Degradation rate of sodium fluoroacetate in three New Zealand soils

The degradation rate of sodium fluoroacetate (SFA) was assessed in a laboratory microcosm study incorporating 3 New Zealand soil types under different temperature (5 °C, 10 °C, or 20 °C) and soil moisture (35% or 60% water holding capacity) conditions using guideline 307 from the Organisation for Economic Co‐operation and Development. A combination of nonlabeled and radiolabeled 14 C‐SFA was added to soil microcosms, with sampling and analysis protocols for soil, soil extracts, and evolved CO 2 established using liquid scintillation counting and liquid chromatography–mass spectrometry. Degradation products of SFA and their rates of formation were similar in the 3 soil types. The major degradation pathway for SFA was through microbial degradation to the hydroxyl metabolite, hydroxyacetic acid, and microbial mineralization to CO 2 , which constituted the major transformation product. Temperature, rather than soil type or moisture content, was the dominant factor affecting the rate of degradation. Soil treatments incubated at 20 °C displayed a more rapid loss of 14 C‐SFA residues than lower temperature treatments. The transformation half‐life (DT50) of SFA in the 3 soils increased with decreasing temperature, varying from 6 d to 8 d at 20 °C, 10 d to 21 d at 10 °C, and 22 d to 43 d at 5 °C. Environ Toxicol Chem 2014;33:1048–1058 . © 2014 SETAC