Abstract. Secondary organic aerosol (SOA) formation from mixtures of volatile precursors may be influenced by the molecular interactions of the products of the components of the mixture. Here, we report measurements of the volatility distribution of SOA formed from the photo-oxidation o-cresol, α-pinene and their mixtures, representative anthropogenic and biogenic precursors, in an atmospheric simulation chamber. The combination of two independent thermal techniques (thermal denuder and the Filter Inlet for Gases and Aerosols coupled to a high resolution time of flight chemical ionisation mass spectrometer) to measure the particle volatility, along with detailed gas and particle phase composition measurements provides links between the chemical composition of the mixture and the resultant SOA volatility. The products that were only present in the SOA of the mixture had higher O:C and lower volatility compared to those deriving from the individual precursors. This suggests that new product formation can reduce the volatility in mixtures. At the same time, some of the larger molecules with lower volatility produced in the single α-pinene and o-cresol system were not present in the mixture leading to an increase of the average volatility. These opposite effects resulted the volatility distribution of the SOA of the mixture to be between those of the individual precursors. For example, compounds with effective saturation concentration less or equal than 0.01 μg m−3 represented 28, 39 and 37 % of the SOA mass in the α-pinene, o-cresol and mixed precursor experiments, respectively. We further explore the sensitivity limitations of our technique to the reported results and we show that the particle volatility can be qualitatively assessed, while caution should be held when linking the chemical composition to the particle volatility. These results provide the first detailed observations of SOA particle volatility and composition in mixed anthropogenic and biogenic systems and provides an analytical context that can be used to explore particle volatility in chamber experiments.

A solvent extraction technique was used to measure the stability constants of the mono-and diligand complexes of Eu 3 + and UOi + with CI" and NOJ at 3.5,6.5,10.0, and 14.1 m (NaC10 4 ) ionic strengths. The experimental values were analyzed by the Specific Interaction Theory and the range (in ionic strength) of the validity of that theory for these complexes is discussed.

Abstract. Secondary organic aerosol (SOA) formation from mixtures of volatile precursors may be influenced by the molecular interactions of the components of the mixture. Here, we report measurements of the volatility distribution of SOA formed from the photo-oxidation of o-cresol, α-pinene, and their mixtures, representative anthropogenic and biogenic precursors, in an atmospheric simulation chamber. The combination of two independent thermal techniques (thermal denuder, TD, and the Filter Inlet for Gases and Aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer, FIGAERO-CIMS) to measure the particle volatility, along with detailed gas- and particle-phase composition measurements, provides links between the chemical composition of the mixture and the resultant SOA particle volatility. The SOA particle volatility obtained by the two independent techniques showed substantial discrepancies. The particle volatility obtained by the TD was wider, spanning across the LVOC and SVOC range, while the respective FIGAERO-CIMS derived using two different methods (i.e. calibrated Tmax and partitioning calculations) was substantially higher (mainly in the SVOC and IVOC, respectively) and narrow. Although the quantification of the SOA particle volatility was challenging, both techniques and methods showed similar trends, with the volatility of the SOA formed from the photo-oxidation of α-pinene being higher than that measured in the o-cresol system, while the volatility of the SOA particles of the mixture was between those measured at the single-precursor systems. This behaviour could be explained by two opposite effects, the scavenging of the larger molecules with lower volatility produced in the single-precursor experiments that led to an increase in the average volatility and the formation of unique-to-the-mixture products that had higher O:C, MW, OSc‾ and, consequently, lower volatility compared to those derived from the individual precursors. We further discuss the potential limitations of FIGAERO-CIMS to report quantitative volatilities and their implications for the reported results, and we show that the particle volatility changes can be qualitatively assessed, while caution should be taken when linking the chemical composition to the particle volatility. These results present the first detailed observations of SOA particle volatility and composition in mixed anthropogenic and biogenic systems and provide an analytical context that can be used to explore particle volatility in chamber experiments.

Abstract. This study describes the design of the Manchester Aerosol Chamber (MAC), initially developed in 2005 and presents for the first time its comprehensive characterisation. The MAC is designed to investigate multi-phase chemistry and the evolution of aerosol physico-chemical properties from the real-world emissions (e.g. diesel engine, plants) or of secondary organic aerosol (SOA) produced from pure volatile organic compounds (VOCs). Additionally, the generated aerosol particles in the MAC can be transferred to the Manchester Ice Cloud Chamber (MICC), which enables investigation of cloud formation in warm, mixed-phase, and fully glaciated conditions (with temperature, T, as low as −55 ∘C). The MAC is an 18 m3 fluorinated ethylene propylene (FEP) Teflon chamber with the potential to conduct experiments at controlled temperature (15–35 ∘C) and relative humidity (RH; 25 %–80 %) under simulated solar radiation or dark conditions. Detailed characterisations were conducted at common experimental conditions (25 ∘C, 50 % RH) for actinometry and determination of background contamination, wall losses of gases (NO2, O3, and selected VOCs), aerosol particles at different sizes, chamber wall reactivity, and aerosol formation. In addition, the influences of chamber contamination on the wall loss rate of gases and particles and the photolysis of NO2 were estimated.