Atmospheric 14C Variability Recorded in Tree Rings from Peninsular India: Implications for Fossil Fuel CO2 Emission and Atmospheric Transport

Abstract

Radiocarbon analysis in annual rings of a teak tree (Tectona grandis) is reported in comparison with previously published results. Samples (disks) were collected from Hoshangabad (22 degrees 30'N, 78 degrees E), Madhya Pradesh, in central India. The previously published sample was collected from Thane (19 degrees 12'N, 73 degrees E), Maharashtra, near the west coast of India (Chakraborty et al. 1994). Two short 14C time series were reconstructed with these tree samples to capture the bomb peak of atmospheric 14C and the spatial variability in this record. These time series represent the periods 1954-1977 and 1959-1980 for Hoshangabad and Thane, respectively. The 14C peaks in these places appear around 1964-1965. The Hoshangabad tree records a peak delta-14C value of 708 +/- 8‰, which conforms to the peak value of Northern Hemisphere Zone 3 as described in Hua and Barbetti (2004). But the peak 14C at Thane is somewhat less (630 +/- 8‰) probably due to the dilution by fossil fuel CO2 free of 14C emanating from the neighboring industrial areas. This depletion of peak values has been used to estimate the local emission of fossil fuel CO2, which is approximately 2.3% of the background atmospheric CO2 concentration.