Changes in CO2 Absorption Efficiency of NaOH Solution Trap with Temperature

Abstract

Under the projected global warming, release of carbon as CO2 through soil organic matter decomposition is expected to increase. Therefore, accurate measurement of CO2 released from soil is crucial in understanding the soil carbon dynamics under increased temperature conditions. Sodium hydroxide (NaOH) traps are frequently used in laboratory soil incubation studies to measure soil respiration rate, but decreasing CO2 gas solubility with increasing temperature may render the reliability of the method questionable. In this study, the influences of increasing temperature on the CO2 capture capacity of NaOH traps were evaluated under 5~35°C temperature range at 10°C interval. Two closed-chamber experiments were performed where NaOH traps were used to capture CO2 either released from acidified Na2CO3 solution or directly injected into the chamber. The sorption of ambient CO2 within the incubators into NaOH traps was also measured. The amount CO2 captured increased as temperature increased within 2 days of incubation, suggesting that increased diffusion rate of CO2 at higher temperatures led to increases in CO2 captured by the NaOH traps. However, after 2 days, over 95% of CO2 emitted in the emission-absorption experiment was captured regardless of temperature, demonstrating high CO2 absorption efficiency of the NaOH traps. Thus, we conclude that the influence of decreased CO2 solubility by increased temperatures is negligible on the CO2 capture capacity of NaOH traps, supporting the use of NaOH traps in the study of temperature effect on soil respiration is a valid method. Changes in the CO2 absorption amount of NaOH solution trap with temperature measured using CO2 emission-absorption method. Standard error bars are provided and some bars are not depicted due to small error. Different letters on the data bars indicate significant (P<0.05)difference among the treatments (temperature and reaction time).