This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Ethylene (C₂H₄) production was monitored in twelve desert soils incubated moist at constant temperature for various incubation periods. In all but two soils with high organic matter content, C₂H₄ production was low. Statistical analysis showed a good correlation between organic matter content and C₂H₄ production. Minimum levels of C₂H₄ were observed in saline and sodic soils. Adding ethanol, glucose, glycerol and methionine to soil samples significantly increased C₂H₄ formation. Methionine induced the highest level of C₂H₄ in all soils tested. Increased concentrations of methionine resulted in further significant increases in C₂H₄ production possibly indicating its role as a precursor for C₂H₄. Chloramphenicol did not have a significant effect except in a saline soil suggesting that bacterial C₂H₄ production is of less significance in the other soils. The addition of salts to the high C₂H₄ producing soils suppressed C₂H₄ production most likely because of a direct effect on C₂H₄ producing microorganisms through toxic salt levels, high osmotic pressure and/or increased pH. Leaching of four saline soils and subsequent incubation resulted in significant increases in C₂H₄ in two soils. Ethylene producers, previously inhibited by salinity, were probably reactivated when the salts were removed. A Fusarium isolate obtained from the highest C₂H₄ producing soil, produced the most C₂H₄ in pure culture followed by isolates belonging to the genera Aspergillus, Penicillium, Curvillaria, and Rhizopus. In a comparative study, a number of species, some of which were known to produce C₂H₄, were tested in culture media. Nine species produced C₂H₄ in varying amounts of which Penicillium digitatum produced the highest concentration. A sterilized saline soil produced significant C₂H₄ when inoculated with spores of Mucor hiemalis and the Fusarium isolate, 5 to 14 times that in non-sterilized soil probably indicating an originally low population of C₂H₄ producing organisms. The amounts of C₂H₄ produced in sterilized inoculated mollisol and garden soils were only a fraction of that produced in non-sterilized samples probably indicating the involvement of a number of species in the production of C₂H₄ in these soils.

The sorption of five chlorinated benzenes and sixteen other organic solutes was investigated by determining the extent of sorption and the sorption rates in a series of 40 batch and 139 column experiments using surface-modified silica of known chemical composition. These surfaces were used to represent important functional groups in soil, and consisted of porous silica with patchy surface coatings of aliphatic chains (C₁, C₈, and C₁₈), and other substituent groups (phenyl, amine, alcoholic, and carboxylic). Three possible rate-limiting steps were examined: diffusion through immobile pore fluid, diffusion through bound organic matter, and the chemical binding and release rate. First-order desorption rate coefficients were observed to be 10⁻¹ to 10⁻² s⁻¹ on unbonded, and C₈, C₁₈, amine, and alcoholic modified surfaces, and 10⁻³ to 10⁻⁵ s⁻¹ on C₁ and phenyl-polymer modified surfaces. Diffusion through immobile pore fluid had only a minor effect on the sorption rate, as evidenced by similar rates on organic-bound porous and solid particles. The diffusion rate through the bound organic layer is not rate limiting due to the small organic layer thickness. The observed slow desorption on the phenyl-polymer surface is consistent with the rate limiting step being the chemical binding and release rate. The changes in the rate with temperature and within a series of chlorinated benzenes support this conclusion. The free energies for sorption onto the phenyl-polymer surface ranged from -4.0 kcal mol⁻¹ for chlorobenzene to -6.9 kcal mol⁻¹ for pentachlorobenzene, which are within the range expected for van der Waals interactions. The observed sorption energies are slightly stronger than predicted for hydrophobic surfaces, possibly reflecting strong binding due to multiple pi-pi electron interactions on the phenyl-polymer surface. Hydrophobic solute partitioning onto natural soils, as observed by others, is less than that observed on aliphatic and phenyl hydrophobic surfaces in this study, but greater than on amine or alcoholic modified surfaces. The sorption of di-, tri-, and tetra-chlorobenzenes onto the phenyl-polymer surface is apparently driven by the overall sorption enthalpy (ΔH° = -3.9 to -4.9 kcal mo1⁻¹) and to a lesser extent by the entropy (TΔS° = 0.5 to 1.5 kcal mol⁻¹). As equilibrium of the reactions observed in this study are reached within hours, these reactions are important at small field scales where residence times are hundreds of hours or less.

