Mediterranean Center for Environmental Studies

Interactions between iron-containing mineral dust and chloride-rich sea salt aerosols lead to the formation of iron(III) chloride salts, which initiate the photocatalytic release of molecular chlorine (Cl2) [1-5]. Photolysis of the chlorine generates reactive Cl radicals—potent atmospheric oxidants with substantial implications for the degradation of methane and other greenhouse gases. This catalytic chlorine production relies on the reoxidation of Fe(II) to Fe(III) through Fenton chemistry. To understand the photolytic chlorine production, the Fenton chemistry in these aerosols must be understood as well. This study presents experimental investigation and multiphase modeling of the dark chlorine production from the reaction of iron(III) chloride aerosols and H2O2. The experiments were performed in the 200 m3 European Photoreactor (EUPHORE) in Valencia, Spain. Measurements were collected with long-path FTIR, OPS, SMPS, PTR-MS, ACSM, Picarro G2108 and G2201-i as well as monitors for O3, NO, NO2, NOx, CO and HCHO. Furthermore, flask samples were collected for analysis of [CO], d13C-CO, [CH4], d13C-CH4 and VOCs at Utrecht University. Multiphase modeling of the experiment has been done through the integration of Fenton reactions and iron chloride chemistry into the kinetic multilayer model for Aerosol Dynamics, gas- and particle-phase chemistry in CHAMber environments (ADCHAM)[6]. A production was observed of 1.14 Cl2 molecules per Fe atom per hour and 4.33 H2O2 were consumed per Cl2 molecule produced. An inhibition of the chlorine production later in the experiment was observed and is under investigation.This work is part of a project supported by the European Commission under the Horizon 2020 –Research and Innovation Framework Program through the ATMO-ACCESS Integrating Activity ATMO-TNA-7—0000000004 (GA N. 101008004)[1] Chen et al. (2024) Environ. Sci. Technol., 58(28), 12585-12597[2] Mikkelsen et al. (2024) Aerosol Research, 2, 31-47[3] Wittmer et al. (2015) Environmental Chemistry, 12(4), 461-475[4] Wittmer et al (2017) Journal of Atmospheric Chemistry, 74, 187-204[5] van Herpen et al. (2023) PNAS, 120, 31[6] Roldin et al. (2014) ACP, 14, 7953–7993

Global warming leads to increased precipitation variability, impacting vegetation and the terrestrial carbon sink. While the impact of mean annual precipitation on vegetation and the carbon cycle is well-studied, recent research emphasizes the importance of intra-annual precipitation variability in precipitation-productivity relationships. In drylands the effects of changed precipitation variability on ecosystem functioning are still not fully understood, and therefore also not captured well in Earth system models. Available studies cover either multiple sites, but focus on the effects of changing inter-annual precipitation variability on productivity, or focus on single dryland sites to assess the effect of changing seasonal precipitation variability on carbon fluxes. A multi-site analysis of the effect of intra-annual precipitation variability on carbon fluxes across global semi-arid savannas is still missing.Here, we contribute to closing this gap by incorporating data from multiple eddy covariance measurement stations located in semi-arid savanna ecosystems around the globe. We examined the impacts of precipitation variability on ecosystem carbon fluxes by: i) assessing the sensitivity of ecosystem CO2 fluxes to precipitation amount, frequency and intensity on the annual scale, ii) evaluating the importance of each metric in explaining seasonal CO2 fluxes, and iii) understanding direct and indirect effects of precipitation metrics on ecosystem CO2 fluxes in different seasons.On the annual scale precipitation variability has a positive effect on both gross primary productivity and ecosystem respiration. However, these effects partly cancel out, with different ecosystem processes dominating in different seasons. On the seasonal scale, both precipitation frequency and intensity explain more variance in net CO2 fluxes than precipitation amount. Linear mixed effect models show that models containing all three metrics together have the most explanatory power. Structural equation models show that across seasons soil water content is the main mediator of precipitation impacts on CO2 fluxes. In the next steps we will investigate how other site properties, such as canopy cover and height, mean annual precipitation or soil composition, modulate the effects of precipitation variability on the ecosystem CO2 fluxes.

