Sorption-desorption and dissipation of trifluralin in agricultural soils of the Zitny ostrov (the Danubian Lowland)

摘要

Leaching of any herbicide through the soil profile to groundwater depends mainly on the sorption-desorption and dissipation processes. In this study, batch sorption, desorption and dissipation experiments were performed with dinitroaniline herbicide trifluralin and three soil types collected from their soil horizons in the Zitny ostrov (SW Slovakia). Trifluralin was strongly sorbed by all soils with Freundlich sorption coefficient and distribution coefficient values between 32.8-239 mg~(1-1)I~(1) kg~(-1) and 34.8-243 I kg~(-1) respectively. Statistical analysis of the results confirmed significant positive correlations of trifluralin sorption with organic components of the soils (r = 0.99, p <0.001). Only low proportions of the sorbed trifluralin could be released from soils into aqueous solution after four successive desorption steps (2.30-6.23 %), indicating an irreversibility of trifluralin sorption. Both sorption and desorption were depth-dependent, when the A soil horizons exhibited higher retention capacity of the herbicide than B or C soil horizons. Trifluralin persisted more in the A soil horizons than the corresponding B or C soil horizons with dissipation half-life values ranging from 57.8 to 99 days in topsoils and from 46.2 to 77 days in subsoils. The stronger the sorption of trifluralin in the soil, the higher its persistence as indicated by positive correlation of distribution coefficients with dissipation half-lives (r = 0.90, p <0.01). It was concluded that trifluralin had no risk of leaching to groundwater, and therefore its past use for agricultural purposes in the study area was safe.