Acrylamide release resulting from sunlight irradiation of aqueous polyacrylamide/iron mixtures.
Linear anionic polyacrylamide (PAM) has been used in irrigation practices as a flocculating agent to minimize water losses through seepage in earthen canals. The stability of PAM is of concern because of the possibility of acrylamide (AMD) monomer release during environmental weathering. Aqueous solutions of commercial PAM mixed with ferric sulfate, subjected to simulated and natural sunlight irradiation, showed polymer chain scission and release of the AMD monomer. At acid/neutral pH, the amount of AMD released was directly related to the concentration of ferric ion and the irradiation time. At alkaline pH (approximately 8), PAM/Fe(3+) mixtures were stable under irradiation. PAM chain scission involved the hydroxyl radical, but specific AMD release appeared to require PAM-bound iron. Low iron concentrations and alkaline pH of irrigation water would limit AMD release. Residual monomer in PAM can contribute AMD to irrigation water, but concentrations would remain below the U.S. EPA drinking water standard of 0.5 ppb.
Woodrow
James E
JE
Natural Resources and Environmental Science, University of Nevada, Reno, Nevada 89557, USA. jwoodrow@unr.nevada.edu
Seiber
James N
JN
Miller
Glenn C
GC
D020106:Acrylamide / Q000737:chemistry* / Q000528:radiation effects*; D000838:Anions; D005290:Ferric Compounds / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D012996:Solutions; D013472:Sunlight; D014867:Water
D000838:Anions; D005290:Ferric Compounds; D012996:Solutions; D014867:Water; D020106:Acrylamide; C024823:ferric sulfate; D007501:Iron