Tuukka Petäjä

TL;DR: In this paper , the authors found that OA was more oxidized in pollution events in autumn than in winter, evidenced by the higher ratios of OA/OC (2.50 ± 0.69) and f44/f43 (1.90 − 0.54) in autumn rather than the corresponding values ( 1.80− 0.39 and 1.64−0.45) in winter).

Abstract: Atmospheric ions are produced after a cascade of reactions starting from initial ionization by high energetic radiation. Such ionization bursts generate ions that rapidly react and generate a suite of ion products. Primary ions are in the atmosphere originate from radioactive decay, gamma radiation from the soil or cosmic ray events. In this work, we modified an existing instrumentation and developed a novel setup for detecting ion bursts. The setup consists of a continuous flow ionization chamber coupled to Atmospheric Pressure interface Time-Of-Flight (APi-TOF) mass spectrometer. The APi-TOF sampling rate was set to 100 Hz in order to detect individual ion bursts from ionization events. Besides counting the individual ionization events, the developed setup is able to follow the rapidly changing chemical composition of ions during ion burst cascade. The setup can give us insights into the primary ionization mechanisms and their importance in atmospheric ion and aerosol dynamics.

TL;DR: The fraction of urban trees nearby the stations was found to be the most important urban morphological characteristic in explaining the PM2.5 air quality, followed by the height-normalized roughness length as the second important parameter.

TL;DR: In this paper , the authors investigated the trends and seasonality of particle number concentrations in nucleation, Aitken, and accumulation modes at 21 measurement sites in Europe and the Arctic, and compared the field measurements with the results from five climate models, namely EC-Earth3,ECHAM-M7, ECHAM-SALSA, NorESM1.2, and UKESM 1.

TL;DR: In this article , the authors studied how wet scavenging and cloud processes impacted particle concentrations and composition during transport to a rural boreal forest site in northern Europe, where they employed air mass history analysis and observational data.