College of Resource and Environment, Qingdao Agricultural University, Qingdao, 266109, Shandong, China.
Environ Sci Pollut Res Int. 2019 Jul;26(19):19606-19614. doi: 10.1007/s11356-019-05241-8. Epub 2019 May 11.
Atmospheric particulate matter (APM) is temporarily settled on the leaf surface of plants and will return to the air via the resuspension process under certain meteorological conditions. How leaf surface characteristics affect the resuspension of settled APM on the leaf surface has been rarely studied. Therefore, the resuspension of APM after settling on plant leaves was analyzed using four common urban greening species, including Prunus triloba, Platanus acerifolia, Lonicera maackii, and Cercis chinensis. The results show that the leaf hair density has a significantly positive correlation with the maximum particulate matter (PM) retention and natural PM retention (p < 0.05). Under the same wind speed, the proportions of the resuspended PM that settled on the leaf surfaces of the four plant species increase with the wind blowing time. During the same wind blowing time, the resuspension rate of the settled PM on leaf surfaces of P. triloba, P. acerifolia, and L. maackii increase with the wind speed. The leaf hair and stomatal density is negatively correlated to the resuspension rate of PM under the wind speed of 1 m s (p < 0.05), and the stomatal density is also negatively correlated to the resuspension rate of PM under the wind speed of 5 m s for 10 min or 20 min (p < 0.05). However, as the wind speed further increase, the leaf characteristics are no longer correlated to the resuspension rate of PM (p > 0.05). These results indicate that when the wind force (wind speed + wind blowing time) is small, the stomatal density and leaf hair density have a significant effect on APM resuspension. When the wind force is large, the influence of leaf surface structure on APM resuspension becomes less profound. APM resuspension is comprehensively affected by the external wind and the leaf surface characteristics, and these two factors jointly determine the fate of the PM after it settles on leaves.
大气颗粒物（APM）暂时沉降在植物叶片表面，在一定气象条件下通过再悬浮过程返回大气。叶片表面特征如何影响沉降在叶片表面的 APM 的再悬浮，这一问题很少得到研究。因此，本研究选用常见的四种城市绿化树种，包括紫叶李（Prunus triloba）、悬铃木（Platanus acerifolia）、金银木（Lonicera maackii）和紫荆（Cercis chinensis），分析了 APM 沉降后再悬浮的情况。结果表明，叶片毛密度与最大颗粒物（PM）截留率和自然 PM 截留率呈显著正相关（p < 0.05）。在相同风速下，四种植物叶片表面沉降 PM 的再悬浮比例随风吹时间的增加而增加。在相同的风吹时间内，紫叶李、悬铃木和金银木叶片表面沉降 PM 的再悬浮率随风速的增加而增加。在风速为 1 m s 时，叶片毛密度和气孔密度与 PM 的再悬浮率呈负相关（p < 0.05），在风速为 5 m s 且吹风 10 min 或 20 min 时，气孔密度与 PM 的再悬浮率也呈负相关（p < 0.05）。然而，随着风速的进一步增加，叶片特征与 PM 的再悬浮率不再相关（p > 0.05）。这些结果表明，当风力（风速+风吹时间）较小时，气孔密度和叶片毛密度对 APM 再悬浮有显著影响。当风力较大时，叶片表面结构对 APM 再悬浮的影响变得不那么明显。APM 的再悬浮受到外部风的和叶片表面特征的综合影响，这两个因素共同决定了 PM 沉降在叶片上的命运。
