Abstract: We explored the spatiotemporal variations of different sized particulate matter (PM) contents in leaves of six common greening tree species located in different functional areas of Urumqi central urban region, i.e., traffic area (TA), residential area (RA), park area (PA), and landscape ecological forest (LA; different altitudes of Yamalik Mountain: 844, 869, 910, 930 and 960 m). The retention of different sized PMs (PM_0.2-3, PM_3-10, PM_>10 and PM_total) were measured, and the spatiotemporal variation patterns of retention were analyzed. There were significant interspecific differences in retention of different sized PM in leaves among the six species across the TA, RA, and PA functional areas (P<0.05), with a pattern of different life-form types being evergreen trees > deciduous shrubs > deciduous trees. The retention of PM_3-10 and PM_total of different green tree species showed Pinus sylvestris var. mongolica > Picea asperata > Ulmus pumila > Ligustrum obtusifolium > Ulmus densa > Fraxinus rhynchophylla. The PM_0.2-3 retention of Picea asperata was higher than that of Pinus sylvestris var. mongolica, and the PM_>10 retention of Ligustrum obtusifolium was higher than that of Ulmus pumila. Temporally, the retention of different sized PMs of different green tree species gradually increased with time, and the lowest value was obtained on day 3 and the highest value was obtained on day 23 after heavy rain (>20.4 mm). Spatially, the retention of different sized PMs of the six species in TA was the highest, medium in RA, and the lowest in PA. The retention of different sized PMs in Ulmus pumila in Yamalik Mountain varied significantly with altitudes. The retention of PM_0.2-3 and PM_3-10 by Ulmus pumila in Yamalik Mountain increased gradually with the altitude, while there was no significant change in the retention of PM_>10 and PM_total. In conclusion, the common green tree species in Urumqi showed spatial and temporal differences in PM retention. Therefore, reasonable selection and management of greening tree species under different polluted environments is helpful to effectively exert the ability of tree species to mitigate atmospheric particulate matter.

Key words: functional area, greening tree species, particle size, particle retention, temporal and spatial variation