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


CONCLUSIONS
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.
Salvestrini
Stefano
S
Department of Environmental Sciences, Second University of Naples, via Vivaldi 43, 81100 Caserta, Italy. stefano.salvestrini@unina2.it
Capasso
Sante
S
Iovino
Pasquale
P
D001673:Biodegradation, Environmental; D006540:Herbicides / Q000737:chemistry / Q000378:metabolism*; D006812:Humic Substances / Q000032:analysis*; D007700:Kinetics; D010671:Phenylurea Compounds / Q000737:chemistry / Q000378:metabolism*; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism
D006540:Herbicides; D006812:Humic Substances; D010671:Phenylurea Compounds; D012989:Soil Pollutants