公园绿地和广场空气颗粒物浓度对比及影响因素研究

Comparative Study on Air Particulate Matter Concentration Differences and Factors Between Urban Park and Urban Square

大气污染是中国城市环境面临的严峻问题之一,场地尺度的污染防治面临巨大压力。一些研究认为城市绿地对改善空气质量具有重要作用,然而也有部分研究提出了质疑,认为绿地植被加剧了空气污染。鉴于结论的不一致性,选择西安地区公园绿地丹枫园和紧邻的开敞广场作为研究对象,开展对比分析,采用更高的时间分辨率,对距道路不同水平距离的颗粒物浓度和气象因子进行为期一周的连续监测,分析其时空变化规律和影响因素。结果表明:(1)温度、气压、湿度和风速对PM2.5和PM10浓度均有显著影响,湿度和风速对颗粒物的影响存在阈值,湿度阈值为70%,风速阈值为1.8 m·s^(-1),颗粒物浓度随着湿度和风速的增大而升高,湿度和风速超过阈值时,颗粒物浓度逐渐降低,但广场风速超过阈值时,广场PM10浓度继续升高。(2)颗粒物浓度日变化呈“峰谷型”,6点至8点,19点至24点颗粒物浓度较高,样地内颗粒物浓度随水平距离增加而升高,绿地内颗粒物浓度低于广场。10点至18点颗粒物浓度较低,颗粒物浓度随距离增加而降低,绿地内颗粒物浓度高于广场。(3)对比硬质广场,绿地能有效削弱颗粒物浓度峰值和PM10浓度。结果表明绿地主要通过影响绿地风速和湿度等气象因子,调控颗粒物的扩散和沉降,可以有效阻滞和清除颗粒物,特别是粗颗粒物。研究结果能为以改善空气质量为目标的公园绿地设计提供理论依据。

Air pollution is one of the serious problems facing urban environments worldwide,and pollution prevention and control under the background of site scale is facing tremendous pressure.Some studies believe that urban green space is essential in improving air quality.However,some studies have questioned that,and they think green space vegetation exacerbates air pollution because of the inconsistency of the conclusions.An urban green space with closed and semi-open structures and the adjacent urban square in Xi’an,China,was selected as the research sample plots.With high temporal resolution,the particle matter concentrations and me-teorological factors at different horizontal distances from the road between the spaces were continuously monitored for one week.When relative humidity and the wind speed increased above certain thresholds,the particle concentration began to decrease gradu-ally,except in the urban square where PM10 concentration increased when wind speed exceeded its threshold.The diurnal variation in particulate matter concentration was double peaks and double valleys.From 6:00 to 8:00 and 19:00 to 24:00,the concentration of particulate matter was highest,the concentration of particulate matter increased with increasing distance from the road,the con-centration of particulate matter in the green space was lower than that in the square,while the concentration of particulate matter was lower from 10:00 to 18:00,the concentration of particulate matter decreased with increasing distance,the concentration of particulate matter in the green space was higher than in the square.Compared with closed green space,semi-open green space,and square,green space can effectively weaken the peak concentration of particulate matter and PM10 concentration.The results show that green space can effectively block and remove particles,especially coarse particles,by regulating the diffusion and settlement of particles mainly by affecting meteorological factors such as wind speed and humidity.This information could be used for better air pollution mitigation strategies,especially when incorporating green spaces in future urban design.