Carbon Dioxide Pressure in Surface Waters of Canadian Lakes

by Raymond H. Hesslein, Dept of Fisheries and Oceans, Winnipeg, Canada,
John W. M. Rudd, Dept of Fisheries and Oceans, Winnipeg, Canada,
Carol Kelly, Dept of Fisheries and Oceans, Winnipeg, Canada,
Patricia Ramlal, Dept of Fisheries and Oceans, Winnipeg, Canada,
Kimberley A. Hallard, Dept of Fisheries and Oceans, Winnipeg, Canada,



Document Type: Proceeding Paper

Part of: Air-Water Mass Transfer

Abstract: Direct measurements of the partial pressure (pCO2) of carbon dioxide were made in lakes of three study areas: ELA (the Experimental Lakes Area) and the NOLSS (Northwestern Ontario Lake Size Series) study area, both in northwestern ontario, and the Mackenzie River delta, N.W.T. Consistent seasonal patterns of pCO2 were found in all three areas. pCO2 was high in the spring just after ice melt, low in the summer, and rising again in the fall. Springtime values were as high as 100. μatm, or about three times equilibrium with the atmosphere. The summer values varied greatly depending on the photosynthetic activity in the lakes. The pCO2 in the least productive lakes stayed near atmospheric equilibrium, but in the most productive lakes the pCO2 was almost undetectable (<10 μatm). Simple carbon dioxide budgets were calculated by a finite difference model. The model included estimates of daily gas exchange, photosynthetic activity, respiration, and CO2 fluxes from the sediments. The pCO2 values generated by the model were in good agreement with the measured values for the lakes.

Subject Headings: Lakes | Carbon dioxide | Surface water | Pressure measurement | Water resources | Equilibrium | Ice | Rivers and streams | Seasonal variations | North America | Ontario | Canada | Colorado | United States

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