Atmospheric CCl₄ degradation in Antarctic tundra soils and the evaluation on its partial atmospheric lifetime with...

Carbon tetrachloride (CCl₄) is an anthropogenic gas with a long atmospheric lifetime and can catalyze the destruction of stratospheric ozone. Natural soils are believed to be important and widespread sinks of atmospheric CCl₄, although poorly characterized due to a limited number of measurements. In this study, for the first time in situ static-chamber measurements and laboratory-based incubations for CCl₄ fluxes were conducted at coastal Antarctic tundra. Results showed that soil in remote Antarctica is also acting as a CCl₄ sink, with an average uptake rate of -2.2 ± 0.6 nmol m^-2 d^-1, which is comparable to the reported soil sinks in other regions of the world. No significant difference (p > 0.05) was found across different types of tundra, such normal upland tundra, coastal marsh tundra, and tundra in the sea animal colonies. Soil CCl₄ fluxes did not show significant correlations (p > 0.05) with soil moisture, pH, TOC, TN, TP and Cl contents. Laboratory-based anoxic incubations showed that the uptake rates of CCl₄ in tundra soil were suppressed; post-thermal sterilization incubations showed that soil CCl₄ sink was enhanced; these results suggested that CCl₄ degradation in tundra soil was likely an abiotic process preferring oxic environments. A rough extrapolation suggested that Antarctic tundra may degrade about 2.4 metric tons of atmospheric CCl₄ each year. Combining soil CCl₄ fluxes from this study and other literature reports, CCl₄ partial lifetime with respect to the soil sink was evaluated to be 354 (235-474) years, which supported the recent viewpoint that the soil sink of CCl₄ is smaller than previously thought.