Thesis (M. Sc.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Graduation date: 1997

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references. Also available in electronic version.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (M.S.)--Oregon State University, 1982. / Typescript (photocopy). Includes bibliographical references (leaves 80-83). Also available on the World Wide Web.

Gaseous transport through soil in the presence of soil microorganisms has been investigated. More recently, modeling of gaseous transport in the unsaturated zone has been investigated. However, the problem of mathematical model of oxygen and carbon dioxide transport through soil, as affected by the climatic conditions, the transport of soil water, and the biological activities, has not been studied. The problem of time-dependent diffusion of oxygen and carbon dioxide through plant canopy and soil system, as affected by the infiltration and evaporation of soil water and the rate of consumption of oxygen and production of carbon dioxide by plant leaves and roots and soil microorganisms was studied, using a one-dimensional mathematical model. This model consists of four sets of non-linear partial differential field equations, which describe the time-dependent simultaneous transport of water, heat, oxygen, and carbon dioxide through the soils. Finite difference methods were used to find the approximate solutions for the four sets of non-linear partial differential field equations. The field equations for the transport of water and heat were approximated by using the implicit scheme. The field equations for the transport of oxygen and carbon dioxide were approximated by using the explicit scheme. A computer program was written in Fortran code to conduct the simulations of the mathematical model. Simultaneous transport of water, heat, oxygen, and carbon dioxide through the unsaturated Indio loam soil, through the compacted and the non-compacted soil during infiltration, redistribution, and evaporation of soil water was evaluated. Diffusion of oxygen and carbon dioxide within the canopy and soil system was examined. Several different functions for the root elongation and the root oxygen consumption rates were used. Root elongation rate was chosen to depend on oxygen or carbon dioxide concentrations, in addition to being a function of time. Root oxygen consumption rate was assumed to be a function of root age, in addition to being a function of oxygen or carbon dioxide concentrations. Results illustrate that the behaviors of the simultaneous transport of water, heat, oxygen, and carbon dioxide were well predicted by the model. / Graduation date: 1991

University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering

Management practices that may increase soil organic matter (SOM) storage include conservation tillage, especially no till (NT), enhanced cropping intensity, and fertilization. My objectives were to evaluate management effects on labile [soil microbial biomass (SMB) and mineralizable, particulate organic matter (POM), and hydrolyzable SOM] and slow (mineral-associated and resistant organic) C and N pools and turnover in continuous sorghum [Sorghum bicolor (L.) Moench.], wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.], sorghum-wheat/soybean, and wheat/soybean sequences under convent ional tillage (CT) and NT with and without N fertilization. A Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochepts) in southern central Texas was sampled at three depth increments to a 30-cm depth after wheat, sorghum, and soybean harvesting. Soil organic C and total N showed similar responses to tillage, cropping sequence, and N fertilization following wheat, sorghum, and soybean. Most effects were observed in surface soils. NT significantly increased SOC. Nitrogen fertilization significantly increased SOC only under NT. Compared to NT or N addition, enhanced cropping intensity only slightly increased SOC. Estimates of C sequestration rates under NT indicated that SOC would reach a new equilibrium after 20 yr or less of imposition of this treatment. Labile pools were all significantly greater with NT than CT at 0 to 5 cm and decreased with depth. SMB, mineralizable C and N, POM, and hydrolyzable C were highly correlated with each other and SOC, but their slopes were significantly different, being lowest in mineralizable C and highest in hydrolyzable C. These results indicated that different methods determined various fractions of total SOC. Results from soil physical fractionation and 13C concentrations further supported these observations. Carbon turnover rates increased in the sequence: ROC < silt- and clayassociated C < microaggregate-C < POM-C. Long-term incubation showed that 4 to 5% of SOC was in active pools with mean residence time (MRT) of about 50 days, 50% of SOC was in slow pools with an average MRT of 12 years, and the remainder was in resistant pools with an assumed MRT of over 500 years.

Thesis (M.S. in chemical engineering)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 20, 2010). "Department of Chemical Engineering and Bioengineering." Includes bibliographical references (p. 63-65).

Includes bibliographical references (p. 202-209).