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 2009-05, Vol.42 (10)
Main Authors: Schroth, A.W., Bostick, B.C., Kaste, J.M., Friedland, A.J.
Format: Article
Language:English
Subjects:
ABSORPTION SPECTROSCOPY
CHARGES
CONIFERS
DECOMPOSITION
DYNAMICS
EARTH ATMOSPHERE
ENVIRONMENT
ENVIRONMENTAL SCIENCES
FOREST LITTER
FORESTS
INVENTORIES
LEAD
METALS
MINERALS
MOBILITY
ORGANIC MATTER
Other,OTHER, ENV
POLLUTANTS
SCAVENGING
SOILS
SURFACES
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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-rayfluorescence and X-ray absorption spectroscopy. When Pb was introduced to fresh forest O{sub i} 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 ({approx}20--35%) and SOM ({approx}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