{HEAD ~ An advancing freeze front} is established in {TAIL ~ a porous region} adjacent to or within contaminated earth 
is established in
{ HEAD ~ An advancing freeze front } is established in { TAIL ~ a porous region } adjacent to or within contaminated earth
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH