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The French Moss Survey employs forest mosses as indicators to monitor the deposition of atmospheric substances, notably focusing on cadmium (Cd), a known carcinogenic and contributor to respiratory illnesses. This comprehensive study encompasses 55 variables to understand Cd accumulation in terrestrial mosses in France. These variables include moss species, tree cover, biogeographical markers, land use area, proximity to road and rail networks, soil concentration of Cd and atmospheric concentration and deposition of Cd using a physical model. The response variable undergoes a complementary log–log transformation to constrain prediction values within the maximum Cd content in mosses. We have built a regression model to improve predictions, considering the impacts of covariates in France. This model retains biogeographical effects, leading to data segmentation into four distinct biogeographical zones: Atlantic, Continental, Mediterranean and Alpine. Subsequently, zone-specific regression models are explored to refine predictions and consider the impacts of covariates specific to each region, such as those related to railways and roads of the Mediterranean zone. Our biogeographical models effectively mitigate spatial correlation issues and yield accurate predictions, as evidenced by the leave-one-out cross-validation assessment. Compared to ordinary kriging map, the regression prediction maps highlight the contributions of certain covariates, such as the EMEP atmospheric transport model, to areas with high Cd concentrations. Furthermore, these maps exhibit new areas with high (resp. low) Cd concentrations due to high (resp. low) values of the covariates. [ABSTRACT FROM AUTHOR]

The flux divergence approach (FDA) is a popular technique for deriving NOx emission estimates from tropospheric NO2 columns measured by the TROPOspheric Monitoring Instrument (TROPOMI) satellite sensor. An attractive aspect of the FDA is that the method simplifies three-dimensional atmospheric chemistry and transport processes into a two-dimensional (longitude–latitude) steady-state continuity equation for columns that balances local NOx emissions with the net outflow and chemical loss of NOx. Here we test the capability of the FDA to reproduce known NOx emissions from synthetic NO2 column retrievals generated with the LOTOS-EUROS chemistry transport model over the Netherlands at high spatial resolution of about 2×2 km during summer. Our results show that the FDA captures the magnitude and spatial distribution of the NOx emissions to high accuracy (absolute bias <9 %), provided that the observations represent the NO2 column in the boundary layer, that wind speed and direction are representative for the boundary layer (PBL) column, and that the high-resolution spatiotemporal variability of the NO2 lifetimes and NOx:NO2 ratio is accounted for in the inversion instead of using single fixed values. The FDA systematically overestimates NOx emissions by 15 %–60 % when using tropospheric NO2 columns as the driving observation, while using PBL NO2 columns largely overcomes this systematic error. This merely reflects the fact that the local balance between emissions and sinks of NOx occurs in the boundary layer, which is decoupled from the NO2 in the free troposphere. Based on the recommendations from this sensitivity test, we then applied the FDA using observations of NO2 columns from TROPOMI, corrected for contributions from free-tropospheric NO2 , between 1 June and 31 August 2018. The NOx emissions derived from the default TROPOMI retrievals are biased low over cities and industrialized areas. However, when the coarse 1×1 ° TM5-MP NO2 profile used in the retrieval is replaced by the high-resolution profile of LOTOS-EUROS, the TROPOMI NOx emissions are enhanced by 22 % and are in better agreement with the inventory for the Netherlands. This emphasizes the importance of using realistic high-resolution a priori NO2 profile shapes in the TROPOMI retrieval. We conclude that accurate quantitative NOx emissions estimates are possible with the FDA, but they require sophisticated, fine-scale corrections for both the NO2 observations driving the method and the estimates of the NO2 chemical lifetime and NOx:NO2 ratio. This information can be obtained from high-resolution chemistry transport model simulations at the expense of the simplicity and applicability of the FDA. [ABSTRACT FROM AUTHOR]

To evaluate the potential of an upcoming large-swath satellite for estimating surface methane (CH₄) fluxes at a weekly scale, we report the results from a series of observing system simulation experiments (OSSEs) that use an established modeling framework that includes the GEOS-Chem 3D atmospheric transport model and an ensemble Kalman filter. These experiments focus on the sensitivity of CH₄ flux estimates to systematic errors (μ) and random errors (σ) in the column average methane (XCH4) measurements. Our control test (INV_CTL) demonstrates that with median errors (μ = 1.0 ± 0.9 ppb and σ = 6.9 ± 1.6 ppb) in XCH₄ measurements over a 1000 km swath, global CH4 fluxes can be estimated with an accuracy of 5.1 ± 1.7%, with regional accuracies ranging from 3.8% to 21.6% across TransCom sub-continental regions. The northern hemisphere mid-latitudes show greater reliability and consistency across varying μ and σ levels, while tropical and boreal regions exhibit higher sensitivity due to limited high-quality observations. In σ -sensitive regions, such as the North American boreal zone, expanding the swath width from 1000 km to 3000 km significantly reduces discrepancies, while such adjustments provide limited improvements for μ -sensitive regions like North Africa. For TanSat-2 mission, with its elliptical medium Earth orbit and 1500 km swath width, the global total estimates achieved an accuracy of 3.1 ± 2.2%. Enhancing the swath width or implementing a dual-satellite configuration is proposed to further improve TanSat-2 inversion performance. [ABSTRACT FROM AUTHOR]

Atmospheric energy transport is central to the cooling of primordial magma oceans. Theoretical studies of atmospheres on lava planets have assumed that convection is the only process involved in setting the atmospheric temperature structure. This significantly influences the ability for a magma ocean to cool. It has been suggested that convective stability in these atmospheres could preclude permanent magma oceans. We develop a new 1D radiative-convective model in order to investigate when the atmospheres overlying magma oceans are convectively stable. Using a coupled interior-atmosphere framework, we simulate the early evolution of two terrestrial-mass exoplanets: TRAPPIST-1 c and HD 63433 d. Our simulations suggest that the atmosphere of HD 63433 d exhibits deep isothermal layers which are convectively stable. However, it is able to maintain a permanent magma ocean and an atmosphere depleted in |$\mathrm{H_{2}O}$|⁠. It is possible to maintain permanent magma oceans underneath atmospheres without convection. Absorption features of |$\mathrm{CO_{2}}$| and |$\mathrm{SO_{2}}$| within synthetic emission spectra are associated with mantle redox state, meaning that future observations of HD 63433 d may provide constraints on the geochemical properties of a magma ocean analogous with the early Earth. Simulations of TRAPPIST-1 c indicate that it is expected to have solidified within |$100 \,\mathrm{M}\rm {yr}$|⁠ , outgassing a thick atmosphere in the process. Cool isothermal stratospheres generated by low-molecular-weight atmospheres can mimic the emission of an atmosphere-less body. Future work should consider how atmospheric escape and chemistry modulates the lifetime of magma oceans, and the role of tidal heating in sustaining atmospheric convection. [ABSTRACT FROM AUTHOR]

