This study provides a direct intercomparison between two assays for quantifying oxidative potential (OP) of ambient particles: the synthetic respiratory-tract-lining fluid (RTLF) assay and the dithiothreitol (DTT) assay. The results suggest that the DTT assay and the ascorbic acid depletion in RTLF are associated with organic species, transition metal ions, and antagonistic interactions between species. The glutathione depletion in RTLF is strongly dependent on water-soluble copper.

Aerosol–cloud–precipitation interaction is a challenging problem in regional climate. Our study contrasted the observed diurnal variation of heavy rainfall and associated clouds over Beijing–Tianjin–Hebei between clean and polluted days during the 2002–2012 summers. We found the heavy rainfall under pollution has earlier start time, earlier peak time and longer duration, and further found the absorbing aerosols and scattering aerosols play different roles in the heavy rainfall diurnal variation.

HONO is a large source of OH radicals, which can drive VOC oxidation, leading to the formation of ozone and secondary organic aerosols. Here we investigate primary vehicle emissions of HONO from measurements in a road tunnel in Birmingham, UK. A HONO/NO_x emission ratio was detemined and compared to previous studies. Results indicate HONO/NO_x has not varied much over the last two decades and technologies aimed at reducing NO₂ may have also resulted in a reduction in direct HONO vehicle emissions.

As Earth's climate warms, the tropical overturning circulation (Hadley circulation) is projected to expand, potentially pushing subtropical dry zones further poleward. This study examines projections of the Hadley circulation from the latest generation of computer models and finds several notable differences from older models. For example, the Northern Hemisphere circulation has expanded northward at a greater rate in recent decades than would be expected from increasing greenhouse gases alone.

Line emission from hydroxyl (OH) molecules at altitudes of about 90 km strongly contributes to the Earth's night-sky brightness and is therefore used as an important indicator of atmospheric chemistry and dynamics. However, interpreting the measurements can be ambiguous since necessary molecular parameters and the internal state of OH are not well known. Based on high-quality spectral data, we investigated these issues and found solutions for a better understanding of the OH line intensities.

Atmospheric O₂ and CO₂ concentrations, along with CO₂ flux, have been observed in a megacity, Tokyo, Japan. The O₂ : CO₂ exchange ratio for net turbulent O₂ and CO₂ fluxes (OR_F) between the urban area and the overlaying atmosphere was obtained, and we applied it to estimate the diurnal cycles of CO₂ fluxes from gas and liquid fuel consumption separately. We found simultaneous observations of OR_F and CO₂ flux are useful in validating CO₂ emission inventories from statistical data.

We flew a large atmospheric research aircraft across a number of different environments in the Amazon basin during the 2012 biomass burning season. Smoke from fires builds up and has a significant impact on weather, climate, health and natural ecosystems. Our goal was to quantify changes in the properties of the smoke emitted by fires as it is transported through the atmosphere. We found that the major control on the properties of the smoke was due to differences in the fires themselves.

It is our responsibility to establish a link between emissions, air pollution, and health impacts for urban combustion sources, typical of Africa. Our results show that the particulate concentrations observed at all sites far exceed the recommendations of WHO. The site influenced by domestic fires is the most polluted site, dominated by a significant fraction of ultrafine particles. These studies will eventually lead to the implementation of emission reduction solutions to improve air quality.

Northeast China faces severe air pollution in regional haze in wintertime. In this study, we revealed a contrasting formation mechanism of two typical haze events: Haze-I was induced by adverse meteorological conditions together with residential coal burning emissions; Haze-II was caused by agricultural biomass waste burning. In particular, we observed large numbers of tar balls as the primary brown carbon in northeast China.

A modeling study through COSMO-ART was used to investigate the implication of downward mixing induced by clouds in transporting biomass burning aerosols from central and southern Africa located between 2 and 4 km into the PBL over southern West Africa. Results showed that individual mixing events south of the coast of Côte d’Ivoire due to mid-level convective clouds injects part of the biomass burning plume into the PBL. 15 % of CO mass from the 2–4 km layer is mixed below 1 km.

Characteristics of atmospheric sulfur and organic carbon species in marine aerosols and the environmental factors influencing their distributions were investigated over the Southern Ocean and the Amundsen Sea, Antarctica, during austral summer. The simultaneous measurements of chemical species in aerosols as well as the chemical and biological properties of seawater in the Amundsen Sea allowed for a better understanding of the effect of the ocean ecosystem on marine aerosols.

