Juan Carlos Gomez Martin

Instituto De Astrofisica De Andalucia · Solar System

Mercury, a global contaminant, enters the stratosphere through convective uplift, but its chemical cycling in the stratosphere is unknown. We report the first model of stratospheric mercury chemistry based on a novel photosensitized oxidation mechanism. We find two very distinct Hg chemical regimes in the stratosphere: in the upper stratosphere, ab...

Sulfur trioxide is a critical intermediate for the sulfur cycle and the formation of sulfuric acid in the atmosphere. The traditional view is that sulfur trioxide is removed by water vapor in the troposphere. However, the concentration of water vapor decreases significantly with increasing altitude, leading to longer atmospheric lifetimes of sulfur...

The rate constants of many reactions currently considered to be important in the atmospheric chemistry of mercury remain to be measured in the laboratory. Here we report the first experimental determination of the rate constant of the gas-phase reaction between the HgBr radical and ozone, for which a value at room temperature of k(HgBr + O 3) = (7....

Iodine chemistry is an important driver of new particle formation in the marine and polar boundary layer. There are however conflicting views about how iodine gas-to-particle conversion proceeds. Laboratory studies indicate that the photooxidation of iodine produces iodine oxides (IxOy), which are well-known particle precursors. By contrast, nitrat...

Objective: To conduct a proof-of-concept study of the detection of two synthetic models of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using polarimetric imaging. Methods: Two SARS-CoV-2 models were prepared as engineered lentiviruses pseudotyped with the G protein of the vesicular stomatitis virus, and with the characteristic Spik...

Plain Language Summary Iodine has a profound impact on tropospheric chemistry and plays a key role in in mammalian metabolism. Marine aerosol is an atmospheric iodine reservoir and its carrier to continental food chains. However, the chemistry behind the varying concentrations of iodine‐bearing species observed in aerosol is poorly understood, whic...

Effective testing is essential to control the coronavirus disease 2019 (COVID-19) transmission. Here we report a-proof-of-concept study on hyperspectral image analysis in the visible and near-infrared range for primary screening at the point-of-care of SARS-CoV-2. We apply spectral feature descriptors, partial least square-discriminant analysis, an...

We have compiled and analyzed a comprehensive dataset of field observations of iodine speciation in marine aerosol. The soluble iodine content of fine aerosol (PM1) is dominated by soluble organic iodine (SOI) (~50%) and iodide (~30%), while the coarse fraction is dominated by iodate (~50%), with non-negligible amounts of iodide (~20%). The SOI fra...

We present the experimental phase function, degree of linear polarization (DLP), and linear depolarization (δ L) curves of a set of forsterite samples representative of low-absorbing cosmic dust particles. The samples are prepared using state-of-the-art size-segregating techniques to obtain narrow size distributions spanning a broad range of the sc...

Optical spectroscopic techniques have been commonly used to detect the presence of biofilm-forming pathogens (bacteria and fungi) in the agro-food industry. Recently, near-infrared (NIR) spectroscopy revealed that it is also possible to detect the presence of viruses in animal and vegetal tissues. Here we report a platform based on visible and NIR...

In this work, we describe the compilation and homogenization of an extensive data set of aerosol iodine field observations in the period between 1963 and 2018 and we discuss its spatial and temporal dependences by comparison with CAM-Chem model simulations. A close to linear relationship between soluble and total iodine in aerosol is found (∼80% ae...

Atmospheric aerosols play key roles in climate and have important impacts on human activities and health. Hence, much effort is directed towards developing methods of improved detection and discrimination of different types of aerosols. Among these, light scattering-based detection of aerosol offers several advantages including applications in both...

The first global atmospheric model (WACCM‐Al) of meteor‐ablated aluminum was constructed from three components: The Whole Atmospheric Community Climate Model (WACCM6); a meteoric input function for Al derived by coupling an astronomical model of dust sources in the solar system with a chemical meteoric ablation model; and a comprehensive set of neu...

In this work we describe the compilation and homogenization of an extensive dataset of aerosol iodine field observations in the period between 1963 and 2018 and we discuss the spatial and temporal dependences of total iodine in bulk aerosol by comparing the observations with CAM-Chem model simulations. Total iodine in aerosol shows a distinct latit...

The first global atmospheric model (WACCM-Al) of meteor-ablated aluminum was constructed from three components: the Whole Atmospheric Community Climate Model (WACCM6); a meteoric input function for Al derived by coupling an astronomical model of dust sources in the solar system with a chemical meteoric ablation model; and a comprehensive set of neu...

Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layers and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules...

Emitted from the oceans, iodine-bearing molecules are ubiquitous in the atmosphere and a source of new atmospheric aerosol particles of potentially global significance. However, its inclusion in atmospheric models is hindered by a lack of understanding of the first steps of the photochemical gas-to-particle conversion mechanism. Our laboratory resu...

Iodine is enriched in marine aerosols, particularly in coastal mid-latitude atmospheric environments, where it initiates the formation of new aerosol particles with iodic acid (HIO3) composition. However, particle formation in polluted and semipolluted locations is inhibited when the iodine monoxide radical (IO) is intercepted by NO2 to form the io...

Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layer and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules h...

We present laboratory measurements of the phase functions and degree of linear polarization (DLP) curves of a selection of millimeter-sized cosmic dust analog particles. The set includes particles with similar sizes but diverse internal structure (compact and porous) and absorbing properties. The measured phase functions are found to be in all case...

Measuring the size distribution of dust particles is of interest in many scientific and technological contexts. One of the most widely used techniques is laser light scattering (LLS), which provides the distribution of surface-equivalent spheres that fits the observed angular dependence of light scattered by a sample. We have revisited the problem...

The ablation of cosmic dust injects a range of metals into planetary upper atmospheres. In addition, dust particles which survive atmospheric entry can be an important source of organic material at a planetary surface. In this study the contribution of metals and organics from three cosmic dust sources – Jupiter-Family comets (JFCs), the Asteroid b...

We present experimental phase function and degree of linear polarization curves for seven samples of cometary dust analogues namely: ground pieces of Allende, DaG521, FRO95002, and FRO99040 meteorites, Mg-rich olivine and pyroxene, and a sample of organic tholins. The experimental curves have been obtained at the IAA Cosmic Dust Laboratory at a wav...

Meteoric ablation produces layers of metal atoms in the mesosphere and lower thermosphere (MLT). It has been known for more than 30 years that the Ca atom layer is depleted by over 2 orders of magnitude compared with Na, despite these elements having nearly the same elemental abundance in chondritic meteorites. In contrast, the Ca⁺ ion abundance is...

Meteoric ablation produces layers of metal atoms in the mesosphere and lower thermosphere (MLT). It has been known for more than 30 years that the Ca atom layer is depleted by over 2 orders of magnitude compared with Na, despite these elements having essentially the same elemental abundance in chondritic meteorites. In contrast, the Ca⁺ ion abundan...

Ablation of Mg from meteoroids entering the Earth's atmosphere was studied experimentally using a Meteoric Ablation Simulator: micron-sized particles of representative meteoritic material were flash heated to simulate atmospheric entry and the ablation rate of Mg with respect to Na measured by fast time-resolved laser-induced fluorescence. Over the...

We present the experimental scattering matrix as a function of the scattering angle of the lunar soil stimulant JSC-1A. The measurements were performed at 488, 520, and 647 nm, covering the range of scattering angles from 3° to 177°. The effect of sub-micron-sized particles on the measured phase function and degree of linear polarization has been s...

The article “Methanol dimer formation drastically enhances hydrogen abstraction from methanol by OH at low temperature” proposes a dimer mediated mechanism in order to explain the large low temperature rate coefficients for the OH + methanol reaction measured by several groups. It is demonstrated here theoretically that under the conditions of thes...

We report the first direct kinetic study of the gas-phase reaction NaOH + H → Na + H2O, which is central to the chemistry of sodium in the upper atmosphere and in flames. The reaction was studied in a fast flow tube where NaOH was observed by multi-photon ionization and time-of-flight mass spectrometry, yielding k(NaOH + H, 230 - 298 K) = (3.8 ± 0....

The ablation of cosmic dust particles entering the Earth’s upper atmosphere produces a layer of Ca atoms around 90 km. Here we present a set of kinetic experiments designed to understand the nature of the Ca molecular reservoirs on the underside of the layer. CaOH was produced by laser ablation of a Ca target in the fast flow tube, and detected by...

A meteoric sulfur input function and a sulfur ion chemistry scheme have been incorporated into a chemistry-climate model, in order to study the speciation of sulfur between the stratosphere and the thermosphere (~20 – 120 km), and the impact of the sulfur input from ablation of cosmic dust. The simulations have been compared to rocket observations...