Atmospheric ammonia (NH3) is a key transboundary air pollutant that contributes to the impacts of nitrogen and acidity on terrestrial ecosystems. Ammonia also contributes to the atmospheric aerosol that affects air quality. Emission inventories indicate that NH3 was predominantly emitted by agriculture over the 19th and 20th centuries but, up to now, these estimates have not been compared to long-term observations. To document past atmospheric NH3 pollution in south-eastern Europe, ammonium (NH 4+) was analysed along an ice core extracted from Mount Elbrus in the Caucasus, Russia. The NH 4+ ice-core record indicates a 3.5-fold increase in concentrations between 1750 and 1990 CE. Remaining moderate prior to 1950 CE, the increase then accelerated to reach a maximum in 1989 CE. Comparison between ice-core trends and estimated past emissions using state-of-the-art atmospheric transport modelling of submicron-scale aerosols (FLEXPART (FLEXible PARTicle dispersion) model) indicates good agreement with the course of estimated NH3 emissions from south-eastern Europe since ∼ 1750 CE, with the main contributions from south European Russia, Türkiye, Georgia, and Ukraine. Examination of ice deposited prior to 1850 CE, when agricultural activities remained limited, suggests an NH 4+ ice concentration related to natural soil emissions representing ∼ 20 % of the 1980–2009 CE NH 4+ level, a level mainly related to current agricultural emissions that almost completely outweigh biogenic emissions from natural soil. These findings on historical NH3 emission trends represent a significant contribution to the understanding of ammonia emissions in Europe over the last 250 years. [ABSTRACT FROM AUTHOR]

In order to reduce the uncertainty of aerosol radiative forcing in global climate models, we need to better understand natural aerosol sources which are important to constrain the current and pre-industrial climate. Here, we analyse particle number size distributions (PNSDs) collected during a year (2015) across four coastal and inland Antarctic research bases (Halley, Marambio, Dome C and King Sejong). We utilise k -means cluster analysis to separate the PNSD data into six main categories. "Nucleation" and "bursting" PNSDs occur 28 %–48 % of the time between sites, most commonly at the coastal sites of Marambio and King Sejong where air masses mostly come from the west and travel over extensive regions of sea ice, marginal ice and open ocean and likely arise from new particle formation. "Aitken high", "Aitken low" and "bimodal" PNSDs occur 37 %–68 % of the time, most commonly at Dome C on the Antarctic Plateau, and likely arise from atmospheric transport and ageing from aerosol originating likely in both the coastal boundary layer and free troposphere. "Pristine" PNSDs with low aerosol concentrations occur 12 %–45 % of the time, most commonly at Halley, located at low altitudes and far from the coastal melting ice and influenced by air masses from the west. Not only the sea spray primary aerosols and gas to particle secondary aerosol sources, but also the different air masses impacting the research stations should be kept in mind when deliberating upon different aerosol precursor sources across research stations. We infer that both primary and secondary components from pelagic and sympagic regions strongly contribute to the annual seasonal cycle of Antarctic aerosols. Our simultaneous aerosol measurements stress the importance of the variation in atmospheric biogeochemistry across the Antarctic region. [ABSTRACT FROM AUTHOR]

Planetary atmospheric detection is an important way to recognize the physical and chemical properties of planets that inform about their formation and evolution, and atmospheric in-situ sampling is an ideal way to obtain high-resolution information. In this paper, a scheme for in-situ sampling of planetary atmosphere based on multi-pass aeroassisted maneuvers is given, and the corresponding design method for multiple traversal trajectories through the atmosphere is proposed. The aeroassisted maneuvering scheme achieves target-area sampling by crossing the atmosphere circularly, and is able to flexibly adjust the sampling altitude, thus having the advantage of three-dimensional and wide-area sampling. The trajectory design method involves algorithms to determine key design parameters separately. Specifically, the minimum entry periapsis altitude is determined by building its mapping relationship with path constraints to satisfy the minimum flight altitude constraint. Besides, the pass number of atmospheric flights is calculated by giving the upper bound of the energy attenuation and mission-time constraints. Then, a rapid inclination correction method via bank angle reversal is given to satisfy the inclination constraint of the maneuver. In numerical simulations, three Martian atmospheric detection scenarios, designated as high-latitude region with superficial ice water, magnetic anomalies region, and the polar region enriched with atmospheric transport properties, are established, with corresponding maneuvering sampling trajectories and characteristic parameter distributions provided. This paper introduces for the first time the use of multi-pass aeroassisted maneuvers for in-situ atmospheric sampling. Simulation results demonstrate the effectiveness and general applicability of the proposed method. • Atmospheric sampling scheme by multi-pass aeroassisted maneuvers is introduced. • General trajectory design method for sampling is proposed. • Properties of the sampling process are demonstrated by different scenarios. [ABSTRACT FROM AUTHOR]

