| Autor: |
Grayson, J. W., Zhang, Y., Mutzel, A., Renbaum-Wolff, L., Böge, O., Kamal, S., Herrmann, H., Martin, S. T., Bertram, A. K. |
| Zdroj: |
Atmospheric Chemistry & Physics Discussions; 2015, Vol. 15 Issue 22, p32967-33002, 36p |
| Abstrakt: |
To predict the role of secondary organic material (SOM) particles in climate, visibility, and health, information on the viscosity of particles containing SOM is required. In this study we investigate the viscosity of SOM particles as a function of relative humidity and SOM particle mass concentration during SOM synthesis. The SOM was generated via the ozonolysis of α-pinene at < 5% relative humidity (RH). Experiments were carried out using the poke-and-flow technique, which measures the experimental flow time (τexp, flow) of SOM after poking the material with a needle. In the first set of experiments, we show that τexp, flow increased by a factor of 3600 as the RH increased from < 0.5 to 50% RH, for SOM with a production mass concentration of 121 μg m-3. Based on simulations, the viscosities of the particles were between 6 × 105 and 5 × 107 Pa s at < 0.5% RH and between 3 × 10² and 9 × 10³ Pa s at 50% RH. In the second set of experiments we show that under dry conditions τexp, flow decreased by a factor of 45 as the production mass concentration increased from 121 to 14 000 μg m-3. From simulations of the poke-and-flow experiments, the viscosity of SOM with a production mass concentration of 14 000 μg m-3 was determined to be between 4 × 104 and 1.5 × 106 Pa s compared to between 6 × 105 and 5 × 107 Pa s for SOM with a production mass concentration of 121 μg m-3. The results can be rationalised by a dependence of the chemical composition of SOM on production conditions. These results emphasise the shifting characteristics of SOM, not just with RH and precursor type, but also with the production conditions, and suggest that production mass concentration and the RH at which the viscosity was determined should be considered both when comparing laboratory results and when extrapolating these results to the atmosphere. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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