Observation of aerosol size distribution and new particle formation at a coastal city in the Yangtze River Delta, China

摘要

Aerosol number size distribution in the range of 10 nm-10 μm, trace gases (O_3, CO, SO_2 and NO_2), particular matter (PM: PM_(2.5) and PM_(10)) and meteorological elements were measured from the 1st to the 31st of May, 2015, in the coastal city of Jiaxing in the Yangtze River Delta (YRD). The average number concentration and surface area concentration were 19,639 cm~(-3) and 427 μm~2 cm~(-3) during the observation period. The different mode particle concentrations ranked in the order of Aitken mode (12,361 cm~(-3)) ＞ nucleation (4926.7 cm~(-3)) ＞ accumulation (23493 cm~(-3)) ＞ coarse mode (1.7 cm~(-3)). The average concentrations of CO, SO_2, NO_2, O_3, PM_(2.5) and PM_(10) were 0.545 mg m~3,14.7,35.1,89.8,43.5 and 64.6 μg m~(-3), respectively. Eight precipitation processes and 15 new particle formation (NPF) events (3 NPF events occurred on a rainy day) were observed. Results show that the precipitation process had greater scavenging effects on particles smaller than 120 nm and larger than 2 μm. The spectral distributions of number concentrations were unimodal at different weather conditions, with peaks at 20 nm, 40-60 nm, 50-80 nm on NPF days, rainy days and normal days. During the NPF events, the formation rate (FR), growth rate (GR), condensational sink (CS), vapor source rate (Q) and condensing vapor concentration (C) were in the range of 4.0-17.0 cm~(-3) s~(-1),2.2-15.7 nm h~(-1) 1.5-5.8 × 10~(-2) s~(-1), 0.5- 7.7 ×10~6 cm~(-3) s~(-1) and 3.0-21.5 × 10~7 cm~(-3), with mean values of 9.6 cm~(-3) s~(-1), 6.8 nm h~(-1),3.4×10~(-2) s~(-1), 3.3 × 10~6 cm~(-3) s~(-1) and 9.4 × 10~7 cm~(-3), respectively. NPF events normally occurred under clean atmospheric conditions with low PM concentrations but high levels of trace gases. It was also found that SO_2 plays an important role in NPF and growth in Jiaxing.