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.