Radionuclides 14C and 129I Tracing Studies in Xi'an AMS Center

Radionuclides ¹⁴C and ¹²⁹I are good tracers for investigation of environmental change. The radiocarbon content (Δ¹⁴CO₂) observations are used to trace recently added fossil fuel CO₂ in the atmosphere for evaluating and constraining the CO₂ emission and ¹²⁹I can be used for monitoring of nuclear environmental safety. Base on newly established multi-elements 3MV AMS in the Xi'an AMS Center, ¹⁴C and ¹²⁹I research for environmental change have been carried out. Here we report some new results. Air samples and annual plants were collected for fossil fuel CO₂ emission in Xi'an area, China. Fossil fuel contributes 1.16%-8.36% of the CO₂ concentration found in air in southeastern Xi'an City. The fossil fuel CO₂ emissions reach at the largest peak at the end of March and the beginning of July. Between April and June, the emissions are lowest. Fossil fuel-derived CO₂ of city center can be an order of magnitude larger than in nearby rural environments. ¹²⁹I and ¹²⁷I concentrations in soil, vegetation, river water and precipitation collected from Xi'an area, China are analyzed, The results indicate the mean value for environmental ¹²⁹I/¹²⁷I ratios in the investigated area is 2.06×10^-9, which is 1-3 orders of magnitude lower than the ratios observed in Europe, but comparable with those observed in the locations far from direct effect of point release sources and at similar latitude. The result indicates Xi'an region is not directly influenced by any nuclear facilities currently and the data can be used to establish the baseline of ¹²⁹I in China and to monitor ¹²⁹I variation for evaluation of the effect and safe operation of the nuclear facilities in the future.