Eolian sand transport in the atmospheric surface layer (ASL) is a typical kind of gas–solid two-phase flow at high Reynolds number. However, direct measurements of high-frequency total saltation mass flux in the ASL are particularly challenging. This study presents a novel method for predicting total saltation mass flux fluctuating time series in the near-neutral ASL based on studying the response of total saltation mass flux to streamwise wind speed. The normalized total saltation mass flux fluctuating time series can be predicted by our model using one-point streamwise wind speed data measured near the surface, and the total saltation mass flux fluctuating time series predicted by the new model have a good correlation with the directly measured results, especially for low-frequency signals. Additionally, the power spectra and the probability density functions of the normalized total saltation mass flux fluctuations demonstrate strong agreement with the measured results, both qualitatively and quantitatively. These findings indicate that our predictive model offers a novel approach for predicting the fluctuating time series of saturated total saltation mass flux in the near-neutral ASL. Furthermore, our model may facilitate scientific research and engineering applications related to eolian sand transport in the ASL. [ABSTRACT FROM AUTHOR]

New data, analyses and modelling are presented concerning the unprecedented mid-May 2010 series of fission product detections in ground level air on and around the Korean Peninsula. For the first time Ba-140 is revealed at Ussuriysk, for which only La-140 had been reported. Thus aerosol particles containing the same parent-daughter pair Ba-140/La-140 were detected at both Ussuriysk and Okinawa, establishing beyond reasonable doubt that their physical, spatial and temporal origins are the same. Together with Ce-141 and Cs-137, all with short-lived xenon isotope parents, a supercritical fission excursion, which experienced a near prompt filtered vent, is the only viable scenario for their explanation. New modelling suggests that the vent occurred around 9 s after the excursion and that the CTBT-relevant xenon isotopes Xe-133 and Xe-135 were 'quenched' around 25 min later and released some 10–20 h afterwards. Published corroborating seismic and infrasound data of an event at the North Korean nuclear test site 8 min and 45 s past midnight on 12 May 2010 is subsequently reviewed. These papers adopted a conventional depth of the event although the data suggested a shallower one. Despite arguments in the seismic community about its exact nature, it is prudent to test how well the waveform signals marry the radionuclide detection pattern. Thus the location and time are input into a new atmospheric transport model. The advanced software suite MATCH was used in forward mode with prompt and delayed releases, revealing the presence of plumes at each detection site at the time of their first detection and extending over the observed timeframe. Thus a very consistent picture of a shallow low yield nuclear test is obtained. [ABSTRACT FROM AUTHOR]

A large number of publications have been devoted to the study of aerosol atmospheric transport, but the low-temperature transfer of metals and metalloids as a part of gas flow remains poorly understood. The present work is devoted to the study of gas stream composition using an approach based on the collection of nascent condensate upon cooling of the air flow formed over the surface of contaminated sites. A special laboratory unit was designed to collect the condensate followed by the study of its composition using atomic emission and mass spectrometry. The main novelty of this work consists of the application of the single-particle ICP‒MS technique to obtain qualitative information concerning the state of the elements in the condensates. Gold and silver are most likely present in the samples as nanoparticles; arsenic, selenium, tin and lead are present both as nanoparticles and as soluble forms; and barium and mercury are present only in soluble forms. The condensed phase contains As, Hg, Au, Ag, Pb and Sn at the ppb level, while the main elements of the tailings material (Fe, Ba, Cu, Zn and others) are present at the ppm level, which exceeds the background concentration. [ABSTRACT FROM AUTHOR]

Many known rocky exoplanets are so highly irradiated that their dayside surfaces are molten, and 'silicate atmospheres', composed of rock-forming elements, are generated above these lava pools. The compositions of these 'lava planet' atmospheres are of great interest because they must be linked to the composition of the underlying rocky interiors. It may be possible to investigate these atmospheres, either by detecting them directly via emission spectroscopy or by observing the dust tails which trail the low-mass 'catastrophically evaporating planets'. In this work, we develop a simple chemical model of the lava pool–atmosphere system under mass-loss, to study its evolution. Mass-loss can occur both into space and from the day to the nightside. We show that the system reaches a steady state, where the material in the escaping atmosphere has the same composition as that melted into the lava pool from the mantle. We show that the catastrophically evaporating planets are likely to be in this evolved state. This means that the composition of their dust tails is likely to be a direct trace of the composition of the mantle material that is melted into the lava pool. We further show that, due to the strength of day-to-nightside atmospheric transport, this evolved state may even apply to relatively high-mass planets (⁠|$\gtrsim 1\mathrm \,{M}_{\oplus }$|⁠). Moreover, the low pressure of evolved atmospheres implies that non-detections may not be due to the total lack of an atmosphere. Both conclusions are important for the interpretation of future observations. [ABSTRACT FROM AUTHOR]

The largest anthropogenic emissions of carbon dioxide (CO2) come from local sources, such as cities and power plants. The upcoming Copernicus CO2 Monitoring (CO2M) mission will provide satellite images of the CO2 and NO2 plumes associated with these sources at a resolution of 2 km × 2 km and with a swath of 250 km. These images could be exploited using atmospheric-plume inversion methods to estimate local CO2 emissions at the time of the satellite overpass and their corresponding uncertainties. To support the development of the operational processing of satellite imagery of the column-averaged CO2 dry-air mole fraction (XCO2) and tropospheric-column NO2, this study evaluates data-driven inversion methods, i.e., computationally light inversion methods that directly process information from satellite images, local winds, and meteorological data, without resorting to computationally expensive dynamical atmospheric transport models. We designed an objective benchmarking exercise to analyze and compare the performance of five different data-driven inversion methods: two implementations with different complexities for the cross-sectional flux approach (CSF and LCSF), as well as one implementation each for the integrated mass enhancement (IME), divergence (Div), and Gaussian plume (GP) model inversion approaches. This exercise is based on pseudo-data experiments with simulations of synthetic true emissions, meteorological and concentration fields, and CO2M observations across a domain of 750 km × 650 km, centered on eastern Germany, over 1 year. The performance of the methods is quantified in terms of the accuracy of single-image emission estimates (from individual images) or annual-average emission estimates (from the full series of images), as well as in terms of the number of instant estimates for the city of Berlin and 15 power plants within this domain. Several ensembles of estimations are conducted using different scenarios for the available synthetic datasets. These ensembles are used to analyze the sensitivity of performance to (1) data loss due to cloud cover, (2) uncertainty in the wind, or (3) the added value of simultaneous NO2 images. The GP and LCSF methods generate the most accurate estimates from individual images. The deviations between the emission estimates and the true emissions from these two methods have similar interquartile ranges (IQRs), ranging from ∼ 20 % to ∼ 60 % depending on the scenario. When taking cloud cover into account, these methods produce 274 and 318 instant estimates, respectively, from the ∼ 500 daily images, which cover significant portions of the plumes from the sources. Filtering the results based on the associated uncertainty estimates can improve the statistics of the IME and CSF methods but does so at the cost of a large decrease in the number of estimates. Due to a reliable estimation of uncertainty and, thus, a suitable selection of estimates, the CSF method achieves similar, if not better, accuracy statistics for instant estimates compared to the GP and LCSF methods after filtering. In general, the performance of retrieving single-image estimates improves when, in addition to XCO2 data, collocated NO2 data are used to characterize the structure of plumes. With respect to the estimates of annual emissions, the root mean square errors (RMSEs) for the most realistic benchmarking scenario are 20 % (GP), 27 % (CSF), 31 % (LCSF), 55 % (IME), and 79 % (Div). This study suggests that the Gaussian plume and/or cross-sectional approaches are currently the most efficient tools for providing estimates of CO2 emissions from satellite images, and their relatively light computational cost will enable the analysis of the massive amount of data to be provided by future satellite XCO2 imagery missions. [ABSTRACT FROM AUTHOR]

