Simulation of future stream alkalinity under changing deposition and climate scenarios

Area of Science:

• Environmental Chemistry
• Hydrology
• Climate Science

Background:

• Traditional acidification models overlook climate change impacts.
• Rising soil CO2 from warming/wetting affects water chemistry.
• Increased soil CO2 can initially raise stream alkalinity.

Purpose of the Study:

• To investigate the impact of climate change on soil and stream water chemistry.
• To simulate future stream water alkalinity under various climate and deposition scenarios.
• To assess the role of soil CO2 and base cation dynamics.

Main Methods:

• Utilized physically based coupled models for soil air CO2 and stream water chemistry.
• Simulated daily stream water alkalinity for a Virginia Blue Ridge catchment over 60 years.
• Employed nine scenarios combining climate (static, gradual, abrupt) and deposition changes.

Main Results:

• Stream water alkalinity declined in most scenarios (avg. decrease 14.4 µeq L⁻¹).
• A notable exception was gradual warming and increased moisture, leading to increased alkalinity (avg. increase 13 µeq L⁻¹).
• Base cation removal from soils limited alkalinity increases in other climate change scenarios.

Conclusions:

• Climate change significantly influences stream water chemistry, often counteracting expected trends.
• The interplay between soil CO2, base saturation, and deposition is crucial for predicting acidification.
• Findings have critical implications for environmental policy regarding deposition and emissions regulations.