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J. HOVORKA 1 , M .B RANI Š 1 , J. SCHWARZ 2 h ovorka @ cesnet.cz , branis @natur.cuni.cz, [email protected] 1 Institute for Environmental Studies, Faculty of Science, Charles University in Prague, Benátská 2, 128 01 Prague 2, Czech Republic - PowerPoint PPT Presentation
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DIURNAL PATTERN OF SUBMICRON AEROSOL SIZE/MASS DISTRIBUTIONS IN URBAN ATMOSPHERE,
PRAGUE WINTER 2004/2005
J. HOVORKA1, M .BRANIŠ1, J. SCHWARZ2
[email protected], [email protected], [email protected]
1 Institute for Environmental Studies, Faculty of Science, Charles University in Prague, Benátská 2, 128 01 Prague 2, Czech Republic
2 Institute of Chemical Process Fundamentals AS CR, Rozvojová 135, 165 02 Prague 6, Czech Republic
The study was conducted within the project „Comprehensive size resolved characterization of atmospheric particulate matter in Prague“ supported by GACR grant No. 205/03/1560
Roof-top (25 m above street level) sampling on building situated on the University Botanic garden (3.5 ha) in Prague centre, NO street canyon conditions
Parameters measured at the station: 5 min. integrates of aerosol size distributions 14 – 710 nm (SMPS-3936L25, TSI)
15 min. integrates of gaseous components concentrations NOx, volatile hydrocarbons CH4 and non-methane – NMHC, CO, O3, SO2 by automatic analysers (Horiba-360 series)
15 min. integrates of wind speed, wind direction, temperature, relative humidity, UV-A,B
24/1/2005, Monday
24/12/2004, Friday12/12/2004, Sunday
24/1/2004, Monday 22/12/2004, Wednesday
Lower values of number and mass concentrations of aerosol particles suspended in the urban air were clearly associated with higher wind speed values regardless the type of day
During cal/moderate wind speed conditions diurnal pattern of aerosol size distribution vary significantly from day to day. The diurnal pattern is characteristic result of multi-phase system influence. Every day has to be treated separately to reveal possible causes of the diurnal patter
Typically, the total aerosol number was dominated by the influence of mobile sources (GMD about 50 nm), while the total aerosol mass is predominantly influenced by stationary (natural gas burning) sources (GMD 80-100 nm)
Working days usually exhibit morning ( 8-10 a.m.) peaks associated with traffic rush hours
Majority of days exhibit late evening, round midnight and very early morning maximas in number size ditributions associated with higher natural gas burn-up in the stationary heating sources nearby
Not a one true nucleation event (“banana” shape graph) was recorded during the measured period
Conclusions
Weekends/holidays
• Sunday 12/12/2004:
By low temperatures induced higher natural
gas burn-up (indicated by CH4, further in the
text abbreviated as “by …”) and calm air
condition resulted in midnight maximum.
Contrary to this maximum, near midday peak
is caused by sources of in-complete
combustion (by CO). This should be
combination of again natural gas burn-up( by
GMD 90 and by CH4, NO2) and mobile
sources (by NO, NMHC) also characterized
by an immediate increase in particle numbers
and maximas in aerosol number distribution
near 50 nm sizes.
• Friday 24/12/2004, Christmas day
Low level of transportation and mainly high
wind speed resulted in exceptionally low
aerosol number and mass. Near-to-midnight
peak is caused by gradually increasing
natural gas burn-up starting from 4 p.m. (by
CH4) when people stay home. Higher
temperature also induced lower natural gas
consumption
Working days
• Monday 24/1/2005:
Low number concentrations are gradually
increasing from 4 a.m. due to gas burn-up
(by CH4) culminating near 9 and 10:30 a.m.
and 3 p.m. in coincidence with transportation
(NO, NMHC). It is difficult to distinguish
influence of mobile from stationary ones on
aerosol number and mass. Sudden peaks in
total aerosol mass at 8 a.m and 4 and 6 p.m.
may indicate the higher activity of stationary
sources.
• Wednesday 22/12/2004:
Low temperature during night-time induced
high natural gas burn-up (by CH4, CO, NO2)
producing aerosol with GMD 90-100 nm
sizes. Then the maximas are formed with
GMD 50 nm at 8,9 and 10 a.m. typically
caused by transportation (by NO, NMHC).
Though the concentrations of NO2 remains
high, gradual increase in temperature and
wind speed causes gradual decrease in total
aerosol number and mass . Smog episode
day.