Kinetics of alachlor and atrazine biotransformation under various electron acceptor conditions

Abstract

Second‐order rate constants were developed for the biotransformation of the herbicides atrazine and alachlor under aerobic, nitrate‐reducing, sulfate‐reducing, and methanogenic conditions. Batch‐reactor techniques were used, with seed cultures taken from acclimated biofilm columns. The reactors were fed acetate as a primary substrate. Pesticide biotransformation appeared to depend upon the continued presence of the primary substrate, indicating co‐metabolic transformations. All four electron acceptor conditions tested resulted in some biotransformation of both pesticides. Rate constants for alachlor ranged from 6.25 × 10−5 to 1.60 × 10−4 L/mg volatile suspended solids (VSS)·h, with the highest rate constant occurring under sulfate‐reducing conditions, and the lowest under methanogenic conditions. Rate constants for atrazine ranged from 1.04 × 10−5 to 3.32 × 10−5 L/mg VSS·h, although differences among the four electron acceptor conditions were not statistically significant.

Atrazine, Deethylatrazine, and Deisopropylatrazine Persistence Measured in Groundwater in Situ under Low-Oxygen Conditions

“…The degradation of atrazine in surface soils has been reported to be slower under anaerobic conditions than under aerobic conditions Schnoor, 1992, 1994;Yanze-Kontchou and Gschwind, 1995). Wilber and Parkin (1995) observed no significant differences in the rate of atrazine degradation by aerobic, nitrate-reducing, sulfate-reducing, or methanogenic microbial cultures. The rate of atrazine degradation has been reported to be slower under lowoxygen conditions than under aerobic conditions in estuarine sediments (Jones et al, 1982) and wetland sediments Ro and Chung, 1995).…”

“…The addition of a carbon source has been shown to enhance the degradation of several compounds under various conditions. Examples include the accelerated degradation of atrazine metabolites (Assaf and Turco, 1994) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) under sulfate-reducing or methanogenic conditions (Gibson and Suflita, 1990), atrazine and alachlor [2-chloro-2′,2′-diethyl-N-(methoxymethyl)acetanilide] under denitrifying conditions (Wilber and Parkin, 1995), and total triazine in atrazine-spiked sediments under anaerobic conditions (Chung et al, 1996).…”

Biotransformation of Herbicides in the Presence of Various Electron Acceptors

“…13,14 Wilber and Parkin report the biotransformation of alachlor in continuous-flow, acetate-fed biofilm reactors and batch reactors, under four different electron acceptor conditions. 9,15 In all cases, the presence of acetate was required for the transformations to continue, though the effect was most pronounced in the sulfate-reducing system. Wilber and Garrett also report the cometabolic biotransformation of propachlor by an acetate-fed nitratereducing mixed culture, although the necessity of simultaneous nitrate reduction was not tested.…”

“…[5][6][7][8][9] Alachlor and propachlor have been demonstrated previously to be biotransformable under a variety of conditions. Novick and co-workers report observing cometabolic biotransformation of alachlor and propachlor in sewage and lake water samples.…”

Effect of compost age and composition on the atrazine removal from solution

“…However, complete mineralization of atrazine has been reported with mixed bacterial cultures and a few pure cultures [19][20][21]. The addition of easily biodegradable carbon substances would generally stimulate atrazine mineralization [22], but the addition of nitrogen sources slows the atrazine mineralization [21,23,24].…”