Some physicochemical and environmental factors affecting transformation rates and sorption of the herbicide metamitron in soil

✍ Scribed by Vink, Jos P. M.; van der Zee, Sjoerd E. A. T. M.

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 501 KB
• Volume: 46
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199602)46:2<113::aid-ps321>3.0.co;2-u

✦ Synopsis

In addition to the molecular structure of a pesticide, environmental conditions may influence its persistence through their effect on the growth and activity of pesticide-degrading micro-organisms. As a result, transformation rates may decrease rapidly when a compolind is leached into subsoil. Metamitron sorption isotherms were determined and incubation series were set up for a sandy loam soil, simulating single and com',ination effects that occur during transport of metamitron into subsoils. KO, values increased with increasing depth from 185 to 700 litre kg-I. A combination of conditions that are unfavourable for microbial activity, such as low temperature (5"C), low concentrations (0.5 mg kg-') and a large sorbed fraction (Koc = 700) resulted in half-lives of over one year. Oxygen inhibition decreased the transformation rate of metamitron from 0.058 to 0.019 day-'. In order of significance, the transformation of metamitron appears to be a function of temperature, oxygen availability and sorption to organic carbon. Increasing doses did not change transformation rates significantly, although different transformation pathways were observed.