Abteilung Umweltchemie

Wicked problems exceed traditional sectoral and jurisdictional boundaries and involve multiple actors as stakeholders, victims, and culprits. Wicked problems inherently feature uncertainty and knowledge gaps. Science plays a crucial role in generating evidence for solving these problems and contributing to societal transformation. However, researchers may perceive and study problems detached from practitioners' perceptions of the world. We use the example of smallholder pesticide management in Uganda and the three types of knowledge approach, a framework borrowed from transdisciplinary research, to disentangle knowledge gaps. To identify these gaps, we integrated and co-produce knowledge in a two-day participatory workshop applying design thinking. Our results show, that a transition towards safe pesticide management depends on changes in the system, such as a revision and implementation of exiting regulation or professionalization of agro-dealers. Furthermore, this transition is only possible if interventions address target groups beyond the individual farmers (e.g. agro-dealers or district government officials). Compared to existing academic knowledge, co-produced knowledge provides a broader systemic perspective and yields more fine grained insights about potential new pathways. This investigation confirms, that practitioners’ knowledge is more fine-grained and detailed, thus exemplifying how knowledge integration is essential to avoid a gap between what researchers investigate and what practitioners need.

Micropollutants (MP) with varying ozone-reactive moieties were spiked to lake water in the influent of a drinking water pilot plant consisting of an ozonation followed by a biological sand filtration. During ozonation, 227 transformation products (OTPs) from 39 of the spiked 51 MPs were detected after solid phase extraction by liquid chromatography high-resolution mass spectrometry (LC-HRMS/MS). Based on the MS/MS data, tentative molecular structures are proposed. Reaction mechanisms for the formation of a large number of OTPs are suggested by combination of the kinetics of formation and abatement and state-of-the-art knowledge on ozone and hydroxyl radical chemistry. OTPs forming as primary or higher generation products from the oxidation of MPs could be differentiated. However, some expected products from the reactions of ozone with activated aromatic compounds and olefins were not detected with the applied analytical procedure. 187 OTPs were present in the sand filtration in sufficiently high concentrations to elucidate their fate in this treatment step. 35 of these OTPs (19%) were abated in the sand filtration step, most likely due to biodegradation. Only 24 (13%) of the OTPs were abated more efficiently than the parent compounds, with a dependency on the functional group of the parent MPs and OTPs. Overall, this study provides evidence, that the common assumption that OTPs are easily abated in biological post-treatment is not generally valid. Nevertheless, it is unknown how the OTPs, which escaped detection, would have behaved in the biological post-treatment.

Spray drift is considered a major pesticide transport pathway to surface waters. Current research and legislation usually only considers direct spray drift. However, also spray drift on roads and subsequent wash-off to surface waters was identified as a possible transport pathway. Hydraulic shortcuts (storm drainage inlets, channel drains, ditches) have been shown to connect roads to surface waters, thus increasing the risk of drift wash-off to surface waters. However, the importance of this pathway has never been assessed on larger scales. To address this knowledge gap, we studied 26 agricultural catchments with a predominance of arable cropping (n = 17) and vineyards (n = 9). In these study sites, we assessed the occurrence of shortcuts by field mapping. Afterwards, we modelled the areas of roads drained to surface waters using a high-resolution digital elevation model (0.5 m resolution) and a multiple flow algorithm. Finally, we modelled drift deposition to drained roads and surface waters using a spatially explicit, georeferenced spray drift model. Our results show that for most sites, the drift to drained roads is much larger than the direct drift to surface waters. In arable land sites, drift to roads exceeds the direct drift by a factor of 4.5 to 18, and in vineyard sites by 35 to 140. In arable land sites, drift to drained roads is rather small (0.0015% to 0.0049% of applied amount) compared to typical total pesticide losses to surface waters. However, substantial drift to drained roads in vineyard sites was found (0.063% to 0.20% of applied amount). Current literature suggests that major fractions of the drift deposited on roads can be washed off during rain events, especially for pesticides with low soil adsorption coefficients. For such pesticides and particularly in vineyards, spray drift wash-off from drained roads is therefore expected to be a major transport pathway to surface waters.

Synthetic Plant Protection Products (PPPs) are a key element for a large part of today's global food systems. However, the transport of PPPs and their transformation products (TPs) to water bodies has serious negative effects on aquatic ecosystems. Small streams in agricultural catchments may experience pronounced concentration peaks given the proximity to fields and poor dilution capacity. Traditional sampling approaches often prevent a comprehensive understanding of PPPs and TPs concentration patterns being limited by trade-offs between temporal resolution and duration of the observation period. These limitations result in a knowledge gap for accurate ecotoxicological risk assessment and the achievement of optimal monitoring strategies for risk mitigation. We present here high-frequency PPPs and TPs concentration time-series measured with the autonomous MS²Field platform that combines continuous sampling and on-site measurements with a high-resolution mass spectrometer, which allows for overcoming temporal trade-offs. In a small agricultural catchment, we continuously measured 60 compounds at 20 minutes resolution for 41 days during the growing season. This observation period included 8 large and 15 small rain events and provided 2560 concentration values per compound.
To identify similarities and differences among the compound-specific concentration time-series, we analysed the entire dataset with positive matrix factorisation. Six factors sufficiently captured the overall complexity in concentration dynamics. While one factor reflected dilution during rainfall, five factors identified PPPs groups that seemed to share a common history of recent applications. The investigation per event of the concentration time-series revealed a surprising complexity of dynamic patterns; physico-chemical properties of the compounds did not influence the (dis)similarity of chemographs. Some PPPs concentration peaks led while others lagged by several hours the water level peaks during large events. During small events, water level peaks always preceded concentration peaks, which were generally only observed when the water levels had almost receded to pre-event levels. Thus, monitoring schemes relying on rainfall or water level as proxies for triggering sampling may lead to systematic biases.
The high temporal resolution revealed that the Swiss national monitoring integrating over 3.5 days underestimated critical concentration peaks by a factor of eight to more than 32, captured 3 out of 11 exceedances of legal acute quality standards (the relevant values in the Swiss Water Protection Law) and recorded 1 out of 9 exceedances of regulatory acceptable concentrations (the relevant values for the PPPs registration process).
MS²Field allowed for observing unexpected and overlooked pesticide dynamics with consequences for further research but also for monitoring. The large variability in timing of concentration peaks relative to water level calls for more in-depth analyses regarding the respective transport mechanisms. To perform these analyses, spatially distributed sampling and time-series of geo-referenced PPPs application data are needed.