Estimation of 14CO2 flux at soil-atmosphere interface and distribution of 14C in forest ecosystem

To realize the dynamical behavior of C-14 among exchangeable carbon reservoirs in terrestrial environment, a method for in situ determination of (CO2)-C-14 flux at soil-atmosphere interface and a high flow rate CO2 sampler were developed. This method allowed us to collect integrated quantity Of CO2 for determining C-14 activity over an extended time period under environmental conditions with minimal site disturbance. The (CO2)-C-14 flux from ground surface was estimated to be 1.59 x 10(-5) Bq m(-2) s(-1) in a forest floor with the method. The specific activities of C-14 in environmental materials such as some biological and air samples were also determined in the vicinity of the place. where the flux measurement was made, to discuss the behavior of C-14 in the forest ecosystem. The results indicated that fresh pine needles had a similar C-14 specific activity to the atmospheric CO2 at the same height due to its fairly rapid equilibrium, C-14 specific activity in the atmospheric CO2 has a concentration gradient near the ground surface and, at least in this site, CO2 with high C-14 specific activity was generated by decomposition of soil organic matter which may be accumulated in soil as a result of former nuclear weapons tests. 2002 Elsevier Science Ltd. All rights reserved.