The processes involved in natural attenuation are operating at all
contaminated sites, but the contribution of natural attenuation to
achieving remediation goals varies in different situations. At some
sites natural attenuation may meet all the remedial goals, and at
other sites natural attenuation may make little or no contribution.
Therefore, before natural attenuation can be selected as a remedial
alternative, it is necessary to study each contaminated site carefully
to determine how effective natural attenuation is for attaining site
remediation goals.
Bulk chlorinated solvents – in the NAPL form, rather than dissolved
in water or sorbed on soil particles – are not readily degraded by
microorganisms. Also, dispersion, dilution and sorption of the
NAPL is slow. Therefore, it is important to determine where this
NAPL may be at a polluted site, in order to remove or contain as much
of it as possible, because the processes of natural attenuation would
not effectively remediate most of this material in a reasonable time frame. Natural attenuation processes are usually of most significance
for the remediation of those contaminants dissolved in water,
sorbed on soil particles, or in the vapor form