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RESEARCH
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Overview
The experiments are performed using the laminar flow-tube ift-LFT (length: 5.05 m, diameter: 8 cm). Special attention is given to particle formation starting from OH + SO2.
Typical reaction conditions are:
- Temperature: 293 ± 0.5 K
- Pressure: 1000 mbar (synth. air with a purity of 99.9999999 vol%)
- Relative humidity: 5 - 65 %
- Maximum residence time: 420 sec
For analysing gaseous compounds and particles the following equipment is used:
- long-path UV spectroscopy
- long-path FT-IR spectroscopy
- GC-MS/FID with a cryo-enrichment unit
- O3-, NOx- and SO2-monitors, humidity sensors
- Particle counter (TSI 3025, TSI 3786, puls-height-CPC)
- DMPS system with UCPC 3025 (size distribution measurements)
- Particle spectrometer NAIS
In accordance with results from ground level measurements in the troposphere the formation of new particle is observed for "H2SO4" concentrations of ~ 106 - 107 molecule cm-3 , cf. figure 1. "H2SO4" stands for all SO2 oxidation products. As OH radical sources serve photolysis of O3 or ozonolysis of trans-butene in a dark reaction. The slopes Δlog (N) / Δlog(["H2SO4"]) are in the range of 1.5 - 2.
Fig. 1: Particle number as a function of "H2SO4" concentration, residence time in the irradiated middle section of IfT-LFT = 290 sec, T = 293 K, r.h. 22 %..
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