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Atmospheric volatile organic compounds (VOCs) constitute a wide range of species, acting as precursors to ozone and aerosol formation. Atmospheric chemistry and transport models (CTMs) are crucial to understanding the emissions, distribution, and impacts of VOCs. Given the uncertainties in VOC emissions, lack of evaluation studies, and recent changes in emissions, this work adapts the European Monitoring and Evaluation Programme Meteorological Synthesizing Centre – West (EMEP MSC-W) CTM to evaluate emission inventories in Europe. Here we undertake the first intensive model–measurement comparison of VOCs in 2 decades. The modelled surface concentrations are evaluated both spatially and temporally, using measurements from the regular EMEP monitoring network in 2018 and 2019, as well as a 2022 campaign. To achieve this, we utilised the UK National Atmospheric Emissions Inventory to derive explicit emission profiles for individual species and employed a tracer method to produce pure concentrations that are directly comparable to observations. The degree to which the modelled and measured VOCs agree varies depending on the specific species. The model successfully captures the overall spatial and temporal variations of major alkanes (e.g. ethane, n -butane) and unsaturated species (e.g. ethene, benzene) but less so for propane, i -butane, and ethyne. This discrepancy underscores potential issues in the boundary conditions for the latter species and in their primary emissions from, in particular, the solvent and road transport sectors. Specifically, potential missing propane emissions and issues with its boundary conditions are highlighted by large model underestimations and smaller propane-to-ethane ratios compared to the measurement. Meanwhile, both the model and measurements show strong linear correlations among butane isomers and among pentane isomers, indicating common sources for these pairs of isomers. However, modelled ratios of i -butane to n -butane and i -pentane to n -pentane are approximately one-third of the measured ratios, which is largely driven by significant emissions of n -butane and n -pentane from the solvent sector. This suggests issues with the speciation profile of the solvent sector, underrepresented contributions from transport and fuel evaporation sectors in current inventories, or both. Furthermore, the modelled ethene-to-ethyne and benzene-to-ethyne ratios differ significantly from measured ratios. The different model performance strongly points to shortcomings in the spatial and temporal patterns and magnitudes of ethyne emissions, especially during winter. For OVOCs, the modelled and measured concentrations of methanal and methylglyoxal show a good agreement, despite a moderate underestimation by the model in summer. This discrepancy could be attributed to an underestimation of contributions from biogenic sources or possibly a model overestimation of their photolytic loss in summer. However, the insufficiency of suitable measurements limits the evaluation of other OVOCs. Finally, model simulations employing the CAMS inventory show slightly better agreements with measurements than those using the Centre on Emission Inventories and Projections (CEIP) inventory. This enhancement is likely due to the CAMS inventory's detailed segmentation of the road transport sector, including its associated sub-sector-specific emission profiles. Given this improvement, alongside the previously mentioned concerns about the model's biased estimations of various VOC ratios, future efforts should focus on a more detailed breakdown of dominant emission sectors (e.g. solvents) and the refinement of their speciation profiles to improve model accuracy. [ABSTRACT FROM AUTHOR]

Denitrifying activity in a sediment from the freshwater part of a polluted estuary in northwest Europe was quantified using two independent approaches. High-resolution N2O microprofiles were recorded in sediment cores to which acetylene was added to the overlying water and injected laterally into the sediment. The vertical distribution of the rate of denitrification supported by nitrate uptake from the overlying water was then derived from the time series N2O concentration profiles. The rates obtained for the core incubations were compared to the rates predicted by a forward reactive transport model, which included rate expression for denitrification calibrated with potential rate measurements obtained in flowthrough reactors containing undisturbed, 1-cm-thick sediment slices. The two approaches yielded comparable rate profiles, with a near-surface, 2- to 3-mm narrow zone of denitrification and maximum in situ rates on the order of 200 to 300 nmol cm-3 h-1. The maximum in situ rates were about twofold lower than the maximum potential rate for the 0- to 1-cm depth interval of the sediment, indicating that in situ denitrification was nitrate limited. The experimentally and model-derived rates of denitrification implied that there was nitrate uptake by the sediment at a rate that was on the order of 50 (± 10) nmol cm-2 h-1, which agreed well with direct nitrate flux measurements for core incubations. Reactive transport model calculations showed that benthic uptake of nitrate at the site is particularly sensitive to the nitrate concentration in the overlying water and the maximum potential rate of denitrification in the sediment. [ABSTRACT FROM AUTHOR]

Highlights from the article: B The Cover Feature b shows a young archer carefully aiming his bow at a target in the background. The synthetic target shown in the foreground incorporates a short alkyne linker that clamps a I meta i -quaterphenyl group, generating strain much like a taut string creates tension in an archer's bow. The synthetic target shown in the foreground incorporates a short alkyne linker that clamps a I meta i -quaterphenyl group, generating strain much like a taut string creates tension in an archer's bow.

Highlights from the article: B The Front Cover b shows the X-ray crystal structure of the dinuclear copper(I) complex obtained from bis(diphenylphosphino)acetylene and 2-phenyl-1,10-phenanthroline (mpp). The phenyl moiety of the mpp ligand contributes to rigidify the conformation of the 10-membered dimetallacycle and has therefore a dramatic effect on the emission properties. B The Front Cover b shows the X-ray crystal structure of the dinuclear copper(I) complex obtained from bis(diphenylphosphino)acetylene and 2-phenyl-1,10-phenanthroline (mpp).

The article provides information related to safety and environmental protection in Europe. The Health and Safety Executive (HSE) has conducted a stakeholder conference in a bid to reduce the risk of exposure to chemical carcinogens in the workplace. HSE has issued a Prohibition Notice on the transportation of acetylene cylinders to an employer after the explosion in County Durham, England. The German Commission of Radiological Protection (SSK) has published three recommendations for safety and environmental health.