Risk reduction options
The study was carried out in connection with the national Action Plan on risk reduction and sustainable use of plant protection products. The scientists now recommend that greater attention should be paid to hydraulic shortcuts in measures designed to reduce pesticide runoff to surface waters. For example, entire catchments should in future be taken into consideration, rather than merely agricultural areas alongside surface waters. Risks could also be reduced by measures restricting hydraulic shortcut structures or requiring the use of vegetated buffer strips.
Read the full article “Shortcuts lead to greater pesticide contamination”
Modelling essential for reliable conclusions
As well as field surveys, various model-based approaches, combined with geographical information systems, were employed in the study. This involved collaboration with scientists led by Peter Reichert, Adjunct Professor at ETH Zurich and, until the end of 2020, Head of Eawag’s Systems Analysis, Integrated Assessment and Modelling department. For even with extensive fieldwork, reliable conclusions as to the situation at the national level are not possible without modelling. Thanks to collaboration between environmental chemists, soil hydrologists and modelling experts, the relevant transport processes were analysed in detail and then extrapolated on the basis of statistical data for the entire Central Plateau and Jura region.
Learn more about the research focus «Hydrological Modelling»
Peak concentrations underestimated
Apart from hydraulic shortcuts, other factors may also lead to peak concentrations of pesticides in surface waters. This was demonstrated by another study – involving scientists from the Environmental Chemistry, Process Engineering and Urban Water Management departments – in which the mobile mass spectro-meter MS2field was deployed on a stream for the first time. While water protection authorities usually make use of composite samples, collected over a period of several days, the MS2field system developed at Eawag can analyse samples automatically every 20 minutes. This provided a real-time picture of the highly dynamic processes of water pollution: concentrations of certain pesticides measured in individual samples were up to 170 times higher than in the 3.5-day composite samples.
Risks of acute toxicity
The peak concentrations recorded by the MS2field system were not only higher than those found in conventional composite samples but, in several cases, they also exceeded the limits specified in the Waters Protection Ordinance, which are designed to prevent acute toxicity to aquatic organisms – by a factor of up to 30 in the case of the insecticide thiacloprid. This is relevant for the assessment of water pollution since, in some cases, peaks lasting for less than an hour can have adverse effects on aquatic organisms. If peak concentrations recur, the impact of the second or third peak may be still greater – even if it is lower than the first – as the organisms have not been able to recover in the meantime.
Read the full article “Short-term peak concentrations are severely underestimated”