Particulate active metallic oxides in dust were proposed to influence the photochemical reactions of ambient volatile organic compounds (VOCs). A case study investigated the origin and transformation of VOCs during a windblown dust-to-haze pollution episode. In the dust event, a sharp decrease in VOC loading and aging of their components was observed. An increase in Ti and Fe and a fast decrease in trans-/cis-2-butene ratios demonstrated that dust can accelerate the oxidation of ambient VOCs.

We present multiyear time series of ground-based Fourier-transform infrared spectroscopy measurements of HCN in densely populated eastern China. The seasonality and interannual variability of tropospheric HCN columns were investigated. The potential sources that drive the observed HCN seasonality and interannual variability were determined using a GEOS-Chem tagged CO simulation, global fire maps, and potential source contribution function values calculated using HYSPLIT back trajectories.

A high level of nitrous acid (HONO) is formed from NO_x emitted by industrial activities; this HONO then promotes secondary air pollutant (e.g., aerosol and O₃) formation within these plumes by contributing to free-radical production. Heterogeneous reactions on aerosol surfaces are found to be one of the major formation routes of HONO. Therefore, HONO plays a synergic role in haze formation in heavily industrialized areas.

Water vapour (WV) is a highly variable and extremely important trace gas in Earth’s atmosphere. Due to its radiative and chemical properties, it is coupled to the climate in an extremely complex manner. This is especially true in the lowermost stratosphere (LMS). Despite its importance, the physical processes that control mixing and the distribution of WV in the LMS are poorly understood. This study provides observational evidence of moistening the LMS via mixing across the subtropical jet.

Mixed-phase clouds, formed of water droplets and ice crystals, appear frequently in Arctic regions. Characterizing the distribution of liquid water and ice inside the cloud appropriately is important because it influences the cloud's impact on the surface temperature. In this study, we combined images of the cloud top with measurements inside the cloud to analyze in detail the 3D spatial distribution of liquid and ice in two mixed-phase clouds occurring under different meteorological scenarios.

In this study, we found that the effective field-derived Henry's law constant for the ground rainwater and the gas-phase H₂O₂ was about 2.5 times that of the theoretical value, and the effective gas–particle partitioning coefficient for the aerosol particle and the gas-phase H₂O₂ was 4 orders of magnitude higher than the theoretical one. We suggested the missing source of H₂O₂ in the particulate phase, e.g. the contribution from the decomposition/hydrolysis of organic peroxides.

We investigate the effects of black carbon (BC) mitigation on Arctic climate and human health, accounting for the concurrent reduction of other aerosol species. While BC is attributed a net warming effect on climate, most other aerosol species cool the planet. We find that the direct radiative effect of mitigating BC induces cooling, while aerosol–cloud effects offset this cooling and introduce large uncertainties. Furthermore, the reduced aerosol emissions reduce human mortality considerably.

The objective of this study was to conduct observational evaluations of the daily cycle of the height of the planetary boundary layer from data that were measured and/or estimated using instruments such as a radiosonde, sodar, ceilometer, wind profiler, lidar and microwave radiometer installed in the central Amazon during 2014 (considered a typical year) and 2015 during which an intense El Niño–Southern Oscillation (ENSO) event predominated during the GoAmazon experiment.

The development of China has caused rapid urbanization and severe air pollution. However, the extent of their individual and combined effects on fog is not well understood. Through numerical experiments, we find that urbanization suppresses low-level fog but probably promotes upper-level fog. Additional aerosols generally promote fog. Urbanization affects fog to a much larger extent than aerosols do.

The physical properties of aerosol particles throughout the Arctic Ocean and Pacific Ocean were measured aboard the Korean icebreaker R/V Araon during the summer of 2017. A number of new particle formation (NPF) events and growth were frequently observed in both Arctic terrestrial and Arctic marine air masses. This suggests that terrestrial ecosystems – including river outflows and tundra – strongly affect aerosol emissions in the Arctic coastal areas, affecting radiative forcing.

Despite being a major source of coarse organic matter, primary biogenic organic aerosols (PBOAs) remain poorly implemented in source-resolved chemical transport models. This study, based on an intensive field sampling of aerosols, combined physicochemical characterizations of PM₁₀ with DNA high-throughput sequencing to provide a comprehensive understanding of the microbial fingerprints associated with primary sugar compounds (tracers of PBOAs) and their main surrounding environmental sources.

We studied the chemical composition and volatility of secondary organic aerosol (SOA) particles formed from emissions of Scots pines and compared those results to SOA formed from α-pinene and from a sesquiterpene mixture. We found that SOA formed from single precursors cannot capture the properties of SOA formed from real plant emissions.

