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Tropospheric ozone (TPO) is considered as a "near-term climate forcer", whose impact on climate depends on its radiative forcing (RF), which is a change in the Earth's energy flux. Here, we use the ground-based and satellite measurements during the period 2005-2020 to deduce the trends of TPO, which is significantly positive in the tropical and extra-tropical northern hemisphere (0.2-0.5 DU/yr) and southern extra-tropics (0.1-0.2 DU/yr). Furthermore, the trends derived using a multiple linear regression model (MLR) also confirm these estimates, which are about 0.05-0.1 DU/yr and the regions with higher trends (>0.06 DU/yr) are statistically significant. We also use a standalone Rapid Radiative Transfer Model coupled with a convective model (Radiative-Convective Model; RCM) to assess the climate forcing of ozone using its vertical profiles from the Modern Era Retrospective Reanalysis (MERRA)-2 reanalysis. The estimated temperature rise due to the radiative forcing of ozone in the tropical troposphere (1000-100 hPa) is about 0.2-0.3 °C for the study period. In brief, there is a positive trend in the tropospheric ozone in the tropics and extra-tropics, which is a great concern for regional warming, public health and ecosystem dynamics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study describes the use of passive sampling followed by pressurised liquid extraction and gas chromatography-mass spectrometry for monitoring high production volume chemicals (HPVCs), such as benzothiazoles, benzesulfonamides, phthalate esters (PAEs), organophosphate esters, ultraviolet stabilizers, and phenolic antioxidants and polycyclic aromatic hydrocarbons (PAHs) in urban atmospheres close to a petrochemical area. To obtain accurate results when applying passive sampling, the uptake rates of each target compound for the sampling time applied must be known. Firstly, passive sampling was calibrated for two months and uptake rates of HPVCs and PAHs in an urban atmosphere determined using active sampling as the reference method. The obtained results showed experimental diffusive uptake rates between 1.6 m 3 day -1 and 27 m 3 day -1 for 32 of the target compounds that will allow enable cost-effective long-term monitoring campaigns of HPVCs to be performed. Secondly, the experimentally obtained uptake rates were used to monitor the concentrations of HPVCs and PAHs at six urban sampling sites close to the two petrochemicals parks in Tarragona (Spain) during a period the two months. Regardless of the sampling campaign, PAEs and PAHs were the families of compounds found at the highest concentration levels, with a sum of their mean values of 23 ng m -3 and 20 ng m -3 , respectively., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Over the past 50 years, fossil fuel consumption has increased dramatically, rising approximately eight-fold since 1950 and doubling since 1980. This surge has led to increased emissions of brown carbon (BrC) into the atmosphere, which are subsequently deposited onto oceans and land through dry or wet deposition processes. However, the source-specific fluxes of atmospheric organic carbon (OC) and BrC into the ocean are not adequately represented in the global carbon cycle. For the first time, we calculated BrC concentration using the optical intensity of organic matter and determined the global wet depositional flux of fossil fuel-derived BrC. Using the ratio of humic-like substances to OC fluxes, we estimated the global wet deposition of fossil fuel-derived BrC to be 2.0 ± 0.6 Tg C yr -1 . Of this amount, the flux into oceans (0.7 ± 0.2 Tg C yr -1 ) represents 1.6% of the production rate of refractory dissolved organic carbon (RDOC) in the ocean (43 Tg yr -1 ). Notably, an increase in the proportion of fossil fuel-derived BrC in atmospheric OC may change the composition of OC in precipitation, resulting in a more refractory composition, which deviates from previously established paradigms. Our findings indicate that the flux of fossil fuel-derived RDOC from the atmosphere into the ocean, which is inadequately represented in current global DOC cycling models, may play a significant role in oceanic carbon cycles. These findings necessitate reconsidering our understanding of oceanic carbon cycling and highlight the need to improve existing models to better account for these newly identified processes and their potential impacts on global carbon dynamics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Tropospheric ozone (O 3 ) pollution often accompanies droughts and heatwaves, which could collectively reduce plant productivity. Previous research suggested that O 3 pollution can alter plant responses to drought by interfering with stomatal closure while drought can reduce stomatal conductance and provide protection against O 3 stress. However, the interactions between O 3 pollution and drought stress remain poorly understood at ecosystem scales with diverse plant functional types. To address this research gap, we used 10-year (2012-2021) satellite near-infrared reflectance of vegetation (NIRv) observations, reanalysis data of vapor pressure deficit (VPD), soil moisture (SM), and air temperature (Ta), along with O 3 measurements and reanalysis data across the Northern Hemisphere to statistically disentangle the interconnections between NIRv, VPD, SM, and Ta under varying O 3 levels. We found that high O 3 concentrations significantly exacerbate the sensitivity of NIRv to VPD while have no notable impacts on the sensitivity of NIRv to Ta or SM for all plant functional types, indicating an enhanced combined impact of VPD and O 3 on plants. Specifically, the sensitivity of NIRv to VPD increased by >75 % when O 3 anomalies increased from the lowest 10 to the highest 10 percentiles across diverse plant functional types. This is likely because long-term exposure to high O 3 concentrations can inhibit stomatal closure and photosynthetic enzyme activities, resulting in reduced water use efficiency and photosynthetic efficiency. This study highlights the need to consider O 3 in understanding plant responses to climate factors and that O 3 can alter plant responses to VPD independently of Ta and SM., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Cities are treated as global methane (CH 4 ) emission hotspots and the monitoring of atmospheric CH 4 concentration in cities is necessary to evaluate anthropogenic CH 4 emissions. However, the continuous and in-situ observation sites within cities are still sparsely distributed in the largest CH 4 emitter as of China, and although obvious seasonal variations of atmospheric CH 4 concentrations have been observed in cities worldwide, questions regarding the drivers for their temporal variations still have not been well addressed. Therefore, to quantify the contributions to seasonal variations of atmospheric CH 4 concentrations, year-round CH 4 concentration observations from 1st December 2020 to 30th November 2021 were conducted in Hangzhou megacity, China, and three models were chosen to simulate urban atmospheric CH 4 concentration and partition its drivers including machine learning based Random Forest (RF) model, atmospheric transport processes based numerical model (WRF-STILT), and regression analysis based Multiple Linear Regression (MLR) model. The findings are as follows: (1) the atmospheric CH 4 concentration showed obvious seasonal variations and were different with previous observations in other cities, the seasonality were 5.8 ppb, 21.1 ppb, and 50.1 ppb between spring-winter, summer-winter and autumn-winter, respectively, where the CH 4 background contributed by -8.1 ppb, -44.6 ppb, and -1.0 ppb, respectively, and the CH 4 enhancements contributed by 13.9 ppb, 65.7 ppb, and 51.1 ppb. (2) The RF model showed the highest accuracy in simulating CH 4 concentrations, followed by MLR model and WRF-STILT model. (3) We further partition contributions from different factors, results showed the largest contribution was from temperature-induced increase in microbial process based CH 4 emissions including waste treatment and wetland, which ranged from 38.1 to 76.3 ppb when comparing different seasons with winter. The second largest contribution was from seasonal boundary layer height (BLH) variations, which ranged from -13.4 to -6.3 ppb. And the temperature induced seasonal CH 4 emission and enhancement variations were overwhelming BLH changes and other meteorological parameters., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The global apprehension regarding the ubiquitous presence of microplastics (MPs) and their associated health risks underscore a significant challenge. However, our understanding on the occurrence and characteristics of this emerging class of pollutants in the different environmental compartments remains limited. For instance, despite housing approximately 20-25% of the global population, the evidence of the atmospheric MPs in Indian Subcontinent is exceedingly rare. Hence, we for the first-time present data on the depositional flux, chemical composition, morphological features of the atmospheric MPs collected from the foothills of Indian Himalayas. The total number of MPs for the collected samples ranged from 65 to 752 particles, with an average of 317 ± 171 particles count. The average flux of atmospheric MPs was 2256 ± 1221 particles/m 2 /day and varied significantly from 462 particles/m 2 /day to 5346 particles/m 2 /day. The highest deposition (5346 particles/m 2 /day) of atmospheric MPs was recorded during the 3rd week of sampling, coinciding with the Diwali festival. Based on the visual characteristics, we determined that the size of MPs ranged from 67 to 2320 μm, with a predominant presence of smaller particles (<1200 μm), primarily composed of fragments and films/sheets. Raman spectroscopy indicated that the analyzed MPs were mainly composed of 4 different polymer types, including PE (46.8 ± 7.2 %), PP (20.9 ± 7.4 %), PS (15.6 ± 3.8 %) and PET (16.7 ± 9.9 %). We further highlighted the extent to which climate variables control the deposition of atmospheric MPs in this urban conglomerate located in the foothills of Himalayas. Our Lagrangian parcel tracking approach showed that the greater frequencies are of local origin and clustered near to the studied region. We also speculate that atmospheric microplastics can be transported along the westerly winds. Though we did not observe any significant relation (p > 0.05) between meteorological parameters and the quantity of atmospheric MPs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study measured the atmospheric concentration and deposition flux of radiocesium in Koriyama City, Fukushima Prefecture, Japan, from November 2011 to October 2014. The results show synchronous seasonal change in atmospheric concentration and deposition flux of radiocesium, which is high during winter to early spring and low during summer to autumn. These seasonal variations are similar to those observed in Fukushima City but differ from those in Namie Town, Fukushima Prefecture, comprising a larger contaminated forest area. The evaluation of the relationship between atmospheric 137Cs concentration or 137Cs specific activity in atmospheric particulate matter (PM) and deposition density of 137Cs in PM source area suggest that stronger winds blowing from areas with relatively large 137Cs deposition (west of Koriyama City) toward the study site affect the site's atmospheric 137Cs concentrations., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

