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

Abstract

Abstract. To date, few comprehensive field observations of new particle formation (NPF) have been carried out at mountaintop sites in China. In this study, simultaneous measurements of particle size distribution, trace gases, meteorological parameters, and mass concentration and chemical composition of PM 2.5 were performed at the summit of Mt. Tai (1534 m a.s.l.) from 25 July to 24 August 2014 (Phase I), 21 September to 9 December 2014 (Phase II), and 16 June to 7 August 2015 (Phase III) to investigate characteristics and favorable conditions of NPF in a relatively clean mountaintop environment. The NPF events were identified based on particle size distribution measured by the neutral cluster and air ion spectrometer (NAIS), and 66 such events were observed during a period of 164 days -corresponding to an occurrence frequency of 40 %. The formation rates of 3 nm particles (J 3 ) and growth rates were in the ranges of 0.82-25.04 cm −3 s −1 and 0.58-7.76 nm h −1 , respectively. On average, the condensation sink (CS), O 3 concentration, air temperature, and relative humidity were lower, whereas the SO 2 concentration was higher on NPF days than that on non-NPF days. The CS on Mt. Tai was at a low level and lower CS was critical for NPF. NPF events were common when wind came from the east-southeast and west-southwest, which was probably associated with relatively lower CS in the east-southeast and higher SO 2 concentration in the west-southwest. O 3 was not a governing factor for NPF in this study, and a high level of NO x concentration might be responsible for the decreased O 3 concentration on NPF days. Three categories of backward trajectories were classified, among which the continental air mass was the majority. The continental air mass passing through more polluted areas (denoted as Type I) favored NPF because of enhanced SO 2 concentration and potential ammonia with it. An in-depth analysis of SO 2 indicated that sulfuric acid was a dominant precursor on Mt. Tai; meanwhile, biogenic organics released from ambient forests in warm seasons and anthropogenic volatile organic compounds emitted from domestic heating in cold seasons also promoted NPF.

New Particle Formation: A Review of Ground-Based Observations at Mountain Research Stations

“…The opposite was, however, found for mid-latitudes, where ultrafine particle concentrations were a factor two to four times higher in the upper Northern hemisphere than in the upper Southern hemisphere. Since the two Southern hemisphere high altitude stations of CHC and MDO are located close to the tropical latitudes, our results were in line with those of Minikin et al (2003) [61]. However, data acquired during the flight campaign represent only a few flights, and more statistical data are needed at stations in the mid-latitude range of the Southern hemisphere.…”

“…At Mount Tai in China (1534 m a.s.l. ), measurements performed during autumn and summer seasons again showed higher frequencies in autumn (56%) than in summer (21%) [61]. The seasonal variation of the NPF frequency observed at MDO also displayed a frequency peak during the Southern hemisphere autumn (March-April) and early spring (August-October).…”

“…Clarke and Kapustin (2002) [21] summarized 10 years of airborne measurements over the Pacific Ocean and showed that ultrafine (dp > 3 nm) particle concentrations were in a similar range in the Southern and the Northern hemispheres. In Minikin et al (2003) [61], aircraft studies showed relatively high concentrations of ultrafine particle concentration (Dp > 6 nm) (up to 10,000 cm −3 ) in the tropical region of the Southern hemisphere for altitudes higher than 7 km, which was found to be relatively higher than the corresponding concentration in the tropics of the Northern hemisphere for the same altitude. The authors found that high concentrations of this geographical area originated from uplifted air masses above the central South American continent.…”

Profile of inhalable bacteria in PM2.5 at Mt. Tai, China: Abundance, community, and influence of air mass trajectories

“…Tai is a tilted fault block mountain with height increasing from the north to the south, facing to the East China Sea and back on the yellow river to the west. In this region, the airborne bacterial populations in cloud system and fungal populations in particles have been reported before [24][25][26] .…”

“…Tai (36.25 o N and 117.10 o E, 1534 m above sea level), a typical tourist area in the North China Plain (Figure 1). The geographical characteristics of the sampling site have been previously described 25,26 . Each collection period lasted 23 h. Before sampling, all the filters were baked at a Muffle furnace at 500°C for h and then placed into sterilized aluminum foil before deposited into a sealed bag.…”