Particle Size Magnifier-hiukkaslaskurin havaintotehokkuus ja herkkyys laitteen supersaturaatiotasolle sekä yleisimmille meteorologisille suureille

Hiukkasten aktivointitodennäköisyys PSM:n sisällä riippuu laitteessa käytettävän kasvattavan fluidin supersaturaatiotasosta siten, että suuremmalla supersaturaatiotasolla saadaan aktivoitua enemmän ja pienempiä hiukkasia. Lisäksi meteorologiset suureet voivat vaikuttaa PSM:n toimintaan. Tämän tutkimuksen tarkoituksena oli selvittää Particle Size Magnifier-mittalaitteen (PSM) herkkyyttä sen asetuksille ja meteorologisille suureille sekä etsiä pienhiukkasmuodostukseen kontribuoivia syitä. Mittausten tarkkuuden kannalta on tärkeää ymmärtää millä PSM:n asetuksilla saadaan mitattua mahdollisimman tarkasti ilmakehän pienhiukkasia kokovälillä 1-3 nanometriä. Tutkimus suoritettiin vertaamalla PSM:n signaalia sekä taustaa eri meteorologisiin suureisiin, hiukkasmittauksiin sekä CI-APi-ToF:lla suoritettuihin höyrymittauksiin. Mittaukset suoritettiin vuosina 2014-2016 SMEAR II-asemalla Hyytiälässä. PSM:n asetuksia säädettiin vuosittain, joten pyrittiin määrittämään optimaaliset asetukset signaali-kohinasuhteen sekä signaalin voimakkuuden kannalta. PSM:n supersaturaation sekä signaalin amplitudin havaittiin laskevan vuosittain ja vastaavasti signaalikohinasuhde parani supersaturaationtason laskiessa. Vuonna 2014 PSM havaitsi selvän päiväsyklin sekä alle 2 nm että 2-3,5 nm hiukkasissa ja päiväsyklin havainnointi vaikeutui sitä seuraavina vuosina. Vuonna 2014 oli myös vahvimmat korrelaatiot CI-APi-ToF:n mittaamien höyryjen kanssa. Kemiallisista yhdisteistä parhaiten PSM:n signaalin kanssa korreloi rikkihappo, ja korrelaatio kaikkien höyryjen kanssa heikkeni supersaturaation heiketessä. PSM:n mittaamilla hiukkaspitoisuuksilla oli myös selkeä korrelaatio lämpötilan ja vesihöyryn pitoisuuden kanssa, mutta tämä saattaa johtua orgaanisten höyryjen vahvasta lämpötilariippuvuudesta. Tuloksista voidaan nähdä, että PSM:n voidaan pitää ainakin tasolla 20-30 hiukkasta per kuutiosenttimetri signaalikohinasuhdetta tai havaintoherkkyyttä merkittävästi vaarantamatta

Long-term measurement of sub-3 nm particles and their precursor gases in the boreal forest

The knowledge of the dynamics of sub-3 nm particles in the atmosphere is crucial for our understanding of the first steps of atmospheric new particle formation. Therefore, accurate and stable long-term measurements of the smallest atmospheric particles are needed. In this study, we analyzed over 5 years of particle concentrations in size classes 1.1-1.7 and 1.7-2.5 nm obtained with the particle size magnifier (PSM) and 3 years of precursor vapor concentrations measured with the chemical ionization atmospheric pressure interface time-of-flight mass spectrometer (CI-APi-ToF) at the SMEAR II station in Hyytiala, Finland. The results show that there are significant seasonal differences in median concentrations of sub-3 nm particles, but the two size classes behave partly differently. The 1.1-1.7 nm particle concentrations are highest in summer, while the 1.7-2.5 nm particle concentrations are highest in springtime. The 1.7-2.5 nm particles exhibit a daytime maximum in all seasons, while the 1.1-1.7 nm particles have an additional evening maximum during spring and summer. Aerosol precursor vapors have notable diurnal and seasonal differences as well. Sulfuric acid and highly oxygenated organic molecule (HOM) monomer concentrations have clear daytime maxima, while HOM dimers have their maxima during the night. HOM concentrations for both monomers and dimers are the highest during summer and the lowest during winter following the biogenic activity in the surrounding forest. Sulfuric acid concentrations are the highest during spring and summer, with autumn and winter concentrations being 2 to 3 times lower. A correlation analysis between the sub-3 nm concentrations and aerosol precursor vapor concentrations indicates that both HOMs (particularly their dimers) and sulfuric acid play a significant role in new particle formation in the boreal forest. Our analysis also suggests that there might be seasonal differences in new particle formation pathways that need to be investigated further.Peer reviewe

The standard operating procedure for Airmodus Particle Size Magnifier and nano-Condensation Nucleus Counter

Measurements of aerosol particles and clusters smaller than 3 nm in diameter are performed by many groups in order to detect recently formed or emitted nanoparticles and for studying the formation and early growth processes of aerosol particles. The Airmodus nano-Condensation Nucleus Counter (nCNC), consisting of a Particle Size Magnifier (PSM) and a Condensation Particle Counter (CPC) is a versatile tool to detect aerosol particles and clusters as small as ca. 1 nm in mobility diameter. It offers several different operation modes: fixed mode to measure the total particle number concentration with a fixed, but adjustable lower cut-off size and stepping and scanning modes for retrieving size-resolved information of ca. 1–4 nm particles. The size analysis is based on changing the supersaturation of the working fluid (diethylene glycol) inside the instrument, which changes the lowest detectable size. Here we present a standard operating procedure (SOP) for setting up, calibrating and operating the instrument for atmospheric field measurements. We will also present recommendations for data monitoring and analysis, and discuss some of the uncertainties related to the measurements. This procedure is the first step in harmonizing the use of the PSM/nCNC for atmospheric field measurements of sub-3 nm clusters and particles.Measurements of aerosol particles and clusters smaller than 3 nm in diameter are performed by many groups in order to detect recently formed or emitted nanoparticles and for studying the formation and early growth processes of aerosol particles. The Airmodus nano-Condensation Nucleus Counter (nCNC), consisting of a Particle Size Magnifier (PSM) and a Condensation Particle Counter (CPC) is a versatile tool to detect aerosol particles and clusters as small as ca. 1 nm in mobility diameter. It offers several different operation modes: fixed mode to measure the total particle number concentration with a fixed, but adjustable lower cut-off size and stepping and scanning modes for retrieving size-resolved information of ca. 1–4 nm particles. The size analysis is based on changing the supersaturation of the working fluid (diethylene glycol) inside the instrument, which changes the lowest detectable size. Here we present a standard operating procedure (SOP) for setting up, calibrating and operating the instrument for atmospheric field measurements. We will also present recommendations for data monitoring and analysis, and discuss some of the uncertainties related to the measurements. This procedure is the first step in harmonizing the use of the PSM/nCNC for atmospheric field measurements of sub-3 nm clusters and particles.Peer reviewe

Measurement report : Increasing trend of atmospheric ion concentrations in the boreal forest

The concentration of atmospheric ions affects the total aerosol particle number concentrations in the atmosphere as well as atmospheric new particle formation via ion-induced nucleation, ion-ion recombination, and effects on condensational growth. In this study, we investigate the concentrations and long-term trends of atmospheric ions in a boreal forest environment using 16 years of cluster ion (0.8-2 nm) and intermediate ion (2-7 nm) measurements and characterize the most important factors that explain those trends. We found that the median concentration of cluster ions in a boreal forest was 710 cm(-3), the median concentration of 2-4 intermediate ions was 14 cm(-3), and the median concentration of 4-7 nm intermediate ions was 9 cm(-3). The concentrations of both cluster and intermediate ions have been increasing over the 16-year measurement period, with cluster ion concentrations increasing by about 1 % yr(-1) and intermediate ion concentrations increasing 1.7 %-3.9 % yr(-1). The increase in cluster ion concentrations can be best explained by the decrease in the coagulation sink caused by larger aerosol particles. Meanwhile, the dependence of intermediate ion concentrations on meteorological conditions is evident, but ionization sources and the coagulation sink do not seem to explain the increasing trend. This is likely because the dynamics of intermediate ions are more complicated, so that ionization sources and the coagulation sink alone cannot directly explain the variation. Season-specific analysis of the ion concentrations suggests that while the coagulation sink is the limiting factor for the ion concentrations in spring and summer, the dynamics are different in autumn and winter. Based on our findings, we recommend that a more comprehensive analysis is needed to determine if the increase in ambient ion concentrations, increasing temperature, and changing abundance of condensable vapors makes ion-mediated and ion-induced nucleation pathways in the boreal forest more relevant in the future.Peer reviewe

Towards a concentration closure of sub-6 nm aerosol particles and sub-3 nm atmospheric clusters

Atmospheric clusters play a key role in atmospheric new particle formation and they are a sensitive indicator for atmospheric chemistry. Both the formation and loss of atmospheric clusters include a complex set of interlinked physical and chemical processes, and therefore their dynamics is highly non-linear. Here we derive a set of simple equations to estimate the atmospheric cluster concentrations in size ranges of 1.5–2 nm and 2–3 nm as well as 3–6 nm aerosol particles. We compared the estimated concentrations with measured ones both in a boreal forest site (the SMEAR II station in Hyytiälä, Finland) and in an urban site (the AHL/BUCT station in Beijing, China). We made this comparison first for 3–6 nm particles, since in this size range observations are more reliable than at smaller sizes, and then repeated it for the 2–3 nm size range. Finally, we estimated cluster concentrations in the 1.5–2 nm size range. Our main finding is that the present observations are able to detect a major fraction of existing atmospheric clusters.Atmospheric clusters play a key role in atmospheric new particle formation and they are a sensitive indicator for atmospheric chemistry. Both the formation and loss of atmospheric clusters include a complex set of interlinked physical and chemical processes, and therefore their dynamics is highly non-linear. Here we derive a set of simple equations to estimate the atmospheric cluster concentrations in size ranges of 1.5–2 nm and 2–3 nm as well as 3–6 nm aerosol particles. We compared the estimated concentrations with measured ones both in a boreal forest site (the SMEAR II station in Hyytiälä, Finland) and in an urban site (the AHL/BUCT station in Beijing, China). We made this comparison first for 3–6 nm particles, since in this size range observations are more reliable than at smaller sizes, and then repeated it for the 2–3 nm size range. Finally, we estimated cluster concentrations in the 1.5–2 nm size range. Our main finding is that the present observations are able to detect a major fraction of existing atmospheric clusters.Peer reviewe

An evaluation of new particle formation events in Helsinki during a Baltic Sea cyanobacterial summer bloom

Several studies have investigated new particle formation (NPF) events from various sites ranging from pristine locations, including forest sites, to urban areas. However, there is still a dearth of studies investigating NPF processes and subsequent aerosol growth in coastal yet semi-urban sites, where the tropospheric layer is a concoction of biogenic and anthropogenic gases and particles. The investigation of factors leading to NPF becomes extremely complex due to the highly dynamic meteorological conditions at the coastline especially when combined with both continental and oceanic weather conditions. Herein, we engage in a comprehensive study of particle number size distributions and aerosol-forming precursor vapors at the coastal semi-urban site in Helsinki, Finland. The measurement period, 25 June-18 August 2019, was timed with the recurring cyanobacterial summer bloom in the Baltic Sea region and coastal regions of Finland. Our study recorded several regional/local NPF and aerosol burst events during this period. Although the overall anthropogenic influence on sulfuric acid (SA) concentrations was low during the measurement period, we observed that the regional or local NPF events, characterized by SA concentrations on the order of 10(7) molec. cm(-3), occurred mostly when the air mass traveled over the land areas. Interestingly, when the air mass traveled over the Baltic Sea, an area enriched with algae and cyanobacterial blooms, high iodic acid (IA) concentration coincided with an aerosol burst or a spike event at the measurement site. Further, SA-rich bursts were seen when the air mass traveled over the Gulf of Bothnia, enriched with cyanobacterial blooms. The two most important factors affecting aerosol precursor vapor concentrations, and thus the aerosol formation, were speculated to be (1) the type of phytoplankton species and intensity of bloom present in the coastal regions of Finland and the Baltic Sea and (2) the wind direction. During the events, most of the growth of sub-3 nm particles was probably due to SA, rather than IA or methane sulfonic acid (MSA); however much of the particle growth remained unexplained indicative of the strong role of organics in the growth of particles, especially in the 3-7 nm particle size range. Further studies are needed to explore the role of organics in NPF events and the potential influence of cyanobacterial blooms in coastal locations.Peer reviewe

Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults

Background Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories. Methods We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5–19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI <18·5 kg/m2) and obesity (BMI ≥30 kg/m2). For schoolaged children and adolescents, we report thinness (BMI <2 SD below the median of the WHO growth reference) and obesity (BMI >2 SD above the median). Findings From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness. Interpretation The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesit

Atmospheric sub-10 nm aerosol number size distributions : measurement, analysis and implications

