Degree Type

Dissertation

Date of Award

1989

Degree Name

Doctor of Philosophy

Department

Agronomy

First Advisor

M. A. Tabatabai

Abstract

An accurate and precise ion chromatographic (IC) method for determination of total Cu, Ni, and Zn in soils was developed. The metals in soil digests were extracted with dithizone in CHCl[subscript]3, and the metal-dithizonate complexes were digested with HNO[subscript]3 before injection into the IC system. After separation on HPIC-CS5 column, the metals were determined by measuring the absorbance of metal complexes formed by postcolumn reaction with 4-(2-pyridylazo) resorcinol (PAR) at 520 nm. The results by this IC method agreed closely with those obtained by atomic absorption spectrophotometry (AA). Comparison of results of total Cu, Mn, Ni, Pb, and Zn with those obtained by AA showed that this method was accurate and precise for determination of metals in sewage sludges;The effect of cropping systems on adsorption of metals by soils was studied for two long-term rotation experiments, each having three crop rotations (continuous corn (CCCC), corn-soybean-corn-soybean, and corn-oats-meadow-meadow) and treatments with (+N) and without (O N) ammoniacal fertilizer. Results for soils under CCC rotations (+N) showed lower metal adsorption than those under CCCC (O N) and other crop rotations, which showed similar metal adsorption. Comparison of results obtained after adjusting the soil-solution pH with those for unadjusted solution pH showed that differences in metal adsorption by these soils were due to solution pH. Plots of the logarithm of the metal distribution coefficient (log K[subscript] d) vs. pH suggested competition of protons with metal ions for exchange sites. In general, proton coefficient values ( H[superscript]+/M[superscript]2+ ratios) followed the sequence: Pb > Cu > Cd = Ni = Zn. Calculated H[superscript]+/M[superscript]2+ ratios of Cu > Ni ≥ Cd = Zn. Competition between metals for common adsorption sites was enhanced as the M[subscript]i increased.

DOI

https://doi.org/10.31274/rtd-180813-11277

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Nicholas Thomas Basta

Language

en

Proquest ID

AAI9014877

File Format

application/pdf

File Size

286 pages

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