We present a protocol to improve confidence in reported radon activity concentrations, facilitating direct site-to-site comparisons and integration with co-located greenhouse gas (GHG) measurements within a network of three independently managed observatories in the UK. Translating spot measurements of atmospheric GHG amount fractions into regional flux estimates ("top-down" analysis) is usually performed with atmospheric transport models (ATMs), which calculate the sensitivity of regional emissions to changes in observed GHGs at a finite number of locations. However, the uncertainty of regional emissions is closely linked to ATM uncertainties. Radon, emitted naturally from the land surface, can be used as a tracer of atmospheric transport and mixing to independently evaluate the performance of such models. To accomplish this, the radon measurements need to have a comparable precision to the GHGs at the modelled temporal resolution. Australian Nuclear Science and Technology Organisation (ANSTO) dual-flow-loop two-filter radon detectors provide output every 30 min. The measurement accuracy at this temporal resolution depends on the characterization and removal of instrumental background, the calibration procedure, and response time correction. Consequently, unless these steps are standardized, measurement precision may differ between sites. Here we describe standardized approaches regarding (1) instrument maintenance, (2) quality control of the raw data stream, (3) determination and removal of the instrumental background, (4) calibration methods, and (5) response time correction (by deconvolution). Furthermore, we assign uncertainties for each reported 30 min radon estimate (assuming these steps have been followed) and validate the final result through comparison of diurnal and sub-diurnal radon characteristics with co-located GHG measurements. While derived for a network of UK observatories, the proposed standardized protocol could be equally applied to two-filter dual-flow-loop radon observations across larger networks, such as the Integrated Carbon Observation System (ICOS) or the Global Atmosphere Watch (GAW) baseline network. [ABSTRACT FROM AUTHOR]

Quantifying emissions from megacities is important for reduction of greenhouse gases. We used atmospheric carbon dioxide (CO2) concentration data obtained at an altitude of around 250 m above the ground on TOKYO SKYTREE (TST; a 634-m-high freestanding broadcasting tower; 35.71°N, 139.81°E), which is located north of central Tokyo, Japan. To use the TST observations for estimating net CO2 fluxes from Tokyo, a global, high-resolution simulation of atmospheric CO2 transport with CO2 flux data from a global inverse analysis was performed. In the simulation, atmospheric CO2 variations were well reproduced at remote sites around Japan. The application of tagged tracers in the simulation revealed that variations of CO2 concentrations at TST were largely driven by fluxes in the southwest region of Tokyo, including the western Tokyo Bay area where huge power plants are located. Then, we performed a regression analysis of modeled and observed Tokyo-originated CO2 concentrations, both of which were derived from the simulated background concentrations, while changing the minimum wind speed used in the analysis. The removal of low wind speeds altered the slope of the regression line, and excluding wind speeds below 7 m s−1 resulted in a stabilized slope of 0.93 ± 0.08. This stabilized regression indicated that the annual net CO2 emission from Tokyo is 79.5 ± 6.6 Tg-C yr−1. Our findings demonstrate that analysis using a global high-resolution model with tagged tracers has the potential to monitor emissions changes in a megacity. [ABSTRACT FROM AUTHOR]

Ignoring the diurnal cycle in surface-to-atmosphere CO2 fluxes leads to a systematic bias in CO2 mole fraction simulations sampled at daytime because the daily mean flux systematically misses the CO2 uptake during the daytime hours. In an atmospheric inversion using daytime-selected CO2 measurements at most continental sites and not resolving diurnal cycles in the flux, this leads to systematic biases in the estimates of the annual sources and sinks of atmospheric CO2. This study focuses on quantifying the impact of this diurnal cycle effect on the annual carbon fluxes estimated with the CarboScope (CS) atmospheric inversion at regional, continental, and global scales for the period of time 2010–2020. Our analysis is based on biogenic fluxes of hourly net ecosystem exchange (NEE) obtained from the data-driven FLUXCOM-X estimates, together with global and regional atmospheric transport models. Differences between CO2 mixing ratios simulated with daily averaged and hourly NEE from FLUXCOM-X range between around - 2.5 and 7 ppm averaged annually throughout a site network across the world. These differences lead to systematic biases in CO2 flux estimates from the atmospheric inversions. Although the impact on the global total flux is negligible (around 2 % of the overall land flux of - 1.79 Pg C yr−1), we find significant biases in the annual flux budgets at continental and regional scales. For Europe, the annual mean difference in the fluxes arising indirectly from the diurnal cycle of CO2 through the boundary condition amounts to around 48 % of the annual posterior fluxes (0.31 Pg C yr−1) estimated with CarboScope-Regional (CSR). Furthermore, the differences in NEE estimates calculated with CS increase the magnitude of the flux budgets for some regions such as North American temperate forests and northern Africa by a factor of about 1.5. To the extent that FLUXCOM-X diurnal cycles are realistic at all latitudes and for the station set including many continental stations as used in our inversions here, we conclude that ignoring the diurnal variations in the land CO2 flux leads to overestimation of both CO2 sources in the tropical lands and CO2 sinks in the temperate zones. [ABSTRACT FROM AUTHOR]

