Cluster Measurements at CLOUD using a High Resolution Ion Mobility Spectrometer - Mass Spectrometer Combination

Mass spectrometry is powerful tool for environmental and atmospheric chemistry analysis. Modern mass spectrometers demonstrate low detection limits, high sensitivity, and high resolving power. However, such high performance is not always enough to identify ambient ion clusters due to the clusters braking at the atmospheric pressure-to-vacuum interface of mass spectrometer. This study presents a high resolution ion mobility spectrometer-time-of-flight mass spectrometer (IMS-TOF) in the CLOUD experiment. This combination of orthogonal analytical techniques allows obtaining structural information in addition to mass-to-charge separation

Molecular Steps of Neutral Sulfuric Acid and Dimethylamine Nucleation in CLOUD

We have run a set of experiments in the CLOUD chamber at CERN, Switzerland, studying the effect of dimethylamine (DMA) on sulfuric acid (SA)-water nucleation using a nitrate based Chemical Ionization Atmospheric Pressure ionization Time-Of-Flight Mass Spectrometer (CI-APi-TOF). Experiment was designed to produce neutral high m/z SA-DMA clusters in close to atmospherically relevant conditions to be detected and characterized by the CI-APi-TOF. We aimed in filling up the gap in measurement techniques from molecular level up to climatically relevant aerosol particles and thus improve our understanding of the role of sulfuric acid and DMA in atmospheric nucleation

Charged and Neutral Binary Nucleation of Sulfuric Acid in Free Troposphere Conditions

We present a data set of binary nucleation of sulfuric acid and water, measured in the CLOUD chamber at CERN during the CLOUD3 and CLOUD5 campaigns. Four parameters have been varied to cover neutral and ion-induced binary nucleation processes: Sulfuric acid concentration (1e5 to 1e8 molecules per cm^(−3)), relative humidity (10% to 80%), temperature (208-293K) and ion concentration (0-4000 ions per cm^(−3)). In addition, classical nucleation theory implemented with hydrates and ion induced nucleation is compared with the data set. Our model and data are also compared with nucleation rates measured at Puy de Dome in the tropopause

How Do Amines Affect the Growth of Recently Formed Aerosol Particles

Growth rates of recently born nanometer-scale particles were measured during the CLOUD experiments at CERN. Combining the data from several recently developed measurement techniques allowed us to follow the growth of the particles starting from molecules to molecular clusters and finally to climatically relevant particles. We studied the binary system with sulphuric acid and water, and the ternary systems with ammonia or dimethylamine added to the chamber, both in purely neutral situation, and with ionization from cosmic rays or the CERN particle beam

Measurement of neutral sulfuric acid-dimethylamine clusters using CI-APi-TOF-MS

Recent studies suggest that dimethylamine could be a key ternary species in the formation and early growth of atmospheric aerosol particles. We report on nucleation studies for the ternary system of sulfuric acid, water and dimethylamine which have been performed at the CERN CLOUD chamber. These studies were conducted at atmospherically relevant concentrations of sulfuric acid and dimethylamine at 278 K and 38% RH. Two newly developed Chemical Ionization-Atmospheric Pressure interface-Time of Flight-Mass Spectrometers (CIAPi-TOF-MS) were used to measure the time-resolved concentration of neutral clusters containing sulfuric acid and dimethylamine. Results from other instrumental techniques are included in the analysis as well to obtain a deeper insight into the occurring mechanisms. It is the first time that the neutral nucleation pathway has been studied in such detail from the early generation of sulfuric acid monomers up to particle sizes reaching several nanometers

Evolution of α-Pinene Oxidation Products in the Presence of Varying Oxidizers: Negative APi-TOF Point of View

Laboratory experiments conducted in the frame of the CLOUD project at CERN investigated the oxidation of α-pinene oxidation products in a carefully controlled environment and with different oxidation conditions: 1) pure ozonolysis (with the use of an hydroxyl radical (⋅OH) scavenger), 2) ozonolysis without use of a scavenger, and 3) pure ⋅OH oxidation using nitrous acid (HONO) to produce ⋅OH. The anions and negatively charged clusters present in the chamber were analyzed and their chemical composition compared for the different oxidation pathways

