Abstract. Multiple atmospheric properties were measured semi-continuously in
the Budapest platform for Aerosol Research and Training laboratory, which
represents the urban background for the time interval of 2008–2018. Data of
6 full measurement years during a decennial time interval were subjected to
statistical time trend analyses by an advanced dynamic linear model and a
generalized linear mixed model. The main interest in the analysed data set
was on particle number concentrations in the diameter ranges from 6 to 1000 nm (N6−1000), from 6 to 100 nm (N6−100, ultrafine particles), from
25 to 100 nm (N25−100) and from 100 to 1000 nm (N100−1000). These
data were supported by concentrations of SO2, CO, NO, NOx,
O3, PM10 mass, as well as air temperature, relative humidity, wind speed,
atmospheric pressure, global solar radiation, condensation sink, gas-phase
H2SO4 proxy, classes of new aerosol particle formation (NPF), and
growth events and meteorological macro-circulation patterns. The trend of
the particle number concentrations derived as a change in the statistical
properties of background state of the data set decreased in all size
fractions over the years. Most particle number concentrations showed
decreasing decennial statistical trends. The estimated annual mean decline
of N6−1000 was (4–5) % during the 10-year measurement interval, which
corresponds to a mean absolute change of −590 cm−3 in a year. This was
interpreted as a consequence of the decreased anthropogenic emissions at
least partly from road traffic alongside household heating and industry.
Similar trends were not observed for the air pollutant gases. Diurnal
statistical patterns of particle number concentrations showed tendentious
variations, which were associated with a typical diurnal activity–time
pattern of inhabitants in cities, particularly of vehicular road traffic.
The trend patterns for NPF event days contained a huge peak from late
morning to late afternoon, which is unambiguously caused by NPF and growth
processes. These peaks were rather similar to each other in the position,
shape and area on workdays and holidays, which implies that the dynamic and
timing properties of NPF events are not substantially influenced by
anthropogenic activities in central Budapest. The diurnal pattern for
N25−100 exhibited the largest relative changes, which were related to
particle emissions from high-temperature sources. The diurnal pattern for
N100−1000 – which represents chemically and physically aged particles
of larger spatial scale – were different from the diurnal patterns for the
other size fractions.