This study investigates the formation of atmospheric molecular clusters containing ammonia (NH 3 , A), methylamine (CH 3 NH 2 , MA), or dimethylamine (CH 3 NHCH 3 , DMA) with nitric acid (HNO 3 , NA) using quantum mechanics. The Atmospheric Cluster Dynamic Code (ACDC) was employed to simulate the total evaporation rate, formation rate, and growth pathways of three types of clusters under dry and hydrated conditions. This study evaluates the enhancing potential of A/MA/DMA for NA-based new particle formation (NPF) at parts per trillion (ppt) levels. The results indicate that A/MA/DMA can enhance NA-based NPF at high nitric acid concentrations and low temperatures in the atmosphere. The enhancing potential of MA is weaker than that of DMA but stronger than that of A. Cluster growth predominantly follows the lowest free energy pathways on the acid-base grid, with the formation of initial acid-base dimers (NA)(A), (NA)(MA), and (NA)(DMA) being crucial. Hydration influences the evaporation rate and formation rate of clusters, especially for initial clusters. When the humidity is at 100%, the formation rate for NA-A, NA-MA, and NA-DMA clusters can increase by approximately 10 9 , 10 7 , and 10 4 -fold compared to the corresponding unhydrated clusters, respectively. These results highlight the significance of nitric acid nucleation in NPF events in low-temperature, high-humidity atmospheres, particularly in regions like China with significant automobile exhaust pollution.

Background and Aims: Leaf elongation is vital for productivity of Poaceae species, influenced by atmospheric CO2 concentration ([CO2]) and climate-induced water availability changes. Although [CO2] mitigates the effects of drought on reducing transpiration per unit leaf area, it also increases total leaf area and water use. These complex interactions associated with leaf growth pose challenges in anticipating climate change effects. This study aims to assess [CO2] effects on leaf growth response to drought in perennial ryegrass (Lolium perenne), tall fescue (Festuca arundinacea) and wheat (Triticum aestivum)., Methods: Plants were cultivated in growth chambers with [CO2] at 200 or 800 ppm. At leaf six to seven unfolding, half of the plants were subjected to severe drought treatment. Leaf elongation rate (LER) was measured daily, whereas plant transpiration was continuously recorded gravimetrically. Additionally, water-soluble carbohydrate (WSC) content along with water and osmotic potentials in the leaf growing zone were measured at drought onset, mid-drought and leaf growth cessation., Key Results: Elevated [CO2] mitigated drought impacts on LER and delayed growth cessation across species. A positive correlation between LER and soil relative water content (SRWC) was observed. At the same SRWC, perennial grasses exhibited a higher LER with elevated [CO2], probably due to enhanced stomatal regulation. Despite stomatal closure and WSC accumulation, CO2 did not influence nighttime water potential or osmotic potential. The marked increase in leaf area across species resulted in similar (wheat and tall fescue) or higher (ryegrass) total water use by the end of the experiment, under both watered and unwatered conditions., Conclusions: Elevated [CO2] mitigates the adverse effects of drought on leaf elongation in three Poaceae species, due to its impact on plant transpiration. Overall, these findings provide valuable insights into CO2 and drought interactions that may help anticipate plant responses to climate change., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Soils accumulate anthropogenic mercury (Hg) from atmospheric deposition to terrestrial ecosystems. However, possible reemission of gaseous elemental mercury (GEM) back to the atmosphere as well as downward migration of Hg with soil leachate influence soil sequestration of Hg in ways not sufficiently understood in global biogeochemical models. Here, we apply fallout radionuclide (FRN) chronometry to understand soil Hg dynamics by revisiting the METAALICUS experiments 20 years after enriched isotope tracers ( 198 Hg, 200 Hg, 201 Hg, and 202 Hg) were applied to two boreal watersheds in northwestern Ontario, Canada. Hg spikes formed well-defined peaks in organic horizons of both watersheds at depths of 3-6 cm and were accurately dated to the year of spike application in 6 of 7 cases (error = -0.8 ± 1.2 years). A seventh site was depleted by ca. 90% of both the 200 Hg spike and background Hg, and the spike was dated 16 years older than its application. Robust FRN age models and mass balances demonstrate that loss of Hg is attributable to its specific physicochemical behavior at this site, but more work is required to attribute this to reemission or leaching. This study demonstrates the potential of FRN chronometry to provide insights into Hg accumulation, mobilization, and fate in forest soils.