Atmospheric particle size distributions with the focus on freshly nucleated particles were measured during the A-LIFE field experiment in Cyprus. A DMA-train was set up for the first time in an atmospheric environment and captures the sub-10 nm particle dynamics. Several new particle formation (NPF) events are studied in detail, of which some did not show particle growth beyond 10 nm indicating that NPF may occur more frequently than estimated when the sub-10 nm size range is not covered.

The impact of anthropogenic aerosols on clouds is a key uncertainty in climate change. This study analyses large-domain simulations with a new high-resolution model to investigate the differences in clouds between 1985 and 2013 comparing multiple observational datasets. The differences in aerosol and in cloud droplet concentrations are clearly detectable. For other quantities, the detection and attribution proved difficult, despite a substantial impact on the Earth's energy budget.

Organosulfates have been identified in atmospheric secondary organic aerosol (SOA). The thermodynamic properties of SOA constituents, such as organosulfates, affect the stability and atmospheric impact of the SOA. Here we present estimated solubility, activity, pK_a, saturation vapor pressure and Henry's law solubility values for several atmospherically relevant monoterpene- and isoprene-derived organosulfate compounds. These properties can be used, for example, in aerosol process modeling.

Aircraft exhaust drives formation of ozone and is a dominant anthropogenic influence in the upper troposphere. These impacts are mitigated by non-linear chemistry inside the aircraft plume, which cuts off part of the ozone production pathway and reduces the long-term impact of aircraft in a way which is not captured by current models. The ice clouds which form in aircraft exhaust ("contrails") also play a role, converting emitted nitrogen oxides into more stable forms such as nitric acid.

Future trends in air pollution and greenhouse gas emissions in China are of great concern to the community. Here we developed a sophisticated dynamic projection model to understand 2015–2050 emission pathways under a range of socio-economic, climate policy, and pollution control scenarios. By coupling strong low-carbon transitions and clean air policy, emissions of major air pollutants in China will be reduced by 58–87 % during 2015–2050. This work can support future co-governance policy design.

We measured concentrations and isotope ratios of plutonium in air filters collected in Finnish Lapland in 1965–2011. Radioactive-contamination sources were global nuclear-testing fallout and the Fukushima and SNAP-9A accidents. Both real and hypothetical nuclear accidents were studied with atmospheric-dispersion modeling. The radioactive-contamination effect on Finnish Lapland would be minor from an intended nuclear power plant and negligible from a floating nuclear reactor in the Barents Sea.

The bare black carbon (BC) was in a fractal structure. With coating thickness increasing, BC changed from a fractal structure to a core–shell structure. In the ambient atmosphere, plenty of BC particles were not in a perfect core–shell structure. This study brought attention to the combined effects of morphology and coating thickness on the absorption enhancement of BC-containing particles, which is helpful for determining the climatic effects of BC.

The atmospheric abundance of the greenhouse gas methane is determined by interacting emission sources and sinks in a dynamic global environment. In this study, its global budget from 1997 to 2016 is simulated with a general circulation model using emission estimates of 11 source categories. The model results are evaluated against 17 ground station and 320 intercontinental flight observation series. Deviations are used to re-scale the emission quantities with the aim of matching observations.

Stable water isotopes (SWIs) are tracers of moist atmospheric processes. We analyse the impact of large- to small-scale atmospheric processes and various environmental conditions on the variability of SWIs using ship-based SWI measurement in water vapour from the Atlantic and Southern Ocean. Furthermore, simultaneous measurements of SWIs at two altitudes are used to illustrate the potential of such measurements for future research to estimate sea spray evaporation and turbulent moisture fluxes.

Estimates of the age of stratospheric air (AoA), its distribution, and trends, obtained by different experimental methods, differ among each other. AoA derived form MIPAS satellite observations, the richest observational dataset on sulfur hexafluoride (SF₆) in the stratosphere, are a clear outlier. With multi-decade simulations of AoA and SF₆ in the stratosphere, we show that the origin of the discrepancy is in a methodology of deriving AoA from observations rather than in observational data.

The transfer of the nitrogen stable isotopic composition in nitrate between the air and snow at low accumulation sites in Antarctica leaves an UV imprint in the snow. Quantifying how nitrate isotope values change allows us to interpret longer ice core records. Based on nitrate observations and modelling at Kohnen, East Antarctica, the dominant factors controlling the nitrate isotope signature in deep snow layers are the depth of light penetration into the snowpack and the snow accumulation rate.