Pesticides entering agricultural surface waters threaten water quality and aquatic communities. Recently, vegetated treatment systems (VTSs) (e.g., constructed wetlands and vegetated ditches) have been proposed as pesticide risk mitigation measures. However, little is known about the effectiveness of VTSs in controlling nonpoint source pesticide pollution and factors relevant for pesticide retention within these systems. Here, we conducted a meta-analysis on pesticide mitigation by VTSs using data from the scientific literature and the European LIFE ArtWET project. Overall, VTSs effectively reduced pesticide exposure levels (i.e., the majority of pesticide retention performances was >70%). A multiple linear regression analysis of 188 retention performance cases identified the two pesticide properties, organic carbon sorption coefficient value and water-phase 50% dissipation time, as well as the VTS characteristics overall plant coverage and hydraulic retention time for targeting high efficacy of pesticide retention. The application of a Tier I risk assessment (EU Uniform Principle) revealed a higher toxicity reduction for hydrophobic and nonpersistent insecticides compared with less sorptive and not readily degradable herbicides and fungicides. Overall, nearly half (48.5%) of all pesticide field concentrations ( = 130) failed Tier I standard risk assessment at the inlet of VTSs, and 29.2% of all outlet concentrations exceeded conservative acute threshold levels. We conclude that VTSs are a suitable and effective risk mitigation strategy for agricultural nonpoint source pesticide pollution of surface waters. Further research is needed to improve their overall efficacy in retaining pesticides.

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A new constraint assignment algorithm and a two-perspective tracking method are presented for threedimensional tracking of motile aquatic organisms. The method aims at providing preferably long tracks of multiple, simultaneously swimming individuals. As an extension to existing tracking and assignment methods, the presented algorithm takes background knowledge about maximum swimming speed and size of the organisms into account. Two strategies, both using the constraint assignment algorithm, were applied to track either a fixed number of objects or to track as many objects as possible in frame-to-frame transitions. Whereas the first strategy provides continuous and distinct tracks of all individuals for the entire measurement sequence, the second strategy does not require interpolation of unresolved positions and is more robust to disappearance or reappearance of organisms within the field of view. Two sets of video records of freely swimming Daphnia magna, differing in abundance, image quality, and record length, are analyzed to assess the tracking success of the proposed algorithm. Although both strategies provide better results for a higher detection rate of organisms, the first strategy is preferable for tracking individuals in tests with smaller organism abundance and higher signalto-noise ratio, whereas the second strategy also provides reasonable pathways under less optimal conditions. Spectral analysis of observed swimming velocities is applied to demonstrate the advantage of obtaining long, continuous, and three-dimensional tracks of moving organisms.

Take Home Message It can be justifiable to determine nitrous oxide and methane flux rates from soil with only two concentration measurements to allow for more spatial precision.

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