Newly developed instrumentation for measuring highly oxidized molecules at atmospheric pressure

<p>The Highly Oxidized Molecule Ion Spectrometer (HOMIS) is a novel instrument for measuring the total concentration of highly oxidized molecules (HOM-s) (Bianchi et al., 2019) at atmospheric pressure. The device combines a chemical ionization charger with a multi-channel differential mobility analyzer. The chemical ionization charger is based on the principles outlined by Eisele and Tanner (1993). The charger is attached to a parallel differential mobility analyzer identical to the ones used in the Neutral cluster and Air Ion Spectrometer (NAIS, Mirme 2011), but with modified sample and sheath air flow rates to improve the mobility resolution of the device. The complete mobility distribution in the range from 3.2 to 0.056 cm<sup>2</sup>/V/s is measured simultaneously by 25 electrometers. The range captures the charger ions, monomers, dimers, trimers but also extends far towards larger particles to possibly detect larger HOM-s that have not been measured with existing instrumentation. The maximum time resolution of the device is 1 second allowing it to detect rapid changes in the sample. The device has been designed to be easy to use, require little maintenance and work reliably in various environments during long term measurements.</p><p>First results of the prototype were acquired from laboratory experiments and ambient measurements. Experiments were conducted at the Laboratory of Environmental Physics, University of Tartu. The sample was drawn from a reaction chamber where alpha-pinene and ozone were introduced. Initial results show a good response when concentrations of alpha-pinene and ozone were changed. </p><p>Ambient measurements were conducted at the SMEAR Estonia measurement station in a hemiboreal forest for 10 days in the spring and two months in the winter of 2020. The HOMIS measurements were performed together with a CI-APi-TOF (Jokinen et al., 2012).</p><p> </p><p>References:</p><p>Bianchi, F., Kurtén, T., Riva, M., Mohr, C., Rissanen, M. P., Roldin, P., Berndt, T., Crounse, J. D., Wennberg, P. O., Mentel, T. F., Wildt, J., Junninen, H., Jokinen, T., Kulmala, M., Worsnop, D. R., Thornton, J. A., Donahue, N., Kjaergaard, H. G. and Ehn, M. (2019), “Highly Oxygenated Organic Molecules (HOM) from Gas-Phase Autoxidation Involving Peroxy Radicals: A Key Contributor to Atmospheric Aerosol”, Chemical Reviews, 119, 6, 3472–3509</p><p>Eisele, F. L., Tanner D. J. (1993), “Measurement of the gas phase concentration of H2SO4 and methane sulfonic acid and estimates of H2SO4 production and loss in the atmosphere”, JGR: Atmospheres, 98, 9001-9010</p><p>Jokinen T., Sipilä M., Junninen H., Ehn M., Lönn G., Hakala J., Petäjä T., Mauldin III R. L., Kulmala M., and Worsnop D. R. (2012), “Atmospheric sulphuric acid and neutral cluster measurements using CI-APi-TOF”, Atmospheric Chemistry and Physics, 12, 4117–4125</p><p>Mirme, S. (2011), “Development of nanometer aerosol measurement technology”, Doctoral thesis, University of Tartu</p>

Secondary new particle formation initiated by sulfuric acid-amine nucleation in Beijing

