Experimental investigation of ion–ion recombination under atmospheric conditions

We present the results of laboratory measurements of the ion–ion recombination coefficient at different temperatures, relative humidities and concentrations of ozone and sulfur dioxide. The experiments were carried out using the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at CERN, the walls of which are made of conductive material, making it possible to measure small ions. We produced ions in the chamber using a 3.5 GeV c^(−1) beam of positively charged pions (π^+) generated by the CERN Proton Synchrotron (PS). When the PS was switched off, galactic cosmic rays were the only ionization source in the chamber. The range of the ion production rate varied from 2 to 100 cm^(−3) s^(−1), covering the typical range of ionization throughout the troposphere. The temperature ranged from −55 to 20 °C, the relative humidity (RH) from 0 to 70 %, the SO_2 concentration from 0 to 40 ppb, and the ozone concentration from 200 to 700 ppb. The best agreement of the retrieved ion–ion recombination coefficient with the commonly used literature value of 1.6 × 10^(−6) cm^3 s^(−1) was found at a temperature of 5 °C and a RH of 40 % (1.5 ± 0.6) × 10^(−6) cm^3 s^(−1). At 20 °C and 40 % RH, the retrieved ion–ion recombination coefficient was instead (2.3 ± 0.7) × 10^(−6) cm^3 s^(−1). We observed no dependency of the ion–ion recombination coefficient on ozone concentration and a weak variation with sulfur dioxide concentration. However, we observed a more than fourfold increase in the ion–ion recombination coefficient with decreasing temperature. We compared our results with three different models and found an overall agreement for temperatures above 0 °C, but a disagreement at lower temperatures. We observed a strong increase in the recombination coefficient for decreasing relative humidities, which has not been reported previously

Charge distribution uncertainty in differential mobility analysis of aerosols

The inference of particle size distributions from differential mobility analyzer (DMA) data requires knowledge of the charge distribution on the particles being measured. The charge distribution produced by a bipolar aerosol charger depends on the properties of the ions produced in the charger, and on the kinetics of charge transfer from molecular ions or ion clusters to the particles. A single parameterization of a theoretically predicted charge distribution is employed in most DMA analyses regardless of the atmospheric conditions being probed. Deviations of the actual charge distribution from that assumed in the data analysis will bias the estimated particle size distribution. We examine these potential biases by modeling measurements and data inversion using charge distributions calculated for a range of atmospheric conditions. Moreover, simulations were performed using the ion-to-particle flux coefficients predicted for a range of properties of both the particles and ions. To probe the biases over the full range of particle sizes, the measurements were simulated through an atmospheric new particle formation event. The differences between the actual charge distribution and that according to the commonly used parametrization resulted in biases as large as a factor of 5 for nucleation-mode particles, and up to 80% for larger particles. Incorrect estimates of the relative permittivity of the particles or not accounting for the temperature and pressure effects for measurements at 10 km altitude produced biases in excess of 50%; three-fold biases result from erroneous estimates of the ion mobility distribution. We further report on the effects of the relative permittivity of the ions, the relative concentrations of negative and positive ions, and truncation of the number of charge states considered in the inversion

Aerosol charging state at an urban site: new analytical approach and implications for ion-induced nucleation

The charging state of aerosol populations was determined using an Ion-DMPS in Helsinki, Finland between December 2008 and February 2010. We extrapolated the charging state and calculated the ion-induced nucleation fraction to be around 1.3 % ± 0.4 % at 2 nm and 1.3 % ± 0.5 % at 1.5 nm, on average. We present a new method to retrieve the average charging state for a new particle formation event, at a given size and polarity. We improve the uncertainty assessment and fitting technique used previously with an Ion-DMPS. We also use a new theoretical framework that allows for different concentrations of small ions for different polarities (polarity asymmetry). We extrapolate the ion-induced fraction using polarity symmetry and asymmetry. Finally, a method to calculate the growth rates from the behaviour of the charging state as a function of the particle diameter using polarity symmetry and asymmetry is presented and used on a selection of new particle formation events

Aerosol dynamics simulations on the connection of sulphuric acid and new particle formation

International audienceWe have performed a series of simulations with an aerosol dynamics box model to study the connection between new particle formation and sulphuric acid concentration. For nucleation either activation mechanism with a linear dependence on the sulphuric acid concentration or ternary H2O-H2SO4-NH3 nucleation was assumed. We investigated the factors that affect the sulphuric acid dependence during the early stages of particle growth, and tried to find conditions which would yield the linear dependence between the particle number concentration at 3?6 nm and sulphuric acid, as observed in field experiments. The simulations showed that the correlation with sulphuric acid may change during the growth from nucleation size to 3?6 nm size range, the main reason being the size dependent growth rate between 1 and 3 nm. In addition, the assumed size for the nucleated clusters had a crucial impact on the sulphuric acid dependence at 3 nm. The simulations yielded a linear dependence between the particle number concentration at 3 nm and sulphuric acid, when a low saturation vapour pressure for the condensable organic vapour was assumed, or when nucleation took place at ~2 nm instead of ~1 nm. Comparison of results with activation and ternary nucleation showed that ternary nucleation cannot explain the experimentally observed linear or square dependence on sulphuric acid

Feasibility of Combining the Phosphatidylinositol 3-Kinase Inhibitor Copanlisib With Rituximab-Based Immunochemotherapy in Patients With Relapsed Indolent B-cell Lymphoma