Tropical wetlands and freshwaters are major contributors to the growing atmospheric methane (CH 4 ) burden. Extensive peatland drainage has lowered CH 4 emissions from peat soils in Southeast Asia, but the canals draining these peatlands may be hotspots of CH 4 emissions. Alternatively, CH 4 oxidation (consumption) by methanotrophic microorganisms may attenuate emissions. Here, we used laboratory experiments and a synoptic survey of the isotopic composition of CH 4 in 34 canals across West Kalimantan, Indonesia to quantify the proportion of CH 4 that is consumed and therefore not emitted to the atmosphere. We find that CH 4 oxidation mitigates 76.4 ± 12.0% of potential canal emissions, reducing emissions by ~70 mg CH 4 m -2 d -1 . Methane consumption also significantly impacts the stable isotopic fingerprint of canal CH 4 emissions. As canals drain over 65% of peatlands in Southeast Asia, our results suggest that CH 4 oxidation significantly influences landscape-scale CH 4 emissions from these ecosystems., Competing Interests: Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Many evidences have shown that both atmospheric and soil droughts can constrain vegetation growth and further threaten its ability to sequester carbon. However, the trigger thresholds of vegetation production loss under different atmospheric and soil drought conditions are still unknown. In this study, we proposed a Copula and Bayesian equations-based framework to investigate trigger thresholds of various vegetation production losses under different atmospheric and soil drought conditions. The trigger thresholds dynamics and their possible causes were also investigated. To achieve this goal, we first simulated the gross primary production, soil moisture, and vapor pressure deficit over China during 1961-2018 using an individual-based, spatially explicit dynamic global vegetation model. The main drivers of the dynamic change in trigger thresholds were then explored by Random Forest model. We found that soil drought caused greater stress on gross primary production loss than atmospheric drought, with a larger impact area and higher probability of damage. In terms of spatial distribution, the risk probability of gross primary production loss was higher in eastern China than in western China, and the drought trigger threshold was also smaller in eastern China. In addition, the trigger thresholds for atmospheric and soil drought in most regions exhibited a decreasing trend from 1961 to 2018, while the CO 2 fertilization enhanced the drought tolerance of vegetation. The reduction in CO 2 fertilization effect slowed down the downward trend of trigger threshold for soil drought, while the increase in temperature exacerbated the downward trend of trigger threshold for atmospheric drought. This study highlighted the larger effect of soil drought on vegetation production loss than atmospheric drought and implied that climate change can modulate the trigger threshold of vegetation production losses under drought conditions. These findings provide scientific guidance for managing the increasing risk of drought on vegetation and optimizing watershed water allocation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In many rapidly urbanizing and industrializing countries, atmospheric pollution causes severe environmental problems and compromises the health of humans and ecosystems. Atmospheric emissions, which encompass gases and particulate matter, can be transported back to the earth's surface through atmospheric deposition. Atmospheric deposition supplies chemical species that can serve as nutrients and/or toxins to aquatic ecosystems, resulting in wide-ranging responses of aquatic organisms. Among the aquatic organisms, phytoplankton is the basis of the aquatic food web and is a key player in global primary production. Atmospheric deposition alters nutrient availability and thus influences phytoplankton species abundance and composition. This review provides a comprehensive overview of the physiological responses of phytoplankton resulting from the atmospheric deposition of trace metals, nitrogen-containing compounds, phosphorus-containing compounds, and sulfur-containing compounds in particulate matter into aquatic ecosystems. Knowledge gaps and critical areas for future studies are also discussed., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Theodora Nah reports financial support was provided by State Key Laboratory of Marine Pollution (SKLMP). Theodora Nah reports financial support was provided by Guangdong Basic and Applied Basic Research Fund Committee. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Black carbon (BC) is a pollutant produced by the combustion of fossil fuels and biomass fuels, which has a huge impact on regional climate, atmospheric environment, and human health. In this study, based on MERRA-2 reanalysis data and ground-based observation data, the Mann-Kendall (MK) test and random forest (RF) model were used to explore the spatiotemporal variation characteristics of atmospheric BC concentration in Xinjiang, China and its correlation with meteorological and environmental covariates in 2010-2022. The results showed that the use of MERRA-2 reanalysis data to explore the spatiotemporal variation characteristics of BC concentration in Xinjiang had high reliability (relative average deviation (RAD) = 0.65). From 2010 to 2022, the annual average concentration of atmospheric BC in Xinjiang was 195.40 ± 15.55 ng/m 3 , and the multi-year average change rate was -0.05%. The winter season had the highest atmospheric BC concentration (145.52 ± 39.31 ng/m 3 ), followed by autumn (124.95 ± 28.82 ng/m 3 ), spring (74.05 ± 9.96 ng/m 3 ), and summer (73.41 ± 5.69 ng/m 3 ). The atmospheric BC concentration had a significant spatial variation, showing two high-BC-concentration areas on the northern slope of the Tianshan Mountains (centered on Urumqi-Changji-Shihezi region) and the urban agglomeration around the Tarim Basin (centered on Kashgar). The RF model analysis showed that meteorological factors including snow depth, surface temperature, and humidity as well as environmental factors including NO 2 , PM 10 , and SO 2 were the main factors affecting the BC concentration. This work is of great significance for clarifying the accumulation and spatial distribution characteristics of atmospheric BC in northwest China and the factors influencing the atmospheric BC concentration, and helps to raise public attention to the increasingly serious climate change and public health problems caused by BC., Competing Interests: The authors declare there are no competing interests., (©2024 Xie et al.)

Arsenic, a toxic element from both anthropogenic and natural sources, reaches surface environments through atmospheric cycling and dry and wet deposition. Biomethylation volatilizes arsenic into the atmosphere and deposition cycles it back to the surface, affecting soil-plant systems. Chemical speciation of deposited arsenic is important for understanding further processing in soils and bioavailability. However, the range of atmospheric transport and source signature of arsenic species remain understudied. Here we report significant levels of methylated arsenic in precipitation, cloud water and aerosols collected under free tropospheric conditions at Pic du Midi Observatory (France) indicating long-range transport, which is crucial for atmospheric budgets. Through chemical analyses and moisture source diagnostics, we identify terrestrial and marine sources for distinct arsenic species. Estimated atmospheric deposition fluxes of methylated arsenic are similar to reported methylation rates in soils, highlighting atmospheric deposition as a significant, overlooked source of potentially bioavailable methylated arsenic species impacting plant uptake in soils., (© 2024. The Author(s).)

Assessing local air quality using traditional methods, such as analyzing precipitation composition, is often difficult due to the complex data, which is influenced by a variety of chemical elements from distant atmospheric sources and cyclone formation areas. This study presents a new approach to overcome these challenges: a multi-elevation sampling method that improves the accuracy of local air quality measurements. By collecting precipitation samples at different ground elevations, the technique takes advantage of the natural process where raindrops and snowflakes collect more elements as they fall through the air. This method helps to distinguish local air quality from background levels found at higher, non-industrial elevations. The primary goal was to isolate and identify the elemental fingerprints of marine influences, while excluding contributions from cyclones. In February 2023, 51 meltwater samples were collected from 17 observation points in the city of Sochi under southeast wind conditions. These samples revealed a spectrum of chemical elements, predominantly of marine origin (Mg > Na > Sr > Ca > K > Ce > Mn). The results showed significant differences in elemental concentrations between upland and coastal areas. The Geochemical Indicator of Marine Origin (GIM) ranged from 22 to 3235, confirming the strong influence of marine aerosols in the area. These findings demonstrate the effectiveness of the multi-elevation sampling method in providing robust environmental assessments. This approach, combined with the GIM index, offers valuable insights for improving environmental policies and public health, particularly in coastal regions affected by marine aerosols., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Monoterpenes, the second most abundant biogenic volatile organic compounds globally, are crucial in forming secondary organic aerosols, making their oxidation mechanisms vital for addressing climate change and air pollution. This study utilized cyclohexene as a surrogate to explore first-generation products from its ozonolysis through laboratory experiments and mechanistic modeling. We employed proton transfer reaction mass spectrometry with NH 4 + ion sources (NH 4 + -CIMS) and a custom-built OH calibration source to quantify organic peroxy radicals (RO 2 ) and closed-shell species. Under near-real atmospheric conditions in a Potential Aerosol Mass-Oxidation Flow Reactor, we identified 30 ozonolysis products, expanding previous data sets of low-oxygen compounds. Combined with simulations based on the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere and relevant literature, our results revealed that OH dominates over ozone in cyclohexene oxidation at typical atmospheric oxidant levels with H-abstraction contributing 30% of initial RO 2 radicals. Highly oxidized molecules primarily arise from RO 2 autoxidation initiated by ozone, and at least 15% of ozone oxidation products follow the overlooked nonvinyl hydroperoxides pathway. Gaps remain especially in understanding RO 2 cross-reactions, and the structural complexity of monoterpenes further complicates research. As emissions decrease and afforestation increases, understanding these mechanisms becomes increasingly critical.

Particulate matter (PM) undergoing various aging processes in the atmosphere changes its toxicity. However, the mechanism of toxicity evolution is not fully clarified currently. This study demonstrates that photoaging promotes an increase in the oxidative potential (OP) of atmospheric PM by about 30%, and the increased OP is mainly attributed to the production of secondary organic compounds, while water-soluble metal ions contribute only 11%. The OP of nonextractable matters (NEMs) of atmospheric PM was mostly increased after photoaging, followed by water-soluble matters (WSMs). NEM can produce quinone-like functional groups and secondary persistent free radicals during photoaging, which are most likely to produce reactive oxygen species (ROS). For WSM, the conversion of low-oxidation humic-like substances (HULIS) to high-oxidation HULIS is the main reason for the increase in OP. Quinones, nitrophenols, and N-containing heterocycles are the OP contributors produced during the conversion process. Among them, quinones are the main secondary oxidizing active compounds, while nitro-phenolic compounds and N-containing heterocyclic compounds may play a catalyst-like role, facilitating the production of oxidizing active compounds and ROS in the newly converted high-oxidation HULIS. This study clarifies the secondary OP generation mechanism and provides new insights into the uncertainty of PM toxicity during atmospheric aging.