The largest anthropogenic emissions of carbon dioxide (CO2) come from local sources, such as cities and power plants. The upcoming Copernicus CO2 Monitoring (CO2M) mission will provide satellite images of the CO2 and NO2 plumes associated with these sources at a resolution of 2 km × 2 km and with a swath of 250 km. These images could be exploited using atmospheric-plume inversion methods to estimate local CO2 emissions at the time of the satellite overpass and their corresponding uncertainties. To support the development of the operational processing of satellite imagery of the column-averaged CO2 dry-air mole fraction (XCO2) and tropospheric-column NO2, this study evaluates data-driven inversion methods, i.e., computationally light inversion methods that directly process information from satellite images, local winds, and meteorological data, without resorting to computationally expensive dynamical atmospheric transport models. We designed an objective benchmarking exercise to analyze and compare the performance of five different data-driven inversion methods: two implementations with different complexities for the cross-sectional flux approach (CSF and LCSF), as well as one implementation each for the integrated mass enhancement (IME), divergence (Div), and Gaussian plume (GP) model inversion approaches. This exercise is based on pseudo-data experiments with simulations of synthetic true emissions, meteorological and concentration fields, and CO2M observations across a domain of 750 km × 650 km, centered on eastern Germany, over 1 year. The performance of the methods is quantified in terms of the accuracy of single-image emission estimates (from individual images) or annual-average emission estimates (from the full series of images), as well as in terms of the number of instant estimates for the city of Berlin and 15 power plants within this domain. Several ensembles of estimations are conducted using different scenarios for the available synthetic datasets. These ensembles are used to analyze the sensitivity of performance to (1) data loss due to cloud cover, (2) uncertainty in the wind, or (3) the added value of simultaneous NO2 images. The GP and LCSF methods generate the most accurate estimates from individual images. The deviations between the emission estimates and the true emissions from these two methods have similar interquartile ranges (IQRs), ranging from ∼ 20 % to ∼ 60 % depending on the scenario. When taking cloud cover into account, these methods produce 274 and 318 instant estimates, respectively, from the ∼ 500 daily images, which cover significant portions of the plumes from the sources. Filtering the results based on the associated uncertainty estimates can improve the statistics of the IME and CSF methods but does so at the cost of a large decrease in the number of estimates. Due to a reliable estimation of uncertainty and, thus, a suitable selection of estimates, the CSF method achieves similar, if not better, accuracy statistics for instant estimates compared to the GP and LCSF methods after filtering. In general, the performance of retrieving single-image estimates improves when, in addition to XCO2 data, collocated NO2 data are used to characterize the structure of plumes. With respect to the estimates of annual emissions, the root mean square errors (RMSEs) for the most realistic benchmarking scenario are 20 % (GP), 27 % (CSF), 31 % (LCSF), 55 % (IME), and 79 % (Div). This study suggests that the Gaussian plume and/or cross-sectional approaches are currently the most efficient tools for providing estimates of CO2 emissions from satellite images, and their relatively light computational cost will enable the analysis of the massive amount of data to be provided by future satellite XCO2 imagery missions. [ABSTRACT FROM AUTHOR]

Perfluoroalkyl acid analogs (PFAAs) are a class of chemically stable environmentally persistent organic pollutants (POPs) that are difficult to degrade and have a strong capacity to accumulate in the human body. PFAAs have been found to be biotoxic to humans and have been detected in various environmental media, especially in the cryosphere at trace concentrations. The cryosphere, sensitively responds to climate change, plays a crucial role in the global water, carbon and energy cycles. However, researches on cryosphere PFAAs especially in Tibetan Plateau (TP) is limited. Therefore, we summarize the physicochemical properties, physiological toxicity, spatiotemporal distribution, sources, diffusion and migration pathways, as well as analysis and removal methods of PFAAs in the cryosphere regions. The results show that PFAAs pollutants are mainly produced and distributed in the more economically developed countries in Europe and the United States, as well as in East Asia, and PFAAs can be transported by atmospheric circulation and water cycle to remote regions including cryosphere regions. The current detection methods for PFAAs in cryosphere need to be further refined for increased accuracy and convenience. There is also a need to develop more effective removal methods that will reduce the environmental and human threats posed by these PFAAs. Finally, we propose key scientific questions for future research in cryosphere including PFAAs redistribution influenced by cryosphere changes, human activities, and the interaction of other spheres. [ABSTRACT FROM AUTHOR]

Measurements of the seasonal cycle of δ13 C of atmospheric CO2 (δ13 Ca) provide information on the global carbon cycle and the regulation of carbon and water fluxes by leaf stomatal openings on ecosystem and decadal scales. Land biosphere carbon exchange is the primary driver of δ13 Ca seasonality in the Northern Hemisphere (NH). We use isotope-enabled simulations of the Bern3D-LPX (Land surface Processes and eXchanges) Earth system model of intermediate complexity and fossil fuel emission estimates with a model of atmospheric transport to simulate atmospheric δ13 Ca at globally distributed monitoring sites. Unlike the observed growth of the seasonal amplitude of CO2 at northern sites, no significant temporal trend in the seasonal amplitude of δ13 Ca was detected at most sites, consistent with the insignificant model trends. Comparing the preindustrial (1700) and modern (1982–2012) periods, the modeled small-amplitude changes at northern sites are linked to the near-equal increase in background atmospheric CO2 and the seasonal signal of the net atmosphere–land δ13 C flux in the northern extratropical region, with no long-term temporal changes in the isotopic fractionation in these ecosystems dominated by C3 plants. The good data–model agreement in the seasonal amplitude of δ13 Ca and in its decadal trend provides implicit support for the regulation of stomatal conductance by C3 plants towards intrinsic water use efficiency growing proportionally to atmospheric CO2 over recent decades. Disequilibrium fluxes contribute little to the seasonal amplitude of the net land isotope flux north of 40° N but contribute near equally to the isotopic flux associated with growing season net carbon uptake in tropical and Southern Hemisphere (SH) ecosystems, pointing to the importance of monitoring δ13 Ca over these ecosystems. We propose applying seasonally resolved δ13 Ca observations as an additional constraint for land biosphere models and underlying processes for improved projections of the anthropogenic carbon sink. [ABSTRACT FROM AUTHOR]

