Regional and local new particle formation events observed in the Yangtze River Delta region, China

Abstract

To study the spatial inhomogeneity of new particle formation (NPF) in the polluted atmosphere of China, we conducted simultaneous measurements at an urban site near a petrochemical industrial area and a regional background site in the Yangtze River Delta region from September to November 2015. At the urban site we observed a type of local NPF event (number of events: n = 5), in which nucleation was limited to a small area but persisted for 6.8 h on average during the daytime. Formation rates of 5 nm particles (J5) were found to be correlated positively with the H2SO4 proxy (log J5 versus log[H2SO4] slope near 1) in both local and regional events. Furthermore, J5 was enhanced by the anthropogenic volatile organic carbon (VOC) plumes from nearby industrial area in the local events compared to the regional events. Size‐dependent aerosol dynamics calculation showed that in comparison with the observed regional events, the local events were featured with high nucleation rate (J1.3 > 1000 cm−3 s−1), high growth rate of sub‐3 nm particles (GRsub‐3 > 20 nm h−1), and high number concentration of nucleation mode particles (mean peak N5‐20: 6 × 104 cm−3). Considering these features, the local NPF events of anthropogenic origin may also be an important contributor to cloud condensation nuclei concentrations in urban and regional scales. In addition, the comparison of simultaneous regional NPF events between the two sites (number of events: n = 7) suggested that regional NPF intensity may be underestimated by the single‐point measurement at an urban site, due to the heterogeneity of air masses.

Atmospheric new particle formation and growth: review of field observations

“…By acting as a sink for LVOC vapors and small clusters, a higher pre-existing aerosol loading is expected to hinder the occurrence of NPF. Existing observations confirm this expectation, since at most measurement sites the average value of CS was found to be lower on NPF event days compared with nonevent days ( Dai et al 2017). An exception to this pattern was the study by Birmili and Wiedensohler (2000) made in Melpitz, Germany, where the average preexisting particle surface areas was somewhat higher on NPF event days compared with all the other days.…”

East Asian Study of Tropospheric Aerosols and their Impact on Regional Clouds, Precipitation, and Climate (EAST‐AIRCPC)

“…This implies that regional NPF intensities are likely substantially underestimated if measurements are solely available from urban sites. Dai et al () also found a type of strong local nucleation event at the urban site where the formation rate of particles (e.g., J5) was positively correlated with H 2 SO 4 and enhanced by anthropogenic volatile organic compounds from nearby industrial emissions. This finding highlights that local NPF events might be an important contributor to CCN in polluted urban environments.…”

“…However, NPF and particle growth in highly polluted environments remains less understood . Dai et al (2017) made nearly two months of simultaneous measurements of particle number size and Guo, Gao, et al (2014) WRF with two-moment bulk-bin cloud microphysics and aerosol radiative effect distributions (4-750 nm) at an urban site and a regional background site in the polluted YRD region. They found that the formation and growth rates at the polluted urban site were always lower than those at the regional background site during seven regional NPF events.…”

New Particle Formation in the Atmosphere: From Molecular Clusters to Global Climate

“…Spatial variations of nucleation and growth in inhomogeneous air masses thus lead to different evolution patterns of the particle size distribution observed at a fixed monitoring location (Kivekäs et al, ). Dai et al () observed that NPF events in Nanjing were sometimes connected to AVOC plumes emitted from nearby industrial areas. In those local NPF events, nucleation was estimated to occur within a distance of ~50 km upwind of the observation site.…”