Roger Seco

Geometrid moth outbreaks are important natural disturbances in mountain birch ( Betula pubescens ssp. czerepanovii ) forests of northern Fennoscandia and are expected to intensify with climate change. Impacts of these outbreaks and moth herbivory on biogenic volatile organic compound (VOC) emissions of birch remain unquantified despite the importance of VOCs in plant-herbivore interactions and atmospheric chemistry. Here, we quantify in situ VOC emission responses of mountain birch ( n = 256) to naturally increasing geometrid herbivory across three consecutive growing seasons. We show that VOC emissions increased with rising herbivore pressure across the years, culminating in the outbreak, during which early-season VOC emissions were higher than at peak herbivory. At peak herbivory, birch emitted more complex VOC blends, indicating seasonal shifts in composition. Following the outbreak, a second leaf flush sustained emissions of some VOCs. Our findings demonstrate that VOC emission rates and compositions are dynamically linked to leaf phenology and herbivory intensity across multiple years.

Insect outbreaks are intensifying across high-latitude forests, yet their effects on biogenic volatile organic compound (BVOC) emissions from understory vegetation remain poorly resolved under natural outbreak conditions. Here, we examine how a severe geometrid moth outbreak alters understory microclimate and BVOC emissions in a subarctic mountain birch forest, using field measurements from two growing seasons spanning increasing herbivory to the peak outbreak year. We find that understory BVOC emissions decline markedly during the outbreak (38-70%), despite more emission-favourable abiotic conditions. We suggest that this decline results from the combined effects of direct herbivory on susceptible understory species and canopy-mediated feedbacks following mountain birch defoliation. These feedbacks likely intensify radiative, thermal, and drought stress in the understory, leading to widespread loss of BVOC-emitting green vegetation. Our findings demonstrate that severe geometrid outbreaks can suppress, rather than enhance, BVOC emissions by shifting emission control from abiotic stimulation to green biomass limitation, while highlighting that BVOC responses to herbivory are context-dependent and species-specific.

Rainwater is a key vector of atmospheric deposition, linking the atmosphere with terrestrial and aquatic ecosystems. While the inorganic chemistry of precipitation (dominated by sulfate, nitrate, ammonium, and trace metals) has been extensively studied, organic compounds in rainwater have received less attention, and Volatile Organic Compounds (VOCs) in particular have been practically overlooked. Recent methodological advances have revealed that a diverse suite of VOCs can be detected in rainwater along with VOC‐derived compounds, challenging the long‐held assumption that wet deposition plays a negligible role in VOC cycling. Although wet deposition is generally thought to be a minor atmospheric sink for VOCs (∼13.3% of total VOC emissions), rainborne VOCs are chemically reactive and biologically labile, such that even small quantities may exert disproportionate effects on soil microbial activity, plants, short‐term biogeochemical cycling, and water chemistry at local to regional scales. This article combines a synthesis of the current state of knowledge on rainborne VOCs and VOCs‐derived compounds with a particular focus on VOC occurrence, sources, partitioning, and transformation processes, with a forward‐looking perspective on the potential significance of rainborne VOCs for carbon cycling and atmosphere–biosphere interactions. We identify major gaps in observations, analytical capability, and modeling frameworks that limit quantitative understanding of VOC wet deposition and its ecological significance. Finally, we outline priority research directions, including improved sampling strategies, advanced analytical techniques, and integration into Earth system models. Together, these advances are needed to reassess the role of precipitation not only as a passive sink for atmospheric pollutants, but as an active driver of ecosystem functioning and Earth system processes in a changing climate.

