摘要:北京城市与区域臭氧浓度逐年升高，对自然生态系统已经构成影响。但地表臭氧在北京城市与远郊梯度空间上的连续递变特征机制尚不清楚。采用移动监测车，搭载臭氧分析仪，选择夏季典型臭氧污染天气，以北京教学植物园为对照点，从北京城市中心向西北远郊方向，多点位连续测定地表臭氧浓度。通过分析臭氧浓度和采样点周围归一化植被指数（NDVI）的关系以及典型臭氧污染情况下的天气形势和气团轨迹，探讨北京城市和区域臭氧浓度连续空间变化特征及机制。结果表明：（1）北京西北山区森林区域臭氧浓度显著高于"城市区域"，约为城市区域的2.00倍。十三陵是地表臭氧浓度的分界点，从十三陵开始臭氧浓度陡然升高，在西北山区方向保持在高水平。空间上从高到低的顺序是西北山区（254.68μg/m³） > 对照点教学植物园（220.89μg/m³） > 城市支路（162.84μg/m³） > 城市快速路和高速路（103.24μg/m³）；（2）植被分布影响臭氧空间格局。在相同时间范围内，臭氧浓度和NDVI正相关，随NDVI增加臭氧浓度呈Logistic增长；（3）西北山区地表臭氧空间变异系数为0.11，城市支路上平均为0.28，城市快速路上为0.26，高速公路上为0.36。山区地表臭氧浓度的空间变异系数最小，高速公路最大，城市快速路、城市支路空间变异较大；（4）大范围均压场、高压后部、低压前部等稳定型天气型易造成南向弱气流，能够把空气污染物输送到西北远郊，但本研究中监测到的西北山区高浓度臭氧并非当天从城区输送而来。北京城市与区域臭氧格局与植被的关系及成因需要深入研究。



Abstract:The increase of surface ozone concentrations in summer is raising the risk on ecosystem health. Site sampling based near-surface ozone concentration has been well analyzed in Beijing. However, very scant work has been done to reveal the continuous changing pattern at urban and rural gradient. Thus, in this research, using mobile vehicle equipped with ozone analyzer,we monitored the ozone concentrations in a typical urban-rural gradient, from central urban to north-west rural gradient of Beijing on typical ozone polluted days in summer, meanwhile, ozone concentrations at Beijing Teaching Botanical Garden which worked as the control was monitored and applied. The location including longitude and latitude of mobile vehicle, the ozone concentrations of the samplers and control sites were obtained at the same start time and frequency. Mean NDVI within each site's 50 meters' buffer was correlated with the ozone concentration. Additionally, to discern the climatic mechanism of ozone distribution pattern of the monitoring days, we did synoptic type analysis using GrADS 2.1 and analyzed the backward air mass trajectories using HYSPLIT model. Results followed:(1)the ozone concentrations were significant higher in north-west mountains than those in other urban and suburban areas. The sequence is:North-west mountain region(254.68μg/m³) > control site, Beijing Teaching Botanical Garden(220.89μg/m³) > branch urban road(162.84 μg/m³) > urban main road and freeway(103.24 μg/m³);The landmark is Min tomb and the ozone concentrations north-west to this break point, where is mountains, were about 2.00 times than those measured at the urban and suburban regions. (2) the distribution of plants affects surface ozone pattern. In the same time, ozone concentrations increase with NDVI with a significant Logistic relationship. (3) the spatial variability coefficients of ozone concentrations in mountain regions were lower than those in free way, urban motor road and branch road; the coefficients in mountain area is 0.11, on branch road of urban is 0.28, on main motor road of urban is 0.26, on free way is 0.36; (4) The precursors of ozone in the north-west Mountains were partly from the urban region due to wind. Large scale uniform pressure field, the background of high pressure field, and the forward of low pressure easily lead to weak south or south-east air flow, which pushed air from urban to north-west rural region, and might partly explain the cause of the ozone pollution pattern in summer in Beijing urban and rural region.





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