In this article, the submersion dose due to a radioactive cloud of pollutants was evaluated at short downwind distances from an emission stack. The atmospheric transport of contaminants was modelled using the Gaussian plume model (GPM). The algorithm for dose computation and its hypotheses were analysed. Two relevant issues were discussed: the semi-infinite cloud approximation used for pre-calculated dose conversion factors and the lack of a radiation transport model for dose computation outside the radioactive cloud. The GPM-based software HotSpot and GENII V2.10 and a FLUKA Monte Carlo GPM implementation were compared in a scenario characterized by a low release height and two different simplified atmospheric conditions. Compared to FLUKA, HotSpot and GENII V2.10 results showed a significant dose overestimation inside the plume. Moreover, in extremely stable meteorological conditions, only the Monte Carlo code could detect the ground-level dose contribution from an overhead plume. [ABSTRACT FROM AUTHOR]

Abstract Nanoplastics are suspected to pollute every environment on Earth, including very remote areas reached via atmospheric transport. We approached the challenge of measuring environmental nanoplastics by combining high-sensitivity TD-PTR-MS (thermal desorption-proton transfer reaction-mass spectrometry) with trained mountaineers sampling high-altitude glaciers (“citizen science”). Particles

• Anthropogenic emissions and air masses with different pollution levels cause seasonal and regional variations of halocarbons in southeastern China. • Industrial activities were the primary sources, accounting for 63.7 % of the total. • CH 2 Cl 2 contributed the most to the total halocarbons, followed by CH 3 Cl and HCFC-22. • It is important to control the rapidly growing unregulated species of halocarbons. • The hotspots in Fujian Province were concentrated in Xiamen, Fuzhou and Sanming. Halocarbons play a vital role in ozone depletion and global warming, and are regulated by the Montreal Protocol (MP) and its amendments. China has been identified as an important contributor to the halocarbon emissions, but the regional sources of halocarbons in China are not yet well comprehended. To investigate the characteristics, emissions, and source profiles, this study conducted a field campaign in Xiamen, a coastal city in southeastern China. Higher enhancements were found in the unregulated halocarbons (CH 3 Cl, CH 2 Cl 2 , CHCl 3) than in the MP eliminated species (CCl 4 , CH 3 Br) and the MP controlled species (HCFCs, HFCs). Many of the measured halocarbons varied seasonally and regionally, depending on the anthropogenic sources and atmospheric transport. Backward trajectory analysis showed that the air masses from inland were polluted over Shandong, Hebei, and northern Fujian in the cold season, while the air masses from the sea in the warm season were clean. Different air masses in two seasons were associated with the halocarbon patterns in the study area. Industrial activities, especially solvent usage, were the primary sources of halocarbons. The emission hot spots in Fujian Province were concentrated in Sanming, Fuzhou, and Xiamen, and the unregulated halocarbons made the largest contribution. This study provides an insight for a deep understanding of the characteristics and potential sources of halocarbons, and for strengthened management of halocarbons in China. [Display omitted] [ABSTRACT FROM AUTHOR]

The depth of convective clouds affects vertical transport of atmospheric constituents, influencing downstream weather and climate. Atmospheric controls on the maximum depth reached by moist convection are investigated with radar‐tracked convective cells tagged with sounding‐derived atmospheric parameters from a field campaign in central Argentina. Regression analyses show that narrow (<12‐km diameter) and wide (>16‐km diameter) cell depths respond to disparate factors, where cell areas are defined using composite reflectivity signatures. Undiluted lifted parcel indices including convective available potential energy (CAPE) and level of neutral buoyancy (LNB) are top predictors of wide cell maximum depth while mid‐tropospheric relative humidity is the top predictor of narrow cell maximum depth. Because narrow cells are more numerous than wide cells, the overall outcome of the full cell population does not strongly correlate with CAPE and LNB conditions. Tracked cells and atmospheric conditions in a simulation with 3‐km grid spacing covering the field campaign produce similar results to those observed. Narrow cells that are relatively deep have a cooler and moister mid‐troposphere with weaker free tropospheric subsidence, while relatively deep wide cells have much warmer and moister lower tropospheric conditions. These atmospheric differences are present 1 hr before cell initiation at both a fixed observing site and variable cell initiation locations. Simulated narrow cell maximum equivalent potential temperature decreases with height at a rate similar to the ambient vertical gradient, causing these cells to fall short of their LNB and supporting the view that entrainment‐driven dilution is a dominant control on their depth. Plain Language Summary: The depth that storms reach impacts where the heat, moisture, momentum, aerosols, and trace gases that they are transporting are deposited, but this depth is difficult to predict because most storms fall short of their theoretically maximum possible depth. The reason for this shortfall is that most storms are narrow, such that they are effectively diminished by mixing with surrounding drier air as the storm deepens. Thus, a dominant control on the depth of these clouds is the humidity of this surrounding air. However, wide storms are less vulnerable to destructive mixing with dry air. As a result, they more consistently reach depths that are well predicted by theory. These conclusions were reached via analysis of over a thousand storms over several months using field experiment measurements and a computer simulation. Key Points: Wide convective cell depth responds most to available instability, while narrow cell depth responds most to midlevel relative humidityEntrainment‐driven reduction of buoyancy decreases as cell width increases, causing disparate narrow and wide cell depth responsesA convection‐permitting simulation with 3‐km horizontal grid spacing generally reproduces observed relationships [ABSTRACT FROM AUTHOR]

