Tuesday, October 18, 2011
Henry Gonzalez Convention Center, Hall C, Street Level
Valerie Bullard, Anthony O'Geen and Randal Southard, UC Davis, Davis, CA
Naturally occurring asbestos (NOA) can be found in serpentinized ultramafic parent
material and associated soils, which appear throughout California
and Oregon.� These landscapes pose a potential danger to
human health if particles are liberated from the soil and inhaled.� The objective of this study was to examine
the weathering patterns of NOA minerals in soil horizons and dust across a
developmental sequence in serpentinitic landscapes.� We have
examined NOA mineral (chrysotile) abundance and
location in the soil profiles using x-ray diffraction, polarized light
microscopy, and transmission electron microscopy.� We have found that there is a negative relationship
between abundance of chrysotile in the solum and weathering intensity.� In soils with a low weathering index (<
30), the abundance of chrysotile bundles in the fine
sand, clay, and dust fractions, generally decreased with proximity to the soil
surface, while needles increased.� In
soils with a moderate weathering index (>30), chrysotile
needles and bundles increased with proximity to the soil surface in the fine
sand and clay fractions, but decreased in the dust fractions. �The results indicated that during initial
stages of development, chrysotile bundles and needles
were liberated from parent material through physical and chemical weathering
processes.� In the moderately weathered
soils, bundles continued to weather further into smaller size fractions,
resulting in more needles in the clay fractions.�� In the dust fractions, numerous chrysotile needles were found in the weakly weathered soils,
while the moderately weathered soils contained few to no needles.� The A horizons of the moderately weathered
soils produced the largest quantities of dust, contained the lowest abundance
of chrysotile, pedogenic
iron and clay, but also the highest percent carbon.� This indicated that soils containing NOA in
intensely weathered environments have a lower potential to release chrysotile needles in dust than soils in mild weathering
environments.�
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See more from this Division:
S09 Soil Mineralogy
See more from this Session:
Minerals, Nanoparticles, and Health: II