An oxidation flow reactor for simulating and accelerating secondary aerosol formation in aerosol liquid water and cloud droplets
Ningjin Xu, Chen Le, David R. Cocker, Kunpeng Chen, Ying-Hsuan Lin, and Don R. Collins
Atmos. Meas. Tech., 17, 4227–4243, https://doi.org/10.5194/amt-17-4227-2024, 2024
A flow-through reactor was developed that exposes known mixtures of gases or ambient air to very high concentrations of the oxidants that are responsible for much of the chemistry that takes place in the atmosphere. Like other reactors of its type, it is primarily used to study the formation of particulate matter from the oxidation of common gases. Unlike other reactors of its type, it can simulate the chemical reactions that occur in liquid water that is present in particles or cloud droplets.
Unfiltering of the EarthCARE Broadband Radiometer (BBR) observations: the BM-RAD product
Almudena Velázquez Blázquez, Edward Baudrez, Nicolas Clerbaux, and Carlos Domenech
Atmos. Meas. Tech., 17, 4245–4256, https://doi.org/10.5194/amt-17-4245-2024, 2024
The Broadband Radiometer measures shortwave and total-wave radiances filtered by the spectral response of the instrument. To obtain unfiltered solar and thermal radiances, the effect of the spectral response needs to be corrected for, done within the BM-RAD processor. Errors in the unfiltering are propagated into fluxes; thus, accurate unfiltering is required for their proper estimation (within BMA-FLX). Unfiltering errors are estimated to be <0.5 % for the shortwave and <0.1 % for the longwave.
Using metal oxide gas sensors to estimate the emission rates and locations of methane leaks in an industrial site: assessment with controlled methane releases
Rodrigo Rivera-Martinez, Pramod Kumar, Olivier Laurent, Gregoire Broquet, Christopher Caldow, Ford Cropley, Diego Santaren, Adil Shah, Cécile Mallet, Michel Ramonet, Leonard Rivier, Catherine Juery, Olivier Duclaux, Caroline Bouchet, Elisa Allegrini, Hervé Utard, and Philippe Ciais
Atmos. Meas. Tech., 17, 4257–4290, https://doi.org/10.5194/amt-17-4257-2024, 2024
We explore the use of metal oxide semiconductors (MOSs) as a low-cost alternative for detecting and measuring CH4 emissions from industrial facilities. MOSs were exposed to several controlled releases to test their accuracy in detecting and quantifying emissions. Two reconstruction models were compared, and emission estimates were computed using a Gaussian dispersion model. Findings show that MOSs can provide accurate emission estimates with a 25 % emission rate error and a 9.5 m location error.
The CHIMERE chemistry-transport model v2023r1
Laurent Menut, Arineh Cholakian, Romain Pennel, Guillaume Siour, Sylvain Mailler, Myrto Valari, Lya Lugon, and Yann Meurdesoif
Geosci. Model Dev., 17, 5431–5457, https://doi.org/10.5194/gmd-17-5431-2024, 2024
A new version of the CHIMERE model is presented. This version contains both computational and physico-chemical changes. The computational changes make it easy to choose the variables to be extracted as a result, including values of maximum sub-hourly concentrations. Performance tests show that the model is 1.5 to 2 times faster than the previous version for the same setup. Processes such as turbulence, transport schemes and dry deposition have been modified and updated.
Micro-business participation in collective flood adaptation: lessons from scenario-based analysis in Ho Chi Minh City, Vietnam
Javier Revilla Diez, Roxana Leitold, Van Tran, and Matthias Garschagen
Nat. Hazards Earth Syst. Sci., 24, 2425–2440, https://doi.org/10.5194/nhess-24-2425-2024, 2024
Micro-businesses, often overlooked in adaptation research, show surprising willingness to contribute to collective adaptation despite limited finances and local support. Based on a study in Ho Chi Minh City in Vietnam, approximately 70 % are ready for awareness campaigns, and 39 % would provide financial support if costs were shared. These findings underscore the need for increased involvement of micro-businesses in local adaptation plans to enhance collective adaptive capacity.
Abstract
Tropospheric ozone (O3) is an important greenhouse gas that is also hazardous to human health. The formation of O3 is sensitive to the levels of its precursors NOx (≡NO + NO2) and peroxy radicals, for example, generated by the oxidation of volatile organic compounds (VOCs). A better understanding of this sensitivity will show how changes in the levels of these trace gases could affect O3 levels today and in the future, and thus air quality and climate. In this study, we investigate O3 sensitivity in the tropical troposphere based on in situ observations of NO, HO2 and O3 from four research aircraft campaigns between 2015 and 2023. These are OMO (Oxidation Mechanism Observations), ATom (Atmospheric Tomography Mission), CAFE Africa (Chemistry of the Atmosphere Field Experiment in Africa) and CAFE Brazil, in combination with simulations using the EMAC atmospheric chemistry—climate model. We use the metric α(CH3O2) together with NO to investigate the O3 formation sensitivity. We show that O3 formation is generally NOx-sensitive in the lower and middle tropical troposphere and is in a transition regime in the upper troposphere. By distinguishing observations impacted by lightning or not we show that NO from lightning is the most important driver of O3 sensitivity in the tropics. NOx-sensitive chemistry predominates in regions without lightning impact, with α(CH3O2) ranging between 0.56 and 0.82 and observed average O3 levels between 35 and 55 ppbv. Areas affected by lightning exhibit strongly VOC-sensitive O3 chemistry with α(CH3O2) of about 1 and average O3 levels between 55 and 80 ppbv.
