Environmental fate of triasulfuron in soils amended with municipal waste compost

The amendment of soil with compost could significantly influence the mobility and persistence of pesticides and thus affect their environmental fate. Factors like adsorption and kinetics and rate of degradation of pesticides could be altered in amended soils. The aim of this study was to determine the effects of the addition of compost, from source-separated municipal waste and green waste, on the fate of triasulfuron, a sulfonylurea herbicide utilized in the post-emergence treatment of cereals. Two native soils with low organic matter content were used. A series of analysis were carried out to evaluate the adsorption and degradation of the herbicide in soil and in solution after the addition of compost as well as extracted organic fractions namely humic acids (HA), fulvic acids (FA) and hydrophobic DOM (HoDOM). Results have shown that the adsorption of triasulfuron to soil increases in the presence of compost, HA and HoDOM giving the greatest contribution to this increase. HoDOM applied to the soils underwent sorption reactions with the soils utilised and in the sorbed state, served as a partitioning domain for triasulfuron. The rate of hydrolysis of triasulfuron in solution was significantly higher at acidic pH and the presence of organic matter fractions extracted from compost further increased the rate of hydrolysis. The rate of degradation in amended and non-amended soils has been explained by two-stage degradation kinetics. During the initial phase, although triasulfuron degradation was rapid with half-lives of 30d, the presence of compost and HoDOM hindered the degradation with respect to non-amended soil.