Unsaturated Zone Studies of the Degradation and Movement of Aldicarb and Aldoxycarb Residues

Abstract

Unsaturated zone studies to measure the movement and degradation of aldicarb and aldoxycarb residues were conducted in 1983 at seven locations: Maricopa, Arizona; Harrellsville, North Carolina; Blackstone, Virginia; Blissfield, Michigan; Bluecast, Indiana; Pasco, Washington; and Fort Pierce, Florida. The Blissfield and Bluecast studies also included monitoring of tile‐drain water and the Fort Pierce test included shallow ground water analyses. These research studies indicate that aldicarb or aldoxycarb residues will not enter drinking water supplies under agricultural conditions similar to those encountered in these seven field studies. Most, if not all, of the residues will degrade in the unsaturated zone at a rate corresponding to half‐lives of between 0.5 and 2.0 months. The field studies also demonstrate that aldicarb and aldoxycarb residues degrade at about the same rate.

Effect of oxygen status on pesticide transformation and sorption in undisturbed soil and lake sediment

“…No sulfoxide and sulfone could be detected during a 180‐d incubation period. This rapid anaerobic transformation has been reported previously [34–37]. The complexity of the possible redox reactions is illustrated in Fig.…”

“…Hence, the often made suggestion that bioavailability is inversely related with sorption may not always hold. This accelerated transformation of aldicarb under reductive conditions was attributed by some authors [35–37] to the catalytic effect of Fe 2+ . Reduced iron is abundant in environments of which the reductive status is beyond denitrification (e.g., sulfur‐reducing or methanogenic conditions).…”