Multiphase Chemistry in the Atmosphere.

Earth's atmosphere comprises a complex mix of gas and condensed phases, where condensed phases facilitate multiphase chemical reactions that would not occur in the gas phase alone. These reactions drive dynamic physical and chemical processes across various spatial and temporal scales, playing a crucial role in the cycling of atmospheric trace constituents. Multiphase chemistry significantly influences geochemical cycles, human health, and climate.

Iron-Containing Seed Particles Enhance α-Pinene Secondary Organic Aerosol Mass Concentration and Dimer Formation.

Secondary organic aerosol (SOA) comprises the majority of submicron particles and is important for air pollution, health, and climate. When SOA mixes with inorganic particles containing transition metals (e.g.

Quantification of Non-refractory Aerosol Nitrate in Ambient Air by Thermal Dissociation Cavity Ring-Down Spectroscopy.

A thermal dissociation cavity ring-down spectrometer (TD-CRDS) for real-time quantification of non-refractory aerosol nitrate in ambient air is described. The instrument uses four parallel detection channels and heated quartz inlets to convert particulate organic nitrate (pON) (at 350 °C) and ammonium nitrate (NHNO) aerosol (at 540 °C) to nitrogen dioxide (NO), whose mixing ratio is monitored via its absorption at 405 nm. Concentrations of aerosol nitrate are determined by difference relative to a parallel TD-CRDS channel in which aerosol is removed by in-line filtering.

Potential interferences in photolytic nitrogen dioxide converters for ambient air monitoring: Evaluation of a prototype.

Unlabelled: Mixing ratios of the criteria air contaminant nitrogen dioxide (NO) are commonly quantified by reduction to nitric oxide (NO) using a photolytic converter followed by NO-O chemiluminescence (CL). In this work, the performance of a photolytic NO converter prototype originally designed for continuous emission monitoring and emitting light at 395 nm was evaluated. Mixing ratios of NO and NO (= NO + NO) entering and exiting the converter were monitored by blue diode laser cavity ring-down spectroscopy (CRDS).