Diffusive CO₂ Flux at the Air-Water Interface of the Robert-Bourassa Hydroelectric Reservoir in Northern Québec : Isotopic Approach (¹³C)

Abstract

Hydroelectric reservoirs and lakes in boreal Québec produce greenhouse gases (GHG) mainly in the form of CO₂. No method exists, however, which can directly measure the flux of CO₂ across the air-water interface and the methods that are currently used are only representative of a small surface area and a specific time period. The objective of the current study is to improve and validate an isotopic approach to estimate the annual CO₂ flux across the air-water interface. The model requires the calibration of isotopic fluxes into and out of the interface. When applied to the Robert- Bourassa hydroelectric reservoir in boreal Québec, this model estimated an average CO₂ diffusive flux across the air-water interface of 225±51 mg CO₂·m⁻²·d⁻¹ in the summer of 2000 and of 446±93 mg CO₂·m⁻²·d⁻¹ in the summer of 2001. These average fluxes are representative of the whole icefree period.