北京奥林匹克森林公园CO_2变化特征及来源解析

Variations and source estimation of atmospheric CO_2 at Beijing Olympic Forst Park

以北京奥林匹克森林公园绿地内外近地层大气为研究对象,测定距离道路不同位置的CO_2浓度和δ^(13)C值,利用Keeling plot方程结合Iso Source软件定量区分CO_2来源。结果表明,奥林匹克森林公园中CO_2浓度随远离道路呈下降趋势,距离五环路500 m处绿地为354. 7μmol·mol^(-1),比五环路低约71. 0μmol·mol^(-1)。CO_2浓度的日变化受车流量变化和植物光合呼吸作用的共同影响,五环路在8:00和20:00时较高,绿地系统内在6:00时较高,二者CO_2浓度差在12:00达到最大,约90. 6μmol·mol^(-1)。不同来源δ^(13)C值差异显著,其中,生态系统呼吸(-22. 01‰)>大气本底(-22. 90‰)>机动车尾气(-28. 13‰)>天然气废气(-33. 39‰),7:00—9:00、12:00—14:00和18:00—20:00的3个时段中绿地系统内空气中CO_2的δ^(13)C值均高于五环路,绿地系统内来源于生态系统呼吸的CO_2比例明显高于五环路,来源于机动车尾气和天然气废气的CO_2比例变化则相反。

Atmospheric CO 2 concentration and stable carbon(δ13 C)isotope ratio on the Fifth Ring Road and in the green space system at Beijing Olympic Forst Park away from the Fifth Ring Road were analyzed with Keeling plot method and IsoSource software.The results demonstrated that CO 2 concentration in Beijing Olympic Forst Park had an obvious declining change with the distance increasing from the Fifth Ring Road.The CO 2 concentration in the green space system 500 meters away from road is 354.7μmol·mol-1 and 71.0μmol·mol-1 lesser than that around the roadside.Daily variations of CO 2 concentrations were affected by vehicle flux and photosynthesis and respiration in plants.The maximum value appears at 8:00,12:00 and 20:00 in roadside but at 6:00 in the green space system,while the maximum difference of CO 2 concentration in this two position appeares at 12:00,which is about 90.6μmol·mol-1.Different sources have a significantly differentδ13 C value and in the order of ecosystem respiration(-22.01‰),atmospheric background(-22.90‰),motor vehicle exhaust(-28.13‰)and natural gas(-33.39‰),from the highest to the lowest.Theδ13 C value of atmospheric CO 2 in the green space system were higher than those on the Fifth Ring Road from 7:00 to 9:00,12:00 to 14:00 and 18:00 to 20:00.The contribution of CO 2 from ecosystem respiration in the green space system was higher than that on the Fifth Ring Road,but a reverse pattern was observed in the contributions of CO 2 from the vehicle exhaust and the natural gas.