In this work, the spatial extent of new particle formation (NPF) events and the relative probability of observing particles originating from different spatial origins around three rural sites in eastern China were investigated using the NanoMap method, using particle number size distribution (PNSD) data and air mass back trajectories. The length of the datasets used were 7, 1.5, and 3 years at rural sites Shangdianzi (SDZ) in the North China Plain (NCP), Mt. Tai (TS) in central eastern China, and Lin'an (LAN) in the Yangtze River Delta region in eastern China, respectively. Regional NPF events were observed to occur with the horizontal extent larger than 500 km at SDZ and TS, favoured by the fast transport of northwesterly air masses. At LAN, however, the spatial footprint of NPF events was mostly observed around the site within 100–200 km. Difference in the horizontal spatial distribution of new particle source areas at different sites was connected to typical meteorological conditions at the sites. Consecutive large-scale regional NPF events were observed at SDZ and TS simultaneously and were associated with a high surface pressure system dominating over this area. Simultaneous NPF events at SDZ and LAN were seldom observed. At SDZ the polluted air masses arriving over the NCP were associated with higher particle growth rate (GR) and new particle formation rate ( J ) than air masses from Inner Mongolia (IM). At TS the same phenomenon was observed for J , but GR was somewhat lower in air masses arriving over the NCP compared to those arriving from IM. The capability of NanoMap to capture the NPF occurrence probability depends on the length of the dataset of PNSD measurement but also on topography around the measurement site and typical air mass advection speed during NPF events. Thus the long-term measurements of PNSD in the planetary boundary layer are necessary in the further study of spatial extent and the probability of NPF events. The spatial extent, relative probability of occurrence, and typical evolution of PNSD during NPF events presented in this study provide valuable information to further understand the climate and air quality effects of new particle formation.

In coastal areas, there is increased concern about emissions from shipping activities and the associated impact on air quality. We have assessed the ship aerosol properties and the contribution to coastal particulate matter (PM) and nitrogen dioxide (NO₂) levels by measuring ship plumes in ambient conditions at a site in southern Sweden, within a Sulfur Emission Control Area. Measurements took place during a summer and a winter campaign, 10 km downwind of a major shipping lane. Individual ships showed large variability in contribution to total particle mass, organics, sulfate, and NO₂. The average emission contribution of the shipping lane was 29±13 and 37±20 ng m⁻³ to PM_0.5, 18±8 and 34±19 ng m⁻³ to PM_0.15, and 1.21±0.57 and 1.11±0.61 µg m⁻³ to NO₂, during winter and summer, respectively. Sulfate and organics dominated the particle mass and most plumes contained undetectable amounts of equivalent black carbon (eBC). The average eBC contribution was 3.5±1.7 ng m⁻³ and the absorption Ångström exponent was close to 1. Simulated ageing of the ship aerosols using an oxidation flow reactor showed that on a few occasions, there was an increase in sulfate and organic mass after photochemical processing of the plumes. However, most plumes did not produce measurable amounts of secondary PM upon simulated ageing.

A large portion of atmospheric aerosol particles consists of secondary material produced by oxidation reactions. The relative importance of secondary organic aerosol (SOA) can increase with improved emission regulations. A relatively simple way to study potential particle formation in the atmosphere is by using oxidation flow reactors (OFRs) which simulate atmospheric ageing. Here we report on the first ambient OFR ageing experiment in Europe, coupled with scanning mobility particle sizer (SMPS), aerosol mass spectrometer (AMS) and proton transfer reaction (PTR)-MS measurements. We found that the simulated ageing did not produce any measurable increases in particle mass or number concentrations during the two months of the campaign due to low concentrations of precursors. Losses in the reactor increased with hydroxyl radical (OH) exposure and with increasing difference between ambient and reactor temperatures, indicating fragmentation and evaporation of semivolatile material.

Concentrations of aerosol particles in Poland and their sources are rarely discussed in peer-reviewed journal articles despite serious air quality issues. A source apportionment of carbonaceous aerosol particles was performed during winter at a rural background environment field site in north-eastern Poland. Data were used of light absorption at seven wavelengths and levoglucosan concentrations along existing monitoring of PM_2.5, organic carbon and elemental carbon (OC/EC) at the Diabła Góra EMEP monitoring site between January 17 and March 19 during the EMEP intensive winter campaign of 2018. Average PM_2.5, OC, EC, equivalent black carbon (eBC) and levoglucosan concentrations and standard deviations amounted to 18.5 ± 9.3, 4.5 ± 2.5, 0.57 ± 0.28, 1.04 ± 0.62 and 0.134 ± 0.084 µg m⁻³ respectively. Various tools for source apportionment were used to obtain a source contribution to carbonaceous matter (CM) with three components. The wood combustion source component contributed 1.63 µg m⁻³ (21%), domestic coal combustion 3.3 µg m⁻³ (41%) and road transport exhaust 2.9 µg m⁻³ (38%). Similar levels and temporal variability were found for the nearby Lithuanian site of Preila, corroborating the Polish results.