Helium tracer experiments were conducted to characterize conservative tracer behavior in a wedge-shaped lysimeter containing alternating layers of unsaturated silty sand, and clay loam. Experiments were conducted with trichloroethylene and 1,1,1-trichloroethane to determine if air stripping in unsaturated soil could be characterized by mass transfer from the sorbed to the liquid to the vapor phase. Batch experiments were conducted to measure liquid--vapor mass transfer. Solid-liquid-vapor mass transfer was characterized by measuring the vapor phase re-equilibration after the air stripping experiment. The Discrete State Compartment model was used to simulate a conservative gas tracer. The results were compared to the helium tracer. Liquid-vapor, and solid-liquid-vapor mass transfer were modeled by fitting simulated data to experimental data. The conservative tracer, and mass transfer models were combined to simulate air stripping in unsaturated soil.

The Microwave-Assisted Process (MAP$ sp{ rm TM}$) is an enhanced extraction technology patented by Environment Canada. MAP uses microwaves to rapidly transfer target compounds from one phase to another by selectively heating the phase containing the target compounds. This thesis presents the results of research performed to determine whether the MAP technique can be further developed into a large-scale soil treatment process that overcomes the limitations of conventional remediation technologies. / The dielectric properties of several mixtures of acetone and hexane over a temperature range from 25$ sp circ$C to 50$ sp circ$C were measured. The dielectric constants of these mixtures were found not to vary significantly with temperature. / A study of microwave absorption by heterogeneous mixtures showed that adding a solid material to a low dielectric constant solvent resulted in energy being preferentially absorbed by the solid. / The results of laboratory extraction tests showed that the ability of the MAP technique to extract contaminants was affected by the organic matter content of soil, particularly in the presence of water. / Use of a closed-vessel system yielded a 60% to 175% increase in the extraction of PAHs from a low organic-content soil relative to that achieved in an open-vessel system. (Abstract shortened by UMI.)

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No description available.

Globally, the forestry sector is the second largest contributor of greenhouse gases, and sustainable forest management is a major target of international environmental policy. However, there is the assumption underlying many policy recommendations that an increase in above-ground carbon stocks correspond to long term increases in ecosystem carbon stocks, the majority of which is stored in soils. We analyzed soil carbon and nitrogen dynamics in forest soils that had undergone twenty years of organic inputs manipulations as part of the Detritus Input and Removal Treatment (DIRT) network. There was no statistically significant effect of the rate of litter or root inputs on the carbon or nitrogen in bulk soil, on respiration rates of soil in laboratory incubations, on the non-hydrolyzed fraction of soil organic matter, or on any organic matter associated with any density. However, there is evidence for positive priming due to increased litter inputs; doubling the rate of litter inputs decreased C and N contents of bulk soil and decreased respiration rates of soil. Furthermore, there is evidence that roots influence soil organic matter dynamics more strongly than above-ground inputs. Both of these results trends match data from other DIRT sites, and are supported by the literature. / Graduation date: 2012

