Pesticide concentrations in agricultural storm drainage inlets of a small Swiss catchment

Urs T Schönenberger,Anne Dax,Birgit Beck,Bernadette Vogler,Christian Stamm

doi:10.1007/s11356-022-18933-5

Abstract

Agricultural pesticides transported to surface waters pose a major risk for aquatic ecosystems. Modelling studies indicate that the inlets of agricultural storm drainage systems can considerably increase the connectivity of surface runoff and pesticides to surface waters. These model results have however not yet been validated with field measurements. In this study, we measured discharge and concentrations of 51 pesticides in four out of 158 storm drainage inlets of a small Swiss agricultural catchment (2.8 km2) and in the receiving stream. For this, we performed an event-triggered sampling during 19 rain events and collected plot-specific pesticide application data. Our results show that agricultural storm drainage inlets strongly influence surface runoff and pesticide transport in the study catchment. The concentrations of single pesticides in inlets amounted up to 62 µg/L. During some rain events, transport through single inlets caused more than 10% of the stream load of certain pesticides. An extrapolation to the entire catchment suggests that during selected events on average 30 to 70% of the load in the stream was transported through inlets. Pesticide applications on fields with surface runoff or spray drift potential to inlets led to increased concentrations in the corresponding inlets. Overall, this study corroborates the relevance of such inlets for pesticide transport by establishing a connectivity between fields and surface waters, and by their potential to deliver substantial pesticide loads to surface waters.

Highlights

Pesticides used in agriculture impair water quality, leading to biodiversity losses in aquatic ecosystems and threaten drinking water resources (Stehle and Schulz, 2015; SánchezBayo and Wyckhuys, 2019; Kiefer et al, 2020)
The collector shaft drains around half of the agricultural and road area in the catchment that is connected to inlets
We found that pesticide concentrations in single inlets can be very high, and that single inlets can be responsible for a large fraction of the pesticide load found in the stream

Summary

Introduction

Pesticides used in agriculture impair water quality, leading to biodiversity losses in aquatic ecosystems and threaten drinking water resources (Stehle and Schulz, 2015; SánchezBayo and Wyckhuys, 2019; Kiefer et al, 2020). Surface runoff (Larsbo et al, 2016; Lefrancq et al, 2017), spray drift (Vischetti et al, 2008; Lefrancq et al, 2013) and macropore flow to tile drainages (Sandin et al, 2018) are considered of major importance. In several studies, roads and ditches were shown to concentrate surface runoff and increase pesticide losses (Rübel, 1999; Heathwaite et al, 2005; Payraudeau et al, 2009; Fiener et al, 2011; Hösl et al, 2012). In a French vineyard, spray drift on roads and subsequent wash off was found to be a major pesticide transport pathway (Lefrancq et al, 2014). In contrast to other countries, roads and adjacent fields in Switzerland are less often drained to ditches, but to inlet and maintenance shafts of storm and tile drainage systems

Methods

Results

Conclusion