Global Centre for Clean Air Research (GCARE), Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, Surrey, United Kingdom.
Global Centre for Clean Air Research (GCARE), Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, Surrey, United Kingdom.
Environ Int. 2022 Jan;158:106883. doi: 10.1016/j.envint.2021.106883. Epub 2021 Sep 25.
Built-up environments limit air pollution dispersion in street canyons and lead to complex trade-offs between green infrastructure (GI) usage and its potential to reduce near-road exposure. This study evaluated the effects of an evergreen hedge on the distribution of particulate matter (PM, PM, PM), black carbon (BC) and particle number concentrations (PNCs) in a street canyon in West London. Instrumentation was deployed around the hedge at 13 fixed locations to assess the impact of the hedge on vertical and horizontal concentration distributions. Changes in concentrations behind the hedge were measured with reference to the corresponding sampling point in front of the hedge for all sets of measurements. Results showed a significant reduction in vertical concentrations between 1 and 1.7 m height, with maximum reductions of -16% (PM and PM) and -17% (PM) at ∼1 m height. Horizontal concentrations revealed two zones between the building façade and the hedge, with opposite trends: (i) close to hedge (within 0.2 m), where a reduction of PM and PM was observed, possibly due to dilution, deposition and the barrier effect; and (ii) 0.2-3 m from the hedge, showing an increase of 13-37% (PM) and 7-21% (PM), possibly due to the blockage effect of the building, restricting dispersion. BC showed a significant reduction at breathing height (1.5 m) of between -7 and -50%, followed by -15% for PNCs in the 0.02-1 µm size range. The ELPI + analyser showed a peak of ∼30 nm. The presence of the hedge led to a ∼39 ± 32% decrease in total PNCs (0.006-10 µm), suggesting a greater removal in different modes, such as a 83 ± 12% reduction in nucleation mode (0.006-0.030 µm), 74 ± 15% in ultrafine (≤0.1 µm), and 34 ± 30% in accumulation mode (0.03-0.3 µm). These findings indicate graded filtering of particles by GI in a near-road street canyon environment. This insight will guide the improved design of GI barriers and the validation of microscale dispersion models.
建成环境限制了街道峡谷中空气污染的扩散，导致绿色基础设施（GI）的使用与其减少近路暴露的潜力之间存在复杂的权衡。本研究评估了常绿树篱对伦敦西部一条街道峡谷中颗粒物（PM、PM、PM）、黑碳（BC）和颗粒数浓度（PNC）分布的影响。在 13 个固定位置围绕树篱部署仪器，以评估树篱对垂直和水平浓度分布的影响。所有测量集都参考树篱前的相应采样点来测量树篱后面浓度的变化。结果表明，在 1 到 1.7 米高度之间，垂直浓度有显著降低，最大降低幅度分别为 -16%（PM 和 PM）和 -17%（PM），在约 1 米高度。水平浓度在建筑立面前面和树篱之间揭示了两个区域，呈现相反的趋势：（i）靠近树篱（在 0.2 米内），观察到 PM 和 PM 的减少，可能是由于稀释、沉积和屏障效应；（ii）在 0.2-3 米距离，观察到 13-37%（PM）和 7-21%（PM）的增加，可能是由于建筑物的阻塞效应限制了扩散。BC 在呼吸高度（1.5 米）显示出-7 至-50%之间的显著降低，随后在 0.02-1 µm 范围内的 PNC 降低-15%。ELPI+分析仪显示出约 30nm 的峰值。树篱的存在导致总 PNC（0.006-10 µm）减少约 39±32%，表明不同模式下的去除率更高，例如在核模态（0.006-0.030 µm）中减少 83±12%，在超细模态（≤0.1 µm）中减少 74±15%，在积累模态（0.03-0.3 µm）中减少 34±30%。这些发现表明，在近路街道峡谷环境中，GI 对颗粒物进行了分级过滤。这一见解将指导 GI 屏障的改进设计和微尺度扩散模型的验证。