We present a path forward on a long-standing issue concerning the flux of small and slow meteoroids, which are believed to be the dominant portion of the incoming meteoric mass flux into the Earth's atmosphere. Such a flux, which is predicted by dynamical dust models of the Zodiacal Cloud, is not evident in ground-based radar observations. For deca...

The rate coefficient of the Al + O2 reaction has been measured in a laser ablation-fast flow tube apparatus by monitoring atomic Al resonance absorption and AlO laser induced fluorescence (LIF). The rate constant has been found to be k(298 K) = (1.68 ± 0.24) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. Under conditions of near-stoichiometric conversion of Al into A...

A newly developed laboratory, Meteoric Ablation Simulator (MASI), is used to test model predictions of the atmospheric ablation of interplanetary dust particles (IDPs) with experimental Na, Fe, and Ca vaporization profiles. MASI is the first laboratory setup capable of performing time-resolved atmospheric ablation simulations, by means of precision...

We have used the Whole Atmosphere Community Climate Model (WACCM), with an updated treatment of loss processes, to determine the atmospheric lifetime of sulfur hexafluoride (SF6). The model includes the following SF6 removal processes: photolysis, electron attachment and reaction with mesospheric metal atoms. The Sodankylä Ion Chemistry (SIC) model...

The dissociative recombination of CaO+ ions with electrons has been studied in a flowing afterglow reactor. CaO+ was generated by the pulsed laser ablation of a Ca target, followed by entrainment in an Ar+ ion/electron plasma. A kinetic model describing the gas-phase chemistry and diffusion to the reactor walls was fitted to the experimental data,...

Supporting Information S1

On entering the Earth's atmosphere, micrometeoroids partially or completely ablate, leaving behind layers of metallic atoms and ions. The relative concentration of the various metal layers is not well explained by current models of ablation. Furthermore, estimates of the total flux of cosmic dust and meteoroids entering the Earth's atmosphere vary...

Observations of surface ozone (O3) mixing ratios carried out during two ground-based field campaigns in the Galápagos Islands are reported. The first campaign, PIQUERO (Primera Investigación sobre la Química, Evolución y Reparto de Ozono) was carried out from September 2000 to July 2002. The second study, CHARLEX (Climate and HAlogen Reactivity tro...

Analogues have been developed and characterised for both interplanetary dust and meteoric smoke particles. These include amorphous materials with elemental compositions similar to the olivine mineral solid solution series, a variety of iron oxides, undifferentiated meteorites (chondrites) and minerals which can be considered good terrestrial proxie...

Silicon monoxide (SiO) is a structurally complex compound exhibiting differentiated oxide-rich and silicon-rich nano-phases at length scales covering nanoclusters to the bulk. Although nano-sized and nano-segregated SiO has great technological potential (e.g. nano-silicon for optical applications) and is of enormous astronomical interest (e.g. form...

We have used the Whole Atmosphere Community Climate Model (WACCM), with an updated treatment of loss processes, to determine the atmospheric lifetime of SF6. The model includes the following SF6 removal processes: photolysis, electron attachment and reaction with mesospheric metal atoms. The Sodankylä Ion Chemistry (SIC) model is incorporated into...

Fluorinated compounds such as NF3 and C2F5Cl (CFC-115) are characterised by very large global warming potentials (GWPs) which result from extremely long atmospheric lifetimes and strong infrared absorptions in the atmospheric window. In this study we have experimentally determined the infrared absorption cross-sections of NF3 and CFC-115, calculate...

Clouds of CO2 ice particles have been observed in the Martian mesosphere. These clouds are believed to be formed through heterogeneous nucleation of CO2 on nanometer-sized meteoric smoke particles (MSPs) or upward propagated Martian dust particles (MDPs). Large uncertainties still exist in parameterizing the microphysical formation process of these...

Silicon is one of the most abundant elements in cosmic dust, and meteoric ablation injects a significant amount of Si into the atmosphere above 80 km. In this study, a new model for silicon chemistry in the mesosphere/lower thermosphere is described, based on recent laboratory kinetic studies of Si, SiO, SiO2 and Si+. Electronic structure calculati...

During the CHARLEX campaign in the Galápagos Islands, a Scanning Particle Mobility Sizer was deployed on San Cristobal Island in July-August 2011 to carry out size-resolved measurements of the concentration of submicron aerosols. To our knowledge these are the first measurements of aerosol concentrations in this unique environment. The particles wi...