城市空气污染对周边区域空气质量的影响

Impact of urban air pollution on surrounding areas in Beijing,Tianjin,and Hebei Provinces

京津冀地区是全球以PM_(2.5)为首要污染物的空气污染最严重的区域之一,并已严重制约区域发展。大区域尺度上(例全国尺度)开展城市与其周边区域的PM_(2.5)的研究通常直接比较二者的浓度差异,以定量地评估城市PM_(2.5)污染对周边区域的影响,但这种方法在小区域较难精细地刻画城市对周边区域的影响的方向性和距离性差异。利用京津冀地区13个城市2000年,2005年,2010年,2015年PM_(2.5)浓度和土地覆盖类型数据,以城市重心到城市边界的平均距离为基本距离,建立每个城市的一级(一倍基本距离)和二级(二倍基本距离)缓冲区,然后将缓冲区分成8个象限,以定量分析城市PM_(2.5)污染对周边区域影响的方向性和距离差异。结果发现:(1)2000—2015年,京津冀城市群各地级市与周边区域空气质量时空分布分为以下两种模式:第一种模式是城区浓度高,周边区域低;第二种模式是城区浓度低,周边区域高且浓度差异很小。(2)各地级市对周边区域影响程度和范围呈上升趋势,并且这种影响具体表现在距离性和方向性两方面:(1)大部分城市距离城区越远,受城市PM_(2.5)污染的潜在影响越大。(2)2000—2015年,除天津、廊坊、衡水和沧州,其余城市空气污染对周边影响的方向性特征差异显著。通过建立城市空气污染对周边区域定量化方法并在京津冀开展实证研究,拓展了城市空气污染对周边区域空气质量影响研究的方法体系,为定量地开展城市化的生态环境效应研究提供了方法和实证拓展。

The Beijing-Tianjin-Hebei region is one of the most air-polluted areas in the world where PM^（2.5） has been identified as the major air pollutant that has become the most restrictive factor in regional development.The study of PM^（2.5） in cities and surrounding areas on a large regional scale（e.g.,national scale） usually directly compares concentration differences and evaluates the impact of urban PM^（2.5） pollution on the surrounding areas simply and quantitatively.This method of assessment of cities and surrounding areas is difficult to apply to small areas to quantify and analyze differences in pollutant direction and distances.Based on the data of PM^（2.5） concentrations and land cover types of 13 cities in Beijing,Tianjin,and Hebei Provinces in 2000,2005,2010,and 2015,the average distance from the city center to the urbanborder was used as the basic distance reference,first-（one-time basic distance） and second-level（two-times basic distance） buffer analyses were performed for each urban area,which was then divided into eight quadrants to quantitatively analyze the impact of urban PM^（2.5） pollution on the surrounding area to determine differences in pollutant direction and distance.The results are as follows：（1） the spatial-temporal distribution of air quality in all prefecture-level cities and surrounding areas in Beijing,Tianjin,and Hebei in 2000—2015 was divided into the following modes：first,high concentrations in urban areas and low concentrations in the surrounding areas;second,low concentrations in urban areas,high concentrations in surrounding areas,and the difference of concentrations is small;（2） the impact and scope of the surrounding cities on the surrounding areas is increasing,and is manifested in two aspects：distance and direction：（1） the farther the majority of the cities are from the urban area,the greater the potential impact of cities on the surrounding areas;（2） in 2000—2015,except for Tianjin,Langfang,Hengshui,and Cangzhou,the other cities had significant differences in the directional characteristics of air pollution.In this study,a quantitative method was established to analyze the impact of urban PM^（2.5） pollution on the surrounding area in Beijing,Tianjin,and Hebei Provinces,and expand the methodology for studying the impact of urban air pollution on the air quality in the surrounding areas.Research on environmental effects provides methodological and empirical methods to quantitatively analyze urban ecology.