This study investigates the effects of biodiesel's chemical composition on the volatility and reactive oxygenate species of fresh and aged diesel particulate matter. Using a potential aerosol mass chamber, changes of volatility and reactive oxygenated species are studied. The study concludes that more saturated and more oxygenated diesel fuels can cause more volatile particles carrying more reactive oxygenated species whether before or after aging.

A detailed chemical mechanism is developed based on laboratory studies that predicts the formation of high molecular weight compounds in the aqueous phase of atmospheric aerosol particles. Model simulations using this mechanism for atmospheric conditions show that these pathways are likely not a substantial source of particle mass, unless unidentified precursors for these compounds exist that were not taken into account so far and/or the solubility of oxygen in aerosol water is overestimated.

The injection of sulfur dioxide is considered as an option for solar radiation management. We have calculated the effects of SO2 injections up to 100 Tg(S)/y. Our calculations show that the forcing efficiency of the injection decays exponentially. This result implies that SO2 injections in the order of 6 times Mt. Pinatubo eruptions per year are required to keep temperatures constant at that anticipated for 2020, whilst maintaining business as usual emission conditions.

The collection between aerosol and a water droplet is an important mechanism for removing particles from the atmosphere, and has an influence on cloud dynamics, precipitation processes and cloud lifetime. In this experiment, the collection process was studied on a single-droplet basis, with atmospherically relevant conditions (droplet sizes, charges and flow). Collection efficiency values were found to be in agreement with previous experimental and theoretical studies.

Cloud condensation nuclei (CCN) production associated with atmospheric new particle formation (NPF) is presented, and this is the first direct evidence of CCN production resulting from NPF in the eastern Mediterranean atmosphere. We show that condensation of both gaseous sulfuric acid and organic compounds from multiple sources leads to the rapid growth of nucleated particles. Sub-100nm particles were found to be substantially less hygroscopic than larger particles during the active NPF period.

We measured near-surface (< 2m) profiles of HONO in a clearing and on a forest floor. Both HONO deposition and emissions were observed. By comparing three postulated sources to observed daytime emissions, we made several important findings: ● conversion of NO2 is mostly independent of light due to light saturation ● HONO emissions from a very acidic soil were low ● photolysis of adsorbed HNO3 could serve as HONO source based on empirical parameters but unlikely via the proposed reaction pathway.

Our study combines process and global chemistry modeling to investigate the potential effect of gas- and particle-phase organic photolysis reactions on the formation and lifetime of secondary organic aerosols (SOAs). Photolysis of the oxidation intermediates that partition between gas and particle phases to form SOA is not included in 3D models. Our results suggest that exposure to UV light can suppress the formation of SOA or even lead to its substantial loss (comparable to wet deposition).

This is the first paper of its kind describing a method for merging the long-term satellite records of global stratospheric temperature from SSU and AMSU to yield a continuous data set from 1979 to present (and beyond). Since global-mean stratospheric temperature is close to radiative equilibrium, our "extended" SSU data set is an important climate record for the detection and attribution of anthropogenic influence.

Secondary organic aerosol affects both the environment and human health. We characterized the aerosol composition in Uintah Basin by measuring the concentration of nitrooxy group moiety which is produced through chemical interaction of volatile organic compounds and NOx emitted largely from local human activity. We found nitrooxy compounds to be a persistent, if not dominant, portion of fine aerosol mass. Similar results may be expected from emissions due to traffic in cities.

Secondary organic aerosol from the dark ozonolysis of α‑pinene was formed at a range of mass loadings from 1 to 800μg m-3. The amount of mass loss during evaporation in a thermodenuder was found to be independent of mass loading. A kinetic model of evaporation was fit to the observations and good agreement was obtained when the particle was either composed of dimers that decompose into semi-volatile monomers or when it was composed of low-volatility compounds that evaporate directly.

Emission sensitivity studies, using WRF-Chem at 1.3km that was validated by observations, indicate the Arizona (AZ) emissions dominate on daily maximum 8-hr average (DMA8) [O3] in Phoenix (PHX). Southern California (SoCal) emission contribute to DMA8 [O3] for the PHX from a few ppb to over 30 ppb. [O3] from SoCal and AZ emissions exhibits diurnal characteristics. Pollutants near the SoCal coasts are transported to PHX by local circulations with different mechanisms.

Iron released from volcanic ash can perturb the biogeochemical cycles in the ocean. However, knowing that the emitted ash from a volcano contains insoluble iron, what processes can solubilize the ash iron while it is airborne? To answer this question, a numerical model is developed in this study to simulate the gas-ash-aerosol interactions within the eruption plume. Results show that the dissolution of the ash mediated by halogen acids exert the key control on ash iron mobilization.

High daytime HONO mixing ratios in experiments suggest that an unknown daytime HONO source (P unknown) could exist. P unknown≈19.60×NO2×J(NO2) was obtained using observed data from 13 field experiments across the globe, then coupled into the WRF-Chem model. Simulations indicated that elevated P unknown was found in the coastal regions of China; the additional HONO sources, especially the P unknown produced significant increases of radicals in the major cities, and accelerated the radical cycles.

