Worldwide herbicide use in agriculture, whilst safeguarding yields also presents water quality issues. Controlling factors in agricultural catchments include both static and dynamic parameters. The present study investigated the occurrence of herbicides in streams and groundwater in two meso-scale catchments with contrasting flow controls and agricultural land use (grassland and arable land). Using a multi-dimensional approach, streams were monitored from November 2018 to November 2019 using Chemcatcher® passive sampling devices and groundwater was sampled in 95 private drinking water wells. The concentrations of herbicides were larger in the stream of the Grassland catchment (8.9–472.6 ng L−1) dominated by poorly drained soils than in the Arable catchment (0.9–169.1 ng L−1) dominated by well-drained soils. Incidental losses of herbicides during time of application and low flows in summer caused concentrations of MCPA, Fluroxypyr, Trichlorpyr, Clopyralid and Mecoprop to exceeded the European Union (EU) drinking water standard due to a lack of dilution. Herbicides were present in the stream throughout the year and the total mass load was higher in winter flows, suggesting a persistence of primary chemical residues in soil and sub-surface environments and restricted degradation.Losses of herbicides to the streams were source limited and influenced by hydrological conditions. Herbicides were detected in 38% of surveyed drinking waterwells. While most areas had concentrations below the EU drinking water standard some areas with well-drained soils in the Grassland catchment, had concentrations exceeding recommendations. Individual wells had concentrations of Clopyralid (619 ng L−1) and Trichlorpyr (650 ng L−1).Despite the study areas not usually associated with herbicide pollution, and annual mass loads being comparatively low, many herbicides were present in both surface and groundwater, sometimes above the recommendations for drinking water. This whole catchment assessment provides a basis to develop collaborative measures to mitigate pollution of water by herbicides.
Bibliographical noteFunding Information:
This work has been carried out under the WaterProtect research project supported by the European Union research and innovation funding programme Horizon 2020 [grant no. 727450]. The authors thank the Teagasc Agricultural Catchments Programme (funded by the Department of Agriculture Food and the Marine) for facilitating the data collection and supporting the study with hydrometric data, technical assistance and expertise. The authors also express their gratitude to the catchments farmers and householders for facilitating the water sampling in the area. Dr. Rachel Cassidy, Agri-Food Biosciences Institute, Belfast, provided the MCPA load calculation from the June 2018 dataset in Morton et al. (2019).
© 2020 The Authors
Copyright 2020 Elsevier B.V., All rights reserved.
- Pesticides, Passive sampling, Agriculture, Surface water, Groundwater, Drinking water