<p>Secondary new particle formation is an important source of the number concentration of atmospheric aerosols. Despite relatively high coagulation sinks contributed by pre-existing aerosols, intensive new particle formation occurs frequently in polluted atmospheric environments such as in urban Beijing. Considering the measured concentrations of sulfuric acid and organic compounds, the contrast between the high coagulation sink and the frequent intensive NPF events in urban Beijing indicates an efficient nucleation mechanism. Based on long-term atmospheric measurements conducted at the campus of Beijing University of Chemical Technology, we show that sulfuric acid-amine nucleation is a governing mechanism to initiate new particle formation in urban Beijing. The molecular-level mechanism of sulfuric acid-amine nucleation, especially with low amine concentrations and high aerosol concentrations, are discussed. We present evidence for the existence of the missing amine molecules in the measured H<sub>2</sub>SO<sub>4</sub>-amine clusters. A neutral cluster needs to be ionized before it is detected by a mass spectrometer. Deprotonation or clustering with an additional reagent ion changes the stability of the original neutral cluster. Therefore, the amine molecules in neutral H<sub>2</sub>SO<sub>4</sub>-amine clusters may dissociate before detection. Combining measurements and cluster kinetic simulations, we show that although not directly detected, a considerable proportion of H<sub>2</sub>SO<sub>4</sub> monomers exist in the form of (H<sub>2</sub>SO<sub>4</sub>)<sub>1</sub>(amine)<sub>1</sub>, where the amine is most likely to be dimethylamine or trimethylamine. The evaporation rate of (H<sub>2</sub>SO<sub>4</sub>)<sub>1</sub>(amine)<sub>1</sub> is moderate and forming (H<sub>2</sub>SO<sub>4</sub>)<sub>1</sub>(amine)<sub>1</sub> is a critical step for H<sub>2</sub>SO<sub>4</sub>-amine nucleation. According to nucleation theory, (H<sub>2</sub>SO<sub>4</sub>)<sub>1</sub>(amine)<sub>1</sub> is the critical cluster at a low amine concentration, whereas H<sub>2</sub>SO<sub>4</sub>-amine nucleation may occur without a free energy barrier at a high amine concentration. The clustering between (H<sub>2</sub>SO<sub>4</sub>)<sub>1</sub>(amine)<sub>1</sub> and (H<sub>2</sub>SO<sub>4</sub>)<sub>n</sub>(amine)<sub>n</sub> is a major reaction pathway for the initial growth of H<sub>2</sub>SO<sub>4</sub>-amine clusters. These findings are supported by the measured H<sub>2</sub>SO<sub>4</sub> dimer concentration and its dependencies on amine concentrations and temperature in urban Beijing. Besides, the enhancement of cluster growth rate due to synergy between amines and ammonia are discussed.</p>

Dietary taste patterns in early childhood: the Generation R Study

ABSTRACT Background Taste preference is an important determinant of dietary intake and is influenced by taste exposure in early life. However, data on dietary taste patterns in early childhood are scarce. Objectives We aimed to evaluate dietary taste patterns in early childhood, to examine their tracking between the ages of 1 and 2 y, and to examine their associations with socioeconomic and lifestyle factors. Methods Dietary intake of children participating in a population-based cohort was assessed with a 211-item age-specific FFQ at the ages of 1 y ( n = 3629) and 2 y (n = 844) (2003–2007). Taste intensity values of FFQ food items were calculated based on a food taste database that had been previously constructed and evaluated using a trained adult sensory panel. Cluster analysis based on taste values identified 5 taste clusters that we named: “neutral,” “sweet and sour,” “sweet and fat,” “fat,” and “salt, umami and fat.” Linear regression models were used to examine associations of percentage energy (E%) intake from these taste clusters with socioeconomic and lifestyle factors. Results At the age of 1 y, 64% ± 13% (mean ± SD) of energy intake was obtained from the “neutral” cluster, whereas at age 2 y, this was 42% ± 8%. At age 2 y, children had higher energy intakes from the “sweet and fat” (18% ± 7%), “fat” (11% ± 4%), and “salt, umami, and fat” (18% ± 6%) clusters than at age 1 y (7% ± 6%, 6% ± 4%, and 11% ± 6%, respectively). In multivariable models, older maternal age, longer breastfeeding duration, and later introduction of complementary feeding were associated with more energy from the “neutral” cluster (e.g., β: 0.31 E%; 95% CI: 0.19, 0.43 E% per 1 mo longer breastfeeding). Higher child BMI was associated with more energy from the “salt, umami, and fat” cluster (β: 0.22 E%; 95% CI: 0.06, 0.38 E% per BMI standard deviation score). Conclusions Dietary taste patterns in this Dutch cohort were more varied and intense in taste at age 2 y than at 1 y, reaching a level similar to that previously observed in Dutch adults. Important factors related to dietary taste patterns of young children are maternal sociodemographic factors and feeding practices. This trial was registered at trialregister.nl as NL6484.