In this contribution, we aim at assessing the detectability of atmospheric water vapor uptake by dry soils at a variety of spatial scales and methodologies, from the ecosystem scale via eddy covariance, through larger scales via earth system models, and gridded products. Water vapor fluxes in the soil and at the soil-atmosphere interface are driven by vapor concentration gradients. Until today, it is mostly assumed that the soil pore air is roughly at 100% relative humidity (RH), resulting in vapor fluxes that are almost always towards the atmosphere. However, the vapor state in soil pore air is linked to the soil water (matric) potential. As the water potential becomes more negative, the equilibrium RH within the soil decreases substantially. Under these conditions, the soil behaves like a ‘thirsty material’: when the atmospheric vapor pressure exceeds that of the soil pores, vapor is adsorbed onto the solid soil particle surfaces, and the net vapor flux is directed towards the soil. Using subdaily measurement data from a globally distributed network of eddy covariance stations, we show an emergent functional relationship between volumetric water content (VWC), RH, and latent heat (λE) flux direction at the ecosystem scale. Vapor fluxes towards the soil under dry conditions can be explained by the soil's sorptive forces inducing very low water potentials. Based on eddy covariance data, we find that soil vapor adsorption most frequently occurred in arid and semi-arid regions, particularly in ecosystems with sparse vegetation such as savannas and dry shrublands. On average, soil vapor adsorption occurs for 4 ± 1.1 hours per night, and may last up to 7 hours and on more than 150 nights per year in some drylands.Furthermore, we demonstrate that the relationship between VWC, RH, and the vapor flux direction is evident in a wide range of in situ measurements in drylands, including lysimeter and humidity profile data. However, this relationship is absent in site-level runs of gridded observation-based data products and land surface models.We demonstrate for the first time that the effect of adsorptive forces can be detected at the ecosystem scale, several meters above the ground. Our findings at the operating scale of flux towers can be used to evaluate and improve model representation of land-atmosphere exchange in dry conditions. Additionally, the results highlight the influence of sorptive forces on sub-daily soil-atmosphere interactions, particularly in sparsely vegetated drylands.

In Europa e in alcune aree del mondo si sono registrati, sin dagli anni Ottanta del Novecento, alcuni flussi migratori provenienti dal Nord globale, noti anche come migrazioni internazionali di ritiro (o per pensionamento) (International Retirement Migration - IRM) che coinvolgono diversi attori – principalmente pre-pensionati/pensionati – il cui profilo sia per formazione culturale che per status sociale ed economico si presenta totalmente diverso rispetto a quello dei migranti proveniente dal Sud del mondo, così come le motivazioni che albergano principalmente nella ricerca di un territorio qualitativamente migliore soprattutto nella dimensione ambientale. Gli effetti territoriali di queste azioni si riverberano sia nelle dinamiche della popolazione in quanto vanno a ripopolare territori caratterizzati da “inverni demografici” sia nella dimensione culturale e sociale in quanto si possono generare azioni di sviluppo territoriale locale, rigenerando paesi rurali, montani e collinari a rischio di abbandono. Queste le ragioni per analizzare il fenomeno a scala europea e nazionale, con la finalità ultima di comprendere quanto, dove e per quale motivo le migrazioni di ritiro si sono sviluppate e quale sia il livello di consolidamento raggiunto.

The Mediterranean Basin is recognized as a Biodiversity Hotspot for conservation priorities, mainly due to the high biodiversity of plants. Different environmental protection categories of the territory can help to ensure the long-term preservation of biodiversity and habitats. Among them, National Park is the legal category providing the highest protection for nature areas with remarkable ecological and cultural value. These areas represent valuable locations for long-term monitoring of ecological conservation and ecosystem functioning. The Spanish National Parks Network comprises 16 natural areas, including mountain ranges, volcanic habitats, different types of forest, scrublands and grasslands, and aquatic and marine ecosystems. All the National Parks are part of the European Natura 2000 network. Moreover, 6 of them are part of the LTER-Spain network. By law, National Parks must include a long-term Monitoring and Evaluation Plan for the Network, including ecological, sociological, and functional monitoring programmes. Within the ecological monitoring programme, besides flora, fauna and ecosystem functioning assessments, climate is also considered as one of the main drivers of global change. Tree crown condition is assessed in all the parks with forests following the methodology of ICP-Forest Level I. The next step is to include air quality, since atmospheric pollution is another important driver of global change that can affect ecosystem health and functioning. Particularly tropospheric ozone and atmospheric nitrogen deposition are expected to be exceeding the limit values for vegetation protection. Air quality monitoring networks are mainly focused on the protection of human health, thus some very valuable areas for biodiversity might not be represented by air monitoring stations. In addition, atmospheric deposition is not included at the air quality monitoring stations. Moreover, the extension of some of the National Parks, the complex orography and the different climate, morphology and air pollution sources that influence the National Parks, represent a challenge for managers to design an air quality monitoring program with an efficient use of resources. To address this challenge and provide the information needed to design an air quality network in National Parks, a new project is being developed combining local monitoring with air quality modelling. The spatial representativeness of background rural monitoring stations has been assessed through relating CHIMERE chemistry-transport (v2013) model simulations at 5 x 5 km2 resolution and measured data at the stations in Spain (including the Canary Islands) for the years 2019-2023 considering NO2, SO2, O3, PM10 and atmospheric deposition. With this analysis, the suitability of current monitoring stations to represent the air quality in National Parks is being assessed. A risk analysis of the effects on terrestrial ecosystems using CLRTAP critical levels and loads is being performed using the CHIMERE model in the different National Parks. Additionally, a new air quality and deposition monitoring programme has been initiated in 2025 in all the National Parks to measure NO2, SO2, O3 and NH3 using passive samplers and atmospheric wet deposition using bulk collectors connected to ion-exchange resins. Local monitoring data will be used to determine the spatial variability of air quality and deposition within the National Parks and will be compared with modelled data. Effects on aquatic ecosystems are being assessed applying the methodology of CLRTAP ICP-Waters in all the National Parks with suitable locations, including the Canary Islands. Preliminary results will be presented discussing representativeness of current monitoring stations, monitoring techniques available in remote locations and the modelling analyses required.

