Assessment of cyanazine persistence in water
1996
Pacepavicius, G.J. | Liu, D. | Maguire, R.J. | Ng, H. | Gaynor, J.D. | Okamura, H. | Aoyama, I.
Cyanazine (2-[[4-chloro-6-(ethylamino)-1,3,5,-triazin-2-yl]-amino]-2- methylpropanenitrile) is an important selective herbicide used for the control of several annual grassy weeds and certain broad-leafed weeds in fields of corn, soybeans, and triazine-resistant canola. It is one of the most heavily used agricultural herbicides in Ontario. There is, however, very little information in the open literature on the aquatic fate and persistence of cyanazine, a fact that hinders the assessment of its ultimate impact on the aquatic ecosystem. This research showed that cyanazine was very stable in natural surface runoff and soil leachate. It was also very resistant to microbial degradation in water under both aerobic and anaerobic conditions. No apparent biodegradation or biotransformation of cyanazine was observed in a test using mixed cocktails of farmland runoff and soil leachate after an incubation period of 98 days. Its biological persistence was further demonstrated by a cyclone fermentor study in which cyanazine was found to be totally immune to the biodegradation potential of a polynuclear aromatic hydrocarbon degrading bacterial culture and sewage microorganisms after an incubation period of 110-195 days. Using the herbicide metolachlor as a biodegradability reference compound and the white rot fungus Phanerochaete chrysosporium as the test organism, cyanazine was estimated to have a persistence in water much greater than that of metolachlor. Thus, the extensive herbicidal use of cyanazine may have a long-lasting impact on Canadian aquatic ecosystems.
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