The Effects of Three Sulfonylurea Herbicides and Their Degradation Products on the Green Algae

the only nitrogen source to stimulate their growth in the order , ~ ~ ~ =~ © 1998 Elsevier Science Ltd. All rights reserved INTRODUCTION Metsulfuron-methyl, cblorsulfttron, bensulfuron are sulfonyhirea herbicides. They display high herbicidal activity and very low mammalian toxicity and they are widely used in agriculture[I,2]. They exist, at neutral or basic pH values, almost exclusively in the anionic form which are much less susceptible to their main degradation pathway, hydrolysis[2,3]. Much research concerning the toxicity of sulfonylurea herbicides on weeds and crops has been reported [1,4,5], there are few reports about their effects on aquatic organisms. In this study, the 96-hour algae growth inhibition toxicity ofmetsulfuron-methyl, chlorsulfuron, bensulfuron and their main degradation products to the green algae (Chlorella pyrenoidosa), as well as bioavailability of organic nitrogen of the degradation products by the tested green algae was studied. MATERIALS AND METHODS Chemicals Three sulfonyhirea herbicides (purity>95%) and their corresponding degradation products, metsulfuron-methyl (compd. 1), chlorsulfuron (compd. 2) and bensulfuron (compd. 3), and their degradation products, compd. 1-], 1-2, 2-1, 2-2, and 3-1, 3-2 were used. The chemical structures were shown as below. *This project is funded by the National Natural Science Foundation of P. R. China **To whom correspondence should be addressed.