Reducing MCPA herbicide pollution at catchment scale using an agri-environmental scheme

R. Cassidy, P. Jordan, L. Farrow, S. Floyd, C. McRoberts, P. Morton, D. Doody

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)
63 Downloads (Pure)

Abstract

In river catchments used as drinking water sources, high pesticide concentrations in abstracted waters require an expensive treatment step prior to supply. The acid herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) is particularly problematic as it is highly mobile in the soil-water environment following application. Here, an agri-environmental scheme (AES) was introduced to a large-scale catchment (384 km 2) to potentially reduce the burden of pesticides in the water treatment process. The main measure offered was contractor application of glyphosate by weed wiping as a substitute for boom spraying of MCPA, supported by educational and advisory activities. A combined innovation applied in the assessment was, i) a full before-after-control-impact (BACI) framework over four peak application seasons (April to October 2018 to 2021) where a neighbouring catchment (386 km 2) did not have an AES and, ii) an enhanced monitoring approach where river discharge and MCPA concentrations were measured synchronously in each catchment. During peak application periods the sample resolution was every 7 h, and daily during quiescent winter periods. This sampling approach enabled flow- and time-weighted concentrations to be established, and a detailed record of export loads. These loads were up to 0.242 kg km −2 yr −1, and over an order of magnitude higher than previously reported in the literature. Despite this, and accounting for inter-annual and seasonal variations in river discharges, the AES catchment indicated a reduction in both flow- and time-weighted MCPA concentration of up to 21% and 24%, respectively, compared to the control catchment. No pollution swapping was detected. Nevertheless, the percentage of MCPA occurrences above a 0.1 μg L −1 threshold did not reduce and so the need for treatment was not fully resolved. Although the work highlights the advantages of catchment management approaches for pollution reduction in source water catchments, it also indicates that maximising participation will be essential for future AES.

Original languageEnglish
Article number156080
Pages (from-to)1-11
Number of pages11
JournalScience of the Total Environment
Volume838
Issue numberPt 2
Early online date20 May 2022
DOIs
Publication statusPublished (in print/issue) - 10 Sept 2022

Bibliographical note

Funding Information:
We thank AFBI technical staff Briege McCarney and Carmel McBarron for help with field work. We also acknowledge contributions to this work from staff at Northern Ireland Water, Irish Water and The Rivers Trust. This work was carried out as part of Source to Tap ( IVA5018 ), a project supported by the European Union 's INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB). The views and opinions expressed in this paper do not necessarily reflect those of the European Commission or the SEUPB.

Funding Information:
We thank AFBI technical staff Briege McCarney and Carmel McBarron for help with field work. We also acknowledge contributions to this work from staff at Northern Ireland Water, Irish Water and The Rivers Trust. This work was carried out as part of Source to Tap (IVA5018), a project supported by the European Union's INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB). The views and opinions expressed in this paper do not necessarily reflect those of the European Commission or the SEUPB.

Publisher Copyright:
© 2022

Keywords

  • MCPA
  • Drinking water
  • Before-after-control-impact
  • Herbicides
  • Agri-environmental scheme
  • Water quality monitoring

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