Consumer-grade economical radon monitors are becoming increasingly popular in private and institutional use, in the contexts of both Citizen Science and traditional research. Although originally designed for screening indoor radon levels in view of radon regulation and decisions about mitigation or remediation—motivated by the health hazard posed by high radon concentrations—researchers are increasingly exploring their potential in some environmental studies. For long time, radon has been used as a tracer for investigating atmospheric transport processes. This paper focuses on RadonEye, currently the most sensitive among low-cost monitors available on the market, and specifically, its potential use for monitoring very low radon concentrations. It has two objectives: firstly, discussing issues of statistics of low count rates, and secondly, analyzing radon concentration time series acquired with RadonEyes outdoors and in low-radon indoor spaces. Regarding the first objective, among other things, the inference radon concentration reported to expected true is discussed. The second objective includes the application of autoregressive methods and fractal statistics to time series analysis. The overall result is that radon dynamics can be well captured using this "low-tech" approach. Statistical results are plausible; however, few results are available in the literature for comparison, particularly concerning fractal methods. The paper may therefore be seen as an incentive for further research in this direction. [ABSTRACT FROM AUTHOR]

This study uses an oceanic energy budget to estimate the ocean heat transport convergence in the North Atlantic during 2005–2018. The horizontal convergence of the ocean heat transport is estimated using ocean heat content tendency primarily derived from satellite altimetry combined with space gravimetry. The net surface energy fluxes are inferred from mass-corrected divergence of atmospheric energy transport and tendency of the ECMWF ERA5 reanalysis combined with top-of-the-atmosphere radiative fluxes from the clouds and the Earth's radiant energy system project. The indirectly estimated horizontal convergence of the ocean heat transport is integrated between the rapid climate change-meridional overturning circulation and heatflux array (RAPID) section at 26.5°N (operating since 2004) and the overturning in the subpolar north atlantic program (OSNAP) section, situated at 53°–60°N (operating since 2014). This is to validate the ocean heat transport convergence estimate against an independent estimate derived from RAPID and OSNAP in-situ measurements. The mean ocean energy budget of the North Atlantic is closed to within ± 0.25 PW between RAPID and OSNAP sections. The mean oceanic heat transport convergence between these sections is 0.58 ± 0.25 PW, which agrees well with observed section transports. Interannual variability of the inferred oceanic heat transport convergence is also in reasonable agreement with the interannual variability observed at RAPID and OSNAP, with a correlation of 0.54 between annual time series. The correlation increases to 0.67 for biannual time series. Other estimates of the ocean energy budget based on ocean heat content tendency derived from various methods give similar results. Despite a large spread, the correlation is always significant meaning the results are robust against the method to estimate the ocean heat content tendency. [ABSTRACT FROM AUTHOR]

Implicit time‐stepping for advection is applied locally in space and time where Courant numbers are large, but standard explicit time‐stepping is used for the remaining solution which is typically the majority. This adaptively implicit advection scheme facilitates efficient and robust integrations with long time‐steps while having negligible impact on the overall accuracy, and achieving monotonicity and local conservation on general meshes. A novel and important aspect for the efficiency of the approach is that only one iteration is needed each time the linear equation solver is called for solving the advection equation. The demonstration in this paper uses the second‐order Runge‐Kutta implicit/explicit time integration in combination with a second/third‐order finite‐volume spatial discretization and is tested using deformation flow tracer advection on the sphere and a fully compressible model for atmospheric flows. Tracers are advected over the poles of highly anisotropic latitude‐longitude grids with very large Courant numbers and on quasi‐uniform hexagonal and cubed‐sphere meshes with the same algorithm. Buoyant flow simulations with strong local updrafts also benefit from adaptively implicit advection. Stably stratified compressible flow simulations require a stable combination of implicit treatment of gravity and acoustic waves as well as advection in order to achieve long time‐steps. Plain Language Summary: Weather and climate prediction models take small time‐steps in order to make predictions about the future, starting from estimates of current conditions. The smaller the time‐steps are, the more of them have to be taken to make a prediction for a given time in the future. The more time‐steps that have to be taken, the more expensive the prediction is. If the time‐steps are too big, models can not only lose accuracy, they can become unstable—inaccuracies can become so large that wild oscillations are generated and the model crashes. These instabilities are often caused by the advective transport of constituents of the atmosphere by the wind. This paper describes a method—adaptive implicit advection—for calculating atmospheric transport using longer time‐steps while maintaining stability. We show that this can be achieved with minimal additional cost, and accuracy is only lost locally, where the time‐step is large relative to the flow speed and model grid size. Key Points: Implicit time‐stepping for advection enables large Courant numbersImplicit time‐stepping for advection is cheap as it combines an explicit correction with a simple first‐order accurate implicit estimateImplicit time‐stepping enables monotonicity, conservation and unconditional stability [ABSTRACT FROM AUTHOR]

A rare phenomenon—the long-range atmospheric transport of dust from the arid and semiarid territories of the Caspian Sea region through the center of the European part of Russia to its Arctic areas—was recorded in December 2023 during a field study of the physicochemical characteristics of airborne particles in Moscow and the snow composition in Arkhangelsk oblast. The analysis of the trajectories of the air mass transport, dynamics of spatial and temporal variability of the mass concentration of PM2.5 and PM10 matter in Moscow oblast, and numerical estimates and spatial distributions of near-surface concentrations and optical characteristics of airborne particles in the European part of Russia (according to the MERRA-2 reanalysis estimates) confirmed an increase in aerosol air pollution in the territories from the Caspian Sea to Arkhangelsk oblast. The snow sample taken in the area of Pinega Nature Reserve, Arkhangelsk oblast, in the spring of 2024, in the snow cover at a height of 18–20 cm (with a total snow thickness of 65 cm), was found to contain a yellowish layer of snow that fell in December 2023. The preliminary studies of the sample from this snow showed the presence of a large amount of organic suspended matter and plant residue, which in winter indicates transport of atmospheric aerosol from the southern regions of Russia. [ABSTRACT FROM AUTHOR]

