Catalytic effect of dissolved humic acids on the chemical degradation of phenylurea herbicides

• Published in: Pest management science Vol. 64; no. 7; pp. 768 - 774
• Main Authors: Salvestrini, Stefano, Capasso, Sante, Iovino, Pasquale
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.07.2008; Wiley; Wiley Subscription Services, Inc
• Subjects: abiotic degradation; abiotic stress; Adsorption; analysis; Biodegradation; Biodegradation, Environmental; Biological and medical sciences; Catalysis; catalysts; Chemical degradation; chemistry; Fundamental and applied biological sciences. Psychology; Herbicides; Herbicides - chemistry; Herbicides - metabolism; Humic acids; Humic Substances; Humic Substances - analysis; kinetic equation; Kinetics; metabolism; Natural waters; Parasitic plants. Weeds; Phenylurea Compounds; Phenylurea Compounds - chemistry; Phenylurea Compounds - metabolism; phenylurea herbicides; phenylureas; Phytopathology. Animal pests. Plant and forest protection; pollution; Soil Pollutants; Soil Pollutants - chemistry; Soil Pollutants - metabolism; sorption isotherms; Weeds; Pesticides; Environmental factor; Chemical degradation; Herbicide; abiotic degradation; Abiotic factor; humic acids; kinetic equation; Adsorption; Phenylureas; Catalysis; Kinetics; Humic acid
• ISSN: 1526-498X; 1526-4998
• DOI: 10.1002/ps.1556

BACKGROUND:Although biodegradation seems to be the main cause of herbicide degradation, abiotic degradation can also be important for chemicals such as phenylureas, which are subject to catalysed soil reactions. The aim of this work is to investigate the effect of dissolved humic acids (HAs), normally present in natural waters, on the hydrolysis of phenylurea herbicides, and it presents a kinetic model that takes into account the role of adsorption.RESULTS:The linearity of the adsorption isotherms indicates that phenylurea-humic acid interaction can be considered in terms of a repartition-like equilibrium of phenylurea between water and HAs. Kinetic experiments show that the degradation rates of phenylureas increase with HA concentration.CONCLUSION:The kinetic equation adopted adequately describes the experimental data trend, allowing the evaluation of the catalytic effect of HAs on the chemical degradation of phenylureas. Carboxyl groups of HAs seem to play a leading role in the catalysis. The kinetic equation derived in this work could be helpful in predicting the persistence of phenylureas and of related compounds in natural water. Copyright