Aerosol particles originating from the Qinghai-Tibet Plateau (QTP) readily reach the free troposphere, potentially affecting global radiation and climate. Although new particle formation (NPF) is frequently observed at such high altitudes, its precursors and their underlying chemistry remain poorly understood. This study presents direct observational evidence of anthropogenic influences on biogenic NPF on the southeastern QTP, near the Himalayas. The mean particle nucleation rate ( J 1.7 ) is 2.6 cm -3 s -1 , exceeding the kinetic limit of sulfuric acid (SA) nucleation (mean SA: 2.4 × 10 5 cm -3 ). NPF is predominantly driven by highly oxygenated organic molecules (HOMs), possibly facilitated by low SA levels. We identified 1538 ultralow-volatility HOMs driving particle nucleation and 764 extremely low-volatility HOMs powering initial particle growth, with mean total concentrations of 1.5 × 10 6 and 3.7 × 10 6 cm -3 , respectively. These HOMs are formed by atmospheric oxidation of biogenic precursors, unexpectedly including sesquiterpenes and diterpenes alongside the commonly recognized monoterpenes. Counterintuitively, over half of HOMs are organic nitrates, mainly produced by interacting with anthropogenic NO x via RO 2 +NO terminations or NO 3 -initiated oxidations. These findings advance our understanding of NPF mechanisms in this climate-sensitive region and underscore the importance of heavy terpene and NO x -influenced chemistry in assessing anthropogenic-biogenic interactions with climate feedbacks.

Earth is expected to have acquired a reduced proto-atmosphere enriched in H 2 and CH 4 through the accretion of building blocks that contain metallic Fe and/or the gravitational trapping of surrounding nebula gas. Such an early, wet, reduced atmosphere that covers a proto-ocean would then ultimately evolve toward oxidized chemical compositions through photochemical processes that involve reactions with H 2 O-derived oxidant radicals and the selective escape of hydrogen to space. During this time, atmospheric CH 4 could be photochemically reprocessed to generate not only C-bearing oxides but also organics. However, the branching ratio between organic matter formation and oxidation remains unknown despite its significance on the abiotic chemical evolution of early Earth. Here, we show via numerical analyses that UV absorptions by gaseous hydrocarbons such as C 2 H 2 and C 3 H 4 significantly suppress H 2 O photolysis and subsequent CH 4 oxidation during the photochemical evolution of a wet proto-atmosphere enriched in H 2 and CH 4 . As a result, nearly half of the initial CH 4 converted to heavier organics along with the deposition of prebiotically essential molecules such as HCN and H 2 CO on the surface of a primordial ocean for a geological timescale order of 10-100 Myr. Our results suggest that the accumulation of organics and prebiotically important molecules in the proto-ocean could produce a soup enriched in various organics, which might have eventually led to the emergence of living organisms.

Rising levels of atmospheric carbon dioxide (CO 2 ) and nitrogen (N) deposition affect plant communities in numerous ways 1-11 . Nitrogen deposition causes local biodiversity loss globally 12-14 , but whether, and if so how, rising CO 2 concentrations amplify or dampen those losses remains unclear and is almost entirely unstudied. We addressed this knowledge gap with an open-air experiment in which 108 grassland plots were grown for 24 years under different CO 2 and N regimes. We initially found that adding N reduced plant species richness less at elevated than at ambient CO 2 . Over time, however, this interaction reversed, and elevated CO 2 amplified losses in diversity from enriched N, tripling reductions in species richness from N addition over the last eight years of the study. These interactions resulted from temporal changes in the drivers of diversity, especially light availability, that were in turn driven by CO 2 and N inputs and associated changes in plant biomass. This mechanism is likely to be similar in many grasslands, because additions of the plant resources CO 2 and N are likely to increase the abundance of the dominant species. If rising CO 2 generally exacerbates the widespread negative impacts of N deposition on plant diversity, this bodes poorly for the conservation of grassland biodiversity worldwide., Competing Interests: Competing interests The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

All over the world, the oceans are the final destination of sewage transported by river estuaries, rainwater and other coastal discharges. The risks to human health related to direct contact with water and consumption of contaminated fish are well known, but little is known about the potential for atmospheric exposure to pollutants and pathogens from contaminated seawater. The release of microbial particles from the sea into the atmosphere occurs mainly by the eruption of rising bubbles through the sea surface microlayer (SML) or by sea spray. We investigated the heterotrophic bacteria density and relative abundance in SML and bioaerosols originated on the seafront of Fortaleza (Atlantic coastal zone, northeastern Brazil) influenced by wastewater disposal. There was a difference in the density of total heterotrophic bacteria (THB) according to the matrix analyzed during two seasons: the bacterial count was highest in the SML during the rainy season while the highest number of bacteria in bioaerosols samples was recorded during the dry season. Twenty-nine bacterial taxonomic groups were identified with variable abundance for both environments. These were the same in both matrices, with environmental variables influencing their abundance and composition. The contribution of the marine and continental environments in shaping the microbiota of the SML and coastal bioaerosols was clear, with the constant and representative presence of Enterobacteria standing out. The aerosolization of bacteria resulting from the discharge of untreated sewage is an important issue related to coastal environmental health and ecological safety., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The Northeast Pacific Ocean (NEP) is one of the important carbon sinks in the global ocean. The causes of carbon flux changes in this region have been widely studied, but the physical processes associated with large scale climate variability remain controversial primarily due to scarcity of spatially and temporally continuous observations. In this study, we constructed a high-resolution sea surface partial pressure of CO 2 (pCO 2 ) from satellite observations for the NEP from 2003 to 2020 using the machine learning based XGBoost model. By analyzing the interannual large-scale high-latitude atmospheric dynamics and ocean physical conditions over the NEP, we find that the CO 2 flux density (FCO 2 ) anomalies have a strong correlation with the Alaskan atmospheric blocking events. In the region north of 48°N, anomalous cyclones triggered by atmospheric blocking increased sea surface height (SSH), which reduced the replenishment of dissolved inorganic carbon (DIC) from deep seawater, leading to enhanced carbon uptake. By contrast, in the region south of 48°N, the increase in sea surface temperature (SST) triggered by atmospheric blocking reduced the solubility of CO 2 in seawater, resulting in a decrease in regional carbon flux. These results provide new perspectives for better understanding and predicting the effects of high-latitude atmospheric dynamics on regional ocean carbon fluxes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Camellia oleifera shell (COS) is a renewable biomass resource abundant in lignin with significant potential for producing phenolic monomers. However, the dearth of research has led to considerable resource wastage and environmental pollution. Herein, reductive catalytic fractionation (RCF) of COS was performed using noble metal catalysts in different solvents. An 11.1 wt% yield of phenolic monomers was achieved with 91% selectivity toward propylene-substituted monomers in H 2 O/EtOH (3:7, v/v) cosolvent under N 2 atmosphere. Notably, the highest phenolic monomer yield of 17.0 wt% was obtained with impressive selectivity (86.9%) toward propanol-substituted monomers in the presence of H 2 . The GPC analysis and 2D HSQC NMR spectra indicated the effective depolymerization of lignin oligomers with catalysts. Phenolic monomers with ethyl, propyl, or propanol side chain could be produced from lignin-derived oligomers through hydrogenolysis, hydrogenation, and decarboxylation reactions. Overall, this study has paved the way for the valorization of COS lignin through the RCF strategy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Global climate zones are experiencing widespread shifts with ongoing rise in atmospheric CO 2 , influencing vegetation growth and shifting its distributions to challenge ecosystem structure and function, posing threats on ecological and societal safety. However, how rising atmospheric CO 2 affects the pace of global climate zone shifts is highly uncertain. More attentions are urgently required to understand the underlying mechanisms and quantifications of regional climate vulnerability in response to rising CO 2 . In this study, we employ nine Earth system models from CMIP6 to investigate global climate zone shifts with rising CO 2 , unravel the effects of vegetation physiological response (PHY), and categorize climate vulnerable regions depending on the extent of climate zone shifts. We find that climate zone shifts over half of the global land area, 16.8% of which is contributed by PHY at 4 × CO 2 . Intriguingly, besides warming, PHY-induced precipitation changes and their interactions with warming dominate about two-fifths of PHY-forced shifts, providing potential direction for model improvement in future predictions of climate zone shifts. Aided with PHY effects, 4 × CO 2 imposes substantial climate zone shifts over about one-fifth of the global land area, suggesting substantial changes in local climate and ecosystem structure and functions. Hence, those regions would experience strong climate vulnerability, and face high risk of climate extremes, water scarcity and food production. Our results quantitatively identify the vulnerable regions and unravel the underlying drivers, providing scientific insights to prioritize conservation and restoration efforts to ensure ecological and social safety globally., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024. Published by Elsevier B.V.)

