Quantifying MCPA load pathways at catchment scale using high temporal resolution data

K. Atcheson, P.-E. Mellander, R. Cassidy, S. Cook, S. Floyd, C. McRoberts, P.A. Morton, P. Jordan

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)
69 Downloads (Pure)

Abstract

Detection of the agricultural acid herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid) in drinking water source catchments is of growing concern, with economic and environmental implications for water utilities and wider ecosystem services. MCPA is poorly adsorbed to soil and highly mobile in water, but hydrological pathway processes are relatively unknown at the catchment scale and limited by coarse resolution data. This understanding is required to target mitigation measures and to provide a framework to monitor their effectiveness. To address this knowledge gap, this study reports findings from river discharge and synchronous MCPA concentration datasets (continuous 7 hour and with additional hourly sampling during storm events) collected over a 7 month herbicide spraying season. The study was undertaken in a surface (source) water catchment (384 km 2—of which 154 km 2 is agricultural land use) in the cross-border area of Ireland. Combined into loads, and using two pathway separation techniques, the MCPA data were apportioned into event and baseload components and the former was further separated to quantify a quickflow (QF) and other event pathways. Based on the 7 hourly dataset, 85.2 kg (0.22 kg km −2 by catchment area, or 0.55 kg km −2 by agricultural area) of MCPA was exported from the catchment in 7 months. Of this load, 87.7 % was transported via event flow pathways with 72.0 % transported via surface dominated (QF) pathways. Approximately 12 % of the MCPA load was transported via deep baseflows, indicating a persistence in this delayed pathway, and this was the primary pathway condition monitored in a weekly regulatory sampling programme. However, overall, the data indicated a dominant acute, storm dependent process of incidental MCPA loss during the spraying season. Reducing use and/or implementing extensive surface pathway disconnection measures are the mitigation options with greatest potential, the success of which can only be assessed using high temporal resolution monitoring techniques.

Original languageEnglish
Article number118654
Pages (from-to)1-13
Number of pages13
JournalWater Research
Volume220
Early online date24 May 2022
DOIs
Publication statusPublished (in print/issue) - 15 Jul 2022

Bibliographical note

Funding Information:
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. Kevin Atcheson's PhD research was funded by the Department for the Economy (Northern Ireland) through Ulster University. We thank technical staff from the Agri-Food Biosciences Institute, Belfast, and Ulster University, Coleraine for help with laboratory and field work, and science staff for help with pesticide application rate reporting. We also acknowledge help from Northern Ireland Water and Irish Water, and advice from The Rivers Trust, and thank three anonymous reviewers for insightful comments and advice.

Funding Information:
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. Kevin Atcheson's PhD research was funded by the Department for the Economy (Northern Ireland) through Ulster University. We thank technical staff from the Agri-Food Biosciences Institute, Belfast, and Ulster University, Coleraine for help with laboratory and field work, and science staff for help with pesticide application rate reporting. We also acknowledge help from Northern Ireland Water and Irish Water, and advice from The Rivers Trust, and thank three anonymous reviewers for insightful comments and advice.

Publisher Copyright:
© 2022

Keywords

  • Pesticides
  • MCPA
  • Catchments
  • Pathways
  • Export loads

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