Pesticides and their transformation products in lentic small water bodies : Influence of hydrology, compound properties and field management
Lentic small water bodies (LSWBs) such as kettle holes and ponds are common landscape features in agricultural regions and, despite their small size, perform important ecosystem functions, for example in terms of biodiversity, groundwater recharge, and the retention of pollutants. However, due to their location in intensively farmed arable land, they are particularly susceptible to inputs of pesticides and their transformation products (TP), but have so far been insufficiently considered in legislation and monitoring. The aim of this dissertation is to comprehensively record the dynamics of pesticides and TPs in and around LSWBs. The focus is on the water balance and its seasonal variability, the function of adjacent soils as storage and sources, the relevant transport pathways, and the relationship between pollution and current land management. The basis for this is high-resolution, multi-year monitoring at two LSWBs in the North German lowlands. Surface water, soil, groundwater, and drainage inflows were sampled, supplemented by tracer experiments, soil analyses, and the collection of application data. The results show that shallow groundwater and, in one case, a drainage contribute significantly to the water and material balance of the LSWBs. Mobile TPs are predominantly transferred to deeper soil layers, groundwater, and the LSWBs, while more sorptive substances remain in the upper soil layers and are persistent over long periods of time. Both short-term pollution peaks and long-lasting concentrations occur in the LSWBs, which cannot be explained by current applications alone and indicate an interaction between recent inputs, mobilized residues, and groundwater transport. The work deepens the understanding of pesticide dynamics in LSWBs and underscores the need for holistic environmental monitoring as a basis for effective protection measures for small aquatic ecosystems in agricultural landscapes.
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