基于城市绿地滞尘模型的上海市绿色空间滞留PM2.5功能评估

绿色空间对大气颗粒物有一定吸收滞留作用,是改善空气环境质量与维护城市生态安全的重要区域。该文基于高分2号卫星影像识别2017年上海市绿色空间,并利用城市绿地滞尘模型,结合上海市降水、风速等气象数据与空气质量监测数据,评估了绿色空间滞留PM_(2.5)功能及其差异。结果表明:2017年上海市绿色空间面积3354 km~2,可滞留PM_(2.5) 3533 t,约合单位面积滞留PM_(2.5) 10.5 kg hm~(-2) a~(-1)。从绿色空间类型来看,林地滞留PM_(2.5)能力最强,可达20.2 kg hm~(-2) a~(-1),远高于草地9.1 kg hm~(-2) a~(-1)和农田8.7 kg hm~(-2) a~(-1)的滞留能力。从季节差异来看,绿色空间夏季滞留PM_(2.5)能力最高,然后依次为秋季、春季和冬季。从植被分布格局来看,林草地和农田吸滞PM_(2.5)的能力随植被盖度的增加而提高。在区域差异上,崇明区绿色空间滞留PM_(2.5)能力最高,其余地区呈现出中心城区低、周边高的趋势。为此建议上海市重点优化中心城区的绿色空间格局,增植立体绿化与高滞尘能力树种。

PM2.5 removal service of green spaces in Shanghai based on the dust retention simulation on urban vegetation

Urban green spaces can intercept particulate matters in the air, and are often served as ecological and economical measures for the urban environment promotion and the ecological security maintenance. However, many studies at present pay more attention to the air purification at the plant scale, and few studies analyze the regional differences on the dust retention function of urban green spaces. Based on the regional dust retention model and combined with the meteorological and particulate characteristics of Shanghai, this paper assessed the PM_2.5 retention service of green spaces in 2017. The results show that there are 3354 km² green spaces in Shanghai. They could remove 3533 tons of PM_2.5, with the average retention capacity of 10.5 kg hm^-2 a^-1. In Shanghai, the forestland can provide the strongest retention capacity of 20.2 kg hm^-2 a^-1. The retention capacity of the grassland and the farmland are both lower with 9.1 kg hm^-2 a^-1 and 8.7 kg hm^-2 a^-1, respectively. The urban green space in summer shows the strongest dust retention capacity, and descends successively in autumn, spring and winter. The retention ability of the woodland, the grassland, and the farmland increases with the increase of the vegetation coverage. In addition, the green spaces in Chongming district present the highest retention capacity of dust PM_2.5 in 2017, and those in other regions emerge the low value in the central urban and the high value in surrounding areas. Therefore, Shanghai should implement the pattern optimization of the green space structure and the green corridor in the urban area. Besides, Shanghai should increase more vertical greening and plant more trees with higher retention capacity in order to promote the PM_2.5 removal service.