Differentiating between particle formation and growth events in an urban environment

Small aerosols at a given location in the atmosphere often originate in situ from new particle formation (NPF). However, they can also be produced and then transported from a distant location to the point of observation where they may continue to grow to larger sizes. This study was carried out in the subtropical urban environment of Brisbane, Australia, in order to assess the relative occurrence frequencies of NPF events and particle growth events with no NPF. We used a neutral cluster and air ion spectrometer (NAIS) to monitor particles and ions in the size range 2–42 nm on 485 days, and identified 236 NPF events on 213 days. The majority of these events (37 %) occurred during the daylight hours with just 10 % at night. However, the NAIS also showed particle growth with no NPF on many nights (28 %). Using a scanning mobility particle sizer (SMPS), we showed that particle growth continued at larger sizes and occurred on 70 % of nights, typically under high relative humidities. Most particles in the air, especially near coastal locations, contain hygroscopic salts such as sodium chloride that may exhibit deliquescence when the relative humidity exceeds about 75 %. The growth rates of particles at night often exceeded the rates observed during NPF events. Although most of these night time growth events were preceded by day time NPF events, the latter was not a prerequisite for growth. We conclude that particle growth in the atmosphere can be easily misidentified as NPF, especially when they are monitored by an instrument that cannot detect them at the very small sizes.

Description of Child and Adolescent Beverage and Anthropometric Measures According to Adolescent Beverage Patterns

Our objective is to retrospectively describe longitudinal beverage intakes and anthropometric measures according to adolescent beverage patterns. Data were collected from Iowa Fluoride Study participants (n = 369) using beverage questionnaires at ages 2–17 years. Weight and height were measured at ages 5, 9, 13 and 17 years. Cluster analyses were used to identify age 13- to 17-year beverage patterns. Treating age and beverage cluster as explanatory factors, sex-specific generalized linear mixed models were used to identify when differences in beverage intakes and anthropometric measures began. Predominant beverage intakes were higher in each of the corresponding clusters by 9–12.5 years; females with high milk intakes during adolescence and males with high 100% juice or sugar-sweetened beverage intakes during adolescence reported higher intakes of that beverage beginning at 2–4.7 years. Females and males in the 100% juice cluster had lower weights than other clusters beginning at 13 years, while females and males in the neutral cluster were shorter beginning at 13 years. Females in the water/sugar-free beverage cluster had higher body mass indices (BMIs) beginning at 9 years. Females and males in the 100% juice cluster had lower BMIs beginning at 5 and 9 years, respectively. Childhood beverage intakes and growth patterns differ according to adolescent beverage patterns.

Differentiating between particle formation and growth events in an urban environment

Small aerosols at a given location in the atmosphere often originate in-situ from new particle formation (NPF). However, they can also be produced and then transported from a distant location to the point of observation where they may continue to grow to larger sizes. This study was carried out in the subtropical urban environment of Brisbane, Australia, in order to assess the relative occurrence frequencies of NPF events and particle growth events with no NPF. We used a neutral cluster and air ion spectrometer (NAIS) to monitor particles and ions in the size range 2–42 nm on 485 days, and identified 236 NPF events on 213 days. The majority of these events (37 %) occurred during the daylight hours with just 10 % at night. However, the NAIS also showed particle growth with no NPF on many nights (28 %). Using a scanning mobility particle sizer (SMPS), we showed that particle growth continued at larger sizes and occurred on 70 % of nights, typically under high relative humidities. Most particles in the air, especially near coastal locations, contain hygroscopic salts such as sodium chloride that may exhibit deliquescence when the relative humidity exceeds about 75 %. The growth rates of particles at night often exceeded the rates observed during NPF events. Although most of these night time growth events were preceded by daytime NPF events, the latter was not a prerequisite for growth. We conclude that particle growth in the atmosphere can be easily misidentified as NPF, especially when they are monitored by an instrument that cannot detect them at the very small sizes.

Квантово-размерная зависимость энергии образования вакансии в заряженных малых металлических кластерах. Капельная модель

Self-consistent computations of the monovacancy formation energy are performed for Na_ N , Mg_ N , and Al_ N (12 < N ≤ 168) spherical clusters in the drop model for stable jelly. Scenarios of the Schottky vacancy formation and “bubble vacancy blowing” are considered. It is shown that the asymptotic behavior of the size dependences of the energy for the vacancy formation by these two mechanisms is different and the difference between the characteristics of a charged and neutral cluster is entirely determined by the difference between the ionization potentials of clusters and the energies of electron attachment to them.