A reassessment of the soil sink for atmospheric carbon tetrachloride based upon static flux chamber measurements
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Static flux chamber measurements of CCl4 uptake by soils in boreal, subtropical and tropical forests have been used to reassess the sink strength for this ozone depleting chemical. Happell and Roche (Geophys. Res. Lett. 30(2), 1088–1091, 2003) used flux estimates from soil concentration gradients to calculate a partial CCl4 atmospheric lifetime (τsoil) of 90 years. More recently, it is has been assumed that a better estimate of τsoil is 195 years (Montzka et al. 2011). In the work here, the rate of CCl4 uptake was calculated from 453 flux chamber measurements using an exponential fit to the chamber CCl4 concentration change with time. This analysis indicated that the flux rate estimate in Happell and Roche (Geophys. Res. Lett. 30(2) 1088–1091, 2003) was overestimated by 2.75, yielding a new estimate of τsoil for CCl4 of 245 years. Significant correlations of CCl4 uptake to temperature, soil moisture, or time of year were not observed. This work provides additional evidence that CCl4 uptake by soils is a common process and needs to be considered when developing an atmospheric budget for this compound.
KeywordsCCl4 Sink Soil uptake Flux chamber Atmospheric budget
This work was supported by National Science Foundation grant number ATM-0400429. We wish to thank Charlene Grall, Jeff Happell, Lisa Matragrano and Nelson Melo for their help in the field. We also need to thank the staffs of the Meanook Biological Research Station and the El Verde Research Station for providing access to field sites and laboratory and housing space. The staff of the Deering Estate provided access to the field sites located there.
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