Measurement report: In situ observations of deep convection without lightning during the tropical cyclone Florence 2018

Hurricane Florence was the sixth named storm in the Atlantic hurricane season 2018. It caused dozens of deaths and major economic damage. In this study, we present in situ observations of trace gases within tropical storm Florence on 2 September 2018, after it had developed a rotating nature, and of a tropical wave observed close to the African continent on 29 August 2018 as part of the research campaign CAFE Africa (Chemistry of the Atmosphere: Field Experiment in Africa) with HALO (High Altitude and LOng Range Research Aircraft). We show the impact of deep convection on atmospheric composition by measurements of the trace gases nitric oxide (NO), ozone (O$_{3}$), carbon monoxide (CO), hydrogen peroxide (H$_{2}$O$_{2}$), dimethyl sulfide (DMS) and methyl iodide (CH$_{3}$I) and by the help of color-enhanced infrared satellite imagery taken by GOES-16. While both systems, i.e., the tropical wave and the tropical storm, are deeply convective, we only find evidence for lightning in the tropical wave using both in situ NO measurements and data from the World Wide Lightning Location Network (WWLLN)

Emission Rates of Volatile Organic Compounds from Humans

Human-emitted volatile organic compounds (VOCs) are mainly from breath and the skin. In this study, we continuously measured VOCs in a stainless-steel environmentally controlled climate chamber (22.5 m3, air change rate at 3.2 h–1) occupied by four seated human volunteers using proton transfer reaction time-of-flight mass spectrometry and gas chromatography mass spectrometry. Experiments with human whole body, breath-only, and dermal-only emissions were performed under ozone-free and ozone-present conditions. In addition, the effect of temperature, relative humidity, clothing type, and age was investigated for whole-body emissions. Without ozone, the whole-body total emission rate (ER) was 2180 ± 620 μg h–1 per person (p–1), dominated by exhaled chemicals. The ERs of oxygenated VOCs were positively correlated with the enthalpy of the air. Under ozone-present conditions (∼37 ppb), the whole-body total ER doubled, with the increase mainly driven by VOCs resulting from skin surface lipids/ozone reactions, which increased with relative humidity. Long clothing (more covered skin) was found to reduce the total ERs but enhanced certain chemicals related to the clothing. The ERs of VOCs derived from this study provide a valuable data set of human emissions under various conditions and can be used in models to better predict indoor air quality, especially for highly occupied environments

Atomic emission detector with gas chromatographic separation and cryogenic pre-concentration (CryoTrap-GC-AED) for atmospheric trace gas measurements

A gas detection system has been developed, characterized and deployed for pressurized gas phase sample analyses and near real-time online measurements. It consists of a cryogenic pre-concentrator (CryoTrap), a gas chromatograph (GC), and a new high-resolution atomic emission detector (AED III). Here the CryoTrap–GC–AED instrumental setup is presented and the performance for iodine (1635 ± 135 counts I-atom-1 pptv-1), sulfur (409 ± 57 counts S-atom-1 pptv-1), carbon (636 ± 69 counts C-atom-1 pptv-1), bromine (9.1 ± 1.8 counts Br-atom-1 pptv-1) and nitrogen (28 ± 2 counts N-atom-1 pptv-1) emission lines is reported and discussed. The limits of detection (LODs) are in the low pptv range (0.5–9.7 pptv) and the signal is linear to at least 4 orders of magnitude, which makes it a suitable method for diverse volatile organic compound (VOC) measurements in the atmosphere, even in remote, unpolluted regions. The new system was utilized in a field study in a boreal forest at Hyytiälä, Finland in late summer 2016 which made monoterpene measurements possible among the other VOCs. Furthermore, pressurized global whole-air sample measurement collected onboard the Lufthansa Airbus A340-600 IAGOS-CARIBIC aircraft in the upper troposphere and lower stratosphere region was carried out with the new setup, providing the observational data of many VOCs, including the long-lived organosulfur compound carbonyl sulfide

Atomic emission detector with gas chromatographic separation and cryogenic pre-concentration (CryoTrap-GC-AED) for atmospheric trace gas measurements