The study of the variability of soil gas concentrations is crucial for defining effective monitoring and remediation strategies and for the risk assessment related to the emission of vapors from the subsurface. The traditional soil gas monitoring strategy consists of seasonal surveys based on short-time-averaged sampling. Soil gas monitoring results are often used to assess the risk associated with the emission of volatile contaminants from the subsurface, using models mainly based on molecular diffusion and therefore assuming continuous emission from the soil. At two contaminated sites located in the Veneto region (Italy), continuous monitoring using a photoionization detector, pressure gauges, and an ultrasonic anemometer was used to relate soil gas variability to surface and subsurface physical parameters. At both sites a cyclic diurnal variation of volatile organic compounds concentration in soil gas was observed, correlated with the variation of several meteorological parameters and in particular with the variation of the differential pressure between soil and atmosphere and the buoyancy vertical flux. These findings question the reliability of the conventional methodology employed in the collection and assessment of soil gas data. Integr Environ Assess Manag 2024;20:2023-2032. © 2024 SETAC., (© 2024 SETAC.)

Current views of O 2 accumulation in Earth history depict three phases: The onset of O 2 production by ∼2.4 billion years ago; 2 billion years of stasis at ∼1 % of modern atmospheric levels; and a rising phase, starting about 500 million years ago, in which oxygen eventually reached modern values. Purely geochemical mechanisms have been proposed to account for this tripartite time course of Earth oxygenation. In particular the second phase, the long period of stasis between the advent of O 2 and the late rise to modern levels, has posed a puzzle. Proposed solutions involve Earth processes (geochemical, ecosystem, day length). Here we suggest that Earth oxygenation was not determined by geochemical processes. Rather it resulted from emergent biological innovations associated with photosynthesis and the activity of only three enzymes: 1) The oxygen evolving complex of cyanobacteria that makes O 2 ; 2) Nitrogenase, with its inhibition by O 2 causing two billion years of oxygen level stasis; 3) Cellulose synthase of land plants, which caused mass deposition and burial of carbon, thus removing an oxygen sink and therefore increasing atmospheric O 2 . These three enzymes are endogenously produced by, and contained within, cells that have the capacity for exponential growth. The catalytic properties of these three enzymes paved the path of Earth's atmospheric oxygenation, requiring no help from Earth other than the provision of water, CO 2 , salts, colonizable habitats, and sunlight., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Although many studies have discussed the impact of Europe's air quality, very limited research focused on the detailed phenomenology of ambient trace elements (TEs) in PM 10 in urban atmosphere. This study compiled long-term (2013-2022) measurements of speciation of ambient urban PM 10 from 55 sites of 7 countries (Switzerland, Spain, France, Greece, Italy, Portugal, UK), aiming to elucidate the phenomenology of 20 TEs in PM 10 in urban Europe. The monitoring sites comprised urban background (UB, n = 26), traffic (TR, n = 10), industrial (IN, n = 5), suburban background (SUB, n = 7), and rural background (RB, n = 7) types. The sampling campaigns were conducted using standardized protocols to ensure data comparability. In each country, PM 10 samples were collected over a fixed period using high-volume air samplers. The analysis encompassed the spatio-temporal distribution of TEs, and relationships between TEs at each site. Results indicated an annual average for the sum of 20 TEs of 90 ± 65 ng/m 3 , with TR and IN sites exhibiting the highest concentrations (130 ± 66 and 131 ± 80 ng/m 3 , respectively). Seasonal variability in TEs concentrations, influenced by emission sources and meteorology, revealed significant differences (p < 0.05) across all monitoring sites. Estimation of TE concentrations highlighted distinct ratios between non-carcinogenic and carcinogenic metals, with Zn (40 ± 49 ng/m 3 ), Ti (21 ± 29 ng/m 3 ), and Cu (23 ± 35 ng/m 3 ) dominating non-carcinogenic TEs, while Cr (5 ± 7 ng/m 3 ), and Ni (2 ± 6 ng/m 3 ) were prominent among carcinogenic ones. Correlations between TEs across diverse locations and seasons varied, in agreement with differences in emission sources and meteorological conditions. This study provides valuable insights into TEs in pan-European urban atmosphere, contributing to a comprehensive dataset for future environmental protection policies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The Tibetan Plateau, a recognized global sink for Persistent Organic Pollutants (POPs), lies adjacent to two major emitting regions, inland China and India. This unique geographical setting makes it a pivotal site for examining the presence and compositional evolution of POPs following their long-range atmospheric transport (LRAT). This study focuses on the current predominant POPs, chlorinated paraffins (CPs). We comprehensively screened 675 homologues of the very short- (vSCCPs), short- (SCCPs), medium- (MCCPs), and long-chain CPs (LCCPs) in six dated sediment cores across the extensive Tibetan area. The findings unveiled pronounced temporal disparities in CP concentrations and compositions between Tibet's southern and eastern sectors, reflecting divergent usage and emission chronicles of inland China and India. Notably, a market shift in China from regulated SCCPs to the in-use MCCPs and LCCPs was observed in the 21st century, contrasting with India's unregulated production of SCCPs. The Organization for Economic Cooperation and Development (OECD) Screening Tool, developed to assess the overall persistence (P OV ) and long-range transport potential (LRTP) of organic chemicals, elucidated the erosion of CP source signatures induced by fractionation, a process that intensifies with transport distance from the source regions. This study enhances our understanding of the emission inventories and LRAT behavior of these transitional regulatory contaminants, highlighting the Tibetan Plateau's crucial role as an environmental sentinel in global pollution dynamics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Anthropogenic emissions alter atmospheric composition and therefore the climate, with implications for air pollution- and climate-related human health. Mortality attributable to air pollution and non-optimal temperature is a major concern, expected to shift under future climate change and socioeconomic scenarios. In this work, results from numerical simulations are used to assess future changes in mortality attributable to long-term exposure to both non-optimal temperature and air pollution simultaneously. Here we show that under a realistic scenario, end-of-century mortality could quadruple from present-day values to around 30 (95% confidence level:12-53) million people/year. While pollution-related mortality is projected to increase five-fold, temperature-related mortality will experience a seven-fold rise, making it a more important health risk factor than air pollution for at least 20% of the world's population. These findings highlight the urgent need to implement stronger climate policies to prevent future loss of life, outweighing the benefits of air quality improvements alone., (© 2024. The Author(s).)

Precipitation scavenging is an important sink for both organic and inorganic pollutants in the atmosphere. However, there has been controversy over the relative importance of different precipitation characteristics (i.e., the precipitation amount, intensity, frequency, and duration) in the removal of air pollutants. It is critical to reach a consensus on which precipitation characteristics are most significant for aerosol wet removal. In this study, the analysis of multisource in situ observations of aerosol wet deposition worldwide indicates that the precipitation frequency plays a first-order role in scavenging aerosols. This is because large amounts of air pollutants are efficiently removed at precipitation initiation. As the duration and amount of precipitation increase, the scavenging efficiency decreases sharply. Consequently, it is featured that light precipitation, due to its high frequency of occurrence, rather than total precipitation, determines climatological aerosol wet deposition. To further confirm this, a state-of-the-art global climate model with convection resolved is modified to reduce the light precipitation frequency in both stratiform and convective cloud regimes. Results show widespread increases in aerosol optical depth (AOD) due to the reduced wet deposition. The spatial distribution of aerosol wet deposition changes resembles that of changes in the light precipitation frequency rather than that of total precipitation changes. These findings are consistent with those from the Coupled Model Intercomparison Project Phase 6 multimodel simulations, which show that the intermodel uncertainty in simulated AOD correlates more strongly with the uncertainty in light precipitation frequency than with that in total precipitation.

Mineral aerosols form a key component of Earth's dynamic biogeochemical systems, yet their composition and mass are variable in time. We reconstruct patterns in mineral aerosol flux from East Asia, the second largest global dust source, in a peat mire in northern Japan. Using geochemical fingerprinting, we show for the past ~3600 years that high but variable tephra flux dominated regional aerosol loads. A human signal was discernible as elevated pollutant metals, along with East Asian mainland dust, identifiable by its geochemical signature. After ~700 years before the present, dust flux increased as the westerly jet intensified and moved south, the summer monsoon strength reduced, and agriculture expanded. From the 20th century, dust flux increased by two times. Attributable largely to human activity, this demarks a major change in aerosol export to the northwestern Pacific with accompanying increases in fluxes for key micronutrients and increased pollution flux by 16 times.

