Factors determining the occurrence and characteristics of new particle formation events - A study over a continent

New Particle Formation (NPF) events, an important source of ultrafine particles in the atmosphere, were studied in multiple sites across Europe. Apart from the importance of meteorological conditions and atmospheric composition variables and compounds, such as the solar radiation intensity, the relative humidity or the condensation sink in the occurrence and development of the events, the importance of the origin of the incoming air masses and the specific characteristics that come with them is underlined. The increased formation rate of particles of 10 nm diameter calculated in the present study (being at a greater size than that of the initial particle formation occurring at about 1.5 nm and thus affected as a metric by the growth of the particles) and growth rates observed within the urban environment are associated with the increased presence of condensable species found in such environments, regardless of the geographical location within the European continent. The NPF process is also studied according to the different aspects that define it, the frequency of the events, the formation and growth rates of the particles, and the specific role of each one of the atmospheric variables was calculated throughout Europe using the large dataset available, providing an insight of the effect of these variables on the NPF mechanisms. Finally, the range of the effect of these events on the ultrafine particle composition in each area was studied and the importance of the events in the air quality of a given area is displayed

Measurement report: Interpretation of wide-range particulate matter size distributions in Delhi

Delhi is one of the world's most polluted cities, with very high concentrations of airborne particulate matter. However, little is known about the factors controlling the characteristics of wide-range particle number size distributions. Here, new measurements are reported from three field campaigns conducted in winter and pre-monsoon and post-monsoon seasons at the Indian Institute of Technology campus in the south of the city. Particle number size distributions were measured simultaneously, using a scanning mobility particle sizer and a GRIMM optical particle monitor, covering 15 nm to >10 μm diameter. The merged, wide-range size distributions were categorized into the following five size ranges: nucleation (15-20 nm), Aitken (20-100 nm), accumulation (100 nm-1 μm), large fine (1-2.5 μm), and coarse (2.5-10 μm) particles. The ultrafine fraction (15-100 nm) accounts for about 52 % of all particles by number (PN10 is the total particle number from 15 nm to 10 μm) but just 1 % by PM10 volume (PV10 is the total particle volume from 15 nm to 10 μm). The measured size distributions are markedly coarser than most from other parts of the world but are consistent with earlier cascade impactor data from Delhi. Our results suggest substantial aerosol processing by coagulation, condensation, and water uptake in the heavily polluted atmosphere, which takes place mostly at nighttime and in the morning hours. Total number concentrations are highest in winter, but the mode of the distribution is largest in the post-monsoon (autumn) season. The accumulation mode particles dominate the particle volume in autumn and winter, while the coarse mode dominates in summer. Polar plots show a huge variation between both size fractions in the same season and between seasons for the same size fraction. The diurnal pattern of particle numbers is strongly reflective of a road traffic influence upon concentrations, especially in autumn and winter, although other sources, such as cooking and domestic heating, may influence the evening peak. There is a clear influence of diesel traffic at nighttime, when it is permitted to enter the city, and also indications in the size distribution data of a mode < 15 nm, which is probably attributable to CNG/LPG vehicles. New particle formation appears to be infrequent and is, in this dataset, limited to 1 d in the summer campaign. Our results reveal that the very high emissions of airborne particles in Delhi, particularly from traffic, determine the variation in particle number size distributions

The effect of meteorological conditions and atmospheric composition in the occurrence and development of new particle formation (NPF) events in Europe

