[Dust absorption effect of urban conifers in northeast China]

Dust pollution is much heavier in winter than in other seasons in the cities of Northeast China, because the urban heating system consumes mainly coal as energy resources. Deciduous trees can hardly absorb dust because of their defoliation, and hence, urban conifer trees become more important in dust absorption in winter. This paper studied the dust absorption ability of 7 conifers under the same and different dust pollution status in Shenyang city, Northeast China. The results showed that the dust absorption ability of conifers was decreased in the order of Abies holophilla > Picea mongolica > P. koraiensis > Taxus cupidata > Pinus bungeana > P. armandi > P. tabulaeformis. Different conifers had different surface structures. Pinus bungeana, P. armandi and P. tabulaeformis had smooth surfaces, their cells and stomata arranged in order, and hence, their dust absorption ability was poor. P. koraiensis, Abies holophilla and Taxus cupidata had coarse surfaces, and their cells and stomata arranged out of order. There were even many tubercular things on the surface of P. koraiensis, and hence, their dust absorption ability was stronger. The dust absorption ability of conifers was related the shape of their leaf sections. The upper leaf surface of Pinus bungeana and P. tabulaeformis was arc, not opted to absorb the dust. The leaf section of P. armandi was prism, and its upper surface was narrow, and hence, its dust absorption ability was also poor. The leaves of Picea mongolica and P. koraiensis had four edges, their upper surfaces were broader and flatter than the former three species, and hence, they had stronger dust absorption ability. The leaf section's shape of Abies holophilla and Taxus cupidata was also broad and flat, which made the dust absorption ability of the two latter's was stronger than other three Pinus species and two Picea species.