Impacts of new particle formation on aerosol cloud condensation nuclei (CCN) activity in Shanghai: case study

Abstract

Abstract. New particle formation (NPF) events and their impacts on cloud condensation nuclei (CCN) were investigated using continuous measurements collected in urban Shanghai from 1 to 30 April 2012. During the campaign, NPF occurred in 8 out of the 30 days and enhanced CCN number concentration (N CCN ) by a factor of 1.2-1.8, depending on supersaturation (SS). The NPF event on 3 April 2012 was chosen as an example to investigate the NPF influence on CCN activity. In this NPF event, secondary aerosols were produced continuously and increased PM 2.5 mass concentration at a rate of 4.33 µg cm −3 h −1 , and the growth rate (GR) and formation rate (FR) were on average 5 nm h −1 and 0.36 cm −3 s −1 , respectively. The newly formed particles grew quickly from nucleation mode (10-20 nm) into CCN size range. N CCN increased rapidly at SS of 0.4-1.0 % but weakly at SS of 0.2 %. Correspondingly, aerosol CCN activities (fractions of activated aerosol particles in total aerosols, N CCN /N CN ) were significantly enhanced from 0.24-0.60 to 0.30-0.91 at SS of 0.2-1.0 % due to the NPF. On the basis of the κ-Köhler theory, aerosol size distributions and chemical composition measured simultaneously were used to predict N CCN . There was a good agreement between the predicted and measured N CCN (R 2 = 0.96, N predicted /N measured = 1.04). This study reveals that NPF exerts large impacts on aerosol particle abundance and size spectra; thus, it significantly promotes N CCN and aerosol CCN activity in this urban environment. The GR of NPF is the key factor controlling the newly formed particles to become CCN at all SS levels, whereas the FR is an effective factor only under high SS (e.g., 1.0 %) conditions.

Measurements of PM10 ions and trace gases with the online system MARGA at the research station Melpitz in Germany – A five-year study

“…Observations of linearity between sulphate and nitrate in PM (2009 to 2011) Leng et al (2014a) Shanghai, CN Role of new particle formation on aerosol cloud condensation nuclei (CCN) activity (2012) Leng et al (2014b) Shanghai, CN Variations of CCN and aerosol activity during fog and haze events (2010) Makkonen et al (2014) Hyytiälä, FI Temporal cycles of NH 3 , HONO and HNO 3 at a boreal forest site (2010 to 2011) Rumsey et al (2014) North Carolina, US Performance study of the MARGA (US Environmental Protection Agency's Clean Air Status and Trends Network, CASTnet) (2010) Shi et al (2014) Shanghai, CN Investigation on PM 1 (variability, formation/dissociation, impacts on visibility) (2012) Zhou et al (2014) Shanghai, CN Measuring and modelling aerosols for haze events (2008 to 2010) a net radiometer CNR1 (Kipp&Zonen, The Netherlands) and a digital barometer (Vaisala, Germany), respectively.…”

Insights into a historic severe haze event in Shanghai: synoptic situation, boundary layer and pollutants

“…Interestingly, both PM 2.5 and PM 10 reached their peaks of 600 and 680 µg m −3 as new historic records on 6 December, approximately 14 times higher than the Grade I criteria of the National Ambient Air Quality Standard of China (50 µg m −3 for PM 10 ), and 24 times the World Health Or- (Leng et al, 2013(Leng et al, , 2014b. In addition, compared to Beijing as another megacity in China, He et al (2001), Sun et al (2004) and Liu et al (2013) .…”

“…Decreasing the height of PBL can normally hold the pollutants within the shallow surface layer, suppress the vertical atmospheric dilution and ultimately cause regional environment shrouded by pollution (Kim et al, 2007). In Shanghai, several field measurements have monitored that PBL height is usually low during hazy episodes (Leng et al, 2014b;Zhang et al, 2015). By utilizing the normalized lidar backscatter signal at 532 nm, the PBL retrieval at 30 s resolution was derived in this study, and the time-height series were plotted in red line in Fig.…”

A new balance formula to estimate new particle formation rate: reevaluating the effect of coagulation scavenging

“…In most previous studies, the above population balance method was used to estimate new particle formation rates in China. The reported formation rates of 3 nm particles and larger ones are typically in the range of 1-10 cm −3 s −1 (Wang et al, 2013;Leng et al, 2014;An et al, 2015;Qi et al, 2015). One study in Shanghai reported a rate of 112.4 to 271.0 cm −3 s −1 for the formation of 1.5 nm particles inferred from a DEG-CPC (Xiao et al, 2015).…”

“…In a typical NPF event, gaseous precursors burst out into particles due to nucleation and lead to a rapid increase in the atmospheric aerosol population. Nucleated particles can grow quickly to increase the number concentration of cloud condensation nuclei Kuang et al, 2009;Leng et al, 2014) and thus have indirect impacts on radiative forcing and global climate (Lohmann and Feichter, 2005). The continuous growth of nucleated particles also provides increasing aerosol surface area for heterogeneous physicochemical processes.…”