Atmospheric reaction of methyl mercaptan with hydroxyl radical as an acid rain primary agent

For the CH3SH + OH atmospheric reaction, we study the mechanism, potential energy surface, thermodynamic parameters of all stationary points, and rate of generation of the main product channels at high, low, and intermediate pressures. In this study, the UMP2, UM062X, UB3LYP, and CCSD(T) methods by Dunning and Pople basis sets are used and the results are compared with the experimental data. It is theoretically predicted that the reaction has fourteen possible pathways with eight different products in the gas phase. The thermodynamic results show that OH radical extracts predominantly the hydrogen of the SH functional group compared to the hydrogen of the CH3 group of CH3SH. Also, the rate constant calculations indicate that the extraction of the hydrogen atom of the SH group has a major role in 150–3000 K, while a good contribution is observed for the hydrogen of methyl group above 1200 K. Our results show that the used methods lead to good agreement with experiment. Finally, we demonstrated that why the main path is the main path.

Trace element emissions during the 2018 Kilauea Lower East Rift Zone eruption

<p>The 2018 eruption on the Lower East Rift Zone of Kilauea volcano, Hawai’i released unprecedented fluxes of gases (>200 kt/d SO<sub>2</sub>) and aerosol into the troposphere [1,2]. The eruption affected air quality across the island and lava flows reached the ocean, forming a halogen-rich plume as lava rapidly boiled and evaporated seawater.</p><p>We present the at-source composition – gas and size-segregated aerosol – of both the magmatic plume (emitted from ‘Fissure 8’, F8) and the lava-seawater interaction plume (ocean entry, OE), including major gas species, and major and trace elements in non-silicate aerosol. Trace metal and metalloid (TMM) emissions during the 2018 eruption were the highest recorded for Kilauea, and the magmatic ‘fingerprint’ of TMMs (X/SO<sub>2</sub> ratios) in the 2018 plume is consistent with measurements made at the summit lava lake in 2008 [3], and with other rift and hotspot volcanoes [4,5].</p><p>We show that the OE plume composition predominantly reflects seawater composition with a small contribution from plagioclase +/- ash. However, elevated concentrations of some TMMs (Bi, Cd, Cu, Zn, Ag) with affinity for Cl-speciation in the gas phase cannot be accounted for by the silicate correction and therefore may derive from degassing of lava in the presence of elevated Cl<sup>-</sup>. In the case of silver and copper, concentrations in the OE plume are elevated above both the F8 plume and seawater.</p><p>At-vent speciation of TMMs in the F8 plume during oxidation (following a correction for ash contributions) was assessed using a Gibbs Energy Minimization algorithm (HSC chemistry, Outotec Research). We also demonstrate the sensitivity of speciation in the plume to the concentration of common ligand-forming elements, chlorine and sulfur. These results could be used as initial conditions in atmospheric reaction models to investigate how plume composition evolves as low-temperature chemistry takes over.</p><p>References:</p><p>[1] Neal C et al. (2019) Science</p><p>[2] Kern C et al. (2019) AGU Fall meeting abstract V43C-0209</p><p>[3] Mather T et al. (2012) GCA 83:292-323</p><p>[4] Zelenzki et al. (2013) Chem Geol 357:95-116</p><p>[5] Gauthier P-J et al. (2016) J Geophys 121:1610-1630</p>

Theoretical H + O3 rate coefficients from ring polymer molecular dynamics on an accurate global potential energy surface: Assessing experimental uncertainties

Thermal rate coefficients and kinetic isotope effects have been calculated for an important atmospheric reaction H/D + O3 → OH/OD + O2 based on an accurate permutation invariant polynomial-neural network...

Atmospheric reaction to the manifestations of the geodynamic activity of the Sulawes phenomenon according to satellite data

Using ATOVS satellite data (NOAA / POES) atmospheric disturbances that arose in the equatorial zone of Indonesia in the fall of 2018 were studied as a reaction to the geophysical manifestations of the geodynamic activity of a strong earthquake with a magnitude of M = 7,5. An archive of satellite information has been formed. A technique has been developed for analyzing the temperature of profiles during strong seismic activity of the Sulawes phenomenon. The atmospheric effects over the seismically active region of this earthquake were studied. It was found that in the troposphere during the study period anomalies with lower temperatures are observed above the epicenter region of the Indonesian earthquake and thermal anomalies with elevated temperatures are formed in the lower stratosphere.

SO2 formation and peroxy radical isomerization in the atmospheric reaction of OH radicals with dimethyl disulfide

The OH + DMDS reaction mainly forms SO2 and CH3O2 with a yield close to two and to a lesser extent RO2 isomerization products.