The Walker circulation is projected to slow down in response to greenhouse gas warming. However, detecting the impact of human activities on changes in the Walker circulation is challenging due to the significant influence of internal variability. Here, based on ensembles of multiple climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), we show evidence that the emergence of the human-induced weakening of Walker circulation tends to occur earlier in the middle-upper troposphere than at the surface. This earlier emergence is attributed to a more pronounced initial weakening response of the middle-upper tropospheric Walker circulation to atmospheric CO 2 radiative forcing. We further reveal that the emergence time of a weaker Walker circulation varies across models. This intermodel spread is governed by an ocean thermostat that operates by modulating the zonal sea surface temperature gradient over the tropical Indo-Pacific region. Our findings address the key question of whether and how to detect human-induced large-scale atmospheric circulation changes and provide valuable insights for assessing the associated risks., (© 2024. The Author(s).)

Biological N 2 fixation (BNF) is traced to the Archean. The nitrogen isotopic fractionation composition (δ 15 N) of sedimentary rocks is commonly used to reconstruct the presence of ancient diazotrophic ecosystems. While δ 15 N has been validated mostly using organisms grown under present-day conditions; it has not under the pre-Cambrian conditions, when atmospheric p O 2 was lower and p CO 2 was higher. Here, we explore δ 15 N signatures under three atmospheres with (i) elevated CO 2 and no O 2 (Archean), (ii) present-day CO 2 , and O 2 and (iii) future elevated CO 2 , in marine and freshwater, heterocytous cyanobacteria. Additionally, we augment our data set from literature for more generalized dependencies of δ 15 N and the associated fractionation factor epsilon ( ε = δ 15 N biomass - δ 15 N N2 ) during BNF in Archaea and Bacteria, including cyanobacteria, and habitats. The ε ranges between 3.70‰ and -4.96‰ with a mean ε value of -1.38 ± 0.95‰, for all bacteria, including cyanobacteria, across all tested conditions. The expanded data set revealed correlations of isotopic fractionation of BNF with CO 2 concentrations, toxin production, and light, although within 1‰. Moreover, correlation showed significant dependency of ε to species type, C/N ratios and toxin production in cyanobacteria, albeit it within a small range (-1.44 ± 0.89‰). We therefore conclude that δ 15 N is likely robust when applied to the pre-Cambrian-like atmosphere, stressing the strong cyanobacterial bias. Interestingly, the increased fractionation (lower ε ) observed in the toxin-producing Nodularia and Nostoc spp. suggests a heretofore unknown role of toxins in modulating nitrogen isotopic signals that warrants further investigation.IMPORTANCENitrogen is an essential element of life on Earth; however, despite its abundance, it is not biologically accessible. Biological nitrogen fixation is an essential process whereby microbes fix N 2 into biologically usable NH 3 . During this process, the enzyme nitrogenase preferentially uses light 14 N, resulting in 15 N depleted biomass. This signature can be traced back in time in sediments on Earth, and possibly other planets. In this paper, we explore the influence of p O 2 and p CO 2 on this fractionation signal. We find the signal is stable, especially for the primary producers, cyanobacteria, with correlations to CO 2 , light, and toxin-producing status, within a small range. Unexpectedly, we identified higher fractionation signals in toxin-producing Nodularia and Nostoc species that offer insight into why some organisms produce these N-rich toxic secondary metabolites., Competing Interests: The authors declare no conflict of interest.

Photooxidation products resulting from volatile organic compounds (VOCs) reacting with sunlight are important contributors to gas-phase air pollution. We characterized the product-weighted mutagenic potencies (rev m 3 mgC -1 h -1 ) in Salmonella TA100 of atmospheres resulting from the hydroxyl radical (OH)-initiated photochemical oxidation of 11 C 4 or C 5 alkenes or dienes in the presence of nitric oxide (NO) and from the ozonolysis of four VOCs without NO (isoprene; 1,3-pentadiene; 1,4-pentadiene; and 1,3-butadiene). Irradiated atmospheres from precursors with a single C═C bond (3-methyl-1-butene, 2-methyl-1-butene, cis/trans -2-pentene, 2-methyl-2-butene, 1-butene, and 1-pentene) had low potencies (<5), whereas linear dienes with terminal C═C bonds had high potencies (50-65). Dienes with a branched structure (isoprene) or internal C═C bonds (1,3-pentadiene) had intermediate potencies (15-20). No VOCs were mutagenic without photochemical oxidation. VOCs+O 3 in the dark produced less mutagenic atmospheres than photochemistry in the presence of NO. Atmospheres induced primarily C to T and C to A mutations, the main base substitutions in nonsmoker lung cancer. Atmospheres from the photooxidation of isoprene and 1,3-pentadiene also induced GG to TT, the signature mutation of peroxyacetyl nitrate. Five molecular compositions identified by Chemical Ionization Mass Spectrometry (CIMS), most containing nitrogen, correlated ( r = 0.76-0.85) with the mutagenic potencies of irradiated atmospheres; most had a likely nitrate functional group. Assessment of the mutagenicity of emitted VOCs should consider VOC photooxidation products, especially dienes with terminal C═C bonds, as these products likely contribute to overall health effects from ambient air pollution.

The ability of plants to uptake nutrients from mineral dust lying on their foliage may prove to be an important mechanism by which plants will cope with increasing CO 2 levels in the atmosphere. This mechanism had only recently been reported and was shown to compensate for the projected dilution in plants ionome. However, this phenomenon has yet to be thoroughly studied, particularly in terms of the expected trends under different dust types and varying atmospheric CO 2 concentrations, as projected by the IPCC. We treated plants grown under ambient (415 ppm) and elevated CO 2 (850 ppm) conditions with either desert dust, volcanic ash, and fire ash analogues by applying it solely on plant foliage and studied their Rare Earth Elements concentrations and patterns. The Rare Earth Elements compositions of the treated plants originated from the dust application, and their incorporation into the plants led to a significant increase in plants vitality, evident in increased photosynthetic activity and biomass. Two trends in the foliar nutrient uptake mechanism were revealed by the Rare Earth Elements, one is that different treatments affected the plant in decreasing order volcanic ash > desert dust > fire ash. The second trend is that foliar intake becomes more significant under elevated CO 2 , an observation not previously seen. This testifies that the use of Rare Earth Elements in the study of foliar nutrient uptake, and other biological mechanisms is fundamental, and that foliar pathways of nutrient uptake will indeed become more dominant with increasing CO 2 under expected atmospheric changes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Protists, known as microeukaryotes, are a significant portion of soil microbial communities. They are crucial predators of bacteria and depend on bacterial community dynamics for the growth and evolution of protistan communities. In parallel, increased levels of atmospheric CO 2 significantly impact bacterial metabolic activity in rhizosphere soils. In this study, we investigated the effect of elevated atmospheric CO 2 levels on the metabolically active protist community composition and function and their co-occurrences with bacteria from bulk and rhizosphere soils from the Giessen Free-Air CO 2 enrichment grassland experiment. Metabarcoding sequencing data analyses of partial 18S rRNA from total soil RNA showed that elevated CO 2 concentrations stimulated only a few ASVs of phagotrophic predators of bacteria and other microeukaryotes, affecting protist community composition (P = 0.006, PERMANOVA). In parallel, phagotrophic and parasitic lineages appeared slightly favoured under ambient CO 2 conditions, results that were corroborated by microbial signature analyses. Cross-comparisons of protist-bacteria co-occurrences showed mostly negative relations between prokaryotes and microeukaryotes, indicating that the ongoing increase in atmospheric CO 2 will lead to changes in microbial soil communities and their interactions, potentially cascading to higher trophic levels in soil systems., (© 2024. The Author(s).)

