Adsorption of 1,2,4-triazine pesticides metamitron and metribuzin on lignin

The 1,2,4-triazine pesticides, metamitron [4-amino-3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one] and metribuzin [4-amino-3-methylthio-6-tert-butyl-1,2,4-triazin-5 (4H)-one] are adsorbed on lignin. The adsorption can be followed by measuring polarographically the concentration of the free pesticide in a slurry, obtained by dispersing rot-wood lignin in an aqueous buffer (pH 4.9). Analogous measurements of desorption in respective steps indicated that 53% of applied metamitron and 62% of metribuzin are adsorbed irreversibly and cannot be leached over a period of 24 h. Such adsorption decreases the bioavailability of the pesticide. (C) 2000 Elsevier Science B.V. All rights reserved.