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Document Type

Thesis - University Access Only

Award Date

1996

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

Abstract

Humic acid, fulvic acid, and humin were isolated from soil by utilizing the traditional alkali method. The association of selected AOC (anthropogenic organic compounds) with humic materials was studied. A major emphasis of this research was elucidate and understand how humic and fulvic acid interact with AOCs. The major thrust of this research was the hypothesis that humic acid does, in fact, form an organized aggregate known as a micelle. This hypothesis was then applied to the lowest molecular weight fraction of humic material-fuvic acid. Another emphasis of this work was to probe the interactions of AOCs with humin. The actual humin fraction was extracted to determine the role of the lipid and brominate-treated to examine the role of organic matter for AOC interactions with humin. Three experimental techniques were employed to determine whether humic and fulvic acid micelle formation is an accurate description of the aggregation process that may be occurring; they are surface tension, solubility measurements utilizing radio-labeled AOCs, and small-angle X-ray scattering spectrophotometry. The results obtained indicated there was not substantial aggregation due to classical micelle formation when the concentration of humic acid was increased. However, this evidence suggested that as the concentration of humic acid increased to a critical point, the humic acid components arrange themselves by directing the hydrophobic portions of the humic acid toward the center of the aggregate. The hydrophobic center of the humic acid, at higher concentrations, was able to substantially solubilize otherwise hydrophobic (low water solubility) AOCs compared to the AOC water solubility. This observation has been reported recently in the literature as the formation of a pseudomicelle of hemimicelle. The ability of humic and fulvic acid to increase the water solubility of DDT, naphthalene, and pyrene with respect of pH and ionic strength was also investigated, and the implications are discussed. The interaction of several AOCs with humin was studied to determine if the partitioning model was considered valid for humin. The humin treated to remove the lipid and organic matter to determine the effects of AOC adsorption to the altered humin. The determination of the amount of AOC that associated (sorbed) to the unaltered humin, extracted lipid humin, and organic free humin was determined utilizing a low pressure liquid chromatograph column. One criterion supporting the partitioning model is the lack of competitive effects upon adsorption with more than one AOC. To validate the partitioning model, the surface area of the sorbent should be lower after adsorption. This was accomplished using Brunauer, Emmett and Teller (BET) surface analyses. The surface areas of the samples were determined before and after application of the AOC. The surface area results and sorption results of humin with AOCs are presented and the implications to soil are addressed.

Library of Congress Subject Headings

Soils -- Organic compound content

Soils -- Humic acid content

Format

application/pdf

Number of Pages

271

Publisher

South Dakota State University

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