利用放射性碳（14C）示踪华山冬季化石源CO2随海拔高度变化特征

摘要

放射性碳（14C）是化石源CO2最有效的示踪剂，为了更好地了解华山冬季化石源CO2的时空变化特征，于2014年冬季在华山三个不同海拔高度——玉泉院（504 m）、北峰（1634 m）、东峰（2079 m）进行大气CO2采样。通过放射性碳同位素分析研究发现：华山冬季不同海拔高度大气CO2浓度随海拔升高而减小，三个海拔高度大气CO2平均浓度依次为461.8±14.1 ppm（ppm表示μL·L–1）、414.6±2.7 ppm和413.2±3.4 ppm，皆高于我国四个大气CO2本底站点的同期浓度水平。不同海拔高度大气CO2浓度及其δ13C值呈显著的反相关关系，R2=0.906，表明华山大气CO2主要受区域生态系统的时空变化和源汇特征影响，而海洋的影响较弱。三个不同海拔高度的化石源CO2浓度均值依次为42.3±5.7 ppm、14.9±3.8 ppm和10.6±1.0 ppm，表明华山不同海拔高度大气CO2都受到化石源CO2不同程度的影响。华山冬季化石源CO2浓度和海拔高度具有显著的反相关关系，R2=0.914，随着海拔的不断升高，化石源CO2浓度逐渐减小。利用Hysplit模式分层后向轨迹分析结果表明：在采样时段内，玉泉院和北峰受到同源路径气团的影响，其化石源CO2浓度呈现出较一致的变化趋势，东峰受到异源路径气团的影响，其化石源CO2浓度呈现出不同的变化趋势。因此，在分析评价高海拔地区化石源CO2浓度时，不仅要考虑到近源排放影响，同样不能忽视远源传输影响。%Radiocarbon (14C) is the most effective tracer of fossil-derived CO2. In order to better understand the spatial and temporal variations of fossil-derived CO2 with altitude, three locations in Mt. Hua area of different altitudes were chosen, Yuquan Temple (504 m), North Peak (1634 m), East Peak (2079 m), for the sampling of atmospheric CO2 in the winter of 2014. Through radiocarbon measurement, we found that atmospheric CO2 concentrations decreased with increasing altitudes. The average concentrations of atmospheric CO2 at three locations were 461.8 ± 14.1 ppm (ppm represents μL·L–1), 414.6 ± 2.7 ppm and 413.2 ± 3.4 ppm respectively. All of them were higher than four background sites’ atmospheric CO2 concentrations in China. The negative correlation between CO2 concentration andδ13C value was also observed (R2= 0.906), suggesting that atmospheric CO2 in Mt. Hua area were mainly affected by regional ecosystem characteristics and source-sink effects, while the impact of ocean was minor. The average concentrations of fossil-derived CO2 at three different altitudes were 42.3 ± 5.7 ppm, 14.9 ± 3.8 ppm, 10.6 ± 1.0 ppm, indicating that atmospheric CO2 at different altitudes are subject to the impact of fossil fuel to varying degrees. There was a strong negative correlation between fossil-derived CO2 and altitude (R2= 0.914). Using the Hysplit mode and backward trajectories simulation analysis showed that, during the sampling period, Yuquan Temple and North Peak were affected by the homologous path air mass whose fossil-derived CO2 exhibited a consistent trend, and East Peak was affected by heterologous path air mass, the fossil-derived CO2 of which showed a different trend. Therefore, tracing the fossil-derived CO2 in the areas of high altitude, we should take into account not only the impact of near-source emissions, but also transmission from the distant sources.