The concentration of air PM10 in six types of green lands in campus of Tsinghua university was measured. The results showed that PM10 concentration exhibited obvious daily and monthly variation,and also had remarkable difference among different seasons. However there was no remarkable difference in concentration of PM10 within the same season over all types of green lands. As for average concentration,the value was lower in arbor land of spring,autumn and winter,and in lawn of summer. The concentration of PM10 was 43% higher in cloudy days than that of sunny ones. Moreover,the difference increased to 137% between cloudy day after raining and sunny day after raining because of the clarification of rain.
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.
The research adopts open sampling method and TCT-GC/MS(Thermodesorption Cold Trap-Gas Chromatography/Mass Spectrometery) apparatus to collect and analyze the volatile organic compounds(VOCs) of Platycladus orientalis forest,with the intention of researching the compounds and diurnal variation of VOCs of P.orientalis forest in natural state in Beijing Western Hills in spring.The results are as follows:(1) There are 160 kinds(11 categories) of volatile organic compounds,containing Alkyl Hydrocarbon,Ketone,Alcohol,Acid,Aldehyde,Alkene,Ester,Aromatic hydrocarbon,Ether,Hydroxybenzene and Amide.The content of Alkyl Hydrocarbon,Ketone,Acid and Aldehyde occupy a greater percentage among all compounds.(2) The diurnal variation curve of total volatile organic compounds(TVOC) is characterized as "one peak at 11:00(36.44%) and one vale at 3:00(12.76%)".Generally,the concentration at daytime is higher than that of night,and higher in morning than in afternoon,with the maximum at noon.(3) The change of Alkyl Hydrocarbon concentration is greater in the morning and about midday,less in the afternoon and night.The diurnal variation curve of Ketone concentration appears as "three peaks and three vales".1:00,5:00—7:00 and 11:00 are peak time,3:00,9:00 and 17:00 are vale time.As to Acid,its concentration appears two obvious phases: the higher phase is from 9:00 to 17:00,with the maximum at 11:00,and the lower phase is from 19:00 to 7:00,with the minimum at 5:00.Concerning Aldehyde concentration,17:00 and 19:00 are the higher phases and also has obvious difference with other time,while the lower phrase has no obvious difference with each other.(4) Alkene is the most important compound to human health.Its concentration appears as "one peak" at 15:00,which has obvious difference with other time.Totally,its content at daytime is higher than that at night,and higher in afternoon than in morning.
