One of the more promising techniques for directly detecting
the presence of organic contaminants is complex resistivity
[ Olhoeft, 1992a]. Complex resistivity measures
the electrical impedance of the ground in the frequency range
of 
Hz, which is controlled by various charge transfer
and electrochemical mechanisms. Laboratory results have shown that
toluene in the presence of montmorillonite will polymerize resulting
in a characteristic and strongly frequency dependent resistivity
[ Olhoeft and King, 1991]. The problem of
clay-organic reactions and their detectability with geophysical
measurements is a promising area of research that
warrants further work.