Comment on acp-2022-843

Abstract

An inversion method has been developed in order to quantify the emission rate of certain aerosol pollution sources across a wide region in the Northern hemisphere, mainly in Europe and Western Asia. The data employed are the aerosol contribution factors (sources) deducted by Positive Matrix Factorization (PMF) on a PM2.5 chemical composition dataset from 16 European and Asian cities for the period 2014 to 2016. The spatial resolution of the method corresponds to the geographic grid cell size of the Lagrangian particle dispersion model (FLEXPART) which was utilized for the air mass backward simulations. The area covered is also related to the location of the 16 cities under study. Species with an aerodynamic geometric mean diameter of 400 nm and 3.1 μm and geometric standard deviation of 1.6 and 2.25 respectively, were used to model the Secondary Sulfate and Dust aerosol transport. PSCF analysis and Generalized Tikhonov regularization were applied so as to acquire potential source areas and quantify their emission rate. A significant source area for Secondary Sulfate on the East of the Caspian Sea is indicated, when data from all stations are used. The maximum emission rate in that area is as high as 10 g * m-2 * s-1. When Vilnius, Dushanbe and Kurchatov data were excluded, the areas with the highest emission factors were the Western and Central Balkans and South Poland. The results display many similarities to the SO2 emission map provided by ECLIPSE database. For Dust aerosol, measurements from Athens, Belgrade, Debrecen, Lisbon, Tirana and Zagreb are utilized. The west Sahara region is indicated as the most important source area and its contribution is quantified, with a maximum of 17.5 g * m-2 * s-1. When we apply the emission rates from every geographic grid cell (1º x 1º) for Secondary Sulfate aerosol deducted with the new method to air masses originating from Vilnius, a good approximation to the measured values is achieved.