Variance estimations in the presence of intermittent interference and their applications to incoherent scatter radar signal processing
Qihou Zhou, Yanlin Li, and Yun Gong
Atmos. Meas. Tech., 17, 4197–4209, https://doi.org/10.5194/amt-17-4197-2024, 2024
We discuss several robust estimators to compute the variance of a normally distributed random variable to deal with interference. Compared to rank-based estimators, the methods based on the geometric mean are more accurate and are computationally more efficient. We apply three robust estimators to incoherent scatter power and velocity processing, along with the traditional sample mean estimator. The best estimator is a hybrid estimator that combines the sample mean and a robust estimator.
Surface equilibrium vapor pressure of organic nanoparticles measured from the dynamic-aerosol-size electrical mobility spectrometer
Ella Häkkinen, Huan Yang, Runlong Cai, and Juha Kangasluoma
Atmos. Meas. Tech., 17, 4211–4225, https://doi.org/10.5194/amt-17-4211-2024, 2024
We report measurements of evaporation kinetics and surface equilibrium vapor pressures for various laboratory-generated organic nanoparticles using the dynamic-aerosol-size electrical mobility spectrometer (DEMS), a recent advancement in aerosol process characterization. Our findings align well with literature values, demonstrating DEMS's effectiveness. We suggest future improvements to DEMS and anticipate its potential for probing aerosol-related kinetic processes with unknown mechanisms.
Abstract
The accurate assessment of hydraulic transmissivity in rock fractures filled with particles is not only a scientific challenge but also a critical need for various industrial applications. However, the intricate dynamics of particle erosion and pore clogging that govern transmissivity evolution remain largely unexplored. In this study, we experimentally examine the fluid-driven particle migration behavior in filled fractures and its consequent impact on fracture transmissivity under various hydraulic gradients, normal stresses, and fracture apertures. We find that escalating hydraulic gradients not only intensify particle erosion through amplified fluid drag forces and hydro-mechanical coupling effects but also lead to an increase in the size of migrating particles, thereby augmenting pore clogging. The dynamics of erosion and clogging define four distinct migration phases within the filled fractures. Variations in normal stress and initial fracture aperture significantly alter the particle arrangement and the soil structure stability within the fractures, thereby modulating the progress of particle migration in response to hydraulic gradients. The pattern of particle migration in filled fractures dictates the development of the internal pore structure and normal deformation, ultimately affecting fracture transmissivity. We propose an empirical expression to encapsulate the comprehensive evolution of fracture transmissivity across different particle migration patterns. Our research advances the understanding of fluid-driven particle migration within filled fractures and provides a practical tool for the precise determination of hydraulic properties of fractured rocks amidst complex geological settings.
Abstract
Methane clumped isotope signatures of abiogenesis may be diagnostic of the origin of methane on Earth and other planetary bodies. We performed synthesis of abiogenic methane in hydrothermal conditions between 130 and 300°C and determined δ13C, δD, Δ13CH3D, and Δ12CH2D2. The experiments were performed by heating water in the presence of Fe0 powder and CO. The reduction of water on metallic iron led to the formation of H2. CO was reacted with both H2 and H2O, generating both CH4 and CO2. Methane δ13C values are isotopically depleted by ∼25‰ relative to the CO starting material. This is consistent with carbon isotopic equilibrium between methane, carbon monoxide and carbon dioxide in our experiments. In contrast, D/H ratios are inconsistent with equilibrium isotopic fractionation, as illustrated by δD values of methane fractionated by ∼500‰ relative to starting H2O. This suggests that under our experimental conditions, hydrogen additions to carbon may be governed by kinetics. Δ13CH3D values track experimental temperature, with values between +1.5‰ and +5.0‰ for most samples. In contrast, Δ12CH2D2 values are displaced from equilibrium. We find exclusively negative Δ12CH2D2 values, showing deficits down to 40‰ relative to thermodynamic equilibrium. We interpret the data as evidence for distinct, kinetically induced D/H pools contributing to methane assembly, that is, a combinatorial effect. The cumulative D/H fractionations associated with CO hydrogenation explain the direction and magnitude of Δ12CH2D2 values during abiotic methane formation. We suggest that near equilibrium Δ13CH3D with negative Δ12CH2D2 signatures will help identify methane formed abiotically in nature.
