| Acrylamide (AMD) is a known animal and suspected human carcinogen and is used to produce polyacrylamide (PAM), which has been proposed as a technology for seepage control in unlined water delivery canals. Previous studies have not quantified the fate and transport of AMD in soil and groundwater systems. In this study, batch experiments and soil column tests (with and without microbial degradation) were conducted on three materials (control sand, gravelly sand and loam soil) to determine the Kd, retardation factor, the form of the sorption isotherm, and determine microbial degradation rates. Soil core tests from samples collected in canals were also conducted to simulate field-scale transport. A numerical model (HYDRUS-2D) was used to simulate a canal environment using the fate and transport parameters of AMD obtained in the laboratory. Results indicate a Freundlich-type sorption isotherm for AMD in the loam soil and a linear isotherm for the sandy material. Sorption values were 0--2.4% in all tests. Results for the soil column tests show that AMD is conservative in all three types of material tested. The bacteria column tests indicated that AMD was quickly degraded (half lives were less than 3 hours), though half lives for the canal column tests were longer (∼31 hours). Numerical modeling shows that AMD would not be detectable 25 meters from the canal, as long as initial AMD concentration is less than 6.65 ppb. Using PAM at concentrations of less than 13 ppm would inhibit detectable contamination of canal water. |
