Atmospheric Chemistry and Physics, vol. 11, issue 4 (2011) pp. 1565-1580
Atmospheric particle number size distributions (size range 0.003–10µm) were measured between March 2008 and August 2009 at Shangdianzi (SDZ), a rural re-search station in the North China Plain. These measurements were made in an attempt to better characterize the tropo-spheric background aerosol in Northern China. The mean particle number concentrations of the total particle, as well as the nucleation, Aitken, accumulation and coarse mode were determined to be 1.2 ± 0.9 × 10 4 , 3.6 ± 7.9 × 10 3 , 4.4 ± 3.4 × 10 3 , 3.5 ± 2.8 × 10 3 and 2 ± 3 cm −3 , respec-tively. A general finding was that the particle number con-centration was higher during spring compared to the other seasons. The air mass origin had an important effect on the particle number concentration and new particle forma-tion events. Air masses from northwest (i.e. inner Asia) fa-vored the new particle formation events, while air masses from southeast showed the highest particle mass concentra-tion. Significant diurnal variations in particle number were observed, which could be linked to new particle formation events, i.e. gas-to-particle conversion. During particle for-mation events, the number concentration of the nucleation mode rose up to maximum value of 10 4 cm −3 . New par-ticle formation events were observed on 36% of the effec-tive measurement days. The formation rate ranged from 0.7 to 72.7 cm −3 s −1 , with a mean value of 8.0 cm −3 s −1 . The value of the nucleation mode growth rate was in the range of 0.3–14.5 nm h −1 , with a mean value of 4.3 nm h −1 . It was an Correspondence to: J. Y. Sun (email@example.com) essential observation that on many occasions the nucleation mode was able to grow into the size of cloud condensation nuclei (CCN) within a matter of several hours. Furthermore, the new particle formation was regularly followed by a mea-surable increase in particle mass concentration and extinction coefficient, indicative of a high abundance of condensable vapors in the atmosphere under study.
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