严寒地区城市街谷底层可吸入颗粒物浓度分布

Experimental Study on Concentration Distribution of Inhalable Particles at the Bottom of Urban Street Canyon in Severe Cold Area

以东北三省的省会城市为代表,对街道峡谷底层可吸入颗粒物PM10的质量浓度进行了实地监测。街谷底层PM10浓度分布状况既受到自然气候条件的制约,又受到以绿化植物为主的街谷设施以及人为活动的强烈影响,二者共同作用下形成了如下特征:①街谷设施扰乱了理想状态下的街谷气流,其所影响的范围为0~22 m;②PM10浓度在每日的9:00和18:00出现峰值,街谷绿化使颗粒物的扩散延迟了约3 h;③季节水平上街谷底层PM10浓度差异显著,冬季高出夏季107 mg·m^-3;④不同绿化郁闭度与疏透度对PM10浓度的垂直分布与水平分布产生的影响,夏季均大于冬季;街谷绿化使PM10滞留在9 m以下、两条隔离带之内的机动车道空间内,而在9~22 m的空间以及隔离带外侧的人行道空间里,颗粒物浓度得到消减;⑤街谷底层PM10日均值与气象参数之间存在显著的线性相关性,相关性顺序为湿度>温度>风速。这些特征为严寒地区城市规划设计以及道路绿化设计提供了理论依据。

Provincial capitals of the three northeastern provinces in China were taken as examples,and the method of site inspection was used to monitor the concentration of particulate matter 10 at the bottom of the street canyon.It is known that the distribution of PM10 concentration in the bottom of the street canyon is not only restricted by the natural climatic conditions,but also influenced by the street canyon facilities such as green plants dominated by human activities.Those features below were formed under the effect of both factors.Under the ideal condition,the air glow in the street canyon is disturbed by the street canyon facilities,and the affect area is about 0 m to 22 m.The concentration of PM10 peaks at 9:00 and 18:00 every day,and the diffusion of PM10 is delayed about 3 h because of Street Canyon Greening.The concentration of PM10 in the bottom layer of the street canyon is significantly 107 mg·m^-3higher in winter than that in summer.The influence created by different greening crown density and porosity on vertical and horizontal distribution of PM10 concentration is greater in summer than in winter.PM10 is influenced by the greening of street canyon that it stays under the line of 9 m and within the stays within the two isolation zones in motorways,while the concentration of particulates decreases in the space of 9 m to 22 m and the space of sidewalk outside the isolation zones.There is a significant correlation between the meteorological parameters and daily mean values of PM10 at the bottom of street canyon,the humidity is most related,then the temperature,and wind speed is the least.All those findings provide a theoretical basis for urban planning and design as well as road greening design in severe cold area.