北京采暖期典型区域环境空气污染特征分析

Characteristics of Air Pollution in Typical Regions of Beijing during Heating Season

北京采暖期空气污染较非采暖期严重得多，但目前针对采暖期北京城市上风向、下风向、中心区和主干道路等典型人类活动区域的主要污染物浓度特征及其受气象条件变化影响的研究还比较缺乏，为了摸清北京市采暖期不同典型区域大气污染特征，更有针对性地制定环境空气污染防治对策，利用2014年采暖期首月（11月15日—12月14日）北京市北郊（八达岭）、南郊（永乐店）、城市中心区（天坛）、城市交通干道（永定门内大街）等典型区域的PM2.5、SO2、NOx、O3质量浓度监测数据和气象数据，分析4类代表性区域的环境空气污染特征和时空变化情况。结果表明，PM2.5是各区域冬季主要污染物，日均质量浓度在61.75~143.81μg.m-3，总体空间分布状况为南郊最严重、城市交通干道和城市中心区次之、北郊的PM2.5污染最轻，除北郊外其余监测点ρ(PM2.5)均超过二级标准限值。各区域的主要污染物略有不同，其中北郊ρ(SO2)较其他区域高，白天12:00时最低（29.09μg.m-3），夜晚18:00—次日01:00持续居高（58.8~63.19μg.m-3），这与燃煤采暖等人类活动规律一致；南郊以PM2.5、NOx混合型污染为主；城市交通干道附近ρ(NOx)和ρ(O3)较高，表明局地光化学反应NOx-O3生消机制作用明显，污染物浓度变化与人类出行时间一致。气象条件对不同污染物浓度的影响存在差异，微风无持续风向、大气扩散条件较差时，PM2.5呈现不断累积状态，SO2、NOx和O3累积效应不明显，但其单日质量浓度峰值显著增加；北风和微风反复交替、大气扩散条件总体较好时，各监测点的SO2、NOx受地区性污染源排放影响波动不大，随扩散条件转差南郊ρ(PM2.5)会迅速增加。城市交通干道机动车排放典型污染物ρ(NOx)及其二次污染物ρ(O3)随着气象条件变化其峰值在日内变化显著。

In Beijing, air pollution during the heating season is much more severe than that in non-heating seasons. In order to study the air pollution condition in typical regions, and thus to formulate the pollution controlling countermeasure more specifically, we collected and analyzed the concentration monitoring data of four typical contaminants (PM2.5, SO2, NOx and O3) as well as the meteorological data from online monitoring points (North suburban station Badaling, South suburban station Yongledian, Urban center station Temple of Heaven, Traffic monitoring station Yongding Gate Avenue) during the first month of heating season in 2014(which is from Nov. 15 to Dec 14). The results showed that PM2.5 (with the daily average concentration between 61.75~143.81μg?m-3) were the main contaminants in each zone. In aspect of space distribution, the Beijing southeast Yongledian area detected thehighest concentrations, followed by the urban traffic roads and the downtown areas. And only the Northwest Beijing Badaling areahad the relatively lower PM2.5 concentrations that were under the secondary standard limitation. The major air contaminants varied intypical regions. During the heating season, the major air contaminant in Northwest Beijing Badaling area is SO2, affected by thecoal-fired heating activities, leading to a lowest concentration is 29.09 μg?m-3 in noon and higher concentrations between 58.8~63.19μg?m-3 in night. Because of the contaminant dispersion from upwind downtown area and the local area discharging, PM2.5, and NOxare the major air contaminants in the Beijing southeast Yongledian area. NOx discharged by vehicles and its secondary pollutant O3contribute most to the air contamination in Yongding Gate Avenue, where the changing of pollutant concentrations are obviouslyrelated to the motor vehicle traffic. The impacts from meteorological conditions to different contaminant concentrations are varied.With gentle breeze, non-continuous wind or low atmospheric diffusion, the concentrations of PM2.5 in the monitoring points showedaccumulating states, which is not observed on SO2, NOx and O3 (even though their peak concentrations were significantly increased).When there were switching from north wind and breezing with higher atmospheric diffusion, concentrations of SO2 and NOx from all monitoring points did not change much; the concentrations of PM2.5 at Southeast area would noticeably increase when the diffusion condition became worse. As for the monitoring point at Yongding Gate Avenue, the concentrations of typical contaminants discharge by vehicles, such as NOx and O3, had remarkable daily fluctuation as the weather changing.