A flow of contaminated liquid phase water migrates toward the freeze front and {HEAD ~ a concentration} of impurities is established in {TAIL ~ front} of the advancing freeze front 
is established in
A flow of contaminated liquid phase water migrates toward the freeze front and { HEAD ~ a concentration } of impurities is established in { TAIL ~ front } of the advancing freeze front
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH