Investigation of new particle formation at the summit of Mt. Tai, China

摘要

To date very few field observations of new particle formation (NPF) have been carried out at the high-elevation mountain sites in China. Simultaneously measurements of particle size distributions, gas species, meteorological conditions and PM were performed at the summit of Mt. Tai (1530 m ASL) from 25 July to 24 October 2014 (І), 21 September to 9 December 2014 (И) and 16 June to 7 August 2015 (Ш). The results showed that: (i) 66 NPF events were observed during 164 days, corresponding to an occurrence frequency of 40 %. Formation rates, growth rates and condensation sinks were in the range of 1.10–57.43 cm s, 0.58–7.76 nm h and 0.40 × 10–6.32 × 10 s, respectively, and Mt. Tai appeared to show the larger formation rate and smaller growth rate relative to other locations in China. The mean value of sulfur dioxide on NPF days was 46 % higher than that on non-NPF days, and a higher sulfur dioxide concentration could improve the possibility of rich precursors for NPF. (ii) Sulfuric acid condensation contributed to 16.20 % of growth rate, and sulfuric acid proxy showed an obvious correlation with total particle concentration of 3–6 nm (). (iii) Low PM was favourable for nucleation, and NPF days with limited higher PM seemed to have larger growth rates which might be related to particles recombination in close sizes. Four NPF events were observed on haze episodes, which could be promoted by potential specific mechanisms or pollutants. (iv) Particles formed via NPF on both clean and polluted days mainly contributed to Aiken mode eventually, and PM variation was always in accordance with particle total volume concentration.