Supplementary material to "Analysis of New Particle Formation (NPF) Events at Nearby Rural, Urban Background and Urban Roadside Sites"

Abstract. New particle formation (NPF) events have different patterns of development depending on the conditions of the area in which they occur. In this study, particle size distributions in the range of 16.6–604 nm (7 years of data) were analysed and NPF events occurring at three sites of differing characteristics – rural Harwell (HAR), urban background North Kensington (NK), urban roadside Marylebone Road (MR), London, UK – were extracted and studied. The different atmospheric conditions in each study area not only have an effect on the frequency of the events, but also affect their development. The frequency of NPF events is similar at the rural and urban background locations (about 7 % of days), with a high proportion of events occurring at both sites on the same day (45 %). The frequency of NPF events at the urban roadside site is slightly less (6 % of days), and higher particle growth rates (average 5.5 nm h−1 at MR compared to 3.4 and 4.2 nm h−1 at HAR and NK respectively) must result from rapid gas-to-particle conversion of traffic-generated pollutants. A general pattern is found in which the condensation sink increases with the degree of pollution of the site, but this is counteracted by increased particle growth rates at the more polluted location. A key finding of this study is that the role of the urban environment leads to an increment of 20 % in N16–20 nm in the urban background compared to that of the rural area in NPF events occurring at both sites. The relationship of the origin of incoming air masses is also considered and an association of regional events with cleaner air masses is found. Due to lower availability of condensable species, NPF events that are associated with cleaner atmospheric conditions have lower growth rates of the newly formed particles. The decisive effect of the condensation sink in the development of NPF events and the survivability of the newly formed particles is underlined, and influences the overall contribution of NPF events to the number of ultrafine particles in an area. The other key factor identified by this study is the important role that pollution, both from traffic and other sources in the urban environment (such as heating or cooking), plays in new particle formation events.

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Characterization of ultrafine particle number concentration and new particle formation in an urban environment of Taipei, Taiwan

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-8935-2013 ◽

2013 ◽

Vol 13 (17) ◽

pp. 8935-8946 ◽

Cited By ~ 29

Author(s):

H. C. Cheung ◽

C. C.-K. Chou ◽

W.-R. Huang ◽

C.-Y. Tsai

Keyword(s):

Growth Rate ◽

Urban Areas ◽

Particle Formation ◽

Number Concentration ◽

Submicron Particles ◽

Radiation Budget ◽

New Particle Formation ◽

Urban Background ◽

Nucleation Mode ◽

Quadratic Relationship

Abstract. An intensive aerosol characterization experiment was performed at the Taipei Aerosol and Radiation Observatory (TARO, 25.02° N, 121.53° E) in the urban area of Taipei, Taiwan, during July 2012. Number concentration and size distribution of aerosol particles were measured continuously, which were accompanied by concurrent measurements of mass concentration of submicron particles, PM1 (d ≤ 1 μm), and photolysis rate of ozone, J(O1D). The averaged number concentrations of total (Ntotal), accumulation mode (Nacu), Aitken mode (NAitken), and nucleation mode (Nnuc) particles were 13.9 × 103 cm−3, 1.2 × 103 cm−3, 6.1 × 103 cm−3, and 6.6 × 103 cm−3, respectively. Accordingly, the ultrafine particles (UFPs, d ≤ 100 nm) accounted for 91% of the total number concentration of particles measured in this study (10 ≤ d ≤ 429 nm), indicating the importance of UFPs to the air quality and radiation budget in Taipei and its surrounding areas. An averaged Nnuc / NOx ratio of 192.4 cm−3 ppbv−1 was derived from nighttime measurements, which was suggested to be the characteristic of vehicle emissions that contributed to the "urban background" of nucleation mode particles throughout a day. On the contrary, it was found that the number concentration of nucleation mode particles was independent of NOx and could be elevated up to 10 times of the "urban background" levels during daytime, suggesting a substantial amount of nucleation mode particles produced from photochemical processes. Averages (± 1σ) of the diameter growth rate (GR) and formation rate of nucleation mode particles, J10, were 11.9 ± 10.6 nm h−1 and 6.9 ± 3.0 cm−3 s−1, respectively. Consistency in the time series of the nucleation mode particle concentration and the proxy of H2SO4 production, UVB · SO2/CS, for new particle formation (NPF) events suggested that photooxidation of SO2 was likely one of the major mechanisms for the formation of new particles in our study area. Moreover, it was revealed that the particle growth rate correlated exponentially with the photolysis of ozone, implying that the condensable vapors were produced mostly from photooxidation reactions. In addition, this study also revealed that Nnuc exhibited a quadratic relationship with J10. The quadratic relationship was inferred as a result of aerosol dynamics and featured NPF processes in urban areas.

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Supplementary material to "New particle formation events observed at the King Sejong Station, Antarctic Peninsula – Part 2: Link with the oceanic biological activities"

10.5194/acp-2018-1181-supplement ◽

2018 ◽

Author(s):

Eunho Jang ◽

Ki-Tae Park ◽

Young Jun Yoon ◽

Tae-Wook Kim ◽

Sang-Bum Hong ◽

...

Keyword(s):

Antarctic Peninsula ◽

Biological Activities ◽

Particle Formation ◽

New Particle Formation ◽

Supplementary Material

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Characterization of ultrafine particle number concentration and new particle formation in urban environment of Taipei, Taiwan

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-8985-2013 ◽

2013 ◽

Vol 13 (4) ◽

pp. 8985-9016 ◽

Cited By ~ 1

Author(s):

H. C. Cheung ◽

C. C.-K. Chou ◽

W.-R. Huang ◽

C.-Y. Tsai

Keyword(s):

Growth Rate ◽

Urban Areas ◽

Formation Rate ◽

Particle Formation ◽

Number Concentration ◽

New Particle Formation ◽

Urban Background ◽

Photo Oxidation ◽

Nucleation Mode ◽

Quadratic Relationship

Abstract. An intensive aerosol characterization experiment was performed at the Taipei Aerosol and Radiation Observatory (TARO, 25.02° N, 121.53° E) in the urban area of Taipei, Taiwan during July 2012. Number concentration and size distribution of aerosol particles were measured continuously, which were accompanied by concurrent measurements of mass concentration of submicron particles, PM (d ≤ 1 μm), and photolysis rate of ozone, J(O1D). The averaged number concentrations of total (Ntotal), accumulation mode (Nacu), Aitken mode (Ntotal), and nucleation mode (Nnuc) particles were 7.6 × 103 cm−3, 1.2 × 103 cm−3, 4.4 × 103 cm−3, and 1.9 × 103 cm−3, respectively. Accordingly, the ultrafine particles (UFPs, d ≤ 100 nm) accounted for 83% of the total number concentration of particles measured in this study (10 ≤ d ≤ 429 nm), indicating the importance of UFPs to the air quality and radiation budget in Taipei and its surrounding areas. An averaged Nnuc/NOx ratio of ~60 cm−3 ppbv−1 was derived from nighttime measurements, which was suggested to be the characteristic of vehicle emissions that contributed to the "urban background" of nucleation mode particles throughout a day. On the contrary, it was found that the number concentration of nucleation mode particles was independent of NOx and could be elevated up to 10 times the "urban background" levels during daytime, suggesting a substantial amount of nucleation mode particles produced from photochemical processes. Consistency in the time series of the nucleation mode particle concentration and the proxy of H2SO4 production, UVB·SO2, for new particle formation (NPF) events showed that photo-oxidation of SO2 was responsible for the formation of new particles in our study area. Moreover, analysis upon the diameter growth rate, GR, and formation rate of nucleation mode particles, J10−25, found that the values of GR (8.5 ± 6.8 nm h−1) in Taipei were comparable to other urban areas, whereas the values of J10−25 (2.2 ± 1.2 cm−3 s−1) observed in this study were around the low end of the range of new particle formation rate reported by previous investigations. It was revealed that the particle growth rate correlated exponentially with the photolysis of ozone, suggesting the condensable vapors were produced mostly from photo-oxidation reactions. In addition, this study also revealed that both GR and J10−25 exhibited quadratic relationship with the number concentration of particles. The quadratic relationship was inferred as a result of aerosol dynamics and featured NPF process in urban areas.

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