Aging aerosol in a well-mixed continuous-flow tank reactor: an introduction of the activation time distribution

Franz Friebel, Amewu A. Mensah
2019 Atmospheric Measurement Techniques  
<p><strong>Abstract.</strong> Two approaches are commonly used to simulate atmospheric aging processes in the laboratory. The experiments are either performed in large aerosol chambers (several m<span class="inline-formula"><sup>3</sup></span>) in order to achieve extended observation times or in small chambers (&amp;lt;&amp;thinsp;1&amp;thinsp;m<span class="inline-formula"><sup>3</sup></span>), compensating for the short observation times by elevated reactant concentrations. We present an
more » ... We present an experimental approach that enables long observation times at atmospherically relevant reactant concentrations in small chamber volumes by operating the aerosol chamber as a continuous-flow stirred tank reactor (CSTR). We developed a mathematical framework that allows the retrieval of data beyond calculating mean values, such as <span class="inline-formula">O<sub>3</sub></span> exposure or equivalent atmospheric aging time, using the new metric, activation time (<span class="inline-formula"><i>t</i><sub>act</sub></span>). This concept was developed and successfully tested to characterize the change in cloud condensation nuclei (CCN) activity of soot particles due to heterogeneous ozone oxidation. We found very good agreement between the experimental results and the theoretical predictions. This experimental approach and data analysis concept can be applied for the investigation of any transition in aerosol particles properties that can be considered a binary system. Furthermore, we show how <span class="inline-formula"><i>t</i><sub>act</sub></span> can be applied to the analysis of data originating from other reactor types such as oxidation flow reactors (OFRs), which are widely used in atmospheric sciences. The new <span class="inline-formula"><i>t</i><sub>act</sub></span> concept significantly supports the understanding of data acquired in OFRs, especially those from deviating experimental results in intercomparison campaigns.</p>
doi:10.5194/amt-12-2647-2019 fatcat:pgy6rqwgg5h5jinzz4vexppevu