移动监测法测量厦门春秋季近地面CO_2的时空分布

Spatial and Temporal Variations of Near Surface Atmospheric CO_2 with Mobile Measurements in Fall and Spring in Xiamen,China

移动监测对研究城市近地面空气污染物时空分布特征具有重要意义.本研究采用野外移动监测车,利用二氧化碳测量仪、粉尘仪及小型气象站,在春秋季共选取14 d,沿厦门不同功能区,在每天不同时间段(09:00~12:00、13:00~16:00、22:00~01:00)进行了CO2与颗粒物(PM)浓度及气象参数的监测,并分析了春秋季不同时段下各功能区近地面CO2空间分布特征以及CO2与颗粒物的相互关系.结果表明:①监测期间,路线从北部的坂头水库背景区经郊区进入市中心最终在城市南部边缘沿海干道结束,CO2浓度的空间分布呈现中间市中心高沿市中心向两边边缘处降低的结构,不同功能区CO2空间分布存在差异,受城市交通,工业,人类活动等排放,地面植物/作物以及气象条件的影响.主要表现为交通繁忙区(仙岳路/厦禾路/嘉禾路,477.33μmol·mol-1±6.11μmol·mol-1)高于商业居民区(杏林/思北,454.95μmol·mol-1±5.45μmol·mol-1)高于自然风景区(文屏/环岛路/演武路,441.01μmol·mol-1±6.24μmol·mol-1)高于耕地(农田,436.79μmol·mol-1±1.87μmol·mol-1)高于山体林地(坂头水库,434.06μmol·mol-1±0.31μmol·mol-1);②监测期间春季平均CO2浓度为452.04μmol·mol-1±20.24μmol·mol-1,最大值出现在2013年4月12日的嘉禾路路段(市内交通繁忙区)为533.10μmol·mol-1,最小值出现在2013年4月10日的坂头水库路段(远离市区,受人为活动影响较小,水库周围有大量植被,可认为监测过程中的背景区域)为413.25μmol·mol-1.秋季平均CO2浓度为451.80μmol·mol-1±21.56μmol·mol-1,其中最大值出现在2012年11月19日的厦禾路路段(市内交通繁忙区)为526.45μmol·mol-1,最小值出现在2012年11月20日的坂头水库路段为415.01μmol·mol-1.这符合Idso等在1998年提出'城市CO2岛'的现象;③不同时间段CO2浓度表现出夜晚时段(22:00~01:00)高于上午时段(09:00~12:00)高于下午时段(13:00~16:00),阴天普遍高于晴天,且不同功能区CO2浓度在夜晚时段(22:00~01:00)和白天时段(09:00~12:00和13:00~16:00)的差异不同,春季的差异范围为-0.66~29.48μmol·mol-1,秋季的差异范围为-4.01~33.69μmol·mol-1;④市区CO2浓度与周围郊区存在差异,市区CO2浓度均高于郊区;⑤移动监测主要受道路车辆排放的影响,CO2浓度与PM2.5呈显著正相关关系(R=0.73,P<0.01).

The study on the spatial distribution of near surface air pollutants carbon dioxide( CO2) and particulate matters( PM) is essential for understanding the pollution characteristics with mobile measurements. Near surface concentrations of CO2,PM and meteorological parameters were measured in Xiamen city,China along the route passing through different functional areas using the mobile laboratory during different time periods of the day [09: 00-12: 00,13: 00-16: 00,22: 00-01: 00( local time) ] in spring( April) and fall( November),2013. Carbon dioxide,PM and meteorological parameters data were analyzed for the spatial distribution of CO2in different functional areas and the relationship of CO2and PM2. 5. During the study period,the measurements started at the northern part of the city,across the suburban area and ended at about 60 km in the southern Xiamen. The spatial distribution of CO2 along the road showed a high CO2level in the central area of the city and low values in the outlying areas. Different CO2concentrations were observed at different functional areas because of the differences in emissions from traffic and industry,the emission and absorption by vegetation,and meteorological conditions. The concentrations of CO2at different areas fell into the following order: areas with heavy traffic( 477. 33 μmol·mol- 1± 6. 11 μmol·mol- 1) > commercial residential area( 454. 95 μmol·mol- 1± 5. 45 μmol·mol- 1) > the natural scenic spot( 441. 01 μmol·mol- 1± 6. 24 μmol·mol- 1) > cultivated land( 436. 79 μmol·mol- 1± 1. 87 μmol·mol- 1) > mountain woodlands( 434. 06 μmol·mol- 1± 0. 31 μmol·mol- 1). The average CO2concentration in spring 2013 was measured to be 452. 04 μmol·mol- 1± 20. 24 μmol·mol- 1with the maximum value of 533. 10 μmol·mol- 1at the heavy traffic area in downtown Jiaheon April 12,2013 and the minimum value of 413. 25 μmol·mol- 1on April 10,2013 at the mountain woodland,which is about 23 km away from the downtown area. The mountain woodland is surrounded by a reservoir and woods and regarded as the background area. The average CO2concentration in fall 2013 was determined to be 451. 80 μmol·mol- 1± 21. 56 μmol·mol- 1with the maximum value of 526. 45 μmol·mol- 1at a heavy traffic area of Xiahe road in downtown,on November 19,2013 and the minimum value of 415. 01 μmol·mol- 1at the mountain woodland on November 10,2013. This phenomenon was called 'CO2dome'by Idso in 1998. In addition,the CO2concentrations tended to be the highest at night( 22: 00-01: 00) and the lowest in afternoon( 13: 00-16: 00). During overcast days,the CO2concentrations were generally higher than those on clear days. At different functional areas,differences between nighttime( 22: 00-01: 00) and daytime( 09: 00-12: 00 and 13: 00-16: 00) ranged from- 0. 66-29. 48 μmol·mol- 1in spring and from- 4. 01 μmol·mol- 1-33. 69 μmol·mol- 1in fall. The CO2concentrations at the urban and the suburban areas were also different in spring and autumn and at different time of the day. The CO2concentration was in significant correlation with PM2. 5( R = 0. 73,P < 0. 01) indicating the important impact of traffic pollution on the ambient CO2concentration.