Dissertation/Thesis Abstract

Urban soil genesis, weathering of waste building materials, and bioavailability of lead in a chronosequence at former demolition sites, Detroit, Michigan
by DuBay, Brian R., M.S., Wayne State University, 2012, 119; 1509042
Abstract (Summary)

An urban soil chronosequence in downtown Detroit, MI spanning 95 years of weathering was studied to determine the effects of time on soil genesis, artifact weathering, and Pb geochemistry. The results show that

Au- and

Cku-horizonscan develop within a few decades, whereas B-horizon development occurs on a scale of centuries. Melanization of

Au-horizons was enhanced by airbornedeposition of soot and flyash, and

Cku horizons have formed by weatheringof calcareous artifacts. Hence, urban soil genesis has been significantly affected by anthropogenic activities. Plaster and mortar artifacts may weather away completely within a few decades. Corrosion of iron-artifacts begins shortly after burial, and is enhanced by deicing salts and solution of gypsic artifacts. However, iron artifacts have survived 95 years of weathering. Weathering of iron artifacts has resulted in pedocementation and mobilization of Fe. This is attributed to fluctuating redox conditions (ferrolysis) produced by seasonal wet-dry and freeze-thaw cycles, and waterlogging caused by reduced permeability associated with densic horizons. All of the demolition site soils are contaminated with Pb, but total Pb concentrations are below the EPA trigger level of 400 mg kg−1. Soot and other carbonaceous microparticles appear to be controlling the bioavailability of Pb in

Au-horizons. Organicallybound-Pb is being leached from

Au-horizons, and accumulating in

Cku-horizonswhere it is sorbed by pedogenic calcite, corroded iron-artifacts and ferruginous microparticles. Pedogenic calcite and ferrihydrite, generated by weathering of calcareous and ferruginous building materials, are potential immobilizing agents for Pb and thus may have ameliorating effects on urban soils. Sand-sized microparticles related to coal combustion are locally abundant in the soils studied. They represent a previously unrecognized sink for heavy metals, but more study is needed because most of this material is likely found in finer size fractions which were not studied. More study is also needed of earthworms in urban soils because levels of bioaccessible Pb were found to be lower in the rhizosphere and earthworm casts than in the bulk

Au-horizons. Hence, earthworms may be significantly reducing the amount of bioavailable-Pb in the rhizosphere through bio-uptake and their extensive casting activity. If so, earthworms could be used as a natural remediation tool for reducing the hazard associated with resuspension of contaminated urban soil.

Indexing (document details)
Advisor: Howard, Jeffrey L.
Commitee: Baskaran, Mark, McElmurry, Shawn P.
School: Wayne State University
Department: Geology
School Location: United States -- Michigan
Source: MAI 50/05M, Masters Abstracts International
Subjects: Geology, Soil sciences, Environmental science
Keywords: Bioaccessinility, Chronosequence, Lead pollution, Sequential extraction
Publication Number: 1509042
ISBN: 9781267294401
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