In 2023 and 2024, record global temperatures and numerous extreme weather events underscored the urgency of addressing climate change and its far-reaching environmental, social, and economic impacts. As these changes intensify, it is more important than ever for the scientific community to effectively communicate their findings to society and decision-makers. Bridging the gap between scientific knowledge and public understanding is essential for favoring informed decision-making and meaningful action on climate issues. Although scientists are among the most trusted professionals, inter- and transdisciplinary collaboration with communication experts is essential to improve scientific outreach on this critical issue. At the 2024 Annual Meeting of the European Meteorological Society (EMS) in Barcelona, we organized a workshop targeted to climate scientists to address challenges in climate science communication. Featuring experts from neuroscience, communication studies, activism, and journalism, the workshop fostered cross-disciplinary dialogue to identify strategies to raise public awareness of the climate crisis. This paper summarizes the key insights of the workshop, emphasizing the importance of training climate scientists in effective communication, enlarging networks for collaborative communication efforts, and integrating neuroscientific knowledge about cognitive biases and attitude change into messaging. Key takeaways from the workshop include: 1. recognizing and valuing the expertise and perspectives of the other party in the dialogue (dialogue-model), 2. understanding the influence of cognitive dissonance and biases in climate science communication, and 3. developing compelling research-based narratives that address both problem and solution through collaboration with communication professionals, such as journalists. These recommendations aim to empower the next generation of climate scientists to engage with society as trusted and impactful communicators.

The photooxidation of volatile organic compounds (VOCs) in the troposphere has important implications for air quality, weather, and climate. A deeper understanding of the underlying mechanisms can be achieved by studying these reactions under controlled conditions and analyzing the emerging photooxidation products. This requires dedicated laboratory infrastructure as well as sensitive and selective analytical techniques. Here, we constructed a new 300 L indoor Teflon atmospheric simulation chamber as part of the Bayreuth ATmospheric simulation CHambers (BATCH) infrastructure. The chamber was irradiated by a bandpass-filtered solar simulator that enabled experiments with realistic photon fluxes and OH radical concentrations. It was coupled to a proton-transfer-reactiontime-of-flightmass spectrometer (PTR-ToF-MS) and a solid phase microextractiongas chromatographymass spectrometry (SPME-GC-MS) system for the on-line analysis of the precursor VOC and its oxidation products in the gas phase. As part of the SPME-GC-MS method, multifunctional oxygenated compounds (carbonyls, alcohols, carboxylic acids) were derivatized with O-(2,3,4,5,6-Pentafluorobenzyl)-hydroxylamine (PFBHA) and N-trimethylsilyl-N-methyl trifluoroacetamide (MSTFA). We designed a permeation source for the on-line addition of internal standards to improve method reproducibility. The joint setup was tested and validated by studying the OH radical-induced photooxidation of toluene, one of the most abundant aromatic hydrocarbons in the atmosphere. For chamber characterization, we first derived the photolysis rates for several typical toluene products in the irradiated BATCH Teflon chamber (1.77×10 −8 -3.02×10 −4 s −1 ). Additionally, wall loss rates were determined empirically (4.54×10 −6 -8.53×10 −5 s −1 ), and then parameterized according to fundamental molecular properties. For the cresols and benzyl alcohol, we compiled a weighted calibration factor for the PTR-ToF-MS, taking into account isomer-specific sensitivities as well as the relative distribution as determined by the SPME-GC-MS. The weighted calibration improved the instrumental agreement to 15 %, whereas the PTR-ToF-MS overestimated the sum of the isomers by 25 % compared to the SPME-GC-MS concentrations when using the averaged calibration factor. Thus, the combined data set offered insight into both temporal trends and the isomeric composition. Finally, we conducted six toluene photooxidation experiments to evaluate the ring-retaining first generation products. Based on the loss-corrected concentrations, we derived formation yields for o-cresol (8.0±1.8 %), m-cresol (0.4±0.1 %), p-cresol (2.4±0.6 %), benzyl alcohol (0.5±0.1 %), and benzaldehyde (4.6±1.7 %) under NOx-free conditions at T = 298±1 K. These yields are consistent with previous studies and therefore serve as proof-of-concept for our applied methods.

