Variation in concentrations of the airborne particulate matters(PM)in three kinds of typical recreation forests in Baiwang Mountain,West Mountain area of Beijing were observed day and night in spring.Results showed that:1)Diurnal variations of PM concentrations in three kinds of typical recreation forests in West Mountain of Beijing area in spring were all synchronous.Curves of diurnal variation of PM concentrations had two peaks and two vales,and two peaks presented at 7:00-9:00 and 21:00-1:00,and two vales presented at 15:00 and 3:00-5:00 respectively.In addition,the larger proportion finer particles took the heavier total particles were in a day;2)Comparatively,peaks in day and vales at night of finer particles presented earlier than that of coarser particles,however the peaks at night were later;3)Weather conditions had influences on PM,and the finer particles were more sensitive to the conditions than the coarse particles.In general,PM concentration was higher at the state of low air temperature,high air relative humidity and soft wind.They also increased at cloudy night,especially for finer particles.
