Regulatory groundwater monitoring: Realistic residues of pinoxaden and metabolites at vulnerable locations

Sarah McManus; Sevil Payvandi; Paul Sweeney; Nick Jones; Richard Andrews; David Schofield; Joseph White; Paul Hamer; Garry Langridge; Tirso García de Oteyza; Victor J Rincón; Regina Dorn; Michael Bird; Mark Greener

doi:10.1016/j.scitotenv.2020.143313

Regulatory groundwater monitoring: Realistic residues of pinoxaden and metabolites at vulnerable locations

Sci Total Environ. 2021 Mar 20:761:143313. doi: 10.1016/j.scitotenv.2020.143313. Epub 2020 Nov 4.

Authors

Affiliations

¹ Syngenta Crop Protection Ltd, Product Safety Department, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, United Kingdom. Electronic address: sarah.mcmanus@syngenta.com.
² Syngenta Crop Protection Ltd, Product Safety Department, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, United Kingdom.
³ Ramboll UK Ltd, Artillery House, 11-19 Artillery Row, London SW1P 1RT, United Kingdom.
⁴ Arcadis UK Ltd, 34 York Way, London N1 9AB, United Kingdom.
⁵ CEM Analytical Services Ltd (CEMAS), Imperial House, Oaklands Business Centre, Oaklands Park, Wokingham, Berkshire RG41 2FD, United Kingdom.
⁶ Syngenta Crop Protection AG, Regulatory and Safety Department, Rosentalstrasse 67, CH-4058 Basel, Switzerland.

PMID: 33218812
DOI: 10.1016/j.scitotenv.2020.143313

Abstract

A bespoke groundwater monitoring programme was designed to generate a database of pinoxaden and metabolite concentrations in shallow groundwater at agricultural locations across Europe. The data generated from this programme represent a higher tier refinement of modelled exposure estimates and provide realistic information on groundwater quality at vulnerable locations which will aid plant protection product (PPP) assessment in Europe in relation to Regulation (EC) No. 1107/2009. The Regulatory GeoPEARL_3.3.3 model developed by RIVM was used to estimate the vulnerability of cereal growing regions to leaching of two pinoxaden metabolites across the entire EU at a 1 km² level using 20 years of daily weather data (MARS, EU JRC). Seventy sites located within the upper 50th percentile of leaching vulnerability from this modelling exercise, crop density and shallow groundwater were selected for monitoring groundwater. Retrospective and prospective pinoxaden product applications at candidate sites were recorded and these data used to place sites in the distribution for Europe. The 70 sites all fulfil the site assessment criteria and have no confining layers which may prevent or delay leaching. All sites equipped with groundwater wells had a minimum of two pinoxaden applications in the preceding four years to cereal crops. A total of 1326 samples were analysed from up to 90 down hydraulic gradient wells at 70 locations between June 2015 and July 2018. Results indicate that pinoxaden and pinoxaden metabolites are very unlikely to reach shallow groundwater at concentrations greater than 0.1 μg/L for relevant metabolites, or 10 μg/L for non-relevant metabolites, respectively (Sanco/221/2000-rev.10). Over 38 months of groundwater monitoring the annual average and 90^th percentile for pinoxaden or its metabolites never exceeded 0.1 μg/L and it is proposed that these data infer that exposure to these metabolites is minimal.

Keywords: FOCUS modelling; Leaching; Regulation (EC) No. 1107/2009; Sanco/221/2000.