Abstract. The photooxidation of volatile organic compounds (VOCs) in the troposphere has important implications for air quality, weather, and climate. A deeper understanding of the underlying mechanisms can be achieved by studying these reactions under controlled conditions and analyzing the emerging photooxidation products. This requires dedicated laboratory infrastructure as well as sensitive and selective analytical techniques. Here, we constructed a new 300 L indoor Teflon atmospheric simulation chamber as part of the Bayreuth ATmospheric simulation CHambers (BATCH) infrastructure. The chamber was irradiated by a bandpass-filtered solar simulator that enabled experiments with realistic photon fluxes and OH radical concentrations. It was coupled to a proton-transfer-reaction – time-of-flight – mass spectrometer (PTR-ToF-MS) and a solid phase microextraction – gas chromatography – mass spectrometry (SPME-GC-MS) system for the on-line analysis of the precursor VOC and its oxidation products in the gas phase. As part of the SPME-GC-MS method, multifunctional oxygenated compounds (carbonyls, alcohols, carboxylic acids) were derivatized with O-(2,3,4,5,6-Pentafluorobenzyl)-hydroxylamine (PFBHA) and N-trimethylsilyl-N-methyl trifluoroacetamide (MSTFA). We designed a permeation source for the on-line addition of internal standards to improve method reproducibility. The joint setup was tested and validated by studying the OH radical-induced photooxidation of toluene, one of the most abundant aromatic hydrocarbons in the atmosphere. For chamber characterization, we first derived the photolysis rates for several typical toluene products in the irradiated BATCH Teflon chamber (1.77×10−8 – 3.02×10−4 s−1). Additionally, wall loss rates were determined empirically (4.54×10−6 – 8.53×10−5 s−1), and then parameterized according to fundamental molecular properties. For the cresols and benzyl alcohol, we compiled a weighted calibration factor for the PTR-ToF-MS, taking into account isomer-specific sensitivities as well as the relative distribution as determined by the SPME-GC-MS. The weighted calibration improved the instrumental agreement to 15 %, whereas the PTR-ToF-MS overestimated the sum of the isomers by 25 % compared to the SPME-GC-MS concentrations when using the averaged calibration factor. Thus, the combined data set offered insight into both temporal trends and the isomeric composition. Finally, we conducted six toluene photooxidation experiments to evaluate the ring-retaining first generation products. Based on the loss-corrected concentrations, we derived formation yields for o-cresol (8.0±1.8 %), m-cresol (0.4±0.1 %), p-cresol (2.4±0.6 %), benzyl alcohol (0.5±0.1 %), and benzaldehyde (4.6±1.7 %) under NOx-free conditions at T = 298±1 K. These yields are consistent with previous studies and therefore serve as proof-of-concept for our applied methods.

[SPA]La educación científica moderna no sólo debería promover la adquisición de conocimientos científicos sino introducir al alumnado en discusiones acerca de las implicaciones tecnológicas y sociales de los problemas científicos. La enseñanza de la Química Ambiental ofrece excelentes oportunidades para poner en práctica esta filosofía. Por otra parte, la reciente inmersión en el Espacio Europeo de Educación Superior obliga a identificar qué competencias debe adquirir el alumnado y cómo valorar éstas. Se proponen dos tipos de actividades docentes (procesos de toma de decisión y mapas conceptuales) que resultan útiles para contemplar los aspectos sociocientíficos de este campo de la Química y se sugieren las respectivas herramientas para la evaluación. [ENG]Modern scientific education should not only stimulate the acquisition of new scientific knowledge but also introduce the students into discussions about technological and social implications of scientific problems. The subject Environmental Chemistry offers excellent opportunities to put into practice this philosophy. On the other hand, the recent immersion in the European Higher Education Area (EHEA) requires to identify the competences that students must acquire and how to evaluate this acquisition. Two different pedagogical activities (decision-making processes and conceptual maps), which are very useful to take into account the socio-scientific aspects of this area of Chemistry, are proposed together with their respective evaluation tools.