Degradation and movement of aldicarb residues in Florida citrus soils

Abstract

The movement and degradation of the pesticide aldicarb was monitored in two Florida citrus groves. One of these was a bedded grove near Oviedo and the other was located in the central ridge near Lake Hamilton. Soil core samples were collected at 0.3 or 0.6 m depth increments six times over an eight-month period and were analyzed for aldicarb and its two oxidation products aldicarb suljoxide and aldicarb suljone. These analyses showed a relatively rapid decrease of aldicarb accompanied by an increase in aldicarb sulfoxide and aldicarb suljone; the levels of these carbamate metabolites peaked after about 50 days and then began to decline. The dissipation rate of aldicarb carbamate residues in surface soils corresponded to a half-life of approximately 20 days at both jield sites. The degradation rate in subsoils appeared to be significantly longer (half-life greater than 60 days), especially at the Lake Hamilton site.Aldicarb carbamate residue concentrations measured in replicate soil analyses were highly variable, with coeflcients of variation ranging up to 300 % for samples collected at the same time and depth. These data point out the need for carefirl design of soil-sampling strategies (including numbers, timing, and location of samples) in order to obtain statistically valid results @om unsaturated zone pesticide monitoring studies. 307 Pestic. Sci. 0031-613X/88/$03.50 0 1988 Society of Chemical Industry. Printed in Great Britain EXPERIMENTAL METHODS Site descriptionThe Oviedo site was a 3.6 ha portion of an orange grove located approximately Also, 0.6 m increments were used below 0.6 m for the 49day samples. At the Lake Hamilton site, soil cores were collected to a depth of 3 m in increments of 0.6 m. For n 9. 9 * 2 s 3 -. 3 0, 0.

Pesticide Properties in the Environment

“…Perhaps the best example is aldicarb, which forms two metabolites, both of which are more mobile than the parent [142,21IJ. Two other examples will suggest the complexity of the problem. One pesticide manufacturer complained to us that we have given a very high solubility for their compound because we assumed the salt value instead of the parent acid.…”

“…[153,245]; 500000 [326]; sodium salt very soluble > 600000 [245,246]; 4250 (acid) [294]; 5000 (methyl ester) [153]; 24C: 4000 [235]; 550000 [116] FIELD HALF LIFE (days): 5-15 [326,327] [59]; 400 (tlc) [232]; 2100 [120,236]; 1900 (30%) [247] VAPOR PRESSURE (mm Hg): 20C: < 10. 5 [245]; 25C: < 1 x W-'O [ [143,189]; 13600, 8500 [88,153]; 14000 [187]; 2500, 4600 [30]; 5300 [59]; 6085 [97]; 14800 [76]; 6100 [223]; 13490 [237] VAPOR PRESSURE (mm Hg): 25C: 1.9 x 10-5 [218,245]; 35C: 9 x 10-5 [245] [142] Property values from literature with references WATER SOLUBILITY (mg/l): 25C: miscible [195,247]; 1000 [59] FIELD HALF LIFE (days): 7 [59]; 20 (50%) [247] SORPTION COEFFICIENT (mIlg): 20 [59]; 75(30%) [247] VAPOR PRESSURE (mm Hg): 20C: 1 x 10" [245]; 7 x 10"5 [246]; 25C: 1.6 x 10"' [247] Selected [245,…”

“…7 , 1.9 X 10"5 [14]; 20C: 1.0 x 10. 5 [246] Selected [142] Property values from literature with references WATER SOLUBILITY (mg/I): 25C: 0.3 [294]; 20C: 0.3 [195]; 25C: 0.31 (PH 7) [247] FIELD HALF LIFE (days): 139-145 [294]; 60(50%) [247] SORPTION COEFFICIENT (mllg): 510(30%) [247]; 570 [116] VAPOR PRESSURE (rom Hg): 20C: 1.2 x 10. 8 [246]; 20C: 3.0 x 10.…”

“…[33,245], 620 [325] FIELD HALF LIFE (days): 60 [313] rotational crops may be injured [325] SORPTION COEFFICIENT (mllg): range 126-691S av 437 [75]; 130 (calculated) [152]; 600 [252]; 1324 (pH5. [142] Property values from literature with references WATER SOLUBILITY (mg/I): 25C: 18 [153,195,326]; 22C: 18 [247] FIELD HALF LIFE (days): 90 [326] SORPTION COEFFICIENT (mllg): 224 (tic) [232]; 890 [118]; 420(30%) [247] VAPOR PRESSURE (mm Hg): 100C: < 10. 3 [326]; 25C: 4.0 x 10"9 [247] Selected property values WATER SOLUBILITY (mg/l): 18 [153,195,245] FIELD HALF LIFE (days): 15 [141] SORPTION COEFFICIENT (ml!g): 670 [120] VAPOR PRESSURE (mm Hg): 20C: < 10.…”

“…dichlorophenyl)-I-methoxy-l-methylurea or N-(3 ,4-dichlorophenyl)-N'methoxy-N'methylurea TRADE NAME: Lorox, Hoe CASRN: 330-55-2 MOLECULAR FORMULA: C.HJOCI,NP, MOLECULAR WEIGHT: 249.11 MANUFACTURERS: DuPont, Hoechst USE: herbicide: vegetables, com, cotton, potatoes, soybeans, sorghum, FORMULATION: wettable pOWder, dispersible granules, dispersible liquid APPLICATION MODE: soil surface spray; 0.15-4.0 Ib/acre/season[142] …”