Time Series Analysis of Size-Segregated Nitrate and Sulfate Particles at Uji during Springtime

概要

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Continuous monitoring was performed to characterize temporal variations of size-segregated sulfate and nitrate particles with high time resolution at Uji during the springtime (April 1 to May 12, 2005) including Kosa events. Simultaneous measurements were also carried out for gaseous components (NO3, SO2, O3), PM2.5 BC, particle number concentration and some meteorological parameters. Nitrate and sulfate concentrations were measured by the R & P Model 8400N equipped with PM 1 and PM 10 inlets and 8400S with similar inlets, respectively. The time series of the size-segregated sulfate and nitrate measurements were analyzed in the frequency space with the corresponding power spectra. Significant peaks were found in the power spectra at the frequencies of 1 and 1/ 3.5 per day for nitrate (both fine and coarse) and of 1/ 2.7 per day for coarse sulfate. The average diurnal variation of the 1-hour-averaged nitrate concentration in fine particles showed a distinct peak around 8 a. m. and quite a similar pattern was obtained for NO3 and BC. This result indicates that traffic contributes the diurnal periodicity in the spectrum. The comparison between the inverse of the band-pass filtered power spectrum and the time series of particle number concentration suggested that the 3.5 day periodicity for coarse nitrate may be attributed to the modified components of Kosa particles.
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