Screening of Pesticide and Biocide Patterns As Risk Drivers in Sediments of Major European River Mouths: Ubiquitous or River Basin-Specific Contamination?

Pesticides and biocides (PaB) are
ubiquitously present in aquatic
ecosystems due to their widespread application and have been detected
in rivers at concentrations that may cause distress to aquatic life.
Many of these compounds accumulate in sediments acting as long-term
source for aquatic ecosystems. However, data on sediment contamination
with current-use PaB in Europe are scarce. Thus, in this study, we
elucidated PaB patterns and associated risks in sediments of seven
major European rivers focusing on their last stretch as an integrative
sink of particles transported by these rivers. Sediments were extracted
with pressurized liquid extraction (PLE) using a broad-spectrum method
recovering many compound classes with a wide range of physicochemical
properties. Altogether 126 compounds were analyzed and 81 of them
were detected with LC-HRMS and GC-NCI-MS/MS at least in one of the
sediments. The highest number of compounds was detected (59) in River
Elbe sediments close to Cuxhaven with outstanding concentrations ranging
from 0.8 to 1691 mg/g organic carbon. Multivariate analysis identified
a cluster with 3 ubiquitous compounds (cyhalothrin, carbendazim, fenpropimorph)
and three clusters of chemicals with higher variability within and
between rivers. Risk assessment indicates an acute toxic risk to benthic
crustaceans at all investigated sites with the pyrethroids tefluthrin
and cyfluthrin together with the fungicide carbendazim as the main
drivers. Risks to algae were driven at most sites almost exclusively
by photosynthesis inhibitors with estuary-specific herbicide mixtures,
while in the rivers Po and Gironde cell division inhibitors played
an important role at some sites. Mixtures of specific concern have
been defined and suggested for integration in future monitoring programs.