2017 PSP

Fog Study at Pinnacle State Park, NY, Sep. 2017

The 2017 Full PSP measurement was designed to measure the new particle formation (NPF), combining FMPS, APS, and model simulation by Dr. Fangqun Yu. Our mobile lab was expected to be used to capture the fine aerosol evolution after new particles formed, and was planned for one week measurement. However, the occurring of early morning fog events blocked the simulated NPF, while providing a chance to investigate the effect of foggy/moist conditions on the characteristics of secondary organic aerosol (SOA).

Highlighted Results (Zhang et al., Fog processing of aerosols in a rural forest environment: insights from high resolution aerosol mass spectrometry. Geophysical Research Letters, 2020. https://doi.org/10.1029/2020GL089714 ):

Biogenic SOA shows similar behavioral trends to aerosol organic nitrates (pNO3,org) as well as HNO3 ;
The organic nitrate was averaged 67% of total nitrates;
Nocturnal NO3 (Nitrate radical)+BVOC reaction could be an important formation pathway;

Based on the transition points of the aerosol compounds, as well as RH and solar irradiation variations, the entire fog life cycle was divided into five fog processing periods namely: 1. fog_before_forming (F-B), 2. fog_forming (F-F), 3. fog_scavenging (F-S), 4. fog_dissipating (F-D) , 5. fog_post_dissipating (F-P).

MO-OOA showed the highest solubility and scavenging efficiency, followed by LOOOA, SO4, and BSOA;
Comparing to the initial period (F-B), the F-P aerosols mass slightly increased about 7% to 15% for the first three nights with an averaged value of 11%, and the O:C ratios decreased while the H:C ratios increased;
That is likely related to the decrease of MO-OOA and the enhancement of LO-OOA+BSOA.

When RH was below 96%, but with RH increasing, BSOA mass concentrations increased in combination with the enhanced RH;
The slopes of these four nights are 0.9-2.6 with an averaged value of 1.9, which means during this study that an increase of 0.1 in the ALW ratio would average lead to an increase of about 0.2 μg m-3 BSOA