Applying non-steady-state compartmental analysis to investigate the simultaneous degradation of soluble and sorbed glyphosate ( N -(phosphonomethyl)glycine) in four soils
✍ Scribed by Eberbach, Philip
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 455 KB
- Volume
- 52
- Category
- Article
- ISSN
- 1526-498X
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✦ Synopsis
The decomposition behaviour of glyphosate in four Victorian soils was investigated at two temperatures using non-steady-state compartmental analysis. At 25¡C, glyphosate degradation was shown numerically to be derived from two di †erent sources where the rate of release from each source behaved in accordance with Ðrst-order kinetics. Over the Ðrst 40 day period for each of the soils, glyphosate was derived simultaneously from the labile and non-labile phase, whilst after the Ðrst 40 days, glyphosate was derived solely from the non-labile phase. At this temperature, the amount of glyphosate partitioned into the labile phase ranged from 24É1 to 34É5%, whilst the amount partitioned into the sorbed, non-labile phase ranged from 67É2 to 74É9%. The half-lives for glyphosate within each phase was calculated and ranged from six to nine days for the labile phase to 222È835 days for the non-labile phase. Glyphosate appeared to be more strongly held in the acidic Rutherglen soil than in the alkaline soils studied, and this was thought to be related to the substantially lower pH and higher Fe content of the acidic soil. At 10¡C, glyphosate was shown numerically to be derived from two di †erent sources for two of the soils. However, for the two remaining soils, glyphosate appeared to be derived either from a single phase or from two phases at either the same rate or at di †erential rates where the rate of release from one phase was sufficiently fast to mask the rate of release from the other. At this temperature, more glyphosate was partitioned into the non-labile phase of the Walpeup and Rutherglen soils than at 25¡C. However, the rate of release of glyphosate from this phase increased for the Walpeup soil relative to that at 25¡C, but decreased substantially for the Rutherglen soil. This suggests that di †erent mechanisms for the binding of glyphosate into the non-labile phase may exist between soils.
1998 SCI.