A study of the interactions of the specifically interacting organic compound pyridine with a model soil organic matter sorbent (Pahokee peat) was carried out from different nonaqueous organic liquid media, including neat n-hexadecane, acetonitrile, acetone and nhexadecane mixtures with either acetone or acetonitrile. Kinetic and equilibrium studies using an activity-based comparison of the organic compounds in solution was used to study the interactions of soil organic matter (SOM) and pyridine sorption capability in the various non-aqueous organic liquid media. Quantification and qualification of pyridine and the other co-solvents were done using Gas Chromatography (GC). Sorption of pyridine from neat organic solvents was not masked by sorption of the organic solvent. The apparent sorbed amount calculated from the change in solute concentration and reported on a dry weight basis was considered to represent the true sorbed concentration of pyridine in the sorbent phase. Pyridine sorption was found to be non-linear and distribution coefficients decreased with solute concentration, by approximately three times in n-hexadecane, more than five times in acetonitrile, and by ten times in acetone over the experimental concentration range. Pyridine sorption from nhexadecane was also found to be comparable with sorbed amounts from acetone, but much lower in comparison to sorption from acetonitrile. Sorption of pyridine from n-hexadecane mixtures with acetonitrile or acetone demonstrated the solvent assisted effect of pyridine sorption. Sorption uptake of pyridine increased as initial acetonitrile concentration increased, this acetonitrile assisted trend for pyridine sorption was found in the presence of a large excess of n-hexadecane. Sorbed concentrations of pyridine measured in the presence of high concentrations of acetonitrile (close to it's solubility limit) were found to be very similar to pyridine sorption from neat acetonitrile. Sorption behaviour of pyridine in n-hexadecane-acetone mixtures showed that increasing acetone concentrations had no effect on pyridine sorption. Pyridine sorbed from n-hexadecane, n-hexadecane-acetonitrile, and n-hexadecaneacetone mixtures showed a hysteretic desorption to n-hexadecane. After a series of repeated solvent extractions with solvents of increasing solvating power(1,4-dioxane, ethanol, dimethylsulfoxide), a fraction of pyridine remained bound to the peat. This nonrecoverable fraction was approximately the same for the different organic media (OA5± 0.09 in n-hexadecane suspensions, 0.57±O.12 in n-hexadecane-acetonitrile mixtures, and OA6±0.07 in n-hexadecane-acetone mixtures). Acetonitrile sorption by peat from nhexadecane was found to be very non-linear and hysteretic. The acetonitrile sorbed was almost fully recoverable, around 90%, for the initial acetonitrile concentration range varying from 0.14-0.7% by volume. However in the presence of pyridine a significant portion of acetonitrile was not recovered even after multiple extractions of polar organic solvents. Pyridine irreversible binding was not induced by acetonitrile additions and was found to occur to the same extent in both neat n-hexadecane and n-hexadecane-acetone mixtures. The solubilities of acetonitrile and acetone were determined by the flask method at 25°C using GC analysis. Solubility in volume percent for acetonitrile in n-hexadecane, 0.9±0.07, 0.57±0.02 for n-hexadecane in acetonitrile, 24.0±OA for acetone in nhexadecane, and 13 A±O.2 for n-hexadecane in acetone, were found. Log Ostwald coefficient (1.63±O.02) for acetonitrile in n-hexadecane was measured at 25°C using head space analysis and was found to be constant in the acetonitrile concentration range 0.10.8% by volume. Log Ostwald coefficient for pyridine in hexadecane used was 3.02, for the pyridine concentration range 50 mgIL-500 mg/L, this value was constant even with 0.5% by volume additions of acetonitrile. Analyses of sorption isotherms were reported on an activity basis to eliminate the effect of differential solute interactions in the solvent, calculated using the solute equilibrium concentration, the concentration of saturated vapour, and the Ostwald coefficient. Dissolution of peat components into n-hexadecane are known to be negligible. Peat components extracted after 12 hours and 3,5 months acetonitrile and acetone treatment (solid liquid ratio 1: 10) Showed 15 to 20 times less visible absorbance respectively (A. 465, 620, and 665, E4:E6 ratios using DV-Visible Spectroscopy), than the 12 hours aqueous peat extract. Quantification of the dissolved humic materials in the aqueous extract was followed using a Total Organic Carbon analyser. The study found the degree of humification to be much lower in non-aqueous organic solvent extracts (2.5 for acetone extracts, and 3 for acetonitrile extracts) than in aqueous solution extracts (8.2). / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002. / The Moshe Greidinger Scholarship Fund.