Atmospheric [14C]CO2 variations in Japan during 1982-1999 based on 14C measurements of rice grains

14C in rice grains is a useful tracer of atmospheric 14C(CO2). 14C measurement in rice grains for 17 years during 1982-1999 reveals the following. There is negative correlation between Δ14C and the population densities of localities in Japan. Under-populated areas in the northern area of Japan and Okinawa remained clean in the 1990s. The 14C(CO2) decline rates at those areas are near to that of Shauinsland. A latitudinal effect due to Chinese nuclear tests is observed in 1982. Small Seuss effects is observed at the middle latitudes in East Asia after 1995.