US EPA, Office of Research and Development, National Risk Management Research Laboratory, Research Triangle Park, NC, USA.
Sci Total Environ. 2012 Mar 1;419:7-15. doi: 10.1016/j.scitotenv.2011.12.002. Epub 2012 Jan 26.
Roadside barriers, such as tree stands or noise barriers, are prevalent in many populated areas and have been shown to affect the dispersion of traffic emissions. If roadside noise barriers or tree stands are found to consistently lower ground-level air pollution concentrations in the near-road environment, this may be a practical strategy for reducing exposures to air contaminants along populated traffic corridors. This study measured ultrafine particle (UFP) concentrations using an instrumented mobile measurement approach, collecting data on major roadways and in near-road locations for more than forty sampling sessions at three locations in central North Carolina, USA. Two of the sampling sites had relatively thin tree stands, one evergreen and one deciduous, along a portion of the roadway. The third sampling site had a brick noise wall along a portion of the road. At 10 m from the road, UFPs measured using a mobile sampling platform were lower by approximately 50% behind the brick noise wall relative to a nearby location without a barrier for multiple meteorological conditions. The UFP trends at the vegetative barrier sites were variable and the barrier effect is uncertain. In some cases, higher concentrations were observed behind the vegetative barrier, with respect to the clearing, which may be due to gaps in the thin tree stands allowing the transport of traffic-related air pollution to near-road areas behind the vegetation. On-road sampling revealed no consistent difference in UFP levels in on-road portions of the road with or without a roadside barrier present. These findings support the notion that solid roadside barriers may mitigate near-road impact. Given the co-benefits of vegetative barriers in the urban landscape, research regarding the mitigation potential of vegetative barriers of other configurations (e.g., greater density, wider buffer) is encouraged.
路边障碍物，如树桩或隔音墙，在许多人口密集地区很常见，并且已经证明会影响交通排放的扩散。如果路边隔音墙或树桩被发现能持续降低近路环境中的地面空气污染浓度，那么这可能是减少人口稠密交通走廊中空气污染物暴露的一种实用策略。本研究使用仪器化移动测量方法测量了超细颗粒（UFP）浓度，在美国北卡罗来纳州中部的三个地点进行了四十多次采样，收集了主要道路和近路位置的数据。两个采样点的道路旁有相对较薄的树桩，一个是常绿的，一个是落叶的。第三个采样点的道路旁有一堵砖制隔音墙。在距道路 10 米处，使用移动采样平台测量的 UFPs 在砖制隔音墙后面的浓度比附近没有障碍物的地方低约 50%，这是多种气象条件下的结果。植被屏障处的 UFP 趋势变化不定，而且屏障的效果不确定。在某些情况下，在植被屏障后面观察到更高的浓度，相对于空旷地带，这可能是由于薄树桩的间隙允许与交通有关的空气污染传输到植被后面的近路区域。道路采样显示，有或没有路边障碍物的道路上的 UFP 水平没有一致的差异。这些发现支持了这样一种观点，即固体路边障碍物可能减轻近路影响。鉴于植被屏障在城市景观中的共同益处，鼓励研究其他配置（例如，更高的密度、更宽的缓冲区）的植被屏障的缓解潜力。
