Influence of gas-to-particle partitioning on the hygroscopic and droplet activation behaviour of α-pinene secondary organic aerosol

Hygroscopic properties of secondary organic aerosol (SOA) formed by photooxidation of different concentrations (10–27 or 220–270 ppb) of α-pinene precursor were investigated at different relative humidities (RH) using a hygroscopicity tandem differential mobility analyzer (HTDMA, RH = 95–97%) and using the mobile version of the Leipzig Aerosol Cloud Interaction Simulator (LACIS-mobile, RH = 98–99.3%). In addition, the cloud condensation nuclei (CCN) activity was measured applying two CCN counters (CCNC). An apparent single-hygroscopicity parameter, κ, of ∼0.09, ∼0.07–0.13, and ∼0.02–0.04 was derived from CCNC, HTDMA and LACIS data, respectively, assuming the surface tension of pure water. Closure between HTDMA and CCNC data was achieved within experimental uncertainty, whereas closure between LACIS and CCNC was only achieved by assuming a concentration-dependent surface tension reduction, consequently resulting in lower CCNC-derived κ values. Comparing different experimental techniques at varying precursor concentrations in more detail reveals further open questions. Varying precursor concentration influences hygroscopic growth factors at subsaturated RH, while it has no effect on the CCN activation. This difference in behaviour might be caused by precursor concentration-dependent surface tension depression or changing droplet solution concentration dependence of the water activity coefficient with varying SOA composition. Furthermore, evidence was found that the SOA might need several seconds to reach the equilibrium growth factor at high RH.

Keywords

Subject (DDC)

550 - Geowissenschaften

Project

Event

Exhibition start date

Exhibition end date

Conference start date

Conference end date

Date of the last check

ISBN

ISSN

1463-9076
1463-9084

Language

English

Created during FHNW affiliation

No

Strategic action fields FHNW

Publication status

Published

Review

Peer review of the complete publication

Open access category

Closed

License

Citation

Jurányi, Z., Gysel, M., Duplissy, J., Weingartner, E., Tritscher, T., Dommen, J., Henning, S., Ziese, M., Kiselev, A., Stratmann, F., George, I., & Baltensperger, U. (2009). Influence of gas-to-particle partitioning on the hygroscopic and droplet activation behaviour of α-pinene secondary organic aerosol. Physical Chemistry Chemical Physics, 11(36), 8091–8097. https://doi.org/10.1039/b904162a

Full item page