, filtration; calculations based on formation, equilibrium, and solubility product constants) was used to identify iron and sulfur species and natural organic matter in the water of Lake Bret, Switzerland. Hydrated Fe 2+, labile Fe(II) species, colloidal Fe(II), particulate Fe(II) and Fe(III), H 2S, HS −, labile S(−II), colloidal S(−II), particulate S(−II), and dissolved and particulate elemental sulfur were identified. The species distribution in the anoxic zone of the lake changed with the seasons. Whereas Fe 2+, H 2S and HS − were the predominant species on 6 August, 1981, colloidal Fe(II) and colloidal S(−II) accounted for most of the iron and sulfur 6 weeks later. Absorbance and fluorescence measurements, responding to largely aromatic pedogenic refractory organic material, indicated that pedogenic material brought into the lake by the River Grenet is not the major source of organic material in the sediments of Lake Bret.

“Primitive” galactic dust in the solar system?

Recent experimental results on the evolution of targets, simulating cometary bodies and interplanetary grains, under the action of energetic protons are summarized. The main finding is that carbon-rich volatiles evolve toward a complex organic material which in turn, when bombarded at higher doses, is transformed to a carbon-like material becoming completely different from the original matrix. The applications of these results to comets and interplanetary grains shows that galactic or solar fast protons are able to build up large amounts of organic refractory material down to depths of ∼ 100 m in a comet and of carbon-like materials on grains that are supposed to be cometary debris. This implies that relevant component materials of comets and grains lose their supposed “primitive” nature and “forget” what they were in the galactic cloud from which the Solar System was generated.

Chemical and Sr-Isotopic Variations During Diagenesis of Miocene Siliceous Sediments of the Monterey Formation, California

The Monterey Formation of California preserves Miocene siliceous sediments at progressive (generally with depth) diagenetic stages: diatomite (opal-A) --> CT-chert (opaI-CT) --> quartz chert for initially clay-poor sediments and diatomaceous shale --> CT-porcelanite (porous opal-CT) --> quartz porcelanite for sediments that were initially clay-rich. The chemistry of most diatomite is controlled by three primary phases (biogenic silica, carbonate, and detrital clay) and several subsidiary phases (organic material, apatite, pyrite, and detrital minerals including quartz and plagioclase). The elemental abundances of the clay-poor diagenetic sequence decrease sharply with advancing diagenetic state for those elements controlled by clay (Al, Ti, K, Rb, Cs, Fe, some Group B metals), carbonate (Ca, Mg, Sr, Ba), apatite (P, Ca, Sr, Ba, V), and organics (V, Ni), while silica shows a congruent increase. These first-order variations reflect the initial compositions of the siliceous sediments modified by the addition of silica, the removal of carbonate and apatite, and the migration of petroleum during silica diagenesis. Anomalous abundances of Mn, Ni, Cr, Mo, and some other Group B metals are associated with trapped refractory organic material and suggest that petroleum catagenesis and migration occurred during silica diagenesis: migration may have been facilitated by the release of bound water during silica-dehydration reactions. Second-order variations (in K/Rb, K/Cs, Rb/Sr, 87 Sr/ 86 Sr) with advancing diagenetic state suggest ion-exchange and ion-expulsion by reaction of detrital phases with pore fluids. Diagenetic processes partially equilibrated, but did not homogenize, depositional 87 Rb/ 86 Sr- 87 Sr/ 86 Sr mixing lines generated by detrital clays and authigenic carbonate and silica in siliceous sediments from the Santa Maria region. However, similar mixing lines in diatomites from the Santa Lucia area are reset to nearly horizontal slopes in associated CT-porcelanites. The degree of equilibration may be a function of the rate of formation of relatively impermeable quartz chert which isolated the siliceous system from further interaction with pore fluids. The rapid formation of quartz chert in the Santa Maria region is believed to have prevented isotopic homogenization processes from reaching completion. Initial chemistry of the siliceous systems controlled the rates and pathways of silica diagenesis. Silica diagenesis, in turn, altered the chemistry of the siliceous sediment.

