Investigating the fate of sodium monofluoroacetate during rain events using modelling and field studies

Abstract

We examined catchment-scale transport of sodium monofluoroacetate ('1080') in rainfall runoff. We developed a hydrological model describing the overland transport of 1080 and validated model results using field data from a headwater catchment, where we intensively sampled a stream during a rainfall event (28 mm in 8 h) that followed 1080 aerial application. Only one stream sample contained a measurable concentration of 1080 (0.1 mg/l; collected 105 min from the start of rainfall), while 1080 was below detection limits (0.1 mg/l) in all other samples. Absence of visually observable overland flow conditions (puddles and saturated areas connected to the stream) early during the rainfall event suggested that overland transport might not have been the dominant mechanism in this catchment. Moreover, analyses of soilwater samples collected from lysimeters installed in the catchment indicated the propensity of 1080 to leach into soil, suggesting the need to investigate subsurface transport pathways.

Managing and eradicating wildlife tuberculosis in New Zealand

“…Other research has investigated the fate of 1080 in the environment once it has been deployed in bait form, assuming it has not been consumed by a pest, and shown that 1080 can leach from baits (Suren 2006 ), but that it is readily degraded in soils at ground temperatures over 5°C (Northcott et al 2014 ). Further, of the 1080 that typically leaches from baits following rain, less than 1% is subsequently found in surface water where it could feasibly pose a risk for terrestrial animals (Srinivasan et al 2012 ).…”

Degradation rate of sodium fluoroacetate in three New Zealand soils

“…Our findings have relevance to Australian contexts where SFA is used as a vertebrate pesticide and where fluoroacetate occurs naturally in some native vegetation but are particularly applicable to New Zealand as the world's major user of SFA and where significant community concerns exist about the environmental effects of broadcast bait application . These data are of potential utility in modeling approaches to describing the environmental fate of SFA in New Zealand soils and climatic conditions . While the SFA degradation data fitted a first‐order decay model as required by the OECD guideline 307 , some of the mineralization kinetic data did not conform well to standard first‐order model functions.…”

“…After application, bait remaining uneaten on the ground is subject to dissipation and degradation through exposure to rainfall . Exposure to environmental moisture results in water‐soluble SFA leaching from bait into litter and soil . Thus, the degradation of SFA and the rate of formation of degradation products in soil are of interest for environmental risk assessment.…”