Lead Sequestration and Species Redistribution During Soil Organic Matter Decomposition

The turnover of soil organic matter (SOM) maintains a dynamic chemical environment in the forest floor that can impact metal speciation on relatively short timescales. Here we measure the speciation of Pb in controlled and natural organic (O) soil horizons to quantify changes in metal partitioning d...

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Bibliographic Details
Published in:Environmental science & technology 2008-05, Vol.42 (10), p.3627-3633
Main Authors: Schroth, Andrew W, Bostick, Benjamin C, Kaste, James M, Friedland, Andrew J
Format: Article
Language:English
Subjects:
ABSORPTION SPECTROSCOPY
Applied sciences
CONIFERS
Decomposition
Environmental Processes
Environmental science
ENVIRONMENTAL SCIENCES
Exact sciences and technology
FLOORS
FLUORESCENCE
FOREST LITTER
FORESTS
INVENTORIES
Lead
Lead - chemistry
Lead - isolation & purification
Organic chemicals
Organic Chemicals - chemistry
ORGANIC MATTER
POLLUTANTS
Pollution
SCAVENGING
Soil - analysis
Soil sciences
SOILS
Spectrum Analysis - methods
X-Rays
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Summary:The turnover of soil organic matter (SOM) maintains a dynamic chemical environment in the forest floor that can impact metal speciation on relatively short timescales. Here we measure the speciation of Pb in controlled and natural organic (O) soil horizons to quantify changes in metal partitioning during SOM decomposition in different forest litters. We provide a link between the sequestration of pollutant Pb in O-horizons, estimated by forest floor Pb inventories, and speciation using synchrotron-based X-ray fluorescence and X-ray absorption spectroscopy. When Pb was introduced to fresh forest Oi samples, it adsorbed primarily to SOM surfaces, but as decomposition progressed over two years in controlled experiments, up to 60% of the Pb was redistributed to pedogenic birnessite and ferrihydrite surfaces. In addition, a significant fraction of pollutant Pb in natural soil profiles was associated with similar mineral phases (∼20−35%) and SOM (∼65−80%). Conifer forests have at least 2-fold higher Pb burdens in the forest floor relative to deciduous forests due to more efficient atmospheric scavenging and slower organic matter turnover. We demonstrate that pedogenic minerals play an important role in surface soil Pb sequestration, particularly in deciduous forests, and should be considered in any assessment of pollutant Pb mobility.
ISSN:0013-936X
1520-5851
DOI:10.1021/es703002b