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.