Abstract
As fine particle (FP) pollution is harmful to humans, previous studies have focused on the mechanisms of FP removal by forests. The current study aims to compare the FP removal capacities of urban forests and wetlands on the leaf, canopy, and landscape scales. Water washing and scanning electron microscopy are used to calculate particle accumulation on leaves, and models are used to estimate vegetation collection, sedimentation, and dry deposition. Results showed that, on the leaf scale, forest species are able to accumulate more FP on their leaf surface than aquatic species in wetlands. On the canopy scale, horizontal vegetation collection is the major process involved in FP removal, and the contribution of vertical sedimentation/emission can be ignored. Coniferous tree species also showed stronger FP collection ability than broadleaf species. In the landscape scale, deposition on the forest occurs to a greater extent than that on wetlands, and dry deposition is the major process of FP removal on rain-free days. In conclusion, when planning an urban green system, planting an urban forest should be the first option for FP mitigation.
Highlights
As fine particle (FP) pollution is harmful to humans, previous studies have focused on the mechanisms of fine particles (FP) removal by forests
Urban green systems, including urban forests, wetlands, and green belts, have gained recognition for their contribution to air cleaning[3], and relevant studies have mainly focused on the leaf, canopy, and landscape scales to estimate the roles of plants and urban green systems in particle removal
Different groove widths perform differently in capturing particles, and a previous study reported that the amount of particles collected increases with increasing groove width[9]. In contrast to these reports, in the present study, we found the opposite result: T. orientalis and I. setosa have wider grooves than P. australis and I. wilsonii but the former accumulates a smaller amount of FP than the latter
Summary
As fine particle (FP) pollution is harmful to humans, previous studies have focused on the mechanisms of FP removal by forests. Urban green systems, including urban forests, wetlands, and green belts, have gained recognition for their contribution to air cleaning[3], and relevant studies have mainly focused on the leaf, canopy, and landscape scales to estimate the roles of plants and urban green systems in particle removal. Results of simulated experiments have shown that the FP collection speed of coniferous trees is about 7.4 μg m−3 s−1 while that of broadleaf species can reach 33.5 μg m−3 s−1 in the full-leaf stage[15] Contrasting with these findings, research conducted next to a highway area in New York, USA, showed that the presence of a green belt between the source and the downwind area reduces the frequency and intensity of concentration spikes but www.nature.com/scientificreports/. The effect of tree belts in mitigating FP in a specific region requires further study
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