Persistence of oxyfluorfen in soil, runoff water, sediment and plants of a sunflower cultivation

Abstract

A field dissipation and transport study of oxyfluorfen in a sunflower cultivation under Mediterranean conditions have been conducted in silty clay plots (cultivated and uncultivated) with two surface slopes (1% and 5%). The soil dissipation and transport of oxyfluorfen in runoff water and sediment, as well as the uptake by sunflower plants, were investigated over a period of 191days. Among different kinetic models assayed, soil dissipation rate of oxyfluorfen was better described by first-order kinetics. The average half-life was 45 and 45.5days in cultivated plots with soil slopes 5% and 1% respectively, and 50.9 and 52.9days in uncultivated plots with soil slopes 5% and 1%. The herbicide was detected below the 10cm soil layer 45days after application (DAA). Limited amounts of oxyfluorfen were moved with runoff water and the cumulative losses from tilled and untilled plots with slope 5% were estimated at 0.007% and 0.005% of the initial applied active ingredient, while for the plots with slope of 1%, the respective values were 0.002% and 0.001%. The maximum concentration of oxyfluorfen in sediment ranged from 1.46μgg−1 in cultivated plot with soil slope 1% to 2.33μgg−1 in uncultivated plot with soil slope 5%. The cumulative losses from tilled and untilled plots with slope 5% were estimated at 0.217% and 0.170% while for the plots with slope of 1%, the respective values were 0.055% and 0.025%. Oxyfluorfen was detected in sunflower plants until the day of harvest; maximum concentrations in stems and leaves (0.042μgg−1) were observed 33DAA and in roots (0.025μgg−1) 36DAA. In conclusion, oxyfluorfen hardly moves into silty clay soil and exhibited low run-off potential so it represents a low risk herbicide for the contamination of ground and adjacent water resources.