Abstract
Abstract. Atmospheric particle number size distributions (size range 0.003–10 μm) were measured between March 2008 and August 2009 at Shangdianzi (SDZ), a rural research station in the North China Plain. These measurements were made in an attempt to better characterize the tropospheric 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 × 104, 3.6 ± 7.9 × 103, 4.4 ± 3.4 × 103, 3.5 ± 2.8 × 103 and 2 ± 3 cm−3, respectively. A general finding was that the particle number concentration 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 formation events. Air masses from northwest (i.e. inner Asia) favored the new particle formation events, while air masses from southeast showed the highest particle mass concentration. 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 formation events, the number concentration of the nucleation mode rose up to maximum value of 104 cm−3. New particle formation events were observed on 36% of the effective 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 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 measurable increase in particle mass concentration and extinction coefficient, indicative of a high abundance of condensable vapors in the atmosphere under study.
Highlights
Atmospheric aerosol particles play a key role in global climate because of combined direct and indirect radiative forcing
This paper focuses on the particle size distribution measurements at SDZ from March 2008 to August 2009, and summarizes the characteristics of particle number concentration, size distribution and new particle formation events at SDZ
elemental carbon (EC) wa6s 1.8f0o–r0m.5a4tio(nds’Aelvmeenitdsainetfaolu.,r1s9e9a1s)o.nTs.he difference dicated that condensational growth of nucleated particles reof extinction coefficient in external or internal mixing states sulted in an increase in the number concentration of potential was less than 10%, and the average of these values was sup- cloud condensation nuclei (CCN), aerosol mass concentration and extinction coefficient, posed as the real extinction coefficient σext,550nm
Summary
Atmospheric aerosol particles play a key role in global climate because of combined direct and indirect radiative forcing They directly affect the radiation balance by scattering and absorbing incoming short-wave solar radiation and absorbing long-wave radiation. The number size distribution is an important characteristic, which can help to understand the behavior and effects of the aerosol particles. Shen et al.: Long-term study of particle number size distributions (Birmili et al, 2001). Measurements of particle size distributions reveal new particle formation (NPF) events and growth are widespread. There is no data about long term of particle number size distribution measurements of the regional polluted aerosol in China yet. This paper focuses on the particle size distribution measurements at SDZ from March 2008 to August 2009, and summarizes the characteristics of particle number concentration, size distribution and new particle formation events at SDZ
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