Although new particle formation (NPF) events have been studied extensively for some decades, the mechanisms that drive their occurrence and development are yet to be fully elucidated. Laboratory studies have done much to elucidate the molecular processes involved in nucleation, but this knowledge has yet to be conclusively linked to NPF events in the atmosphere. There is great difficulty in successful application of the results from laboratory studies to real atmospheric conditions due to the diversity of atmospheric conditions and observations found, as NPF events occur almost everywhere in the world without always following a clearly defined trend of frequency, seasonality, atmospheric conditions, or event development. The present study seeks common features in nucleation events by applying a binned linear regression over an extensive dataset from 16 sites of various types (combined dataset of 85 years from rural and urban backgrounds as well as roadside sites) in Europe. At most sites, a clear positive relation with the frequency of NPF events is found between the solar radiation intensity (up to R-2 = 0.98), temperature (up to R-2 = 0.98), and atmospheric pressure (up to R-2 = 0.97), while relative humidity (RH) presents a negative relation (up to R-2 = 0.95) with NPF event frequency, though exceptions were found among the sites for all the variables studied. Wind speed presents a less consistent relationship, which appears to be heavily affected by local conditions. While some meteorological variables (such as the solar radiation intensity and RH) appear to have a crucial effect on the occurrence and characteristics of NPF events, especially at rural sites, it appears that their role becomes less marked at higher average values. The analysis of chemical composition data presents interesting results. Concentrations of almost all chemical compounds studied (apart from O-3) and the condensation sink (CS) have a negative relationship with NPF event frequency, though areas with higher average concentrations of SO2 had higher NPF event frequency. Particulate organic carbon (OC), volatile organic compounds (VOCs), and particulate-phase sulfate consistently had a positive relation with the growth rate of the newly formed particles. As with some meteorological variables, it appears that at increased concentrations of pollutants or the CS, their influence upon NPF frequency is reduced.Peer reviewe

A phenomenology of new particle formation (NPF) at 13 European sites

New particle formation (NPF) events occur almost everywhere in the world and can play an important role as a particle source. The frequency and characteristics of NPF events vary spatially, and this variability is yet to be fully understood. In the present study, long-term particle size distribution datasets (minimum of 3 years) from 13 sites of various land uses and climates from across Europe were studied, and NPF events, deriving from secondary formation and not traffic-related nucleation, were extracted and analysed. The frequency of NPF events was consistently found to be higher at rural background sites, while the growth and formation rates of newly formed particles were higher at roadsides (though in many cases differences between the sites were small), underlining the importance of the abundance of condensable compounds of anthropogenic origin found there. The growth rate was higher in summer at all rural background sites studied. The urban background sites presented the highest uncertainty due to greater variability compared to the other two types of site. The origin of incoming air masses and the specific conditions associated with them greatly affect the characteristics of NPF events. In general, cleaner air masses present higher probability for NPF events, while the more polluted ones show higher growth rates. However, different patterns of NPF events were found, even at sites in close proximity (<ĝ€¯200ĝ€¯km), due to the different local conditions at each site. Region-wide events were also studied and were found to be associated with the same conditions as local events, although some variability was found which was associated with the different seasonality of the events at two neighbouring sites. NPF events were responsible for an increase in the number concentration of ultrafine particles of more than 400ĝ€¯% at rural background sites on the day of their occurrence. The degree of enhancement was less at urban sites due to the increased contribution of other sources within the urban environment. It is evident that, while some variables (such as solar radiation intensity, relative humidity, or the concentrations of specific pollutants) appear to have a similar influence on NPF events across all sites, it is impossible to predict the characteristics of NPF events at a site using just these variables, due to the crucial role of local conditions. © Author(s) 2021

Research data supporting "A study on the performance of low-cost sensors for source apportionment at an urban background site"

Meteorological data and low-cost sensor and regulatory grade instrument particle composition data from BAQS (16/10/2020 - 30/10/2020

Research data supporting "Assessing the sources of particles at an urban background site using both regulatory instruments and low-cost sensors – A comparative study"

Chemical composition and meteorological data for a period of about 1.5 month (January – March 2020) from the Birmingham University Air Quality supersite. The dataset supports paper that explores the potential of low-cost sensors in particle source identificatio

Low-cost sensor data for source apportionment

The zipped folder contains low-cost sensor particulate matter data from 3 sites in England, UK, Curzon Street in Birmingham, Montsorrel quarry in Leicestershire and Market Street in Charlbury

Research data supporting "Monitoring and apportioning sources of indoor air quality using low-cost particulate matter sensors"

Particle concentration measurements using an Alphasense OPC-N3 and a TSI from 4 locations at a house in Birmingham. Meteorological data from the station at the Birmingham International