Aquatic Risks at the Landscape Scale: A Case Study for Pyrethroid Use in Pome Fruit Orchards in Belgium.

Area of Science:

• Environmental Science
• Ecotoxicology
• Computational Modeling

Background:

• Current pesticide environmental risk assessment (ERA) procedures are debated, particularly at higher tiers.
• Existing ERA systems largely ignore spatiotemporal dynamics of pesticide exposure and effects at the landscape scale.
• There is a lack of concrete guidance for landscape-scale ERA within regulatory frameworks.

Purpose of the Study:

• To present an integrated, modular simulation model for spatiotemporally explicit pesticide ERA.
• To simulate pesticide application, fate, and effects on aquatic organisms at the landscape scale.
• To quantify risks to aquatic organisms using a toxicokinetic/toxicodynamic (TK/TD) model.

Main Methods:

• Development of an integrated modular simulation model system.
• Application of the landscape model to the Rummen river catchment in Belgium.
• Simulation of pyrethroid pesticide application, drift deposition, and fate dynamics.
• Quantification of aquatic organism risk using TK/TD models across spatial scales.

Main Results:

• The model successfully simulated pesticide application, fate, and drift deposition in a case study catchment.
• Aquatic organism risk was quantified using TK/TD models at various spatial aggregation levels.
• The study demonstrated the feasibility of deriving landscape-scale risk assessment endpoints.

Conclusions:

• The developed model addresses the limitations of current ERA by incorporating spatiotemporal landscape dynamics.
• A community dialogue is essential to establish appropriate endpoints and representative landscape scenarios for regulatory ERA.
• This case study provides a concrete example to facilitate discussions on advancing landscape-scale pesticide risk assessment.