Radiocarbon(¹⁴C) Tracing The Vertical Variations Offossil-derived CO₂ In Typical Area Of Shaanxi Province

Global warming has attracted worldwide attention, and one of themaincontributors is considered to be the increasinggreenhousegasemissions. TherisinglevelsofatmosphericCO2 is mainly due to the use of fossil fuels by human being. Considering the differences of 14 C between fossil-derived and non-fossil-derived CO2, we can quantitatively calculate the proportion of fossil-derived CO2 in the total atmospheric CO2, thus 14 C tracingis considered to be the most direct and effective method for the emission offossil-derived CO2. This thesis analyzed the spatial and temporal variations of atmospheric fossil-derived CO2 using experimental samples from Mt. Hua, high residence building in Xi'an City, Bailu tableland, Ziwu valley and Mt.Taibai. Through the analysis of atmospheric gas and plant samples of Mt. Hua in the summer and winter, we found that the fossil-derived CO2 decreased with the increasing altitude and fossil-derived CO2 concentrations in winter are significantly higher than that in summer. The analysis of atmospheric gas samples in high residence building in Xi'an City showed that fossil-derived CO2 decreases with the increase of floor height and the source will be more complicated with taller buildings. Plant sample is another effective tracer of fossil-derived CO2. Through comparing four kinds of plants :Pinusarmandii, Artemisia argyi, Endarachnebinghamiaeand Ditrichumflexicaule,the resultsshowed that plants with moderate height and broad leaves havethemost pronouncedimpacton fossil-derived CO2, reflecting that plant samples are more sensitive to the local fossil-derived CO2 conditions than atmospheric gas samples during the plantgrowth stages and different plantspecies have different response. By comparion, it is shown that Mt. Taibai has agoodgeographicaladvantage over Mt. Hua since its ?14C is consistentwiththe global background values, which makes it possible to be the background site of atmospheric ?14C in the Guanzhong Plain area of China. It not only helps perfect the knowledge about space-time change rules of atmospheric fossil-derived CO2 in China, but offers datasupportfor modeling the 3-D Propagation of the CO2.This providesreliabletheoreticalbasis for evaluating the currentsituationsof fossil-derived CO2 emission and reduction.