Aqueous chemistry in the clouds of Venus

<p>Droplet chemistry in the clouds of Venus may play a role in regulating the depletion of sulfur dioxide and water vapor in and above the clouds. The specific nature of this chemistry is unknown. In this talk, I present three different scenarios for aqueous chemistry in the cloud droplets:</p><ul><li>Hydroxide salts</li> <li>Reduced sulfites</li> <li>Iron sulfates</li> </ul><p>I will discuss the effects of these three different aqueous chemistries, some of which may be accessible via remote observation. The iron sulfate chemistry in particular provides a candidate for the unknown UV absorber.</p>

New Insights into Health Risk Assessments for Inhalational Exposure to Metal(loid)s: The Application of Aqueous Chemistry Modelling in Understanding Bioaccessibility from Airborne Particulate Matter

Aqueous modelling of chemical speciation in simulated lung fluid (SLF) enables a better understanding of the underlying chemical factors that influence metal(loid) inhalation bioaccessibility from airborne particulate matter. Such an approach can be used to supplement experimental techniques that are integral to the health risk assessment of metal(loid) exposure by inhalational routes. In this paper, we modelled the aqueous chemistry of airborne particulate-bound metal(loid)s (As, Cu, Mn, Pb and Zn) in a SLF based on Gamble’s solution (neutral pH). The modelling was performed using two software packages (Geochemist’s Workbench 14 and OLI Studio 9.5) and a total of five thermochemical databases (GWB Thermo, MINTEQ, PHREEQC, WATEQ4F and the default database for OLI Studio). Modelled results were compared with experimentally determined bioaccessibilities for the NIST 2710a standard reference material (SRM) and with literature-reported bioaccessibilities for NIST 1648a and BCR 038 SRMs. Whilst the models correctly describe the observed increase in bioaccessibility for more dilute solid/liquid extraction ratios, the performance of the models against the fractional bias of the mean (FBmean) and the normalised mean square error (NMSE) statistical metrics was generally outside the acceptance criteria. Findings from an analysis of the main aqueous chemical species predicted to be present in SLF indicate that carbonate and chloride complexes of Cu, Mn, Pb and Zn predominate, whilst free cations (for Cu, Mn and Zn) and hydroxides (for Cu) also play a role in solubilisation. Arsenic is not predicted to form significant complexes with the SLF components and is present in solution mainly as the HAsO42− ion and its conjugate acid, H2AsO4−. For modelled runs where glycine and citrate were present, significant increases in the bioavailability of Cu and Zn were predicted as a result of complexation with these ligands. An additional finding from our experimental bioaccessibility results for NIST 2710a was that the inclusion of the lung fluid surfactant dipalmitoylphosphatidylcholine (DPPC) in the SLF did not significantly affect the bioaccessibility. Our study provides useful insights into the likely aqueous- and solid-phase speciation of metal(loid)s in SLF and highlights that future developments in this area should consider the role of mineralogy and surface interactions.

Unraveling the critical role of Zn-phyllomanganates in zinc ion batteries

Rechargeable batteries based on MnO2/Zn aqueous chemistry have emerged as a viable alternative to Li-ion batteries (LIB), owing to their low material cost, high safety, sustainable redox chemistry, and remarkable...

Expanding manganese(IV) aqueous chemistry: unusually stable water-soluble hexahydrazide clathrochelate complexes

Mn cage complexes are rare, and the ones successfully isolated in the solid state are not stable in water and organic solvents. Herein, we present the first report of mononuclear...

Quantification of solid fuel combustion and aqueous chemistry contributions to secondary organic aerosol during wintertime haze events in Beijing

In recent years, intense haze events in megacities such as Beijing have received significant study. Although secondary organic aerosol (SOA) has been identified as a major contributor to such events, knowledge of its sources and formation mechanisms remains uncertain. We investigate this question through the first field deployment of the extractive electrospray ionisation time-of-flight mass spectrometer (EESI-TOF-MS) in Beijing, together with an Aerodyne long time-of-flight aerosol mass spectrometer (L-TOF AMS). Measurements were performed during autumn and winter 2017, capturing the transition from non-heating to heating seasons. Source apportionment resolved four factors related to primary organic aerosols (traffic, cooking, biomass burning, and coal combustion), as well as four related to secondary organic aerosol (SOA). Of the SOA factors, two were related to solid fuel combustion (SFC), one to SOA generated from aqueous chemistry, and one to mixed/indeterminate sources. The SFC factors were identified from spectral signatures corresponding to aromatic oxidation products, while the aqueous SOA factor was characterised by signatures of small organic acids and diacids, and unusually low CO+/CO2+ fragment ratios measured by the AMS. Solid fuel combustion was the dominant source of SOA during the heating season. However, a comparably intense haze event was also observed in the non-heating season, and was dominated by the aqueous SOA factor. Aqueous chemistry was promoted by the combination of high relative humidity and air masses passing over high NOx regions to the south and east of Beijing, leading to high particulate nitrate. The resulting high liquid water content was highly correlated with the concentration of the aqueous SOA factor. These results highlight the strong compositional variability between different haze events, indicating the need to consider multiple formation pathways and precursor sources to describe SOA during intense haze events in Beijing.