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MARTIN ALEXANDER
Liberty Hyde Bailey Professor Emeritus

 

Department of Soil and Crop Sciences 708 Bradfield Hall
Cornell University Telephone: 607-255-1717
Ithaca, NY, 14853 e-mail: ma59@cornell.edu

December 7, 2001
Dear Josh:

| am sorry for the slow response to your note of November 26, but it only arrived
here in Sarasota yesterday after being forwarded by my secretary at Comell. |
am doing some extensive writing, and Sarasota is a much more hospitable place
than upstate New York in the winter.

Many thanks for forwarding a copy of the paper by Schneour. | am familiar with
some of the work on graphite biodegradation, but | do not recollect this specific
paper.

However, | believe that wnat he studied and the focus of our current research are
somewhat different. Our data show that organic compounds become
progressively less available for microbial metabolism, uptake by animals and
toxicity to a variety of species, probably including man. In some soils, ca. 90% of
what we measure chemically is not available biologically. In other soils, the
values are substantially less. The practical implications: current analytical
methods for organic pollutants overestimate, sometimes appreciably, the severity
of pollution at some and possibly many sites—-and that decisions should be
made on the basis of availability to organisms and not to some arbitrary
extractant.

The likely mechanism of this sequestration: penetration of the organic molecules
into minute pores in the soil (we have made measurements showing that some
soils have an abundance of pores even as small as 8 nm [ others have measured
even smaller pores]) and their sorption on the pore surfaces and/or the very slow
diffusion of the molecules into the solid phase of the soil. We have data with
models to support both postulated mechanisms. Pores of diameters 8 nm or less
are obviously too small for any bacterium or even for extracellular enzymes. If
diffusion out of the nanopores or solids is very slow, bioavailability would be
drastically affected.

Regards,

1631 Starling Drive, Sarasota, FL 34231