Elucidation of the chemical speciation of trace metals in the natural aquatic environment will lead to a better understanding of their distribution and ecological effects. One approach which can provide useful information about the chemical reactivity of metal ions is the measurement of their activity. Phase equilibrium methods are required and liquid-liquid partition equilibria are applicable. This study utilized model systems to demonstrate this applicability. The partitioning of copper(II) ions as a chelate of acetylacetone was used to determine the trace activity coefficients of the copper(II) electrolyte in the CU(N03)2-HN03-KN03, Cu(N03)2-HCl04-NaCl04 and CuC12-HCl-KCl systems over a wide range of ionic strengths (u). By careful control of pH and acetylacetone concentration only 1-3% of the metal ion was extracted. Under these conditions the amount extracted is proportional to the activity. The concentration of the bis(Acetylacetonato) Copper(II) was determined in the organic phase by spectrophotometric and atomic absorption methods but any convenient concentration technique could be used to measure the amount extracted. A comparison of activity measurements by liquid-liquid partitioning was made with electrochemical measurements by utilizing a copper ion selective electrode. The significantly lower activity coefficient values obtained by the electrochemical method were explained in terms of the liquid junction potential and the necessity for extrathermodynamic approaches to single ion activities. Potential application of the liquid-liquid partitioning method to the determination of trace activity coefficients in natural aquatic systems was demonstrated by extension of the method to measurements in copper(II) amino acid solutions at u = 0.001 and u = 0.723. The ionic strength adjustments in this case were made with NaCl. A significant difference in the free copper (II) ion activity was observed between solutions of copper(II) glycinate and copper(II) alaninate under identical conditions of metal and ligand concentrations, pH and ionic strength. The copper(II) activity measurements made in the presence of the amino acids at u = 0.723 are not possible with copper ion selective electrodes due to chloride interference.

No description available.

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography: leaves 147-157. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Bibliography: leaves 47-52. / by Wei Min Hao. / M.S.

Optoacoustic spectroscopy is a relatively old technique first described by Alexander Graham Bell in 1881. However, over the intervening years, little use was made of the technique due to its low sensitivity. This was due to low source intensities of available infrared light sources which limited the optoacoustic signal strength. With the advent of laser infrared light sources in the 1960's, there has been a resurgence of interest in optoacoustics. No longer is low source intensity a major limitation to successful optoacoustic spectroscopy. Although adequate infrared light sources are available, the large window background signal observed in all optoacoustic systems has been the major limitation in extending trace gas detection limits to the ppb or sub-ppb level. Similarly, there has been little demonstration of the use of the optoacoustic technique in environments where mixtures of gases are present which have severe spectral overlap. This work will discuss a new windowless cell design that largely eliminates the signal background problem ubiquitous to all presently available optoacoustic cells. New methodologies will be discussed that allow analyses of mixtures to be performed even in cases where spectral overlap is severe. Limitations to both the windowless cell and the various multicomponent analysis strategies are discussed.

Risk assessment of trace-metal contamination in soils requires predictive models that can accurately describe the complex uptake processes at the soil-plant interface, which are usually characterized by the coexistence of and interaction between multiple components. Competing cations such as Ca and H can affect metal availability to plants and subsequent rhizotoxicity. The biotic ligand model (BLM) has been proposed as a promising approach to model these interactive processes. Under the BLM assumption, we designed experiments to investigate how the solution chemistry is correlated with metal uptake and rhizotoxicity. Our first goal is to acquire a set of BLM parameters that can accurately represent the experimental data over varied solution conditions and parameters that are easy to integrate with general speciation models. The second objective is to get insight into the physical nature of the interactions. Our titration experiments revealed three types of biotic ligands in the pea roots with defined site densities and stability constants with H. Our ion sorption experiments estimated the surface-adsorption stability constants of Ca, Mg, Cd, Cu, Ni, and Zn with excised fresh pea roots. Our 48-h root growth tests have established the formation constants (KMe's) of living pea roots with Ca, Cd, Cu, Ni, and Zn. In these studies, we hypothesized and confirmed that the concentration of the metal-root complexes correlated with observed rhizotoxicity and that Ca, H, and trace metals competed for root absorption where lower solution pH decreased both Ca and metal uptake. Root elongation was found to be highly sensitive to root Ca content rather than merely to the direct toxic effects of the trace metals. It is shown that the physiological complexity arising from a living root affected our modeling so that adjustable KMe values, as a function of solution and root chemistry, are required for good model fits. The established model parameters were tested in hydroponic mixture solutions for their ability to predict the uptake of multiple metals simultaneously. The joint effects of Cd, Cu, and Ni in mixtures on root growth were studied and the potential interactions between these ions were also investigated.

There are two main components to the research: the theoretical and the experimental. Chapter 2 contains an analysis of the state of soil quality guidelines and the scientific methods used to determine them. A number of recommendations to improve soil quality criteria for trace metals are offered including the importance of considering bioavailability and the need to use realistic conditions, trace metal sources and organisms. / A critical review of the literature dealing with predicting the availability of trace metals to plants is presented in Chapter 3. We found little agreement among hundreds of similar studies which relate plant metal uptake to the amount of metal extracted by selective chemical dissolution procedures. An extensive summary of the data shows clearly that the extraction methods are not widely applicable. Differences between individual soils, their metal retention capacities, as well as plant factors and environmental conditions contribute to the variability of the results. Alternative ways of assessing bioavailability are suggested. / The experimental component of the thesis focuses on the availability of trace metals to plants. In Chapter 4 the uptake of Cu from different soil pools was examined and the free metal ion (Cu2+) was found to be the best predictor of uptake by lettuce (Latuca sativa cv. Buttercrunch), ryegrass (Lolium perenne cv. Barmultra) and radish (Raphanus sativus cv. Cherry Belle). / In Chapters 5 and 6 we examined the effect of low-cost in-situ treatments on the availability of metals to plants in greenhouse and field experiments. Synthetic zeolites, P amendments, organic matter and clean soil were used and their effect on the bioavailability of Cd, Cu, Pb, Ni and Zn evaluated. The plants for the experimental work were lettuce and perennial ryegrass. Only the clean soil treatment was consistently effective in reducing the concentration of metals in the plant. We also wanted to determine whether the trace metals in the plant tissue came from the soil or from direct deposition of pollutants on the leaf surfaces. We found little evidence that metals in plants were a result of atmospheric fallout. / A method for the accurate analysis of total metal concentrations in a range of contaminated soils including those containing oil and grease was developed (Chapter 7). For this research the trace metals of concern are Cd, Cu, Ni, Pb and Zn---all commonly found in urban/industrial soils. The proposed method using HNO3/HClO4 has several advantages over the common HNO3/H2O2 procedure. We were able to digest larger soil samples and hence the final concentration of trace metals was usually in the range for analysis by inductively coupled plasma atomic absorption spectrometry or flame atomic absorption spectrometry.

Thesis (M.S. - Hydrology)--University of Arizona, 1984. / Includes bibliographical references (leaves 68-72).

Thesis (Ph. D.)--McMaster University (Canada), 1989. / Source: Dissertation Abstracts International, Volume: 62-13, Section: A, page: 0000.

Thesis (M. Sc.)--University of Hong Kong, 1993.