Brownfields
are often also contaminated land, polluted by a range of chemicals.
These may have been dumped, or escaped from industrial uses and storage
tanks on site, and a sad fact is that every site where chemicals have
been used seems to be polluted. Information on what types of pollution
to expect can be found in industry profiles here.
Many pollutants
are initially released as non-aqueous phase liquids (NAPLs, in the
jargon) such as petrol, coal tar or solvents. These can flow through
the soil and rock, often to considerable depths, before coming to
rest and beginning to dissolve in groundwater. An educational website
on dense NAPLs can be found here,
and an illustrated handbook was prepared under Environment Agency
sponsorship which can be accessed here.
Many organic
pollutants are transformed to harmless compounds by biodegradation,
if the conditions re-suitable. The CORONA
website gives information on assessing these processes of natural
attenuation.
