Institut Scientifique de Service Public

<strong class="journal-contentHeaderColor">Abstract.</strong> Volatile organic compounds (VOCs) and ozone (O₃) are key constituents of tropospheric chemistry, affecting both air quality and climate. Forests are major emitters of biogenic VOCs (BVOCs), yet large uncertainties remain regarding the diversity of exchanged compounds, the drivers of their bidirectional fluxes, and their in-canopy chemistry. Long-term and comprehensive in situ datasets remain scarce, limiting our understanding of these complex processes. We conducted a three-year field campaign (2022&ndash;2024) at the Integrated Carbon Observation System forest station of Vielsalm (BE-Vie), combining vertical concentration profile and eddy covariance flux measurements above and below the canopy. Using a PTR-ToF-MS and a dedicated open-source processing pipeline, we identified 51 significantly exchanged VOCs. The vertical and diurnal gradients of the mixing ratios reflected the interplay between emission, deposition, chemistry, and transport. Combined with a profile of turbulence statistics, these observations offer an opportunity to investigate their behaviour within the canopy. The forest acted as a net VOC source in summer (&sim; 1.25 <em>&mu;</em>g m^&minus;² s^&minus;¹), while deposition dominated in autumn. Many oxygenated VOCs displayed bidirectional exchange. Monoterpenes, isoprene, and methanol were the most abundant flux contributors, but 15&ndash;30 (30&ndash;43) compounds were needed to account for 90 % of total emissions (depositions), depending on the season. Below-canopy BVOC and O₃ fluxes reached &sim; 10 % of above-canopy ones, with proportionally enhanced below-canopy ozone uptake at night. This study provides one of the most detailed long-term datasets of VOC and O₃ exchange in a temperate forest and serves as a key reference for improving process-based models of biogenic, physical, and chemical exchange in forest ecosystems.

<strong class="journal-contentHeaderColor">Abstract.</strong> BTEX (benzene, toluene, ethylbenzene, m,p,o-xylene) are significant urban air pollutants. This study examines BTEX variability across seven European countries using data from 22 monitoring sites in different urban settings (urban background, traffic, industry, and suburban background). Results indicate that the relative abundance of BTEX in urban areas follows the order: toluene &gt; benzene &gt; m,p-xylene &gt; o-xylene &gt; ethylbenzene, with mean mixing ratios of 391 &plusmn; 451, 252 &plusmn; 324, 222 &plusmn; 297, 92 &plusmn; 119, and 78 &plusmn; 107 ppt from 2017 to 2022, respectively. Seasonal trends show benzene had similar median concentrations across urban background, traffic, and industrial sites, indicating mixed sources. Toluene levels were highest in traffic and industrial areas, highlighting road traffic and industrial emissions. Ethylbenzene and xylenes showed equivalent levels in traffic and industrial areas but were lower in urban backgrounds. Peak BTEX levels occurred during morning and evening rush hours, linked to traffic, heating, and atmospheric stagnation. B/T ratios ranged from 0.29 &plusmn; 0.11 to 1.35 &plusmn; 0.95, and X/E ratios ranged from 1.75 &plusmn; 0.91 to 3.68 &plusmn; 0.30, indicating primary pollution from local traffic, followed by solvents, coatings, and biomass burning. Lifetime Cancer Risk (LCR) values for BTEX exposure were below the definite risk threshold (10^&minus;4) but above the permissible risk level (10^&minus;6), suggesting moderate risk from benzene and ethylbenzene, particularly in traffic and industrial areas. This study offers essential insights into BTEX pollution in European urban environments.

Since 2017, a reinforcement programme was developed to save the last, endangered, Belgian population of black grouse (Lyrurus tetrix), in the High Fens Natural Park. To improve the success of this programme, an analysis of past data of this population was undertaken to understand the causes of its past decline. A time series analysis was applied, using annual spring male census data recorded between 1967 and 2016. In the period 1967–1993, there was a fluctuation around an equilibrium of a population of ca. 40–45 males. The peak of 85 males observed in 1971 was probably due to a succession of several favourable years in terms of environmental conditions, albeit without an exceptional annual growth rate. It seems that fox density, by using the occurrence of rabies as a proxy, has an impact on the black grouse population. After 1993, the population dynamic changed drastically, decreasing continuously until finally reaching quasi-extinction. On average, the population lost 15.4% of its size each year. Climate models, applied in previous studies to explain these population trends in the High Fens, failed to describe this major modification in this population’s dynamic and its recent decline. We suggest that this negative effect was mainly induced by a significant increase in predation by red fox (Vulpes vulpes), whose abundance has increased considerably since the 1990s, in particular, as a consequence of the eradication of fox rabies. We also discuss alternative hypotheses, such as the impact of other predator species, modification of the natural environment and climatic modifications.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10344-023-01642-w.

Humans spend the majority of their time indoors, where they are potentially exposed to hazardous pollutants. Within this context, over the past few years, there has been an upsurge of low-cost sensors (LCS) for the measurement of indoor air pollutants, motivated both by recent technological advances and by increased awareness of indoor air quality (IAQ) and its potential negative health impacts. Although not meeting the performance requirements for reference regulatory-equivalent monitoring indoors, LCS can provide informative measurements, offering an opportunity for high-resolution monitoring, emission source identification, exposure mitigation and managing IAQ and energy efficiency, among others. This article discusses the strengths and limitations that LCS offer for applications in the field of IAQ monitoring; it provides an overview of existing sensor technologies and gives recommendations for different indoor applications, considering their performance in the complex indoor environment and discussing future trends.