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.     

Biogeochemistry of fatty acids in recent sediments from Narragansett Bay,Rhode Island

The fatty acid composition of sediments from Narragansett Bay show significant variation between certain areas of the Bay. Both the organic carbon and fatty acid concentrations decrease with increasing distance from the Providence River area—an area which received municipal sewage and industrial effluents. The ratio of the fatty acid concentration to organic carbon concentration is fairly constant for all stations sampled. The variations in the relative abundance of fatty acids may reflect either the influence of fatty acids discharged to the river area by sewage effluents or the synthesis of fatty acids by microbial populations which probably differ for the areas compared. Temporal variations in fatty acid composition and fatty acid concentration are minimal. Lipolytic activity has been demonstrated and probably acts on glycerides deposited to the sediments releasing free fatty acids shortly after deposition. A model for the diagenesis of fatty acids in Recent sediments is proposed based upon the above findings and upon earlier reports by the authors and by other investigators.     

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.     

The solubility of medium molecular weight aromatic hydrocarbons and the effects of hydrocarbon co-solutes and salinity

The solubilities of several medium molecular weight aromatic hydrocarbons were determined at 25°C in aqueous binary, ternary, and quaternary systems. The binary systems consisted of distilled water plus one each of the following: naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, biphenyl, 2-ethylnaphthalene, 1,5-dimethylnaphthalene, 2,3-dimethylnaphthalene, 2,6-dimethylnaphthalene, acenaphthene and phenanthrene. The ternary systems consisted of distilled water plus one of the following hydrocarbon pairs: naphthalene/biphenyl, naphthalene/acenaphthene, naphthalene/phenanthrene, biphenyl/phenanthrene, biphenyl/2-methylnaphthalene, acenaphthene/phenanthrene and 2-methylnaph-thalene/phenanthrene. Quaternary systems consisted of distilled water and one of the following hydrocarbon mixtures: naphthalene/biphenyl/phenanthrene, 2-methylnaphthalene/biphenyl/phenanthrene and naphthalene/acenaphthene/phenanthrene. In binary systems at S%. = 0, solubilities ranged from 31.3 ppm for naphthalene to 1.07 ppm for phenanthrene. The alkyl naphthalenes exhibited solubilities which were a function of molar volume and substituent size and position. In ternary and quaternary systems, solubilities often deviated from values obtained in binary systems presumably due to solute-solute interactions and/or formation of solid solutions. Aromatic hydrocarbons are ‘salted out’ by increasing concentrations of inorganic salts. At S%. = 35, the solubility of naphthalene is 22.0 ppm and of phenanthrene, 0.71 ppm. The empirical salting parameters are identical in both binary and quaternary systems.     

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.     

Microbial lipids of an intertidal sediment—I. Fatty acids and hydrocarbons

A detailed study has been made of the solvent extractable monocarboxylic, dicarboxylic and hydroxylated fatty acids and n-alkanes in a surface intertidal sediment, and the distributions compared to microorganisms cultured from the sediment. Diatoms are shown to contribute most of the monocarboxylic acids, particularly the significant amounts of polyunsaturated acids present, and a small proportion of the n-alkanes. Bacteria contribute between 11 and 14% of the monocarboxylic acids and markers for this, including trans-monounsaturated acids, are proposed. Detritus from the sea-grass Zostera muelleri is a major source of the α-hydroxy-, ω-hydroxy and α,ω-dicarboxylic acids in the sediment and a minor contributor of n-alkanes and long-chain fatty acids.     

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.     

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.     

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.     

Carbonate equilibria in hydrothermal systems: First ionization of carbonic acid in NaCl media to 300°C

The ionization quotients of aqueous carbon dioxide (carbonic acid) have been precisely determined in NaCl media to 5 m and from 50° to 300°C using potentiometric apparatus previously developed at Oak Ridge National Laboratory. The pressure coefficient was also determined to 250°C in the same media. These results have been combined with selected information in the literature and modeled in two ways to arrive at the best fits and to derive the thermodynamic parameters for the ionization reaction, including the equilibrium constant, activity coefficient quotients, and pressure coefficients. The variation with temperature of the two fundamental quantities $\text{Δ}\text{V}\text{?}{}^{\mathrm{o}}$ and $\text{Δ}\text{C}\text{?}{}^{\mathrm{o}}{}_{\mathrm{p}}$ were examined along the saturation vapor pressure curve and at constant density. The results demonstrated again that for reactions with minimal electrostriction changes the magnitudes and variations of $\text{Δ}\text{C}\text{?}{}^{\mathrm{o}}{}_{\mathrm{p}}$ and $\text{Δ}\text{V}\text{?}{}^{\mathrm{o}}$ with temperature are small and, in addition, $\text{Δ}\text{C}\text{?}{}_{\mathrm{p}}$ and $\text{Δ}\text{V}\text{?}$ are approximately independent of salt concentration.The results have also been applied to an examination of the solubility of calcite as a function of pH (in a given NaCl medium) for the neutral to acidic region both for systems with fixed CO₂ pressure and systems where the calcium ion concentration equals the concentration of carbon. The pH of saturated solutions of calcite with P_CO2 of 12 bars increases from 5.1 to 5.5 between 100° and 300°C.     

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.     

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.     

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.     

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.     

Oxidation products of Mn(II) in lake waters

Oxygenation of Mn(II)-rich water samples taken from two English lakes (Esthwaite Water, Cumbria, and Rostherne Mere, Cheshire) during the summer months caused the precipitation of Mn-oxide, the process being catalysed by particulate matter. The Mnoxide formed resembles vernadite (δ-MnO₂) with regard to: (1) Mn oxidation state (> 3.6 in all but one case); and (2) its fine morphology (crumpled thin sheets) as determined by electron microscopy. The precipitates are, however, rather amorphous to X-rays, giving only very weak reflections which cannot be assigned unequivocally. Electron probe microanalysis shows the presence of a number of other elements in the Mn-containing phase. The most abundant is Ca (Ca/Mn weight ratio $\text{? 0.1}$), others are Mg, Si, P, S, Cl, K, Ba and Fe. The precipitates contain much organic matter (20–30 wt.%) but little appears to be associated directly with the Mn phase. Only small amounts (～ 1 wt.%) of humic substances are present. Some but not all of the specimens examined had the gross morphology of Metallogenium, a Mn-depositing bacterium.Naturally occurring Mn-oxides present in Esthwaite Water during the summer resemble, the products of oxygenation in their fine morphology and contents of other elements. Mn-oxides present during the winter are somewhat different morphologically. In one summer sample of particulate matter from Esthwaite Water no Mn-oxide could be found by electron microscopic examination, but Mn was found concentrated in bacteria. This observation, the rapid rates of oxidation and the high Mn oxidation states, suggest that bacteria might play a rôle in catalysing the oxidation of Mn(II).     

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.     

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.