Evolution of alpha-pinene oxidation products in the presence of varying oxidizers: CI-APi-TOF point of view

Alpha-pinene oxidation was studied in the CERN CLOUD chamber under near atmospheric conditions using varying levels of different oxidizers (i.e., O_3 , HO_x and NO_x with differing gas mixture compositions) in the presence and absence of UV-radiation, SO_2 and additional organic traces; ammonia (NH_3) and dimethylamine (DMA). The oxidation products and their evolution due to aging in the chamber were studied using a novel CI-APi-TOF technique, with the nitrate ion (NO^−_3 ) based chemical ionization (CI) scheme. We aimed to the results that would indicate how different oxidizing pathways lead to different product distributions in the product clusters detected

Measuring Composition & Growth of Ion Clusters of Sulfuric Acid, Ammonia, Amines & Oxidized Organics as First Steps of Nucleation in the CLOUD Experiment

The mechanisms behind the nucleation of vapors forming new particles in the atmosphere had been proven difficult to establish. One main aim of the CLOUD experiment was to explore in detail these first steps of atmospheric new particle formation by performing extremely well controlled laboratory experiments. We examined nucleation and growth in the presence of different mixtures of vapors, including sulfuric acid, ammonia, dimethylamine, and oxidation products of pinanediol or α-pinene. Among the employed state-of-the-art instrumentation, a high-resolution mass spectrometer that directly sampled negatively charged ions and clusters proved particularly useful. We were able to resolve most of the chemical compositions found for charged sub-2nm clusters and to observe their growth in time. These compositions reflected the mixture of condensable vapors in the chamber and the role of each individual vapor in forming sub-2nm clusters could be explored. By inter-comparing between individual experiments and ambient observations, we try to establish which vapors participate in nucleation in the actual atmosphere, and how

Highly Oxidized Second-Generation Products from the Gas-Phase Reaction of OH Radicals with Isoprene

The gas-phase reaction of OH radicals with isoprene has been investigated in an atmospheric pressure flow tube at 293 ± 0.5 K with special attention to the second-generation products. Reaction conditions were optimized to achieve a predominant reaction of RO₂ radicals with HO₂ radicals. Chemical ionization–atmospheric pressure interface–time-of-flight mass spectrometry served as the analytical technique in order to follow the formation of RO₂ radicals and closed-shell products containing at least four O atoms in the molecule. The reaction products were detected as adducts with the reagent ions using acetate, lactate, or nitrate in the ionization process. Observed signals were attributed to a series of C₅-products with multiple hydroxy, hydroperoxy, and probably carbonyl groups. H/D exchange experiments supported the product identification. The generation of the detected second-generation products can be mechanistically explained starting from the OH radical reaction of hydroxy hydroperoxide isomers, HO–C₅H₈–OOH. These isomers represent the dominant products of the initial OH radical attack on isoprene. Dihydroxy dihydroperoxides, (HO)₂–C₅H₈–(OOH)₂, were analyzed as the main second-generation products beside the dihydroxy epoxides. A simple kinetic analysis revealed that the observed second-generation products in total (other than dihydroxy epoxides) were formed with an estimated molar yield of 10.0_–1.5^+2.1 % with respect to converted hydroxy hydroperoxides. A formation yield of 5.8_–0.9^+1.3 % has been deduced for the main product (HO)₂–C₅H₈–(OOH)₂. The detected, highly oxidized isoprene products represent potential secondary organic aerosol precursors. An annual, global (HO)₂–C₅H₈–(OOH)₂ formation strength of (16–35) × 10⁶ metric tons is estimated based on product measurements of this study and literature data regarding the formation of the dihydroxy epoxide isomers for an annual isoprene emission of 454 × 10⁶ metric tons of carbon