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Box 2 Example on pesticide research project: Nationwide monitoring of small streams in Germany

One of the objectives of the German National Action Plan (NAP) on Sustainable Use of Pesticides (to implement Directive 2009/128/EC) requires a representative sampling of small water bodies. Furthermore, by the year 2023, 99 % of the event-driven monitoring samples of one year should comply with the regulatory acceptable concentration (RAC) regulated within the authorization of pesticides.

Streams may be sampled for chemical analysis once a month, with pesticides seldom being found, even during the application period. However, when samples are taken event controlled with a rise of the water level of 5 cm and after pesticide application (= “event-driven”), pesticides are found much more often. Until now, such sampling was made in scientific studies only, e.g. (Liess, et al., 1999; Moschet, et al., 2014; Gustavsson, et al., 2017). To determine the proportion of RAC exceedances for the German NAP, a concept was developed for the representative monitoring of pesticides in small waters in the agricultural landscape (Szöcs, et al., 2017). The German Environment Agency (UBA), together with the Helmholtz-Centre for Environmental Research (UFZ) and in close cooperation with the state authorities, has conducted two sampling campaigns in 2018 and 2019.

The aim of the monitoring program is to realistically assess the input of agriculturally used active substances into small water bodies, which are currently not monitored within the Water Framework Directive (2000/60/EG). Catchments with an area of <30 km², an agricultural proportion of > 40 %, and a distance of at least 3 km to wastewater treatment plants upstream of the sampling sites were selected. The distribution of the 120 sites across the individual Federal states of Germany was based on the respective percentages of agricultural land. Each site was sampled once between spring to early summer over the course of the two years. To accurately capture the pollution of the waters and assess the resulting risk to the aquatic community, automatic, event-driven sampling after the occurrence of rain events - in addition to grab sampling - was put into practice. A uniform substance list of over 90 active substances and 40 metabolites was analysed.

The first results of the sampling campaign 2018 at 60 monitoring sites indicate that measured pollution exceeds RACs for one or several substances in more than 50 % of the event-driven samples. These exceedances occurred at more than 80 % of the monitoring sites. At about 40 % of the sites 5 or more RAC exceedances occurred. Rain events triggering the sampling devices occurred at 90 % of the sites within the sampling period from spring to early summer even in the very dry year 2018, capturing at most 9 consecutive events at two sites.

11 of the monitored pesticides are regulated under the WFD with maximum EQS. With event-driven sampling at 6 % of the monitoring sites were found 17 exceedances of these EQS. With regular monthly grab sampling at 3 % of the monitoring sites were found 8 exceedances only.