Investigating the Vapour Pressures of Nitroaromatic Compounds Using Knudsen Effusion Mass Spectrometry
Authors: Shelley Petroc , Bannan Thomas , Worrall Stephen , Krieger Ulrich , Alfarra M. Rami , Topping David 
Published: March 2020

&lt;p&gt;Deeper understanding of the behaviour of aerosol particles in the atmosphere is essential for the continued improvement of aerosol representation within models. The saturation vapour pressure (P&lt;sup&gt;sat&lt;/sup&gt; ) of secondary organic aerosols (SOA) can be used to predict partitioning between the gaseous and particulate phase. The extent of this partitioning affects the behaviour of SOA in the atmosphere&lt;sup&gt;1&lt;/sup&gt;.&lt;/p&gt;&lt;p&gt;Typically P&lt;sup&gt;sat&lt;/sup&gt;&amp;#160; of SOA are estimated using group contribution methods (GCMs) due to a lack of experimental data. The reliability of GCMs, when applied to a certain compound, depend on the how well represented the functionality present in the compound of interest is represented in the fitting data set of the GCM&lt;sup&gt;2&lt;/sup&gt;.&lt;/p&gt;&lt;p&gt;Nitroaromatics are a class of compound that are useful atmospheric tracers for anthropogenic emissions&lt;sup&gt;3&lt;/sup&gt;, and many nitroaromatic compounds are noted to be toxic&lt;sup&gt;4&lt;/sup&gt;. There is a lack of atmospherically relevant experimental data available for nitroaromatic compounds. This leads to poor performance of GCMs when they try and predict P&lt;sup&gt;sat&lt;/sup&gt; . Additional experimentally determined P&lt;sup&gt;sat&lt;/sup&gt; data can be used to expand the fitting data sets of GCMs allowing for more accurate prediction in the future.&lt;/p&gt;&lt;p&gt;In this study we present results from recent experiments using Knudsen Effusion Mass Spectrometry (KEMS) and differential scanning calorimetry (DSC) and compare these results with predicted values from multiple GCMs. The KEMS measurements are supported by additional data from diffusion controlled evaporation rates of single particles in an electrodynamic balance (EDB). In many cases the differences between the experimental data and the predicted values was several orders of magnitude. The limited nitroaromatic data within the GCM fitting sets are then investigated so that the mostly likely causes of the multiple order of magnitude differences between the predicted values and experimental values can be identified.&lt;/p&gt;&lt;p&gt;1&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; M. Bilde, K. Barsanti, M. Booth, C. D. Cappa, N. M. Donahue, E. U. Emanuelsson, G. McFiggans, U. K. Krieger, C. Marcolli, D. Topping, P. Ziemann, M. Barley, S. Clegg, B. Dennis-Smither, M. Hallquist, &amp;#197;. M. Hallquist, A. Khlystov, M. Kulmala, D. Mogensen, C. J. Percival, F. Pope, J. P. Reid, M. A. V Ribeiro da Silva, T. Rosenoern, K. Salo, V. Pia Soonsin, T. Yli-Juuti, N. L. Prisle, J. Pagels, J. Rarey, A. A. Zardini and I. Riipinen, Chem. Rev, 2015, &lt;strong&gt;115&lt;/strong&gt;, 4115&amp;#8211;4156.&lt;/p&gt;&lt;p&gt;2&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; T. Kurt&amp;#233;n, K. Tiusanen, P. Roldin, M. Rissanen, J.-N. Luy, M. Boy, M. Ehn and N. Donahue, J. Phys. Chem. A, 2016, &lt;strong&gt;120&lt;/strong&gt;, 2569&amp;#8211;2582.&lt;/p&gt;&lt;p&gt;3&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; D. Grosjean, Atmos. Environ. Part A. Gen. Top., 1992, &lt;strong&gt;26&lt;/strong&gt;, 953&amp;#8211;963.&lt;/p&gt;&lt;p&gt;4&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160; P. Kovacic and R. Somanathan, J. Appl. Toxicol., 2014, &lt;strong&gt;34&lt;/strong&gt;, 810&amp;#8211;824.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;