Combining oral PI3K inhibitors with immunochemotherapy for indolent B-cell lymphoma has been associated with toxicity. In the Phase III CHRONOS-4 safety run-in, 21 patients received intravenous copanlisib plus rituximab-based immunochemotherapy. There were no dose-limiting toxicities, and preliminary objective response rates were 90% to 100%. Copanlisib is the first PI3K inhibitor to demonstrate safe, tolerable, and effective combinability with immunochemotherapy, with evaluation ongoing. Background: When treating indolent B-cell lymphoma, combining continuously administered oral phosphatidylinositol 3-kinase (PI3K) inhibitors with immunochemotherapy has been associated with toxicity. CHRONOS-4 (Phase III; NCT02626455) investigates the intravenous, intermittently administered pan-class I PI3K inhibitor copanlisib in combination with rituximab plus bendamustine (R-B) or rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) in patients with relapsed indolent B-cell lymphoma. We report safety run-in results. Patients and Methods: Patients aged >= 18 years with relapsed CD20-positive indolent B-cell lymphoma received copanlisib (45 mg, increasing to 60 mg if no dose-limiting toxicities) weekly on an intermittent schedule with R-B or R-CHOP. Primary objective was to identify a recommended Phase III dose (RP3D). We also assessed objective response, safety, and tolerability. Results: Ten patients received copanlisib plus R-B and 11 received copanlisib plus R-CHOP. No dose-limiting toxicities were reported; RP3D was 60 mg. All patients had >= 1 treatment-emergent adverse event (TEAE), most commonly (all grade/grade 3/4) for copanlisib plus R-B: decreased neutrophil count (80%/50%), nausea (70%/0%), decreased platelet count (60%/10%), hyperglycemia (60%/50%); for copanlisib plus R-CHOP: hyperglycemia (82%/64%), hypertension (73%/64%), decreased neutrophil count (64%/64%). Two and 8 patients had serious TEAEs with copanlisib plus R-B and R-CHOP, respectively. Among evaluable patients, objective response rates were 90% (5 complete, 4 partial) and 100% (3 complete, 7 partial) with copanlisib plus R-B and R-CHOP, respectively. Conclusion: Copanlisib is the first PI3K inhibitor to demonstrate safe, tolerable, and effective combinability with immunochemotherapy in patients with relapsed indolent B-cell lymphoma at full dose (60 mg). Further evaluation is ongoing. (C) 2021 The Author(s). Published by Elsevier Inc.Peer reviewe

Using measurements of the aerosol charging state in determination of the particle growth rate and the proportion of ion-induced nucleation

The fraction of charged nucleation mode particles as a function of particle diameter depends on the particle growth rate and the proportion of particles formed via ion-induced nucleation. In this study we have tested the applicability of recent data analysis methods to determine the growth rate and the proportion of ion-induced nucleation from the measured charged fractions. For this purpose we have conducted a series of aerosol dynamic simulations covering a wide range of atmospheric conditions. The growth rate and initial fraction of charged particles were estimated from simulated data using these methods and compared with the values obtained directly from the simulations. We found that the data analysis methods used in this study should not be used when the nuclei growth rate is less than ~3 nm h<sup>−1</sup>, or when charged particles grow much more rapidly than neutral ones. Furthermore, we found that the difference in removal rates of neutral and charged particles should be taken into account when estimating the proportion of ion-induced nucleation. Neglecting the higher removal rate of charged particles compared with that of neutral ones could result in an underestimation of the proportion of ion-induced nucleation by up to a factor of 2. This underestimation is further increased if charged particles grow more rapidly than neutral ones. We also provided a simple way of assessing whether these methods are suitable for analyzing data measured under specific conditions. The assessment procedure was illustrated using a few examples of actual measurement sites with a more detailed examination of the typical conditions observed at the SMEAR II station in Hyytiälä, Finland

Experimental investigation of ion-ion recombination under atmospheric conditions

We present the results of laboratory measurements of the ion–ion recombination coefficient at different temperatures, relative humidities and concentrations of ozone and sulfur dioxide. The experiments were carried out using the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at CERN, the walls of which are made of conductive material, making it possible to measure small ions. We produced ions in the chamber using a 3.5 GeV c−1 beam of positively charged pions (π+) generated by the CERN Proton Synchrotron (PS). When the PS was switched off, galactic cosmic rays were the only ionization source in the chamber. The range of the ion production rate varied from 2 to 100 cm−3 s−1, covering the typical range of ionization throughout the troposphere. The temperature ranged from −55 to 20 °C, the relative humidity (RH) from 0 to 70 %, the SO2 concentration from 0 to 40 ppb, and the ozone concentration from 200 to 700 ppb. The best agreement of the retrieved ion–ion recombination coefficient with the commonly used literature value of 1.6 × 10−6 cm3 s−1 was found at a temperature of 5 °C and a RH of 40 % (1.5 ± 0.6) × 10−6 cm3 s−1. At 20 °C and 40 % RH, the retrieved ion–ion recombination coefficient was instead (2.3 ± 0.7) × 10−6 cm3 s−1. We observed no dependency of the ion–ion recombination coefficient on ozone concentration and a weak variation with sulfur dioxide concentration. However, we observed a more than fourfold increase in the ion–ion recombination coefficient with decreasing temperature. We compared our results with three different models and found an overall agreement for temperatures above 0 °C, but a disagreement at lower temperatures. We observed a strong increase in the recombination coefficient for decreasing relative humidities, which has not been reported previously