"A Chemical Extraction Study of Lead Contaminated Soil from Granite Cit" by Yan Zhang

Degree Name

Master of Science (MS)

Semester of Degree Completion

1997

Thesis Director

Douglas G. Klarup

Abstract

Granite City, IL, surface soil ( 0-10 cm ) contaminated with lead was studied by both single- and a four-step sequential chemical extraction procedures designed to establish the partitioning, mobility and availability of lead in soil. The five fractions corresponding to the selected extractants were exchangeable, carbonates-bound, Fe-Mn oxides bound, organic matter and residual. Lead contamination of the soil was determined as a function of particle size and soil depth.

The contaminated sample had the highest lead content of 573.1 mg/kg at the 4 cm soil depth level, and on average was about 8.8 times that of background soil. Most of the lead ( over 87% ) is concentrated in the Fe-Mn oxides bound, organic matter, and residual fractions, and only about 9-13% of the total lead remain in the first two fractions. The lead content in the residual fractions decreased as the depth increased and suggests the presence of undefined lead-containing large particles.

The intermediate particle size range (90-125 μm) contained the highest lead content, 563.3 mg/kg. Here, over 80% of total lead is found in the Fe-Mn oxides bound, organic matter and residual fractions. Lead content in the more accessible fractions, exchangeable and carbonates-bound, increased slightly as particle size decreased.

Extraction experiments showed that low pH water may cause mobilization of lead from soil to water. Oxalic acid releases only a limited amount of lead into solution, and surfactant Triton solution may be used as a soil containment reagent to prevent lead release from soil.

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