The effect of different temperature and pH levels on uptake of CO2 in Solonchaks

Abstract

Previous studies have observed a negative CO2 efflux from semi-desert and desert soil, but the carbon uptake in alkaline soils has not been measured quantitatively in laboratory. The present study aims at closing this gap considering the effect of temperature, soil pH and pCO2. CO2 uptake was studied with the help of the Barometric Process Separation (BaPS) technique. CO2 uptake was studied at 3 different temperatures viz. 15, 20 and 25 °C. CO2 uptake was observed after CO2 injection with pH values ranging from 8 to 10 in desert Solonchak soils. We found that CO2 uptake depended on pCO2 and temperature. CO2 uptake occurred rapidly within the first 10 min after the CO2 injection and gradually slowed down afterwards. Results showed that 72%–97% of injected CO2 was taken up by soils (pH 8–10). CO2 uptake increased as soil pH increased and its uptake reached equilibrium faster in soil with a lower pH level (pH < 9) than in soil with a higher pH level (pH ≥ 9). Dissolved CO2 (CO2aq) (μmol ml−1) increased with increasing CO2 partial pressure (pCO2) with equation y = a (1-bx) (r2 > 0.96) and pH. The lower temperature produced a higher CO2aq for the same pCO2 value. In conclusion, desert soils can rapidly uptake of CO2, and the main controlling process of CO2 uptake in the desert soils was decided by soil pH and temperature. The CO2 uptake by the soil solution may be an important pathway for C sequestration in semi-desert and desert regions.