New particle formation (NPF) is a major source of atmospheric aerosol in terms of number concentration. As the newly formed particles grow, they can affect climate both directly and indirectly. However, understanding the first steps of NPF is an ongoing challenge. This is challenging in terms of the complexity of the process in question, but also in terms of directly observing NPF by measuring sub-10 nm particle number size distributions and NPF precursor vapors. In this thesis, the standard operation procedure (SOP) for measuring sub-3 nm particle number size distributions is first defined: how to setup the instrument, maintain it, and treat and quality control the data. I also determine the best settings for running the instrument in boreal forest conditions. A second key element of this thesis is the analysis of long-term time series data. I show that in the past twenty years, the number concentration of sub-10 nm charged aerosol particles has increased in the boreal forest while total aerosol number concentration has decreased. Our results suggest that the decreasing aerosol sink can lead to increased sub-10 nm aerosol concentrations and make NPF a larger source of aerosol loading in the future. I also studied the connection between NPF precursor vapors and sub-10 nm particle number concentrations at two sites. I confirmed that sulfuric acid and highly oxygenated molecules (HOMs) can participate in NPF in the boreal forest and discovered that in Po Valley the sulfuric acid clusters are likely stabilized by bases after which HOMs participate in the growth of the particles alongside sulfuric acid and bases. Overall, this thesis focuses on improving and analyzing measurements of sub-10 nm particle number size distributions. I demonstrated that changes in the aerosol num- ber concentration can imply how atmospheric particle dynamics change in the future. Furthermore, by linking variation in sub-10 nm particle number concentrations to pre- cursor vapor concentrations, precursors relevant to NPF in a given environment are determined.Ilmakehässä tapahtuva hiukkasmuodostus on yksi suurimmista pienhiukkasten lähteistä ilmakehässä. Kun nämä pienet vain muutaman nanometrin kokoiset hiukkaset kasvavat, vaikuttavat ne ilmastoon eri tavoin. Tähän hiukkasmuodostukseen liittyvien prosessien ymmärtämiseen tarvitaan kehittyneitä mittalaitteita ja analyysimenetelmiä. Tämän väitöskirjan tarkoituksen on standardisoida alle kolmen nanometrin hiukkasten kokojakaumamittausmenetelmät ja hyödyntää ilmakehän pienimpien, alle 10 nanometrin kokoisten hiukkasten pitoisuuksien pitkiä aikasarjoja ilmakehässä tapahtuvan hiukkasmuodostuksen ymmärtämiseen. Lisäksi haluan tässä väitöskirjassa kvantifioida alle 10 nanometrin hiukkasten pitoisuuksien pitkän ajan muutoksia. Tämän väitöskirjan tulokset osoittavat, että rikkihappo ja pitkälle hapettuneet orgaaniset yhdisteet tuottavat havumetsässä pienhiukkasia. Lisäksi osoitan että Po-joen laaksossa rikkihappo ja emäkset kuten amiinit muodostavat ensimmäiset vakaat klusterit jotka alkavat kasvaa suuremmiksi hiukkasiksi. Viimeiseksi, alle 10 nanometrin hiukkasten pitoisuuden kasvu vaikuttaa selittyvät lähinnä pienenevällä ilmakehän hiukkasten kokonaispitoisuudella, alleviivaten ilmakehän hiukkaspitoisuuden monimutkaisia dynamiikoita

Overview of measurements and current instrumentation for 1-10 nm aerosol particle number size distributions

Interest in understanding gas-to-particle phase transformation in several disciplines such as at-mospheric sciences, material synthesis, and combustion has led to the development of several distinct instruments that can measure the particle size distributions down to the sizes of large molecules and molecular clusters, at which the initial particle formation and growth takes place. These instruments, which include the condensation particle counter battery, a variety of electrical mobility spectrometers and the particle size magnifier, have been usually characterized in lab-oratory experiments using carefully prepared calibration aerosols. They are then applied, alone or in combination, to study the gas-to-particle transition in experiments that produce particles with a wide range of compositions and other properties. Only a few instrument intercomparisons in either laboratory or field conditions have been reported, raising the question: how accurately can the sub-10 nm particle number size distributions be measured with the currently available instrumentation? Here, we review previous studies in which sub-10 nm particle size distributions have been measured with at least two independent instruments. We present recent data from three sites that deploy the current state-of-the-art instrumentation: Hyytiala, Beijing, and the CLOUD chamber. After discussing the status of the sub-10 nm size distribution measurements, we present a comprehensive uncertainty analysis for these methods that suggests that our present understanding on the sources of uncertainties quite well captures the observed deviations be-tween different instruments in the size distribution measurements. Finally, based on present understanding of the characteristics of a number of systems in which gas-to-particle conversion takes place, and of the instrumental limitations, we suggest guidelines for selecting suitable in-struments for various applications.Peer reviewe