Gypsum-organic interactions in the marine environment: sorption of fatty acids and hydrocarbons

Free fatty acids make up the bulk (50–84% wt/wt) of lipid materials recovered from artificial gypsum precipitates and crystals collected from sea salt evaporation pans. Both the fatty acids and hydrocarbons associated with artificial gypsum tend to be of longer mean chain length than organic materials dissolved in the mother liquor. Increased specific adsorption of n-fatty acids at Ca²⁺ sites on gypsum surfaces is positively correlated with alkyl chain length. Neutral lipids were not significantly enriched in either type of gypsum precipitates. The fatty acids associated with gypsum from sea salt evaporation pans are branched fatty acids in contrast to the predominantly normal acids associated with artificial gypsum samples. Differences in the two adsorbed acid distributions are attributed to the unique lipids of hypersaline biota.     

Mathematical models for petroleum-forming processes: n-paraffins and isoprenoid hydrocarbons

Mathematical models have been developed which simulate both random and nonrandom thermal cracking of branched and straight-chain hydrocarbons. Application of these models to n-paraffins suggests that thermal cracking alone cannot be the dominant mechanism in formation of the n-paraffin distributions present in crude oils. Application to isoprenoid hydrocarbons indicates that nonrandom cracking could be important in producing the isoprenoid distributions found in oils.Results of the mathematical modeling show that methane formation should, as predicted from energy considerations, be kinetically disfavored. It therefore is likely that substantial quantities of methane are produced from saturated hydrocarbons only under thermal conditions more severe than those under which oil is produced.The mathematical models employed are adaptable for other geochemical applications, such as isotope fractionation.     

Geochemical distribution of hydrocarbons in sediments from mid-Narragansett Bay,Rhode Island

The concentration of hydrocarbons (saturated and aromatic) and synthetic chlorinated compounds (Chlordane, DDT, and PCBs) decreased with depth in sediment cores from mid-Narragansett Bay and reached background levels at different depths. These depths were in general agreement with those expected based on the chronological inputs of these materials to the Bay. Although the total hydrocarbons concentration decreased with depth, the biogenic n-alkanes (n-C_{25,27,29,31,33}) showed a fairly constant concentration with depth as did the organic carbon content of these sediments. The n-alkane odd/even ratio increased with depth in the cores. Size fractionation (> 45 μm and < 45 to > 0.3 μm) of two core sections showed more hydrocarbons associated with the smaller size fraction in the surface section, while the lower section had approximately equal concentrations in both fractions. These trends suggest that over the time period covered by these cores the inputs of biogenic materials has remained relatively constant, while the input of anthropogenic hydrocarbons has increased dramatically during the last 100 yr. This increase is probably due to the expanded use of petroleum over this time period and subsequent chronic inputs to this estuarine environment.     

The contribution of humic substances to the acidity of colored natural waters

An operationally defined carboxyl content of humic substances extracted from rivers, streams, lakes, wetlands, and groundwaters throughout the United States and Canada is reported. Despite the diversity of the samples, only small variations were observed in this humic carboxyl content. The dissociation behavior of two combined fulvic/humic acid extracts was studied and it was found that the dissociation of the humics varied in a predictable manner with pH. Using a carboxyl content of 10 μeq/ mg humic organic carbon, and mass action quotient calculated from sample pH, the ionic balances of three highly colored Nova Scotia rivers were estimated.     

Infrared study of the pyrolysis products of sporopollenin and lignite

The effect of pyrolysis at increasing temperature on sporopollenin, lignite and sporopollenin oxidized at 200°C has been investigated using measured infrared band absorption coefficients.Oxidation of sporopollenin in air at 200°C is marked by a decrease in the content of saturated hydrocarbon chains and a strong increase in the concentration of carboxylic acid groups.Pyrolysis of a thick bed of sporopollenin at increasing temperatures leads to the removal of a large proportion of oxygenated functions, before the removal of hydrocarbons. For lignite and oxidized sporopollenin, the loss of both types of functional groups extends over a broader temperature range. Reorganization of the carbonaceous residue at high temperature is hindered if a sufficiently low content of oxygenated functions, carbonyl and carboxyl as well as hydroxyl and ether groups, is not reached before the elimination of hydrocarbons.     

A thermochemical study of glasses and crystals along the joins silica-calcium aluminate and silica-sodium aluminate

Enthalpies of solution in molten 2PbO · B₂O₃ at 985 K are reported for series of glasses xCa_0.5AlO₂-(1?x)SiO₂ (O ≤ x ≤ 0.99) and xNaAlO₂-(1?x)SiO₂ (0 ≤ x ≤ 0.56). The data are compared to values for the corresponding crystalline aluminosilicates and to preliminary data for systems containing KAlO₂ and Mg_0.5AlO₂. The enthalpies of mixing of glasses become more exothermic with increasing basicity of the mono- or divalent oxide. The tendency toward immiscibility on the silica-rich side, indicated by the shape of the heat of mixing curve between x = 0 and x = 0.4, is pronounced in the calcium aluminate system, but not in the sodium aluminate system. The shape of the heat of mixing curve, which is roughly symmetrical about x = 0.5, can be rationalized in terms of glass structure by considering essentially random substitution of Si and Al on a continuous three dimensional tetrahedral framework, with stabilization arising from electrostatic interactions between aluminum and the nonframework cation balancing the destabilizing effects arising from perturbation of the aluminosilicate framework by the nonframework cation. These trends are consistent with the variation of physical properties of aluminosilicate melts.     

