Historic binnacle of 14C/12C concentration in Mexico City

The radiocarbon concentration is reduced in urban areas, generally due to high CO2 emissions derived from fossil fuels. In this paper, new Δ14C measurements in cellulose extracted from the growth rings of two trees over a 43-year period are presented. The first is in a zone with clean air (El Nayar, Durango, Mexico) and the second is from the Greater Mexico City area (Chapultepec). Data from El Nayar is consistent with that reported for Zone 2 of the Northern Hemisphere while that from the urban area shows a significant decrease in Δ14C. Our results are compared with data from other cities (Nagoya, Japan and Valladolid, Spain).