A precise potentiometric method for determination of algal activity in an open CO2 system |
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Authors: | OLOF HOFSLAGARE GORAN SAMUELSSON† STAFFAN SJÖBERG NILS INGRI |
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Institution: | Department of Inorganic Chemistry, University of Umeå, S-901 87 Umeå, Sweden;Department of Plant Physiology. University of Umeå, S-901 87 Umeå, Sweden |
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Abstract: | Abstract. The activity of the green alga Scenedesmus obliquus was studied in simplified nutrient solutions (20 mol m?3 NaNO3, 20 mol m?3 NH4C1, 20 mol m?3 NH4NO3, and 20 mol m?3 NaCl, respectively) at 25 °C. The experiments were performed under welldefined incident photon density fluxes ranging from 10 to 200 μmol m2 s?1, Light-dependent changes in pH and alkalinity (A) were followed by means of a potentiometric method using a glass electrode. In the experiments, carbon dioxide with known partial pressure was bubbled through the algal suspension, and during dark periods ul intervals of 1 h, the solution was allowed to equilibrate with the gas phase. This technique was applied to calculate equilibrium values of pH and alkalinity at regular intervals during a 12-h period. Results obtained in NaNO3, solution show a linear increase in A with time, at each level of illumination studied. After an initial drop, A also increases in NH4NO3, solution in a similar way to that in NaNO3 solution. The change in A with time was also found to increase linearly with the photon density flux studied and no saturation level could be defined. In experiments in NaCl solution, no changes in A were registered while measurements in NH4Cl solution showed a decrease in A with time. |
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Keywords: | Scenedesmus obliquus nitrate assimilation poientiometrie measurements |
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