Quantifying the characteristics of particulate matters captured by urban plants using an automatic approach
Jingli Yan
,
Lin Lin
,
Weiqi Zhou
,
Lijian Han
,
Keming Ma
DOI:10.1016/j.jes.2015.11.014
Received August 03, 2015,Revised November 26, 2015, Accepted November 27, 2015, Available online January 07, 2016
Volume 28,2016,Pages 259-267
It is widely accepted that urban plant leaves can capture airborne particles. Previous studies on the particle capture capacity of plant leaves have mostly focused on particle mass and/or size distribution. Fewer studies, however, have examined the particle density, and the size and shape characteristics of particles, which may have important implications for evaluating the particle capture efficiency of plants, and identifying the particle sources. In addition, the role of different vegetation types is as yet unclear. Here, we chose three species of different vegetation types, and firstly applied an object-based classification approach to automatically identify the particles from scanning electron microscope (SEM) micrographs. We then quantified the particle capture efficiency, and the major sources of particles were identified. We found (1) Rosa xanthina Lindl (shrub species) had greater retention efficiency than Broussonetia papyrifera (broadleaf species) and Pinus bungeana Zucc. (coniferous species), in terms of particle number and particle area cover. (2) 97.9% of the identified particles had diameter ≤ 10 μm, and 67.1% of them had diameter ≤ 2.5 μm. 89.8% of the particles had smooth boundaries, with 23.4% of them being nearly spherical. (3) 32.4%–74.1% of the particles were generated from bare soil and construction activities, and 15.5%–23.0% were mainly from vehicle exhaust and cooking fumes.
