Mobility and metabolic fate of mexacarbate in soil columns containing sandy and clay loam forest soils

Abstract

Mobility and metabolic fate of ¹⁴C‐mexacarbate (4‐dimethlyamino‐3,5‐xylyl N‐methylcarbamate) were studied using columns containing sandy and clay loam forest soils. Flooding and subsequent analysis of the soil segments showed the presence of free and bound (nonextractable) residues. The bulk of the ¹⁴C‐labelled material was adsorbed onto the litter layers. However, when the columns were saturated with 454 μg of the material, a small part of the radioactivity moved beyond the column length into the leachate. Analysis of the litter segments and the leachate showed carbamate moieties, phenols and other metabolites. Incubation of the soil columns under aerobic (dry) and anaerobic (wet) conditions for 30 d showed the retention of radioactivity in litter layers. The quantities of mexacarbate and its degradation products found were influenced, to some extent, by the soil type and incubation conditions. Except for phenolic and polar metabolites, no intact carbamate moieties were found in the litter after the 30‐d incubation period. Mexacarbate seemed to breakdown rapidly in forest soil columns into various degradation products. A metabolic pathway for its degradation in soil is proposed.

Key words:

• soil horizons
• leachate
• thin‐layer chromatography
• aerobic and anaerobic conditions
• free and bound residues
• degradation pathways