A 1-year aerosol chemical speciation monitor (ACSM) source analysis of organic aerosol particle contributions from anthropogenic sources after long-range transport at the TROPOS research station Melpitz
Authors: Atabakhsh Samira , Poulain Laurent , Chen Gang , Canonaco Francesco , Prévôt André S. H. , Pöhlker Mira , Wiedensohler Alfred , Herrmann Hartmut 
Published: June 2023

Abstract. Atmospheric aerosol particles are a complex combination of primary emitted
sources (biogenic and anthropogenic) and secondary aerosol resulting from
aging processes such as condensation, coagulation, and cloud processing. To
better understand their sources, investigations have been focused on urban
areas in the past, whereas rural-background stations are normally less
impacted by surrounding anthropogenic sources. Therefore, they are
predisposed for studying the impact of long-range transport of anthropogenic
aerosols. Here, the chemical composition and organic aerosol (OA) sources of
submicron aerosol particles measured by an aerosol chemical speciation
monitor (ACSM) and a multi-angle absorption photometer (MAAP) were
investigated at Melpitz from September 2016 to August 2017. The location of
the station at the frontier between western and eastern Europe makes it the
ideal place to investigate the impact of long-range transport over Europe.
Indeed, the station is under the influence of less polluted air masses from
westerly directions and more polluted continental air masses from eastern
Europe. The OA dominated the submicron particle mass concentration and
showed strong seasonal variability ranging from 39 % (in winter) to 58 % (in summer). It was followed by sulfate (15 % and 20 %) and
nitrate (24 % and 11 %). The OA source identification was performed
using the rolling positive matrix factorization (PMF) approach to account
for the potential temporal changes in the source profile. It was
possible to split OA into five factors with a distinct temporal variability
and mass spectral signature. Three were associated with anthropogenic
primary OA (POA) sources: hydrocarbon-like OA (HOA; 5.2 % of OA mass in
winter and 6.8 % in summer), biomass burning OA (BBOA; 10.6 % and 6.1 %) and coal combustion OA (CCOA; 23 % and 8.7 %). Another two are
secondary and processed oxygenated OA (OOA) sources: less oxidized OOA (LO-OOA;
28.4 % and 36.7 %) and more oxidized OOA (MO-OOA; 32.8 % and 41.8 %). Since equivalent black carbon (eBC) was clearly associated with the
identified POA factors (sum of HOA, BBOA, and CCOA; R2= 0. 87), eBC's
contribution to each of the POA factors was achieved using a multilinear
regression model. Consequently, CCOA represented the main anthropogenic
sources of carbonaceous aerosol (sum of OA and eBC) not only during winter
(56 % of POA in winter) but also in summer (13 % of POA in summer),
followed by BBOA (29 % and 69 % of POA in winter and summer,
respectively) and HOA (15 % and 18 % of POA in winter and summer,
respectively). A seasonal air mass cluster analysis was used to understand
the geographical origins of the different aerosol types and showed that
during both winter and summer time, PM1 (PM with an aerodynamic
diameter smaller than 1 µm) air masses with eastern influence were
always associated with the highest mass concentration and the highest coal
combustion fraction. Since during wintertime CCOA is a combination of
domestic heating and power plant emissions, the summer contribution of CCOA
emphasizes the critical importance of coal power plant emissions to
rural-background aerosols and its impact on air quality, through long-range
transportation.