The stereoisomeric composition of phytanyl chains in lipids of Dead Sea sediments

Lipid extracts from five recent Dead Sea sediments were analyzed for isoprenoid compounds and the following were isolated: free and phospholipid-bound di-O-phytanylglycerol, free phytanol and free and esterifled phytanic acid. The phytanyl groups of the diether and the free phytanol were oxidized to the corresponding phytanic acid; the stereoisomeric composition of the derived phytanic acids as well as of the ester-bound phytanic acid was determined by open-tubular gas-liquid chromatography of the corresponding methyl esters on butanediolsuccinate polyester. Only the 3R,7R,11R-isomer of phytanic acid was detected in each of the phytanate samples, indicating that these phytanyl chains in the Dead Sea sediments are most likely derived from extremely halophilic bacteria rather than from phytol of chlorophyll origin. These findings also provide further evidence that the mixtures of RRR and SRR-phytanic acids previously isolated from organic-rich shales were most likely derived from the phytyl chain in chlorophyll.     

Polycyclic aromatic hydrocarbons in an anoxic sediment core from the Pettaquamscutt River (Rhode Island,U.S.A.)

Fifteen sections from an anoxic sediment core were analyzed for polycyclic aromatic hydrocarbons (PAH). Two types of PAH were observed: (a) those from combustion sources such as pyrene and chrysene and (b) those from natural sources such as retene and perylene. The combustion PAH levels in core sections dated between 1900 and 1970 were much higher than in earlier sections; this indicated an anthropogenic origin of these PAH at this location. The perylene and retene core profiles show significant anomalies during the period 1850–1880. Organic carbon does not fluctuate markedly but δC-13 of organic carbon shows several unexplained excursions; one of which correlates with the perylene and retene anomalies.     

Predominance of isoprenoids among the alkanes in the Irati oil shale,Permian of Brazil

An alkane distribution in which isoprenoid alkanes are present in excess of n-paraffins and pristane, phytane, and norpristane (in this order) are the major components, has been found in two different beds of the Irati oil shale, Brazilian Permian formation of São Mateus do Sul, Paranã.     

Sulfur speciation and associated trace metals (Fe,Cu) in the pore waters of Great Marsh,Delaware

The pore waters of sediments from a salt marsh along the Delaware estuary have been analyzed for sulfur species and associated trace metals. Since the sediment interface is usually in contact with the atmosphere, the sulfur species are dependent on the production of hydrogen sulfide by sulfate reduction and subsequent oxidation by diffusing oxygen. The most important species observed are hydrogen sulfide, polysulfide ions and thiosulfate. Secondary reactions of hydrogen sulfide and polysulfides with decomposing organic matter yield significant concentrations of both thiols and organic polysulfides. Upon isolation of the sediment from the atmosphere due to tidal inundation, bacterial sulfate reduction becomes the dominant process. This results in the reduction of the polysulfides in agreement with thermodynamic predictions, and suggests that the redox couple sulfide/polysulfide is a good redox indicator under such reducing environments.The concentrations of trace elements Cu and Fe in the pore waters are mainly controlled by sulfide formation. Calculations show that copper is strongly complexed probably with organo-sulfur ligands. Iron might be complexed as such sulfur species to a much lesser extent than copper.     

Phylogeny of transfer RNA and origins of organelles

By using nucleotide sequences of transfer RNA's, the endosymbiotic model for the origin of chloroplasts and mitochondria is examined. The endosymbiotic origin of the chloroplasts is confirmed, but concerning the origin of the mitochondria no conclusion can be drawn. Phyletic relations of euglenoids to higher plants and to animals are also discussed. Finally, phylogeny of fungi is discussed in terms of tRNA sequences and it is proposed that the classical taxonomy of fungi should be reconsidered in terms of molecular taxonomy or molecular paleontology.     

On the formation of perylene in recent sediments: kinetic models

The concentration of perylene increases regularly with depth in a radiometrically dated sediment core from Mountain Pond, Coburn Mountain, Maine, U.S.A. This concentration profile was fit to simple reaction kinetic models which indicate that perylene forms in this core either by a first order reaction characterized by a rate constant of 0.012 yr^?1 or by a second order reaction characterized by a rate constant of 0.0013 nmole^?1g yr^?1.     

