es8b00077_si_001.pdf (3.32 MB)
Pesticide Risks in Small StreamsHow to Get as Close as Possible to the Stress Imposed on Aquatic Organisms
journal contribution
posted on 2018-03-27, 00:00 authored by Simon Spycher, Simon Mangold, Tobias Doppler, Marion Junghans, Irene Wittmer, Christian Stamm, Heinz SingerThe risks associated
with pesticides in small streams remain poorly
characterized. The challenges reside in understanding the complexities
of (1) the highly dynamic concentration profiles of (2) several hundred
active substances with (3) differing seasonality. The present study
addressed these three challenges simultaneously. Five small streams
in catchments under intensive agricultural land use were sampled using
half-day composite samples from March to August 2015. Of 213 active
substances quantified using liquid chromatography–high resolution
mass spectrometry, a total of 128 was detected at least at one of
the sites. Ecotoxicological acute and/or chronic quality criteria
were exceeded for a total of 32 different active substances. The evaluation
of risks over time revealed the necessity to evaluate the sequences
of different active substances that are imposed on aquatic organisms.
In contrast, a substance-specific perspective provides only a very
limited assessment. Scenarios for reduction of either temporal resolution,
number of substances or seasonal coverage were defined. It could be
shown that risks can be underestimated by more than a factor of 10
in vulnerable catchments and that an increased temporal resolution
is essential to cover acute risks but that a focused selection of
substances is a possibility to reduce expenditures.