Laboratory study on the interaction between herbicide MCPA and two different soils
2006
Hiller, E.,Comenius University, Bratislava (Slovak Republic). Faculty of Natural Sciences. Department of Geochemistry | Dubovský, D.,Water Research Institute, Bratislava (Slovak Republic). Department of Water Quality and Water Treatment Technology | Bartaľ, M.,Water Research Institute, Bratislava (Slovak Republic). National Water Reference Laboratory for Slovakia | Zemanová, L.,Comenius University, Bratislava (Slovak Republic). Faculty of Natural Sciences. Department of Geochemistry | Khun, M.,Comenius University, Bratislava (Slovak Republic). Faculty of Natural Sciences. Department of Geochemistry
Acidic herbicide MCPA (4-chloro-2-methylphenoxyacetic acid) is applied to post-emergence control of annual and perennial broad-leaved weeds, mostly in cereals. This study was undertaken with two soils of different properties sampled from two soil horizons to determine the extent of degradation, sorption and desorption of MCPA. These processes are the most important to evaluate the fate of the herbicide in soil and its potential to leach from soil into groundwater. Two soils were used: a calcareous, sandy-loam soil with organic carbon content of 2.486 % (Pararendzina) taken from surface A horizon (the A topsoil) and a calcareous, loamy-sand soil with organic C content of 0.600 % (Fluvisol) sampled from subsurface C horizon (the C subsoil). The extent of degradation, sorption and desorption of MCPA were measured in laboratory batch experiments. Degradation followed first-order kinetics, with the MCPA half-lives of 11 and 24 d for the A topsoil and C subsoil, respectively. Soil organic carbon influenced MCPA degradation. Sorption followed a Freundlich isotherm equation and linear isotherm equation, as well. The distribution coefficient KD was higher in the A topsoil (0.387 per 1 kg) than in the C subsoil (0.165 per 1 kg), consistent with the higher organic C content of the A soil. The results indicate that MCPA is potentially mobile and might pose a threat to future groundwater quality due to its low sorption, relatively high water solubility and slow degradation in the C subsoil.
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