We examined aerosol particles from wildfires and identified tarballs (TBs) from the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign. This study reveals the compositions, abundance, sizes, and mixing states of TBs and shows that TBs formed as the smoke aged for up to 5 h. This study provides measurements of TBs from various biomass-burning events and ages, enhancing our knowledge of TB emissions and our understanding of their climate impact.

We present records of the triple oxygen isotope signature (Δ(¹⁷O)) of atmospheric CO₂ obtained with laser absorption spectroscopy from two mid-latitude stations. Significant interannual variability is observed in both records. A model sensitivity study suggests that stratosphere–troposphere exchange, which carries high-Δ(¹⁷O) CO₂ from the stratosphere into the troposphere, causes most of the variability. This makes Δ(¹⁷O) a potential tracer for stratospheric intrusions into the troposphere.

A study in the rural North China Plain showed environmentally persistent free radicals (EPFRs) in atmospheric particulate matter (PM), with a notable water-soluble fraction likely from atmospheric oxidation during transport. Significant positive correlations between EPFRs and the water-soluble oxidative potential of PM_2.5 were found, primarily attributable to the water-soluble fractions of EPFRs. These findings emphasize understanding EPFRs' atmospheric evolution for climate and health impacts.

Our research on city bus emissions reveals that alternative fuels (compressed natural gas and biofuels) reduce fresh particle emissions compared to diesel. However, all fuels lead to secondary air pollution. Aiming at guiding better environmental policies, we studied 76 buses using advanced emission measurement techniques. This work sheds light on the complex effects of bus fuels on urban air quality, emphasizing the need for comprehensive evaluations of future transportation technologies.

In this study, we found large spatial discrepancies in the physical and chemical properties of black carbon over the Tibetan Plateau (TP). Elevated anthropogenic emissions from low-altitude regions can significantly change the mass concentration, mixing state and chemical composition of black-carbon-containing aerosol in the TP region, further altering its light absorption ability. Our study emphasizes the vulnerability of remote plateau regions to intense anthropogenic influences.

Changes in vegetation alongside biomass burning impact regional atmospheric composition and air quality. Using satellite remote sensing, we find a clear linear relationship between forest cover and isoprene and a pronounced non-linear relationship between burned area and nitrogen dioxide in the southern Amazon, a region of substantial deforestation. These quantified relationships can be used for model evaluation and further exploration of biosphere-atmosphere interactions in Earth System Models.

Aerosol particles impact cloud properties which influence Greenland Ice Sheet melt. Understanding the aerosol population that interacts with clouds is important for constraining future melt. Measurements of aerosols at cloud height over Greenland are rare, and surface measurements are often used to investigate cloud–aerosol interactions. We use a tethered balloon to measure aerosols up to cloud base and show that surface measurements are often not equivalent to those just below the cloud.