Use of Undisturbed Soil Columns under Controlled Conditions To Study the Fate of [¹⁴C]Deethylatrazine

Abstract

The fate of [14C]deethylatrazine [2-chloro-4-amino-6-(isopropylamino)-s-triazine] was studied under controlled conditions by using undisturbed soil columns in the laboratory. In a 13-week leaching study, the percentage of [14C]deethylatrazine recovered was greatest in the first leaching event (1.3% of the applied 14C), suggesting that preferential flow occurred. The total concentration of deethylatrazine leached from soil columns over the 13-week period was 4.9 μg/L (3.6% of the applied 14C). Unidentified polar degradates made up 3.8% of the applied radioactivity recovered in the leachate, and didealkylatrazine [2-chloro-4,6-(diamino)-s-triazine] and deethylhydroxyatrazine [2-hydroxy-4-amino-6-(isopropylamino)-striazine] occurred in trace quantities. Sixty-seven percent of the applied 14C remained in the top 10 cm of soil columns, with 48% as bound residues, 12% as unidentified polar degradates, 5.5% as deethylatrazine, 0.2% as didealkylatrazine, and less than 0.1% as deethylhydroxyatrazine. KeywordsAtrazine, deethylatrazine, didealkylatrazine, deethylhydroxyatrazine, mobility, leaching Disciplines Entomology | Soil Science CommentsThis article is from Journal of Agricultural and Food Chemistry 44 (1996) The fate of [ 14 C]deethylatrazine [2-chloro-4-amino-6-(isopropylamino)-s-triazine] was studied under controlled conditions by using undisturbed soil columns in the laboratory. In a 13-week leaching study, the percentage of [ 14 C]deethylatrazine recovered was greatest in the first leaching event (1.3% of the applied 14 C), suggesting that preferential flow occurred. The total concentration of deethylatrazine leached from soil columns over the 13-week period was 4.9 µg/L (3.6% of the applied 14 C). Unidentified polar degradates made up 3.8% of the applied radioactivity recovered in the leachate, and didealkylatrazine [2-chloro-4,6-(diamino)-s-triazine] and deethylhydroxyatrazine [2-hydroxy-4-amino-6-(isopropylamino)-s-triazine] occurred in trace quantities. Sixty-seven percent of the applied 14 C remained in the top 10 cm of soil columns, with 48% as bound residues, 12% as unidentified polar degradates, 5.5% as deethylatrazine, 0.2% as didealkylatrazine, and less than 0.1% as deethylhydroxyatrazine.

Fate of Atrazine and Atrazine Degradates in Soils of Iowa

“…Soil columns were brought back to the laboratory and prepared for experimentation as previously described by Kruger et al [8]. A modification to the top of the soil column allowed for monitoring of 14 C0 2 , 14 C-organic volatiles, and aerobicity of the headspace [9]. Soil columns were treated with either 14 C-ATR or 14 C-DEA (2 replications each) and then leached weekly with 3.8 cm of simulated rainfall [8,9].…”

Mobility and Degradation of Pesticides and Their Degradates in Intact Soil Columns

“…DEA was more mobile than ATR in the soil column studies (3,6). The comparative fate of ATR and DEA in surface (0 to 30 cm) and subsurface (65 to 90 cm) soils was studied in the laboratory (55).…”

“…A study was conducted to determine the fate of deethylatrazine (DEA), a major metabolite of ATR, in large undisturbed soil columns (6). Soil columns ( 15-cm diameter χ 60-cm length) were obtained from a field with no previous ATR history, as described in the ATR section.…”

“…Two soil columns were prepared for laboratory experiments by using a modification of the method described by (3) ( Figure 1B). In order to obtain a mass balance of the applied 14 C, the top of the column was sealed with an additional section of PVC pipe (20-cm diameter by 20-cm length), and the top of this section was capped with a plexiglas plate and sealed with silicon rubber adhesive sealant (General Electric Co., Waterford, NY) (6). Within the Plexiglas™ plate, three holes were cut.…”

“…For a deethylatrazine mobility study (6), the soil column set up was modified to enable trapping of 14 C0 2 in order to improve the mass balance of C-deethylatrazine applied to the column. Evolution ofthe modification of the soil column continued with the study of metolachlor mobility (7).…”