Microplastics (MPs) are pervasive across ecosystems, likely posing significant environmental and health risks based on more and more evidence. In this study, we searched through the Web of Science Core Collection and obtained 1039 papers for visualization and analysis. In order to discuss the chemical composition, migration, transformation and potential risk of MPs, 135 sets of relevant data in soil, water, and atmosphere were collected in China as a typical region, which is a hotspot region for investigation of MPs. The results showed that the primary polymer categories of MPs in the environment to be polypropylene, polyethylene, and polystyrene. The soil contains a significant quantity of MPs, averaging at 12,107.42 items·kg dw -1 , while water contains averaging at 97,271.18 items m -3 . The total pollution load indexes for all three environments are at risk level I. Based on current risk assessment methods, the potential ecological risk of MPs is low. However, based on the polymer components, migration and transformation patterns, and especially the complexes with other pollutants, it indicates an increasing indirect risk. Interactions with some other pollutants are likely amplify the ecological and health risks associated with MPs. Aggregative results showed that the present risk assessment models could not assess the risks of MPs well. Thus, we suggested develop a risk assessment methodology for MPs based on relevant research progress. Some factors such as the size and form of MPs, sources and distribution, bioaccumulation, social acceptance and economic costs could be considered adding in the present risk assessment models. Finally, promotion of development and application of green chemically synthesized bioplastics such as using synthetic biology to help degrade plastics would be an alternative and sustainable option to relieve the adverse environmental and health concerns of MPs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Current understanding of atmospheric transport of semivolatile organic contaminants (SVOCs) in alpine areas is limited due to complex meteorology and topography. Salt Lake City, Utah borders protected wilderness areas in the Wasatch Mountains, exhibiting a useful model system in which an urban source of SVOCs, including polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), is located directly adjacent to an alpine sink. Our objective was to investigate the impacts of topographical features on the transport and deposition of SVOCs across an urban-alpine boundary. To do so, we measured PAHs and PCBs in soils along a transect starting at the urban-mountain interface and extending into an alpine wilderness, crossing several prominent ridgelines. Concentrations of PAHs and PCBs in soils were heavily influenced by soil organic carbon content, air temperature, and proximity to the urban boundary. However, the role of source proximity was only revealed after normalizing concentrations in soil to organic carbon content and air temperature. Further, we present evidence of SVOC emission/deposition cycles driven by diurnal alpine winds that do not extend past topographical features. Our results illustrate the roles of multiple competing processes on SVOC transport in alpine systems and their importance at an urban-alpine boundary.

Biomass burning organic aerosol (BBOA), containing brown carbon chromophores, plays a critical role in atmospheric chemistry and climate forcing. However, the effects of evaporation on BBOA volatility and viscosity under different environmental conditions remain poorly understood. This study focuses on the molecular characterization of laboratory-generated BBOA proxies from wood pyrolysis emissions. The initial mixture, "pyrolysis oil (PO 1 )", was progressively evaporated to produce more concentrated mixtures (PO 1.33 , PO 2 , and PO 3 ) with volume reduction factors of 1.33, 2, and 3, respectively. Chemical speciation and volatility were investigated using temperature-programmed desorption combined with direct analysis in real-time ionization and high-resolution mass spectrometry (TPD-DART-HRMS). This novel approach quantified saturation vapor pressures and enthalpies of individual species, enabling the construction of volatility basis set distributions and the quantification of gas-particle partitioning. Viscosity estimates, validated by poke-flow experiments, showed a significant increase with evaporation, slowing particle-phase diffusion and extending equilibration times. These findings suggest that highly viscous tar ball particles in aged biomass burning emissions form as semivolatile components evaporate. The study highlights the importance of evaporation processes in shaping BBOA properties, underscoring the need to incorporate these factors into atmospheric models for better predictions of BBOA aging and its environmental impact.

Whereas inhalation exposure to organic contaminants can negatively impact human health, knowledge of their spatial variability in the ambient atmosphere remains limited. We analyzed the extracts of passive air samplers deployed at 119 unique sites in Southern Canada between 2019 and 2022 for 353 organic vapors. Hierarchical clustering of the obtained data set revealed four archetypes of spatial concentration variability in the outdoor atmosphere, which are indicative of common sources and similar atmospheric dispersion behavior. "Point Source" signatures are characterized by elevated concentration in the vicinity of major release locations. A "Population" signature applies to compounds whose air concentrations are highly correlated with population density, and is associated with emissions from consumer products. The "Water Source" signature applies to substances with elevated levels in the vicinity of water bodies from which they evaporate. Another group of compounds displays a "Uniform" signature, indicative of a lack of major sources within the study area. We illustrate how such a data set, and the derived spatial patterns, can be applied to support the identification of sources, the quantification of atmospheric emissions, the modeling of air quality, and the investigation of potential inequities in inhalation exposure.

During the period from 2019 to 2021, a series of experiments were carried out to study the uptake of tritium by crops in an area heavily contaminated with atmospheric tritium oxide (HTO), at the former Semipalatinsk test site in Kazakhstan. A quantitative assessment is given of the tritium uptake by typical crops (lettuce, tomatoes, peppers and beans) cultivated all over Kazakhstan in the case of a short-term tritium oxide vapor exposure. The plant samples were collected during and after exposure and analyzed for the tritium concentration in two chemical forms: tissue-free water tritium (TFWT) and organically bound tritium (OBT). During the entire series of experiments, the tritium concentration in free water from leaves and ambient air was of the same order of magnitude. The tissue water tritium concentrations of stems and edible parts was 1 to 2 orders of magnitude lower than in the surrounding air. The average value of the TFWT/HTOatm ratio in the leaves and the edible part was (0.73±0.2) and (0.04±0.002), respectively. The organically-bound tritium concentration is 1-2 orders of magnitude lower than the tissue water tritium and ambient air concentrations. Under aerial tritium oxide uptake, the distribution of tritium in non-leafy crops was as follows: leaf-stem-fruit (in decreasing order). After exposure, a non-significant amount of tritium is firmly retained in plants for a long time. The tissue water tritium concentrations correlate closely with atmospheric tritium oxid (r = 0.76), correlate weakly with temperature (r = 0.43) and relative humidity (r = -0.43), and correlate moderately with solar radiation intensity (r = 0.56). There was no reliable correlation between the concentration of tritium in organic matter and in ambient air. The concentration of tritium in the free water of leaves is closely correlated with the concentration in the free water of the stems (r = 0.95) and fruits (r = 0.78). The organically-bound tritium concentration in leaves is closely correlated with the organically-bound tritium concentration in stems (r = 0.99) and fruits (r = 98). The results of the study should be considered when evaluating the impact of tritium oxide emissions on the population living near nuclear power., Competing Interests: The authors stated that there are no competing interests., (Copyright: © 2024 Polivkina et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Gaseous oxygenated organic molecules (OOMs) are crucial precursors of atmospheric organic aerosols. OOMs in urban atmospheres have complex compositions, posing challenges to understanding their formation, evolution, and influences. In this study, we identify 2403 atmospheric gaseous OOMs in urban Beijing using online nitrate-based chemical ionization Orbitrap mass spectrometry based on one-year atmospheric measurements. We find that OOMs in urban atmospheres can be identified with higher accuracy and wider coverage, compared to previously used online mass spectrometry. With optimized OOM resolving capabilities, previous knowledge of OOMs in urban atmospheres can be expanded. First, clear homologous and oxygen-addition characteristics of the OOMs are revealed. Second, OOMs with lower concentrations or higher masses are identified and characterized with high confidence, e.g., OOMs with masses above 350 Da. In particular, dimers of OOMs (e.g., C 20 H 32 O 8-15 N 2 ), crucial species for organic nucleation, are identified. During four seasons, nitrogen-containing OOMs dominate the total concentration of OOMs, and OOMs are mainly from aromatic and aliphatic oxidation. Additionally, radicals with similar composition as OOMs, intermediates for OOM formation, are identified with clear diurnal variation, e.g., C n H 2 n -5 O 6 radicals ( n = 8-10) and C m H 2 m -4 NO 9 radicals ( m = 9-10), peak during the daytime and nighttime, respectively, previously having scarce measurement evidence in urban atmospheres.

In this hypothesis article, we discuss the basic requirements of planetary environments where aerobe organisms can grow and survive, including atmospheric limitations of millimeter-to-meter-sized biological animal life based on physical limits and O 2 , N 2 , and CO 2 toxicity levels. By assuming that animal-like extraterrestrial organisms adhere to similar limits, we define Earth-like habitats (EH) as rocky exoplanets in the habitable zone for complex life that host N 2 -O 2 -dominated atmospheres with minor amounts of CO 2 , at which advanced animal-like life or potentially even extraterrestrial intelligent life can in principle evolve and exist. We then derive a new formula that can be used to estimate the maximum occurrence rate of such Earth-like habitats in the Galaxy. This contains realistic probabilistic arguments that can be fine-tuned and constrained by atmospheric characterization with future space and ground-based telescopes. As an example, we briefly discuss two specific requirements feeding into our new formula that, although not quantifiable at present, will become scientifically quantifiable in the upcoming decades due to future observations of exoplanets and their atmospheres. Key Words: Eta-Earth-Earth-like habitats-oxygenation time-nitrogen atmospheres-carbon dioxide-animal-like life. Astrobiology 24, 897-915.

