Date of Award

1988

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Robert J. Gale

Abstract

Part One. Acidity and chemical composition of precipitation in Baton Rouge, Louisiana; The synergistic effects of acidity and aluminum on fish. Acid precipitation which consists of both wet precipitation and dry deposition has recently become a significant environmental problem. It has been shown that the effects of acid rain are deleterious to soil, vegetation, aquatic life and buildings. Wet-precipitation-only samplers were used to collect acid rainfalls in the vicinity of Louisiana State University, Baton Rouge and subjected to appropriate chemical analysis for the purpose of characterization of general composition and acidity. About 50% of precipitation is within pH range of 4.0-5.0. Acidity is largely due to the presence of sulfuric and nitric acid. There is seasonal variation in acidity of precipitation, namely rain water is more acidic in summer than winter. Study of pH of rainfall versus wind directions indicated no correlation between average pH and any specific local wind directions. Light showers yielded much higher values of conductance than did large storms. The concentration of the major anions (SO$\sb4\sp{-2}$, NO$\sb3\sp-$, Cl$\sp{-}$) and major cations (Na$\sp{+}$, NH$\sb4\sp{+}$, K$\sp{+}$) were measured utilizing ion chromatography. Inductively coupled plasma was utilized in determination of minor trace metals in the precipitation. Addition of aluminum ion to acidified waters caused increased toxicity to aquatic life, especially in the pH range of 4.5-5.0. Part Two. Electrochemical preconcentration of trace mercury on carbon fiber for atomic absorption analysis; Capillary GC-AA for speciation of mercury compounds. Speciation is critically important in assessing the potential toxic effects of a specific element on susceptible organisms and ecosystems. Mercury and its compounds are highly toxic and organomercury compounds are far more toxic than elemental or inorganic mercury. A capillary gas chromatographic interfaced atomic absorption unit has been developed and used for the speciation and determination of volatile mercury compounds in environmental samples. Use of AA as a specific detector for GC combines the high resolving power of chromatography with specificity, selectivity and sensitivity of AA for the determination of organometallic compounds in environmental samples. Mercuric chloride, methyl mercuric chloride, and dimethyl mercury were separated. Resolution was excellent and reproducibility is within 5-10%. 100 pg of mercury can easily be detected. (Abstract shortened with permission of author.).

Pages

275

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