Estuary is a complex region due to the mixing of fresh and sea water as well as the mixing of terrestrial and marine dissolved organic matters (DOM), so that the sorption behavior between hydrophobic organic compounds and dissolved organic matters is very complicated to estimate. By applying fluorescence quenching method, we investigated the influence of the mixing of binary dissolved organic matters from different sources on the binding constant (Kdoc) of pyrene and DOM. Results show that the kinetic of mixing of binary DOMs influences the binding constant, that means if there weren¡¦t enough standing time for mixing of binary DOMs, it would cause some bias in estimating the binding constants of pyrene and DOMs mixture. In this study, we also found that there exists a linear relationship on the binding constants between pyrene and DOMs mixture against mixing ratios. In addition, the mixing mechanism of SRNOM and LHA was dominated by diffusion process from the results of initial mixing efficiency. However, the diffusion process might not be the only mechanism of the mixing reaction of SHHA and LHA, other factors should be considered. Further investigations should be done to find out the dominating factors on the mixing of SHHA and LHA system in the future.

ABSTRACT Hydrophobic organic pollutants (HOPs) are in general characterized by high toxicity, long environmental half-life and high bio-accumulation factors. Due to their hydrophobicity, HOPs tend to sorb onto particles in environment. The influence of the dissolved organic matters (DOMs) on the sorption partition coefficient is observed because of their interactions with HOPs. This binding between DOM and HOPs increases apparent solubility and mobility of the HOPs in natural aquatic system. On the purpose of obtaining data closer to the real world, many aquatic factors, such as the concentration and types of DOM, pH value and ionic strength, are studied intensively recently. There are many studies about the mechanisms in the association of DOM and HOPs. Most of them assume achievement of equilibrium in their measurement. Recently, it was reported (Engebretson and von Wandruszka, 1998) that slow, revering, and even oscillating kinetics are observed. It is great concern and interest to those related studies in literatures. Complicated kinetic may in fact be a cause of the reproducibility problems for measurements of HOPs associated with both humic acid and metals. As such, by monitoring fluorescence intensity, we investigate the equilibrium kinetic of pyrene in HA solutions. In this study, results show that there are two stages of the fluorescence intensity after pyrene spiked into HA solutions: First, the fluorescence intensity decreases steeply due to the first dispersion of pyrene and the reaction of pyrene and HA (the front is dominance). Secound, fluorescence intensity decreases gently because of wall-effect. The dispersion rate of pyrene in HA solutions is difference with HA molecular size and quantity. As the ionic strength rising, cations reacting with specific binding sites on HA, the molecules¡¦ configuration of HA is changed, and less obstruct for dispersing of pyrene. It works as well as little molecular quantity. For second stage when ionic strength rising, wall- associations is less because of the hydrophobic-binding of pyrene and LHA is more stronger. Furthermore, it is not observed the ¡§migration¡¨ of Mg2+ within the LHA molecular structure as described by Engebretson and von Wandruszka .The reasons that make different results may depend on the species of humic acid. Therefore, the observations of Engebretson and von Wandruszka could not be used directly questioning those results in literatures. In addition, the effects of various cations (Mg2+, Ca2+and Sr2+) on Kdom are studied. It is believed different cation reacts with different specific binding sites on HA. As such, both charge density and affinity of cation with specific binding sites on HA should be considered in discussing the effects of metal ionic on the binding constants between PAHs and DOM.

Thesis (M. Sc.)--York University, 1998. Graduate Programme in Geography. / Typescript. Includes bibliographical references (leaves 82-88). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ39192.

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The storage or disposal of nuclear waste is one of the major concerns faced by governments, communities, and environmentalists. This radioactive waste, as a source of ionising radiation, represents a potential hazard to human health and must be carefully managed so as to reduce the associated risks to acceptable levels for both now and in the future. The migration of radioactive waste (radionuclides) in the environment is controlled by many factors, such as the interaction of the radionuclides with soil. Humic acid (plant material) has substantial chelating properties for metal ions and can therefore considerably affect the migration behaviour of radionuclides in a soil layer. To manage the radioactive waste effectively, it is important to know the presence and interaction of humic acid with radionuclides released from radioactive waste repositories. The aim of this study is therefore to investigate the influence of humic acid on the distribution coefficients of radionuclides found in both Thabana and Vaalputs waste repositories. The technique employed in this study is based on a laboratory batch method to study the influence of humic acid on the distribution coefficients of (131)^I and (137)^Cs on soil samples from Thabana and Vallputs waste repositories at different concentrations. The results of this study show that (131)^I and (137)^Cs do not form any complexes with humic acid and therefore the presence of humic acid does not have a significant effect on the migration of (131)^I and (137)^Cs. / MSc (ARST) North-West University, Mafikeng Campus, 2005

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Thesis (MPharm.--Faculty of Health Sciences)-University of Pretoria, 2007. / Includes bibliographical references.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2005. / Michael Saunders, Committee Chair ; Paul Work, Committee Member ; Jaehong Kim, Committee Member. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 151-161). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 151-161). Also available on the Internet.