Photolysis of Atrazine and Ametryne Herbicides in Barbados Sugar Cane Plantation Soils and Water

Abstract

The photodegradation kinetics of atrazine (2‐chloro‐6‐(ethylamino)‐4‐isopropylamino‐1,3,5‐triazine) and ametryne (2‐methylthio‐4‐ethylamino‐6‐isopropylamino‐s‐triazine), in fresh and coastal salt water from Barbados, were measured under irradiation with artificial solar and UV₂₅₄‐radiation. The first‐order rate constants were greater for ametryne than for atrazine, and the rates were reduced in seawater relative to fresh water, and in soil slurries relative to fresh water. However, rates were accelerated in the presence of iron(III) at pH 3 due to photo‐Fenton type processes. This rate enhancement was reduced at ambient pH values (pH 7–7.5) representative of surface water in Barbados. These results have important implications for the relative persistence of these contaminants in aquatic environments in tropical areas.

Keywords:

• Photolysis
• Atrazine
• Ametryne
• Groundwater
• Agricultural soils
• Barbados

Acknowledgments

The authors thank Jefferson Dyall at the Government Analytical Laboratory, Ministry of Agricultural and Rural Development in St. Michael, Barbados; Kerry Peru at the National Water Research Institute, Environment Canada in Saskatoon, SK; Duane Friesen at the Malaspina University–College in Nanaimo, BC; and Shannon Braithwaite at the WateResearch Corporation in Saskatoon, SK for their technical support. Thanks also to Anthony Newton at the University of the West Indies, Cave Hill Campus, Barbados for chemical and geological information.