Volatilization of metolachlor from water

Abstract

The volatilization of metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐l‐methylethyl)acetamide]from water was studied in the laboratory and in an outdoor open‐channel experiment. As expected, volatilization was not significant at temperatures ≤ 25 °C. However, at temperatures ≥ 30 °C, there was significant volatilization (e.g., half‐life of 20 days at 40 °C in unstirred solutions). This increased volatility reflected the rapid increase of the Henry's law constant with temperature. Additional experiments indicated that aeration of water significantly accelerated volatilization losses. Such air‐stripping may be important in very turbulent streams and rivers and when water flows over hydraulic structures such as weirs. The experiments reported here indicate the importance that ecosystem‐specific characteristics can have on the persistence of environmental contaminants.

Key words:

• Metolachlor
• volatility
• Henry's law
• temperature effect