Modeling surface water critical loads with PROFILE: possibilities and challenges

Area of Science:

• Environmental Chemistry
• Ecology
• Geochemistry

Background:

• Critical load concept is vital for European emission reduction policies.
• Validation of critical load methodology is crucial for policy defensibility.
• Steady State Water Chemistry (SSWC) is the current standard for calculating acidity critical loads.

Purpose of the Study:

• To explore the PROFILE model as an alternative to SSWC for critical load calculations.
• To test the hypothesis that using soil properties reduces uncertainty in predicting preindustrial base cation leaching.
• To assess the viability of PROFILE using paleolimnological data and soil survey data.

Main Methods:

• Utilized the steady state soil chemistry model PROFILE.
• Employed paleolimnological reconstructions of preindustrial lake chemistry for validation.
• Used soil survey data distributions for five lake catchments due to lack of catchment-level soil data.
• Calibrated effective soil depth to align PROFILE predictions with paleolimnological data.

Main Results:

• A calibrated effective soil depth of approximately 0.6 m was hydrologically active in supplying acid neutralizing capacity (ANC) through weathering.
• PROFILE model's performance against paleolimnological data requires further investigation.
• The study highlights the importance of catchment hydrology characterization.

Conclusions:

• Insufficient evidence currently exists to recommend or reject the PROFILE model for surface water critical loads.
• Further testing in diverse regions is necessary.
• Investigating catchment hydrology definitions is essential for future model application.