ABSTRACT
We presented a prototype of an operative air quality modelling system for Helsinki region that utilizes measurement data of variable quality (stations and sensors). The system continuously taps into various sources of real-time activity data to support the modelling. Being an updated version of FMI-Enfuser and developed during UIA-HOPE project we refer to this new modelling system as HOPE-Enfuser. Using public cloud storage, the modelling output is freely accessible for 3rd party applications. This is also the first time when we provide modelled Lung Deposited Surface Area (LDSA), and black carbon (BC) concentration predictions with our modelling system. For shipping, we present a novel near-real-time approach for the dynamic modelling of shipping emissions. HOPE-Enfuser uses data fusion to adjust the modelling and learn from the measurement evidence. The Covid-19 pandemic caused disruptions in the behavior of people and in the patterns of local emission sources. In this paper we will also discuss how these disruptions were perceived and captured by the model. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
ABSTRACT
Particle size distribution is a major factor in the health and climate effects of ambient aerosols, and it shows a large variation depending on the prevailing atmospheric emission sources. In this work, the particle number size distributions of ambient air were investigated at a suburban detached housing area in northern Helsinki, Finland, during a half-year period from winter to summer of 2020. The measurements were conducted with a scanning mobility particle sizer (SMPS) with a particle size range of 16–698 nm (mobility diameter), and the events with a dominant particle source were identified systematically from the data based on the time of the day and different particle physical and chemical properties. During the measurement period, four different types of events with a dominant contribution from either wood-burning (WB), traffic (TRA), secondary biogenic (BIO), or long-range transported (LRT) aerosol were observed. The particle size was the largest for the LRT events followed by BIO, WB, and TRA events with the geometric mean diameters of 72, 62, 57, and 41 nm, respectively. BIO and LRT produced the largest particle mode sizes followed by WB, and TRA with the modes of 69, 69, 46, and 25 nm, respectively. Each event type had also a noticeably different shape of the average number size distribution (NSD). In addition to the evaluation of NSDs representing different particle sources, also the effects of COVID-19 lockdown on specific aerosol properties were studied as during the measurement period the COVID-19 restrictions took place greatly reducing the traffic volumes in the Helsinki area in the spring of 2020. These restrictions had a significant contribution to reducing the concentrations of NOx and black carbon originating from fossil fuel combustion concentration, but insignificant effects on other studied variables such as number concentration and size distribution or particle mass concentrations (PM1, PM2.5, or PM10). © 2022 The Authors