Calibration and field evaluation of the Chemcatcher® passive sampler for monitoring metaldehyde in surface water

Glenn D Castle; Graham A Mills; Adil Bakir; Anthony Gravell; Melanie Schumacher; Ian Townsend; Lewis Jones; Richard Greenwood; Stuart Knott; Gary R Fones

doi:10.1016/j.talanta.2017.10.053

Calibration and field evaluation of the Chemcatcher® passive sampler for monitoring metaldehyde in surface water

Talanta. 2018 Mar 1:179:57-63. doi: 10.1016/j.talanta.2017.10.053. Epub 2017 Nov 22.

Authors

Affiliations

¹ School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Road, Portsmouth PO1 3QL, UK.
² School of Pharmacy and Biomedical Sciences, University of Portsmouth, White Swan Road, Portsmouth PO1 2DT, UK.
³ Natural Resources Wales, NRW Analytical Services at Swansea University, Faraday Building, Swansea University, Singleton Campus, Swansea SA2 8PP, UK.
⁴ South West Water Limited, Peninsula House, Rydon Lane, Exeter EX2 7HR, UK.
⁵ School of Biological Sciences, University of Portsmouth, King Henry I Street, Portsmouth PO1 2DY, UK.
⁶ Anglian Water Group, Lancaster House, Lancaster Way, Ermine Business Park, Huntingdon, Cambridgeshire PE29 6XU, UK.
⁷ School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Road, Portsmouth PO1 3QL, UK. Electronic address: gary.fones@port.ac.uk.

PMID: 29310277
DOI: 10.1016/j.talanta.2017.10.053

Abstract

Metaldehyde is a potent molluscicide. It is the active ingredient in most slug pellets used for crop protection. This polar compound is considered an emerging pollutant. Due to its environmental mobility, metaldehyde is frequently detected at impacted riverine sites, often at concentrations above the EU Drinking Water Directive limit of 0.1µgL^-1 for an individual pesticide. This presents a problem when such waters are abstracted for use in the production of potable water supplies, as this chemical is difficult to remove using conventional treatment processes. Understanding the sources, transport and fate of this pollutant in river catchments is therefore important. We developed a new variant of the Chemcatcher® passive sampler for monitoring metaldehyde comprising a Horizon Atlantic™ HLB-L disk as the receiving phase overlaid with a polyethersulphone membrane. The sampler uptake rate (R_s) was measured in semi-static laboratory (R_s = 15.7mLday^-1) and in-field (R_s = 17.8mLday^-1) calibration experiments. Uptake of metaldehyde was linear over a two-week period, with no measurable lag phase. Field trials (five consecutive 14day periods) using the Chemcatcher® were undertaken in eastern England at three riverine sites (4th September-12th November 2015) known to be impacted by the seasonal agricultural use of metaldehyde. Spot samples of water were collected regularly during the deployments, with concentrations of metaldehyde varying widely (~ 0.03-2.90µgL^-1) and often exceeding the regulatory limit. Time weighted average concentrations obtained using the Chemcatcher® increased over the duration of the trial corresponding to increasing stochastic inputs of metaldehyde into the catchment. Monitoring data obtained from these devices gives complementary information to that obtained by the use of infrequent spot sampling procedures. This information can be used to develop risk assessments and catchment management plans and to assess the effectiveness of any mitigation and remediation strategies.

Keywords: Calibration; Chemcatcher® passive sampler; Field trials; Metaldehyde; Molluscicide; Surface water.