Measurements of surface-atmosphere carbon dioxide (CO ₂ ) and methane (CH ₄ ) fluxes have been relatively sparse across the Arctic tundra and boreal biomes, causing significant uncertainties in carbon budget estimates from the region. While the availability of Arctic-boreal carbon flux data has increased substantially over the past decade, the data have remained spread across different repositories, scientific articles, and unpublished sources, making it difficult to leverage. Here we present a new dataset of monthly Arctic-boreal carbon fluxes (ABCFlux v2) across terrestrial (wetlands and uplands) and freshwater (lakes and rivers) ecosystems compiled from previous syntheses including the Arctic-boreal CO ₂ flux database (ABCFlux v1), the Boreal-Arctic Wetland and Lake Methane Dataset (BAWLD-CH4), and the Global River Methane Database (GRiMeDB). In addition, we consider data from general-purpose (e.g., Zenodo) and flux network repositories, literature, and site principal investigators. The dataset includes surface-atmosphere CO ₂ fluxes of gross primary production (GPP), ecosystem respiration (Reco), and net ecosystem exchange (NEE), alongside CH ₄ fluxes. For aquatic ecosystems, we split CH ₄ fluxes into diffusive and ebullitive flux pathways, and included potential emissions from transient storage in the water column (“storage fluxes”), alongside CO ₂ and CH ₄ concentrations dissolved in the surface water. Fluxes are measured through a variety of methods including chamber and eddy covariance techniques alongside bubble traps, ice-surveys, and concentration-based turbulence-driven modelling in aquatic ecosystems. The monthly flux data are reported together with supporting methodological and environmental metadata. The resulting ABCFlux v2 has 23 847 flux site-months, 8182 concentration site-months, and 199 seasonal observations from 1024 sites, and includes 56 139 reported fluxes (i.e. sum of GPP, Reco, NEE, and CH ₄ fluxes) from the years 1984 to 2024. The majority of monthly observations occurred after 1999. Wetlands had the highest number of site-month observations (8758), followed by boreal forest (6981), lotic ecosystems (6275), lentic ecosystems (3799) and upland tundra (3308). Measurements of CO ₂ dominated the dataset across most ecosystem types (25 222) except for lentic ecosystems, where CH ₄ flux site-months (3098) were more frequent than CO ₂ flux site-months (2915). Overall, ABCFlux v2 includes 160 % more site-months for terrestrial CO ₂ flux data compared to ABCFlux v1. Integrating and updating BAWLD-CH4 flux data from growing season averages to monthly fluxes resulted in 5671 site-months of chamber CH ₄ data compared to 762 site-years. This collaborative initiative, involving contributions from over 260 researchers, provides a comprehensive overview of the current state of the Arctic-boreal carbon flux network and its data, and serves as an important step in reducing uncertainties in Arctic-boreal carbon budgets and in enhancing our understanding of climate feedbacks. The data can be accessed at ORNL DAAC at https://doi.org/10.3334/ORNLDAAC/2448 (Virkkala et al., 2026).

Background/Objectives: Synthetic cathinones are a rapidly evolving class of new psychoactive substances whose structural diversity complicates toxicological risk assessment. Methylenedioxy cathinones occupy a pharmacological space between MDMA-like entactogens and more dopaminergic stimulant cathinones, but their direct cardiac liabilities remain poorly characterized. This study aimed to compare the cardiotoxic and neurobehavioral profiles of methylone, butylone, pentylone and their N,N-dimethyl analogues, and to determine how alkyl-chain extension and terminal amine substitution shape functional toxicity. Methods: Wild-type short-fin zebrafish (Danio rerio) embryos were used as a multiparametric New Approach Methodology. Cardiac rhythmicity was assessed in 3 days post-fertilization embryos after acute exposure to methylone, butylone, pentylone, dimethylone, dibutylone, dipentylone, dihexylone and diheptylone by high-speed video microscopy and dynamic pixel-based analysis, focusing on atrial chronotropy and atrioventricular conduction. Basal locomotor activity was evaluated in 5 days post-fertilization eleutheroembryos over 120 min using automated video tracking. Results: Negative chronotropy increased with alkyl-chain extension, with the monoalkyl subset following the rank order methylone < butylone < pentylone. Among dialkyl analogues, dihexylone and, especially, diheptylone produced the strongest atrial-rate inhibition. AV conduction impairment was more heterogeneous but became prominent among higher-liability analogues, with diheptylone showing the lowest AV-block midpoint descriptor and complete lethality at 1000 µM. Locomotor profiling revealed predominantly hypoactive phenotypes, with sustained late-phase inhibition especially for dipentylone, dihexylone and diheptylone. Conclusions: Alkyl-chain extension and terminal amine substitution shaped cardiac and neurobehavioral toxicity in a structure-dependent manner. The zebrafish workflow provides a structure-oriented framework for prioritizing emerging methylenedioxy cathinones with comparatively higher functional cardiac liability.

