Degradation of atrazine and related s‐triazines

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Abstract
Atrazine, simazine, and propazine are closely related herbicides that can be used for weed control. The degradation of s‐triazines in soil, water, and sediments has received considerable attention. In this review, the literature related to degradation of atrazine and related s‐triazines is reviewed. Particular emphasis is directed toward those substances formed along the degradative pathways and to the biodegradation aspects of mineralization. The s‐triazines are unusual in that the carbon and nitrogen ring contains no available electrons for aerobic biodegradation. The only sources of energy for aerobic biodegradation of atrazine are found on the ethyl and isopropy I groups. There is some evidence to support the concept that dealkylation of s‐triazines occurs to support the bioenergetic needs of microorganisms. Biodegradation studies with simazine or atrazine as the carbon and energy source have generally shown biodegradation of the alkyl side chains with evolution of radioactive carbon dioxide from chain‐labeled carbon. Under these conditions, ring‐labeled carbon is evolved as carbon dioxide in much smaller quantities. As a nitrogen source, microorganisms will use this s‐triazine‐ring nitrogen as well as the nitrogen in the amino groups attached to the carbons at the 4 and 6 positions of atrazine and simazine. A carbon and energy source to support microbial growth is important for biodegradation of s‐triazines for their nitrogen content.