厦门秋季近郊近地面CO_2浓度变化特征研究

Near Surface Atmospheric CO_2 Variations in Autumn at Suburban Xiamen,China

利用CO2监测仪在厦门近郊中国科学院城市环境研究所超级监测站进行了秋季CO2数据采集,并结合监测站气象要素和气体污染物监测,分析了近地面CO2浓度变化特征、风速风向对其变化特征的影响以及CO2与部分气体污染物的相互关系.结果表明,厦门近郊秋季近地面CO2浓度主要集中分布在375～415μmol.mol-1范围内,约占70.87%;近地面大气CO2日变化曲线呈单峰型结构,CO2浓度日变化范围375.74～418.18μmol.mol-1,日平均最高值出现在黎明前后(408.54μmol.mol-1),最小值出现在午后附近(379.14μmol.mol-1),夜晚(18:00～05:00,北京时间)平均浓度(400.87±4.05)μmol.mol-1高于白天(06:00～17:00)平均浓度(388.86±9.40)μmol.mol-1;风速日变化曲线与CO2呈现完全相反的变化趋势,夜晚时段(22:00～04:00)风速波动范围在1.0～1.5 m.s-1时,对应的CO2浓度变化平稳,基本稳定在(400.72±2.12)μmol.mol-1.白天时段(09:00～18:00)风速变化范围在2.0～2.5 m.s-1时,对应的CO2浓度变化范围较大为379.14～394.83μmol.mol-1;用指数函数模型估测到该站点区域CO2背景浓度为386.84μmol.mol-1;观测期间该站点主要风向为东北偏东,统计该方向上CO2浓度与风速的相关关系,得出CO2浓度与风速呈极显著负相关(r=-0.67),相关系数高于所有方向统计的CO2浓度与风速的相关系数(r=-0.41,P<0.01),不同风向上CO2浓度贡献来源不同;此外,CO2浓度与温度、辐射量呈负相关(r=-0.541/-0.515,P<0.01),与湿度呈正相关(r=0.66,P<0.01);与其它大气气体污染物相比CO2与CO、NO的相关程度较高(r=0.469/0.436,P<0.01),与SO2相关程度较弱(r=0.126,P<0.01),经分析推测监测站点区域CO2排放源部分来自机动车排放,而燃煤排放贡献较小.

Near surface concentrations of carbon dioxide（CO2） were measured at the super station of atmospheric monitoring located at the suburban area of Xiamen in the fall of 2011.The results were analyzed together with the meteorological data and concentrations of other gaseous pollutants to study the diurnal variations of near-surface atmospheric CO2 concentration and the relationships of CO2 with wind speed and gaseous pollutants.The diurnal variation of CO2concentrations showed a single-peak pattern with the highest value（408.54 μmol·mol-1） observed in dawn when the atmosphere was stable and the lowest value（379.14 μmol·mol-1） was recorded in late afternoon following several hours of relatively unstable condition.The average CO2 concentration at night（400.87±4.05） μmol·mol-1 was higher than that of daytime（388.8±9.40） μmol·mol-1.Overall,the CO2 concentrations ranged from 375.74 μmol·mol-1 to 418.18 μmol·mol-1.CO2 and wind speed showed opposite trends.At night,the CO2 concentration（400.72±2.12） μmol·mol-1 was stable with wind speed of 1.0-1.5 m·s^-1.During daytime,the CO2 concentrations 379.14-394.83 μmol·mol-1 were more variable with wind speed of 2.0-2.5 m·s^-1.The background CO2 concentration of this site was estimated to be 386.84 μmol·mol-1 using an exponential function model.Northeast wind was dominant at this site.The correlation coefficient between the wind speed and the CO2 concentrations（r=-0.67,P〈0.01） was higher for wind direction of NE than other directions（r=-0.41,P〈0.01）.The source contributions were different for different wind directions.Moreover,the CO2concentration had a significant negative correlation with temperature and irradiation,and had a significant positive correlation with humidity.CO2 had a higher correlation with primary air pollutants CO and NO（r=0.469/0.436,P〈0.01） than SO2（r=0.126,P〈0.01）,indicating that the source of CO2 emission in this area was motor vehicle emission in part,with little contribution from coal combustion.