The Chemical and Physical Evolution of Interstellar Dust

The chemical and physical evolution of interstellar dust is studied by theoretical interpretations combining observations and laboratory experiments. Following the various stages of evolution leads to a picture of grains as consisting of basically two distinct size populations: tenth micron and hundredth (or less) micron. The larger particles are core-mantle structures with cores of silicates, inner mantles of a complex organic refractory material and outer mantles of various ices dominated by frozen H2O. The key to the evolution of grain mantles is solid state photoprocessing by ultraviolet radiation while fully taking into account the gas phase and surface reactions of interstellar atoms and molecules. After a mean lifetime of several thousand million years most grains are consumed by star formation. Some, however, survive essentially intact during aggregation into comets. It is shown that the ultimate observation of interstellar dust particles will have to await the recovery of a sample of a comet nucleus which has preserved the interstellar dust as it was 4½ thousand million years ago.

Some observations on the effect of ozone treatment on suspended particulate matter in seawater

Effects of ozone treatment on suspended particles in seawater have been observed. The observations consist of measuring the particle size distribution using an electronic particle counter before and after treating the sample with ozone. Three kinds of response have been observed in the laboratory and in the field: (i) the total elimination of a peak in the size spectra; (ii) a shift of a peak to a smaller size with correspondingly less volume; and (iii) a mild decrease in the total particle concentration. Our interpretation of these responses as observed in the field are respectively: (i) phytoplankton with a very small amount of refractory structural materials (e.g. naked flagellates); (ii) particles that individually contain both refractory and non-refractory components (e.g. diatoms); and (iii) primarily non-organic and refractory organic materials.

Organic Facies of Middle Cretaceous Black Shales in Deep North Atlantic

The middle Cretaceous black shales of the deep North Atlantic consist of alternating layers of sediment rich in total organic carbon (TOC) that contains abundant amorphous types of organic matter and sediment poor in TOC that contains mostly woody and coaly types of organic matter. The amorphous materials are derived mostly from marine organisms in the eastern North Atlantic off Africa, in the Caribbean, and on the Demerara Rise off Surinam and from higher land plants in the western North Atlantic and off Europe. Marine amorphous material is important off Africa because this was an area of upwelling and highly productive surface water. Amorphous marine organic matter was deposited across the entire North Atlantic Basin in the Cenomanian in response to an ocean-wide upwell ng event connected with the opening of the equatorial Atlantic. The difference between the TOC-rich and background TOC layers reflects deposition of the former under reducing conditions, which allowed the preservation of labile amorphous materials of marine and terrestrial orgin, and of the latter under oxidizing conditions, when nearly all that was preserved was refractory organic material.

Organic Facies of Mid-Cretaceous Black Shales in Deep North Atlantic: ABSTRACT

The mid-Cretaceous black shales of the deep North Atlantic consist of alternating layers of sediment rich in total organic carbon (TOC) that contain abundant amorphous types of organic matter, and sediment poor in TOC that contain mostly woody and coaly types of organic matter. The amorphous materials are derived mostly from marine organisms in the eastern North Atlantic off Africa, in the Caribbean, and on the Demarara Rise off Surinam, and from higher land plants in the western North Atlantic and off Europe. Marine amorphous material is important off Africa because this was an area of upwelling and highly productive surface water. Amorphous marine organic matter was deposited across the entire North Atlantic basin in the Cenomanian in response to an ocean-wide upwelling event connected with the opening of the equatorial Atlantic. The difference between the TOC-rich and background TOC layers reflects deposition of the former under reducing conditions, which allowed the preservation of labile amorphous materials of marine and terrestrial origin, and of the latter under oxidizing conditions, when all that was preserved was refractory organic material. End_of_Article - Last_Page 790------------