Impact of polyacrylamide treatment on sorptive dynamics and degradation of 2,4-D and atrazine in agricultural soil.

摘要

High-molecular-weight, anionic polyacrylamide (PAM) is added to irrigation water to reduce soil erosion during furrow irrigation of crops. The chemical nature of PAM, together with the observation that the polymer can be biotransformed by soil bacteria, led us to question the impact of PAM treatment on the fate of coapplied agrochemicals. The herbicides, atrazine (nonionic) and 2,4-D (anionic), were tested for pesticide sorption, desorption, and degradation in PAM-treated and untreated soils in Idaho, USA. Sorption of atrazine and 2,4-D in soil was unaffected by PAM treatment, as was atrazine desorption. However, 2,4-D desorbed more readily from the PAM-treated soil than from untreated soil. With respect to pesticide degradation, mineralization ofthe 2,4-D aromatic ring was not impacted by PAM treatment, but decarboxylation of the 2,4-D carboxylic acid side chain was significantly reduced in the PAM-treated soil. Limited mineralization (7 to 10%) of atrazine was observed in both soils. However,in PAM-treated soils atrazine conversion to 14CO2 and bound residue components was significantly reduced, and there was an increase in the level of methanol extractable metabolites. These results may indicate that PAM application can alter the environmental fate of some pesticides in soils, especially under the high dose treatment conditions examined in this study.