We derived the NOx emissions from the OMI satellite observations. We find a NOx emission reduction of at least 25% during the Youth Olympic Games in Nanjing in 2014. The emission estimate algorithm has detected an emission reduction of 10% during the Chinese Spring Festival. This paper also shows that the observed concentrations and the derived emissions from space have different patterns that provide complimentary information.

The concentrations of sulfate, black carbon and other aerosols in the Arctic are characterized by high values in late winter and spring (so-called Arctic Haze) and low values in summer. Models have long been struggling to capture this seasonality. In this study, we evaluate sulfate and BC concentrations from different updated models and emissions against a comprehensive pan-Arctic measurement data set. We find that the models improved but still struggle to get the maximum concentrations.

We evaluate isotopic composition of NO3- in different environments across East Antarctica. At high snow accumulation sites, isotopic ratios are suggestive of preservation of NO3- deposition. At low accumulation sites, isotopes are sensitive to both the loss of NO3- due to photolysis and secondary formation of NO3- within the snow. The imprint of post-depositional alteration is not uniform with depth, making it difficult to predict the isotopic composition at depth from near-surface data alone.

We evaluate HadGEM3-UKCA over Europe for the period 1960-2009 against observations of aerosol mass and number, aerosol optical depth (AOD) and surface solar radiation (SSR). The model underestimates aerosol mass and number but is less biased if compared to AOD and SSR. Observed trends in aerosols are well simulated by the model and necessary for reproducing the observed increase in SSR since 1990. European all-sky top of atmosphere aerosol radiative forcing increased by > 3 Wm-2 from 1970 to 2009.

We quantify the contribution of long-range transport to PM levels in the NW-IGP through back-trajectory climatology analysis. Transport from the west significantly enhanced coarse- and fine-mode PM mass loadings during all seasons. Local pollution episodes enhanced coarse-mode PM only during winter and fine-mode PM during winter and summer seasons. South-easterly air masses (source region: SE-IGP) were associated with significantly lower fine- and coarse-mode PM mass loadings during all seasons.

Stabilised Criegee intermediates (SCIs) are formed through alkene-ozone reactions, which occur throughout the atmospheric boundary layer. Recent direct laboratory studies have shown that SCI react rapidly with SO2, NO2 and other trace gases, affecting air quality and climate. We present experimental data from the EUPHORE atmospheric simulation chamber, in which we determine the effects of the ozonolysis of isoprene, on the oxidation of SO2 as a function of H2O and dimethyl sulfide concentration.

The radiative effect of dust over the Arabian Peninsula for different surfaces and for a range of optical depths is calculated and tested using satellite and ground-based observations.

We use ozone measurements at a suburban site in Punjab to estimate ozone-related crop yield losses for wheat, rice, cotton and maize in Punjab and Haryana for the years 2011-2013. Crop production losses amount to 10.3-20.8 Mt yr-1 for wheat and 3.2-5.4 Mt yr-1 for rice, enough to feed 225-437 million of India’s poor. The lower limit for the ozone-related economic losses is 3.7-6.5 billion USD (Punjab and Haryana), while the upper limit amounts to 3.5-20% of Indian GDP (all of India).

A detailed characterization of air quality in the Paris (France) agglomeration, a megacity, during two summer and winter intensive campaigns and from additional 1-year observations, revealed that about 70% of the fine particulate matter (PM) at urban background is transported into the megacity from upwind regions. Unexpectedly, a major part of organic PM is of modern origin (woodburning and cooking activities, secondary formation from biogenic VOC).

Simulations conducted in the GeoMIP and IMPLICC model intercomparison studies for climate engineering by stratospheric sulfate injection and marine cloud brightening via sea salt are analysed and compared to the reference scenario RCP4.5. The focus is on extremes in surface temperature and precipitation. It is found that the extreme changes mostly follow the mean changes and that extremes are also in general well mitigated, except for in polar regions.

Observations from this study indicate that continental pollution largely affects the atmospheric composition and structure of the western Mediterranean basin. Pollution plumes reach 3000-4000 m in altitude and present a very complex and highly stratified structure, characterized by fresh and aged layers both in the boundary layer and in the free troposphere. Also we report the observations of high levels of ultrafine particles over the basin, possibly linked to new particle formation events.

Aerosols particles reach via long-range transport the high Arctic and have significant impacts on Arctic climate. This article demonstrates the comparison of measured and modeled aerosol mass concentrations for black carbon and sulfate particles at a high Arctic site. Based on the findings aging processes during transport seem to prolong the lifetimes of the two species and favor the possibility for their transport to the high Arctic.

Extended measurements of equivalent black carbon (eBC) derived from light absorption measurements have been made with a PAX over a 13 month period. The daily trends in eBC and other co-pollutants are evaluated with respect to season. The primary factors that led to large changes between the wet and dry seasons are the accelerated vertical mixing of boundary layer and free tropospheric air, by the formation of clouds and decreased actinic flux that reduces the production of ozone.

We use water vapor profiles from ground-based microwave radiometers at five locations distributed over the Northern Hemisphere and operated in the frame of NDACC (Network for the Detection of Atmospheric Composition Change) to generate hemispheric water vapor maps based on the so-called trajectory mapping technique. The novelty is to show that a mini network of instruments is capable of providing information about the hemispheric distribution of water vapor under most conditions.