EGU2020-12255
https://doi.org/10.5194/egusphere-egu2020-12255
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Aerosol Composition, Physiochemical Properties, and Source Apportionment at a Forest Site in Taiwan

Ting-Yu Chen1, Chia-Li Chen1, Hui-Ming Hung1, Yi-Chi Chen2, Haojia Ren2, Wei-Nai Chen3, and Charles C. -K. Chou3
Ting-Yu Chen et al.
  • 1National Taiwan University, Department of Atmospheric Sciences, Taipei, Taiwan
  • 2Department of Geosciences, National Taiwan University, Taipei, Taiwan
  • 3Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan

To investigate the interaction between local circulation and aerosol major chemical composition and hygroscopicity, a series of studies in Xitou Experimental Forest of National Taiwan University (23.40°N, 120.47°E, 1,178 m asl) in December 2018 was conducted. The isotopes of δ15N and δ18O from the filter samples were applied to identify the possible formation pathways. The single hygroscopicity parameter, κ, of aerosols between 9-437 nm in diameter was derived from the measurements of a cloud condensation nuclei counter (CCNc), an ultrafine condensation particle counter (UCPC) and a scanning mobility particle sizer (SMPS) using the κ-Köhler equation. Filter samples collected by a multi-orifice uniform deposit impactor (MOUDI) were applied to quantify the major aerosol composition based on the absorbance of selected functional groups (NH4+, SO42-, NO3-, elemental carbon) by a Fourier transform infrared spectroscopy with an attenuated total reflection accessory (FT-IR-ATR). The δ15N of particulate NH4+ (p-NH4+) and particulate NO2- or NO3- (p-NOx-) and the δ18O of p-NOx- were analyzed by an isotopic ratio mass spectroscopy (IR-MS) to infer the source and chemical pathway of aerosols. The mean κ value of aerosol is mostly between 0.07 and 0.22 during the field study period. The aerosol concentration shows a significant correlation with the local circulation, sea-land breeze combined with the mountain-valley circulation, and is significantly higher in the daytime than that in the nighttime. The foggy period has revealed a higher concentration of NH4+, SO42-, NO3-, and elemental carbon (or black carbon, BC), which may be caused by the lower boundary layer and weaker upward turbulent mixing during the foggy period. Aerosols containing NH4+, SO42- shifted to the larger size distribution during the foggy period and that is likely due to the hygroscopic growth of aerosols containing these functional groups at higher RH. The observed stable and high NO3- concentration of aerosol in the diameter of 0.56-1 µm during foggy periods is likely caused by the partition of HNO3 in the aqueous phase under a basic condition or further stabilized by the dissolved ammonium to form particulate NO3-. The daily mass-weighted δ15N of p-NH4+ is ranged from +3.7‰ to +16.3‰ and δ15N of p-NOx- from +1.5‰ to +5.2‰, indicating that p-NH4+ and p-NOx- are likely contributed from anthropogenic sources such as coal-burning and traffic. The δ18O of p-NOx- is in the range of +70‰ to +80‰, similar to the result of southeast Asia in winter. The observed high δ18O might be contributed through the pathways of the oxidation of NO with O3 to form NO2, which is further oxidized by OH radicals to form HNO3.

How to cite: Chen, T.-Y., Chen, C.-L., Hung, H.-M., Chen, Y.-C., Ren, H., Chen, W.-N., and Chou, C. C.-K.: Aerosol Composition, Physiochemical Properties, and Source Apportionment at a Forest Site in Taiwan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12255, https://doi.org/10.5194/egusphere-egu2020-12255, 2020

Displays

Display file