Abstract. Anthropogenic emissions are dominant contributors to air pollution.
Consequently, mitigation policies have been attempted since the 1990s in
Europe to reduce pollution by anthropogenic emissions. To evaluate the
effectiveness of these mitigation policies, the German Ultrafine Aerosol
Network (GUAN) was established in 2008, focusing on black carbon (BC) and
sub-micrometre aerosol particles. In this study, long-term trends of
atmospheric particle number concentrations (PNCs) and equivalent BC (eBC)
mass concentration over a 10-year period (2009–2018) were determined for 16
GUAN sites ranging from roadside to high Alpine environments. Overall,
statistically significant decreasing trends are found for most of these
parameters and environments in Germany. The annual relative slope of eBC
mass concentration varies between −13.1 % and −1.7 % per year. The
slopes of the PNCs vary from −17.2 % to −1.7 %, −7.8 % to −1.1
%, and −11.1 % to −1.2 % per year for 10–30, 30–200, and
200–800 nm size ranges, respectively. The reductions in various
anthropogenic emissions are found to be the dominant factors responsible for
the decreasing trends of eBC mass concentration and PNCs. The diurnal and
seasonal variations in the trends clearly show the effects of the mitigation
policies for road transport and residential emissions. The influences of
other factors such as air masses, precipitation, and temperature were also
examined and found to be less important or negligible. This study proves
that a combination of emission mitigation policies can effectively improve
the air quality on large spatial scales. It also suggests that a long-term
aerosol measurement network at multi-type sites is an efficient and
necessary tool for evaluating emission mitigation policies.
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