In Lammer et al. (2024), we defined Earth-like habitats (EHs) as rocky exoplanets within the habitable zone of complex life (HZCL) on which Earth-like N 2 -O 2 -dominated atmospheres with minor amounts of CO 2 can exist, and derived a formulation for estimating the maximum number of EHs in the galaxy given realistic probabilistic requirements that have to be met for an EH to evolve. In this study, we apply this formulation to the galactic disk by considering only requirements that are already scientifically quantifiable. By implementing literature models for star formation rate, initial mass function, and the mass distribution of the Milky Way, we calculate the spatial distribution of disk stars as functions of stellar mass and birth age. For the stellar part of our formulation, we apply existing models for the galactic habitable zone and evaluate the thermal stability of nitrogen-dominated atmospheres with different CO 2 mixing ratios inside the HZCL by implementing the newest stellar evolution and upper atmosphere models. For the planetary part, we include the frequency of rocky exoplanets, the availability of surface water and subaerial land, and the potential requirement of hosting a large moon by evaluating their importance and implementing these criteria from minima to maxima values as found in the scientific literature. We also discuss further factors that are not yet scientifically quantifiable but may be requirements for EHs to evolve. Based on such an approach, we find that EHs are relatively rare by obtaining plausible maximum numbers of 2.5 - 2.4 + 71.6 × 10 5 and 0.6 - 0.59 + 27.1 × 10 5 planets that can potentially host N 2 -O 2 -dominated atmospheres with maximum CO 2 mixing ratios of 10% and 1%, respectively, implying that, on average, a minimum of ∼ 10 3 - 10 6 rocky exoplanets in the HZCL are needed for 1 EH to evolve. The actual number of EHs, however, may be substantially lower than our maximum ranges since several requirements with unknown occurrence rates are not included in our model ( e.g. , the origin of life, working carbon-silicate and nitrogen cycles); this also implies extraterrestrial intelligence (ETI) to be significantly rarer still. Our results illustrate that not every star can host EHs nor can each rocky exoplanet within the HZCL evolve such that it might be able to host complex animal-like life or even ETIs. The Copernican Principle of Mediocrity therefore cannot be applied to infer that such life will be common in the galaxy.

Air pollution in South Asia is a health emergency, responsible for 2 million deaths every year 1 . Crop residue burning accounts for 40-60% of peak pollution during the winter harvest months 2,3 . Despite being illegal, this practice remains widespread 4,5 . Any solution to curb the problem necessitates government action at scale. Here we study whether leveraging the incentives of bureaucrats tasked with controlling burning can mitigate this phenomenon. Using a decade of wind, fire and health data from satellites and surveys from the Demographic and Health Surveys Program, we show that crop burning responds to bureaucrat incentives: fires increase by 15% when wind is most likely to direct pollution to neighbouring jurisdictions, and decrease by 14.5% when it pollutes their own. These effects intensify with stronger bureaucratic incentives and capacity. We also find that bureaucrat action against burning deters future polluters, further reducing fires by 13%. Finally, using an atmospheric model, we estimate that one log increase in in utero exposure to pollution from burning raises child mortality by 30-36 deaths per 1,000 births, underscoring the importance of bureaucrat action. Contrary to the growing beliefs that the problem of crop burning is intractable 6,7 , these findings highlight specific ways in which existing bureaucrats, when properly incentivized, can improve environmental management and public health outcomes., (© 2024. The Author(s).)

In this study, a total of 1425 atmospheric fine particulate matter (PM 2.5 ) samples were collected and analyzed for four water-soluble inorganic ions from 2016 to 2021 in Shenzhen. The average PM 2.5 concentrations exhibit an overall decreasing trend, with a total decrease of 57.5% during the six-year period, which is related to the reduction of emissions due to the 13th Five-Year Plan, the COVID-19, and the introduction of new energy conservation and emission reduction policies. The analyzed ions were all detected in PM 2.5 during the observation period in the concentration order of SO 4 2-  > NO 3 -  > NH 4 + >Cl - . These ions also showed a declining trend over the six years, with the average concentrations of the four ions decreasing to 3.95, 2.25, 1.59, and 0.17 μg m -3 until 2021, respectively. Seasonally, the concentration of SO 4 2- peaks in autumn and winter, and Cl - peaks in spring, while both NO 3 - and NH 4 + peak in winter and spring. Variations in meteorological factors are the main contributors to their different seasonal concentrations. The average mass percentages of SO 4 2- , NO 3 - , Cl - and NH 4 + in PM 2.5 are 51.2%, 25.5%, 2.7% and 20.6%, respectively. Three secondary ions (SO 4 2- , NO 3 - and NH 4 + ) contribute significantly to the formation of PM 2.5 as well as having a stronger correlation with it., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In drylands, where water scarcity limits vascular plant growth, much of the primary production occurs at the soil surface. This is where complex macro- and microbial communities, in an intricate bond with soil particles, form biological soil crusts (biocrusts). Despite their critical role in regulating C and N cycling in dryland ecosystems, there is limited understanding of the fate of biologically fixed C and N from biocrusts into the mineral soil, or how climate change will affect C and N fluxes between the atmosphere, biocrusts, and subsurface soils. To address these gaps, we subjected biocrust-soil systems to experimental warming and drought under controlled laboratory conditions, monitored CO 2 fluxes, and applied dual isotopic labeling pulses ( 13 CO 2 and 15 N 2 ). This allowed detailed quantification of elemental pathways into specific organic matter (OM) pools and microbial biomass via density fractionation and phospholipid fatty acid analyses. While biocrusts modulated CO 2 fluxes regardless of the temperature regime, drought severely limited their photosynthetic C uptake to the extent that the systems no longer sustained net C uptake. Furthermore, the effect of biocrusts extended into the underlying 1 cm of mineral soil, where C and N accumulated as mineral-associated OM (MAOM <63μm ). This was strongly associated with increased relative dominance of fungi, suggesting that fungal hyphae facilitate the downward C and N translocation and subsequent MAOM formation. Most strikingly, however, these pathways were disrupted in systems exposed to warming, where no effects of biocrusts on the elemental composition of the underlying soil nor on MAOM were determined. This was further associated with reduced net biological N fixation under combined warming and drought, highlighting how changing climatic conditions diminish some of the most fundamental ecosystem functions of biocrusts, with detrimental repercussions for C and N cycling and the persistence of soil organic matter pools in dryland ecosystems., (Global Change Biology© 2024 The Author(s). Global Change Biology published by John Wiley & Sons Ltd.)

Suspended atmospheric microplastics (SAMPs) display varying occurrence characteristics on different underlying surfaces in urban areas. This study investigated the occurrence characteristics, source apportionment, and transportation patterns of SAMPs in two typical underlying surfaces: the downtown area (Site T) and the industrial area (Site C) of a coastal city in China. In the spring of 2023, a total of 32 types comprising 1325 SAMPs were detected. The average MP abundances were found to be 3.74 ± 2.86 n/m 3 in Site T and 2.67 ± 1.68 n/m 3 in Site C. In Site T, SAMPs attributed to living source constituted 78.05%, while industry was the main source in Site C with a proportion reaching 42.89%, consistent with the functional zoning of the underlying surface. Furthermore, HYSPLIT analysis revealed that there was no significant difference between these two sites in long-distance horizontal transport affected by external airflow regardless of altitude; conversely, PCA indicated a notable correlation between vertical velocity and both abundance and species diversity. According to the hourly average wind speeds, the maximum transmission distance was computed as 350 km for updraft and the minimum transmission distances was as low as 32 m for downdraft. Subsequently, the coincidence between the source proportion of SAMPs on random day and meteorological parameters confirmed the synergistic impact on SAMPs transport influenced by functional zoning, geographic environment, and vertical velocity., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)