Factors affecting the association of fatty acids with mineral particles in sea water

Certain factors influencing the incorporation, transport and release of fatty acids by clay minerals, calcite and marine sediments have been investigated.Salinity was found to be an important factor. The adsorption of heptadecanoic acid by bentonite clay at 4%. was nearly triple that at 0%.. However, from 4%. to 35%., only a minor adsorption increase occurred. This behavior is believed to be related to flocculation of the clay at the lower salinity range. The pH over the range of 6.0–8.5 has a small influence on fatty acid-clay association, depressing it somewhat as the basicity increases.When the temperature of the fatty acid solution was increased from 0°C to 50°C, a decrease in adsorption on to clay was found. This effect may be due to increased water solubility of the acid at higher temperatures, since solubility is very important in controlling the degree of fatty acid-mineral interaction. Furthermore, apparent solubilization of fatty acids by indigenous dissolved organic matter in sea water reduces adsorption on to clay minerals.Based upon the heat of adsorption of ?14.6 kcal/mole, fatty acids are physically bound to clay minerals by weak van der Waals forces and hydrogen bonds.Bentonite and kaolinite were found to be the most adsorptive minerals investigated, followed in order by illite, montmorillonite and calcite. Sediments from Narragansett Bay were found to lie between illite and montmorillonite in adsorptive capacity after indigenous sediment organic matter had been removed. Sediment organic matter reduced fatty acid uptake by a factor of 1.6.     

Infrared study of the adsorption on silica of a collector with an oxyethylene chain

Positive results obtained for the flotation of quartz at low pH by a molecule containing a polyoxyethylene chain ($\text{OPEG}\text{=}\text{Triton}\text{× 100}$) led us to examine the nature of the interactions between this collector and the quartz surface, using infrared spectroscopy and considering a porous silica as a model adsorbent.The infrared spectra obtained after adsorption of increasing amounts of OPEG show the disappearance of the free OH groups of silica surface and the development of a band due to bridged hydroxyls. This indicates the formation of hydrogen bonds between ether groups of the collector and silica surface hydroxyls.     

Polymer-stabilized emulsions and fine-particle recovery,II. The chalcopyrite-quartz system

The interaction between fine, generally ?2 μm chalcopyrite and polymer-stabilized oil droplets has been studied as a function of pH and weight percent solids in the pH range from 5 to 12. Oil droplets stabilized by partially esterified polymethacrylic acid and cellulose xanthate have been used as collectors. Chalcopyrite may be efficiently separated from fine quartz gangue at pH 11, using cellulose xanthate stabilized emulsions. Good recovery and grade may be obtained at pH 11 up to pulp densities of at least 5.1 wt.%. At other pH values, selectivity is poor due to Cu¹¹ species from chalcopyrite activating the quartz surface.     

Polymer-stabilized emulsions and fine-particle recovery,I. The calcite-quartz system

The interaction between polymer-stabilized oil droplets and fine calcite particles has been studied at pH 10. Large calcite-droplet aggregates form and may be efficiently separated from fine quartz gangue. The influence of particle size, pulp density, oil-droplet size, oil volume, stirring speed and stirring time on separation efficiency have been investigated.     

Stable carbon isotope evidence for two sources of organic matter in coastal sediments: seagrasses and plankton

Organic carbon from sediments collected in Texas seagrass meadows was enriched in ¹³C by an average of 6.6% relative to organic carbon from offshore sediments. Within the South Texas hay system examined. δ¹³C values became increasingly more typical of offshore sediments with increasing distance from seagrass meadows. This permits the use of carbon isotope data as a measure of the relative contributions of seagrasses and plankton to sedimentary organic matter.     

Closed system Fischer-Tropsch synthesis over meteoritic iron,iron ore and nickel-iron alloy

Meteoritic iron, iron ore and nickel-iron alloy (either alone or in some cases mixed with alumina, carbonaceous chondrite, potassium carbonate or sodium carbonate) were used to catalyze the reaction of deuterium and carbon monoxide in a closed reaction vessel. The mole ratio of deuterium to carbon monoxide ranged from 1/2:1 to 10:1, the reaction temperature from 195 to 370°C, and the reaction time from 6 to 480 hr. Analysis of the reaction products showed that normal alkanes and alkenes (C₁₁-C₂₅), their monomethyl substituted isomers and aromatic hydrocarbons (e.g. naphthalene, acenaphthene, fluorene, phenanthrene and the methyl derivatives of these hydrocarbons) were synthesized. In addition to the aforementioned hydrocarbons, one reaction product was shown to contain perdeutero normal fatty acids (10:0–16:0).     

Maximum carbon isotope fractionation in photosynthesis by blue-green algae and a green alga

The maximum carbon isotope fractionation occurring in photosynthetic fixation of carbon dioxide in pure cultures of blue-green algae was ?23.9%. and for a green alga was ?22.6%., Maximum fractionations were obtained where cell densities were low and carbon dioxide concentrations were greater than 0.5%. Fractionation was reduced at higher temperatures using a thermophilic blue-green alga. For filamentous blue-green algae wherein clumping occurs and localized cell concentrations were high, fractionation was also lower. Fractionations reported in literature for Precambrian organic materials are comparable to the maximum fractionations reported here. This suggests that the early photosynthetic organisms developed under conditions of high carbon dioxide availability, i.e. slow growth rates and/or low population densities.