A gas detection system has been developed, characterized, and deployed for pressurized gas-phase sample analyses and near-real-time online measurements. It consists of a cryogenic pre-concentrator (CryoTrap), a gas chromatograph (GC), and a new high-resolution atomic emission detector (AED III HR). Here the CryoTrap–GC–AED instrumental setup is presented, and the performance for iodine (1635 ± 135 counts I atom−1 pptv−1), sulfur (409 ± 57 counts S atom−1 pptv−1), carbon (636 ± 69 counts C atom−1 pptv−1), bromine (9.1 ± 1.8 counts Br atom−1 pptv−1), and nitrogen (28 ± 2 counts N atom−1 pptv−1) emission lines is reported and discussed. The limits of detection (LODs) are in the low parts per trillion by volume range (0.5–9.7 pptv), and the signal is linear to at least 4 orders of magnitude, which makes it a suitable method for diverse volatile organic compound (VOC) measurements in the atmosphere, even in remote unpolluted regions. The new system was utilized in a field study in a boreal forest at Hyytiälä, Finland, in late summer 2016, which made monoterpene measurements possible among other VOCs. Furthermore, pressurized global whole-air samples, collected on board the Lufthansa Airbus A340-600 IAGOS–CARIBIC aircraft in the upper troposphere and lower stratosphere region, were measured with the new setup, providing data for many VOCs, including the long-lived organosulfur compound carbonyl sulfide

The Indoor Chemical Human Emissions and Reactivity Project (ICHEAR): Methods

Here we present the new project “Indoor Chemical Human Emissions and Reactivity” (ICHEAR), which is focused on examining the role of human emissions on indoor air chemistry. The specific goal of this project is to investigate the impact of exhaled and dermally emitted human bioeffluents on the chemical compounds present in indoor air, their chemical transformations and total OH reactivity (overall loss rate of OH radical) under different conditions comprising a variety of factors (temperature, relative humidity, ozone, clothing level, age of human participants). The measurements were conducted in stainless steel climate chambers at the Technical University of Denmark (DTU) using state-of-the-art instruments from the Max Planck Institute for Chemistry (MPIC), the Swedish Environmental Research Institute (IVL), and École Polytechnique Fédérale de Lausanne (EPFL). During April-May 2019, groups of four persons (two males and two females) occupied the chamber daily and their emissions were quantified. This poster describes the chambers, instrumentation and the overall experimental approach used in ICHEAR

Shipborne measurements of methane and carbon dioxide in the Middle East and Mediterranean areas and contribution from oil and gas emissions

The increase of atmospheric methane (CH4) and carbon dioxide (CO2), two main anthropogenic greenhouse gases, is largely driven by fossil sources. Sources and sinks remain insufficiently characterised in the Mediterranean and Middle East areas, where very few in situ measurements area available. We investigated the atmospheric distribution of CH4 and CO2 in the region through shipborne measurement in July and August 2017. High mixing ratios were observed over the Suez Canal, Red Sea and Arabian Gulf, while generally lower mixing ratios were observed over the Gulfs of Aden and Oman. We probe the origin of CO2 and CH4 excess mixing ratio by using correlations with light alkanes and through the use of a Lagrangian model coupled to two different emission inventories of anthropogenic sources. We find that the CO2 and especially the CH4 enhancements are mainly linked to nearby oil and gas (O&G) activities over the Arabian Gulf, and a mixture of other sources over the Red Sea. The isomeric ratio of pentane is shown to be a useful indicator of the O&G component of atmospheric CH4 at the regional level. Upstream emissions linked to oil in the Northern Arabian Gulf seem to be underestimated while gas-related emissions in the Southern Gulf are overestimated in our simulations. Our results highlight the need for improvement of inventories in the area to better characterize the changes in magnitude and the complex distribution of the O&G sources in the Middle East

The human oxidation field

Hydroxyl (OH) radicals are highly reactive species that can oxidize most pollutant gases. In this study, high concentrations of OH radicals were found when people were exposed to ozone in a climate-controlled chamber. OH concentrations calculated by two methods using measurements of total OH reactivity, speciated alkenes, and oxidation products were consistent with those obtained from a chemically explicit model. Key to establishing this human-induced oxidation field is 6-methyl-5-hepten-2-one (6-MHO), which forms when ozone reacts with the skin-oil squalene and subsequently generates OH efficiently through gas-phase reaction with ozone. A dynamic model was used to show the spatial extent of the human-generated OH oxidation field and its dependency on ozone influx through ventilation. This finding has implications for the oxidation, lifetime, and perception of chemicals indoors and, ultimately, human health