Formation of bound residues of 8-hydroxybentazon by oxidoreductive catalysts in soil.
This study was performed to determine which oxidoreductive catalysts were most efficient in catalyzing the binding of 8-hydroxybentazon to soil humic substances. 8-Hydroxybentazon was completely transformed by an oxidoreductive enzyme, laccase of Myceliophthora thermophila, at pH 3.0-7.0 within 30 min. When abiotic catalysts, manganese(IV), iron(III), and aluminum oxides were used in the same pH range, 8-hydroxybentazon was completely transformed only by manganese(IV) oxide (delta-MnO2), but a relatively small amount of 8-hydroxybentazon was transformed by iron(III) oxide and aluminum oxide. The adsorption of 8-hydroxybentazon in the soil showed an H-type and coincided well with the Langmuir isotherm. To better understand the factors involved in the rapid and strong binding of 8-hydroxybentazon with soil humic substances, 8-hydroxybentazon transformation by oxidoreductive catalysts was studied in various soil conditions: air-dried, preincubated, sterilized, and iron(III) oxide and manganese(IV) oxide free. 8-Hydroxybentazon was completely transformed within 24 h in the decreasing order of preincubated, air-dried, and sterilized soils. However, little transformation was observed in the iron(III) oxide and manganese(IV) oxide free soils. These results suggest that the major catalyst responsible for the rapid and strong binding of 8-hydroxybentazon to soil humic substances is a metal oxide, manganese(IV) oxide, not a soil oxidoreductive enzyme.
Kim
Jong-Soo
JS
Department of Agricultural Chemistry, Kyungpook National University, 1370 Sankyuck-Dong, Buk-Gu, Daegu 702-701, Korea.
Park
Jong-Woo
JW
Lee
Sung-Eun
SE
Kim
Jang-Eok
JE
D000327:Adsorption; D000537:Aluminum Oxide / Q000737:chemistry; D001581:Benzothiadiazines / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D002384:Catalysis; D005290:Ferric Compounds / Q000737:chemistry; D006540:Herbicides / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006900:Hydroxylation; D007700:Kinetics; D042845:Laccase; D017895:Manganese Compounds / Q000737:chemistry; D003904:Mitosporic Fungi / Q000201:enzymology; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D010088:Oxidoreductases / Q000378:metabolism; D012987:Soil / Q000032:analysis*
D001581:Benzothiadiazines; D005290:Ferric Compounds; D006540:Herbicides; D017895:Manganese Compounds; D010087:Oxides; D012987:Soil; C000499:ferric oxide; C027424:manganese oxide; D010088:Oxidoreductases; D042845:Laccase; D000537:Aluminum Oxide; C002003:bentazone