Conductometric model for the determination of dissolved carbon dioxide concentration in Vossoroca Reservoir, Brazil

ABSTRACT:

A conductometric model was developed as a less costly technique to determine the dissolved carbon dioxide concentration in reservoirs and was applied in Vossoroca Reservoir, Brazil. A main portion of Vossoroca Reservoir is located in the Environmental Protection Area of Guaratuba and was built for regulate flows to a hydroelectric power plant, considered a clean and renewable form of exploitation; however, there is evidence that hydroelectric reservoirs could be potential emitters of greenhouse gases. The model uses parameters as electrical conductivity, temperature and pH of the water reservoir. It was possible to observe in the results the thermal and chemical stratification that occurs in the reservoir through the parameters temperature (18º to 25ºC), pH (5.9 to 8.4), dissolved oxygen (with upper limit of 8 mg.L^-1) and electrical conductivity (0.04 to 0.2 mS.cm^-1). The campaign results showed good determination coefficients (R²), above 0.9, for all campaigns for the determination of dissolved carbon dioxide concentration obtained by alkalimetric titration, also made on the study site, and by the conductometric model (with upper limit of approximately 250 mg.L^-1), but at depths close to the bed of the reservoir discrepancies were found. The statistical significance test (Student) did not show significant difference between the values obtained by alkalimetric titration and by the conductometric model.

Keywords:
conductometric model; dissolved carbon dioxide; Vossoroca Reservoir