Synthetic cathinones are a class of new psychoactive substances (NPS) whose structural diversity and rapid evolution complicate toxicological risk assessment. Methylenedioxy cathinones, including methylone, butylone, pentylone and their N,N-dimethyl analogues, occupy a pharmacological space between MDMA-like entactogens and more dopaminergic stimulant cathinones. Although their monoamine transporter profiles and psychostimulant effects have been partially characterized, their direct cardiac liabilities remain poorly understood. Here, we used zebrafish embryos as a multiparametric New Approach Methodology to compare the cardiotoxic and neurobehavioral profiles of methylone, butylone, pentylone, dimethylone, dibutylone, dipentylone, dihexylone and diheptylone. Cardiac rhythmicity was assessed after acute exposure by high-speed video microscopy and dynamic pixel-based analysis, focusing on atrial chronotropy and atrioventricular (AV) conduction. Negative chronotropy increased with alkyl-chain extension, with the monoalkyl subset following the rank order methylone < butylone < pentylone. Among dialkyl analogues, dihexylone and especially diheptylone produced the strongest atrial rate inhibition. AV conduction impairment was more heterogeneous but became prominent among the higher-liability analogues, with diheptylone showing the lowest AV-block EC50 and complete lethality at 1000 µM. Time-resolved locomotor profiling revealed predominantly hypoactive phenotypes, with the most sustained late-phase inhibition observed for dipentylone, dihexylone and diheptylone. Integration of locomotor and cardiac endpoints showed that locomotor effects generally occurred below concentrations producing severe AV conduction impairment, although endpoint separation varied across analogues. Overall, this study provides a structure-oriented zebrafish framework for prioritizing emerging methylenedioxy cathinones with comparatively higher functional cardiac liability.

This study presents results from an Intensive Measurement Period (IMP2022) conducted during the European heatwave of July 2022, focusing on ozone, volatile organic compounds (VOCs), and carbonaceous aerosols at 31 sites across Europe. The episode featured persistent high-pressure systems, record-breaking temperatures, widespread ozone exceedances and concurrent atmospheric new particle formation and growth events. Coordinated measurements and chemistry transport modelling were used to examine the spatial variability of ozone, VOC composition, and secondary organic aerosol (SOA) formation under extreme meteorological conditions. Oxygenated VOCs (O-VOCs) constituted the largest fraction of total measured VOC mixing ratios, followed by non-methane hydrocarbons (NMHCs) and aromatics, with contributions from both anthropogenic and biogenic sources. Sensitivity simulations indicate that ozone formation was predominantly NO_x-limited across most regions during IMP2022. However, the highest ozone peaks occurred under conditions of elevated NO_x in combination with enhanced BVOC emissions. In contrast, SOA formation was slightly enhanced under low-NO_x conditions and reduced in elevated NO_x. Isoprene, aliphatic NMHCs, and O-VOCs dominated the ozone formation potential, while aromatics and monoterpenes were major contributors to SOA potential. Model simulations indicated that higher NO_x concentrations can reduce SOA formation by about 10 %. The campaign also highlighted observational gaps underscoring the need for broader and higher-resolution VOC monitoring across Europe. Overall, further reductions in NO_x emissions, alongside targeted control of key anthropogenic VOCs, would benefit air quality under future climate extremes.

Early-morning toluene peaks in 2021–2023 summers at Montseny's Mediterranean forest were linked to high temperatures and low humidity, suggesting a biogenic response to Quercus ilex drought stress.

The rapid emergence of New Psychoactive Substances (NPS), particularly pyrrolidinophenone derivatives, poses a significant challenge for public health and forensic toxicology. While their neuropharmacological profiles as dopamine transporter inhibitors are well-documented, their cardiac toxicity remains poorly understood. This study employs a multiparametric New Approach Methodology (NAM) using zebrafish embryos to integrate neurobehavioral and cardiotoxic endpoints for comparative hazard prioritization. We evaluated nine pyrrolidine-containing cathinones, including α-PVP, MDPV, α-PiHP, MDPiHP, α-D2PV, 3-Cl-, 4-Cl-, and 3,4-Cl-α-PVP, and 4-F-3-Me-α-PVP, on locomotor activity and cardiac rhythmicity using high-speed video microscopy and dynamic pixel analysis. Across the series, compounds induced concentration-dependent negative chronotropy and, in most cases, locomotor suppression. Crucially, we identified a functional dissociation between atrial rate control and atrioventricular (AV) conduction. The 3,4-dichloro substitution (3,4-Cl-α-PVP) was the most potent inducer of negative chronotropy (EC₅₀ = 52.6 μM), whereas 4-Cl-α-PVP exhibited a distinct pro-arrhythmic liability, increasing the incidence of 2:1 AV block. Time-course locomotor profiling indicated that α-PVP and chlorinated analogs were among the most potent behavioral modifiers. Using a Functional Safety Index (AV block EC₅₀/locomotor EC₅₀-like), we show that most compounds exhibit wide separations between neurobehavioral inhibition and severe conduction impairment, while specific substitutions, particularly para-chlorination, are associated with comparatively reduced functional separation between these endpoints within the assay. Overall, these data demonstrate that subtle structural changes within the pyrrolidinophenone scaffold can shape distinct arrhythmic phenotypes and functional safety profiles, supporting zebrafish-based integrated screening as a rapid platform for prioritizing emerging synthetic cathinones with comparatively higher cardiac liability within this experimental framework.