珠江三角洲地区大气CO_(2)浓度特征及地面风的作用

CHARACTERISTICS OF ATMOSPHERIC CO_(2) CONCENTRATION AND THEIR CORRELATIONS WITH SURFACE WIND IN THE PEARL RIVER DELTA

利用光腔衰荡光谱(CRDS)技术在线观测了广州番禺大气成分站(GPACS)的大气CO_(2)浓度特征,分析了地面风对CO_(2)的作用。结果表明:(1)大气CO_(2)在珠江三角洲地区存在明显的地域不均匀特征,2014—2016年期间GPACS的年均本底浓度比全球背景地区平均增加了22.5×10-6(22.5 ppm);(2)大气CO_(2)浓度在春季最高,冬、秋季次之,夏季最低,年均值为426.64±15.76 ppm;(3) CO_(2)的日变化为双峰结构,峰值分别在05:00—07:00和21:00—22:00,谷值在13:00—15:00,表明受到了自然过程以及人为排放源的复合影响;(4)风场显著影响CO_(2)的浓度分布,春、夏季CO_(2)浓度距平日变化与地面风速为显著负相关,秋、冬季则为显著正相关。在春、夏季,S-WSW和NNE-N风向上CO_(2)浓度较低,在秋、冬季,SSE-S和N方向均导致CO_(2)浓度下降。NW和NE-ENE风向在四季中均能提升CO_(2)浓度,其中NW-NNW和NNE-ENE为弱的CO_(2)源区,分别贡献了0.42 ppm和0.32 ppm的CO_(2)浓度。

By using cavity ring-down spectroscopy(CRDS)technology,the present study measured the CO_(2) mole fraction(1×10-6,ppm)for the period 2014—2016 in the Guangzhou Panyu Atmospheric Composition Site(GPACS),a suburban site in the Pearl River Delta(PRD)region of China,and the correlations of CO_(2) concentration with surface wind were also investigated.Results show that:(1)Atmospheric CO_(2) has obvious geographical inhomogeneity in the PRD region,and the annual average value of background concentration in GPACS is 22.5 ppm higher than the value in the global background area.(2)The CO_(2) concentration is the highest in spring,moderate in winter and autumn,and the lowest in summer,with the annual average value being 426.64±15.76 ppm.The diurnal CO_(2) shows two peaks:one peak at 05:00—07:00 and the other at 21:00—22:00 Local Standard Time,and the minimum value appears at 13:00—15:00.Together,these patterns indicate that the CO_(2) is affected by the combined effects of anthropogenic and biogenic processes.(3)The diurnal CO_(2) anomaly and wind speed show a significant negative correlation(p<0.01)during spring and summer,but they show a significant positive correlation(p<0.01)during autumn and winter.In spring and summer,winds from the directions of S-WSW and NNE-N result in lower CO_(2) concentrations.By contrast,in autumn and winter,winds from the directions of SSE-S and N substantially lower the CO_(2).Winds from the directions of NW and NE-ENE significantly increase the CO_(2) concentration throughout the year,and furthermore,winds from the directions of NW-NNW,and NNE-ENE contribute 0.42 ppm and 0.32 ppm to the corresponding CO_(2) concentration,which indicates that the CO_(2) may have a potential source in these sectors.