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The impact of airport activities on air quality, is not sufficiently documented. In order to better understand the magnitude and properly assess the sources of emissions in the sector, it is necessary to establish databases with real data on those pollutants that could have the greatest impact on both health and the environment. Particulate matter (PM), especially ultrafine particles, are a research priority, not only because of its physical properties, but also because of its ability to bind highly toxic compounds such as polycyclic aromatic hydrocarbons (PAHs). Samples of PM were collected in the ambient air around the runways at Barajas International Airport (Madrid, Spain) during October, November and December 2021. Samples were gathered using three different sampling systems and analysed to determine the concentration of PAHs bound to PM. A high-volume air sampler, a Berner low-pressure impactor, and an automated off-line sampler developed in-house were used. The agreement between the samplers was statistically verified from the PM and PAH results. The highest concentration of PM measured was 31 μg m−3, while the concentration of total PAH was 3 ng m−3, both comparable to those recorded in a semi-urban area of Madrid. The PAHs showed a similar profile to the particle size distribution, with a maximum in the 0.27–0.54 μm size range, being preferentially found in the submicron size fractions, with more than 84% and around 15–20% associated to UFPs. It was found that the ratio [PAHs(m)/PM(m)] was around 10–4 in the warmer period (October), whereas it more than doubled in the colder months (November–December). It is significant the shift in the relative distribution of compounds within these two periods, with a notable increase in the 5 and 6 ring proportions in the colder period. This increase was probably due to the additional contribution of other external sources, possibly thermal and related to combustion processes, as supported by the PAH diagnostic ratios. [Display omitted] • PM and PAH at runaways of Barajas Airport were below the EU Directives limit values. • Low and high volume samplers were comparable for PM and PAH measurements. • PAH profiles similar to particle size distribution with mode at range 0,27–0,54 μm. • More than 85% of measured PAHs bound to submicron particles and 15–20% to UFPs. • Abundance of Higher MW PAHs linked to submicron particles during the colder months. [ABSTRACT FROM AUTHOR]

Traditionally, enzymatic synthesis of nucleoside-5′-monophosphates (5′-NMPs) using low water-soluble purine bases has been described as less efficient due to their low solubility in aqueous media. The use of enzymes from extremophiles, such as thermophiles or alkaliphiles, offers the potential to increase solubilisation of these bases by employing high temperatures or alkaline pH. This study describes the cloning, expression and purification of hypoxanthine-guanine-xanthine phosphoribosyltransferase from Thermus thermophilus ( Tt HGXPRT). Biochemical characterization indicates Tt HGXPRT as a homotetramer with excellent activity and stability across a broad range of temperatures (50–90 °C) and ionic strengths (0–500 mM NaCl), but it also reveals an unusually high activity and stability under alkaline conditions (pH range 8–11). In order to explore the potential of Tt HGXPRT as an industrial biocatalyst, enzymatic production of several dietary 5′-NMPs, such as 5′-GMP and 5′-IMP, was carried out at high concentrations of guanine and hypoxanthine. [ABSTRACT FROM AUTHOR]