We conducted a WSOC-specific ¹³C analysis of submicron marine aerosols over the eastern equatorial Pacific for the first time. The analysis of ¹³C combined with monosaccharides provides evidence of a significant contribution of marine dissolved organic carbon (DOC) to submicron particles in the MBL regardless of the oceanic area. The study demonstrates that DOC is closely correlated with the submicron WSOC and implies that it may characterize background OA in the MBL over the study region.

Here we present a day of case study measurements of the vertical distribution of bromine monoxide over the coastal region of the Gulf of Mexico. These measurements are used to assess the contribution of bromine radicals to the oxidation of elemental mercury in the troposphere. We find that the measured levels of bromine in the troposphere are sufficient to quickly oxidize mercury, which has significant implications for our understanding of atmospheric mercury processes.

Using a global chemical transport model (GEOS-Chem) with additional iodine emissions, chemistry, and deposition we show that iodine is responsible for ~ 9 % of global ozone loss but has negligible impacts on global OH. Uncertainties are large in the chemistry and emissions and future research is needed in both. Measurements of iodine species (especially HOI) would be useful. We believe iodine chemistry should be considered in future chemistry-climate and in air quality modelling.

Tropospheric halogens and small oxygenated VOC (OVOC) modify tropospheric HOx and NOx, O3 and aerosols. We have measured bromine monoxide (BrO), iodine monoxide (IO), glyoxal (CHOCHO) profiles from research aircraft in the tropical troposphere and compare with ship- and aircraft-based in situ sensors. Our measurements point to the need to improve the representation of halogens and organic carbon sources in atmospheric models.

Measurements of α-dicarbonyl compounds, like glyoxal (CHOCHO) and methyl glyoxal (CH3C(O)CHO), are informative about the rate of hydrocarbon oxidation, oxidative capacity, and secondary organic aerosol (SOA) formation in the atmosphere. We have compared nine instruments and seven techniques to measure α-dicarbonyl, using simulation chamber facilities in the US and Europe. We assess our understanding of calibration, precision, accuracy and detection limits, as well as possible sampling biases.

This paper presents ground-based direct-sun and airborne multi-axis DOAS measurements of O2O2 absorption optical depths under atmospheric conditions in two wavelength regions (335-–390nm and 435--490nm). Our results show that laboratory-measured σ(O2O2) is applicable for observations over a wide range of atmospheric conditions. Temperature dependence of σ(O2O2) is about 9±2.5% from 231K to 275K.