Local and remote processes have been suggested to drive Arctic amplification (AA)—the enhanced warming of the Arctic region relative to other areas under increased greenhouse gases. We use Polar Amplification Model Intercomparison Project (PAMIP) simulations with changes in Arctic sea-ice with fixed global sea surface temperature (SST), or changes in global SST with fixed Arctic sea-ice to untangle the climate response to Arctic sea-ice loss or SST-induced warming, respectively. In response to Arctic sea-ice loss, the surface albedo feedback activates in summer mainly to increase oceanic heat uptake, leading to weak summertime warming. During winter, Arctic sea-ice loss greatly enhances oceanic heat release, which produces Arctic bottom-heavy warming and triggers positive lapse rate and cloud feedbacks, leading to large AA. In contrast, enhanced atmospheric energy convergence into the Arctic becomes the dominant contributor to relatively small AA under global SST-induced warming. Water vapor feedback contributes to Arctic warming but opposes AA due to larger tropical than Arctic moistening under SST-induced warming with fixed Arctic sea-ice. We also find top-heavy to uniform (bottom-heavy) Arctic warming and moistening in the Arctic mid-upper (lower) troposphere in the SST (Arctic sea-ice) perturbation runs, producing a negative-neutral (positive) Arctic lapse rate feedback, respectively. Lastly, we show that the responses to global SST or polar SIC perturbations are linearly separable. Our results suggest that large AA is caused primarily by sea-ice loss and resultant local changes in surface fluxes, while increased poleward energy transport can only produce weak AA under fixed sea ice. [ABSTRACT FROM AUTHOR]

Global warming has changed both the amount of global precipitation and the atmospheric capacity to retain water. In this paper, a novel definition of the long‐term Capturability of Atmospheric Water (CAW) based on horizontal atmospheric water transport is proposed, describing the ability of a certain area to intercept and convert the atmospheric water transported by horizontal moisture flux into local precipitation. The significant decrease of the CAW in Amazon and Congo rainforests and Inside Greenland indicates that these areas were having less precipitation with the same water vapor in the past 42 years, while in Asia (especially China), CAW is showing a large‐scale increasing trend, verifying the regional humidifying. Considering the change of both the CAW and the background atmospheric water simultaneously, their mismatch degree is also investigated. The positive mismatch in Qinghai Tibet Plateau, Greenland, and the Andes, suggests higher susceptibility to climate change, and in the areas of negative mismatch (Amazon, Maritime Continent, southeastern China, the Eastern United States, India, and Japan), a more stable precipitation response to climate change is expected. The proposed concept of CAW provides a novel perspective to analyze the precipitation response to climate change on a global scale. Key Points: A novel definition of long‐term Capturability of Atmospheric Water (CAW) based on horizontal transport is proposedIn the past 42 years, the CAW in the Amazon and Congo rainforests and the Greenland ice sheet has degraded significantlyThe findings provide a perspective to analyze the precipitation response to global climate change [ABSTRACT FROM AUTHOR]

Air‐sea heat and moisture fluxes modulate the surface energy balance and oceanic and atmospheric heat transport across all timescales. Spatial gradients of these fluxes, on a multitude of spatial scales, also have significant impacts on the ocean and atmosphere. Nevertheless, analysis of these gradients, and discussion regarding our ability to represent them, is relatively absent within the community. This letter discusses their importance and presents a wintertime climatology. Their sensitivity to spatiotemporal scale and choice of data set is also examined in the mid‐latitudes. A lead‐lag analysis illustrates that wintertime air‐sea heat flux gradients in the Gulf Stream can precede the North Atlantic Oscillation by ∼1 month. A lack of observations and thus validation of air‐sea heat flux gradients represents a significant gap in our understanding of how air‐sea processes affect weather and climate, and warrants increased attention from the observational and modeling communities. Plain Language Summary: The oceans impact both weather and climate by heating and cooling the lower atmosphere. Surface latent (sensible) heat flux is a quantity that measures the exchange of heat associated with evaporation of seawater (an air‐sea temperature difference). In addition to the absolute exchange, the manner in which the exchange varies spatially (the heat flux gradients) is also known to be important for the development of weather systems and longer‐term climate. Despite this, relatively little attention is paid in the literature to variability in these gradients. This study provides a brief overview of their importance and provides a wintertime climatology in these gradients. It is also illustrated that when considering gradients, the importance of specifying the spatial scale over which the gradient is calculated is critical. Although many differences exist between air‐sea heat flux data products in these gradients, there are currently almost no observations to validate them in key areas of interest, which represents a significant deficiency in our understanding of ocean‐atmosphere interactions. This is emphasized by demonstrating that these gradients in the mid‐latitudes can statistically precede variability in the North Atlantic Oscillation, the most important mode of monthly atmospheric variability in the North Atlantic. Key Points: Air‐sea heat and moisture flux gradients modulate important oceanic and atmospheric processes across a multitude of spatiotemporal scalesAir‐sea heat flux gradient variability can statistically precede mid‐latitude atmospheric variabilityNotable air‐sea heat and moisture flux gradient inconsistencies exist in data products, yet the ability to validate them remains elusive [ABSTRACT FROM AUTHOR]

Extreme integrated vapor transport (IVT) is a crucial driving factor of extreme precipitation events (EPEs). This paper presents a complex network‐based characterization of propagations from extreme IVT to EPEs. Specifically, the propagations are tracked from extreme IVT to EPEs by event synchronization; and then the source zones of extreme IVT contributing to EPEs are identified by two‐layer complex network. A case study is devised for North America based on the daily NCEP/NCAR Reanalysis 1 from 1948 to 2021. Overall, eight communities of EPEs are identified: the west coast of United States (US) tend to receive substantial EPEs from the Pacific Ocean; the Gulf of Alaska tends to receive oceanic EPEs propagating inland; western Canada typically experiences large amount of out tendencies and the EPEs tend to accumulate in the Baffin Island and Labrador Peninsula; the southeastern US and the northern Great Plains tend to experience northward propagations from Mexico. Along the west coast of North America, the propagations from extreme IVT to EPEs typically originate from the eastern North Pacific between 160°W and 110°W, and make landfalls in 4 days. These propagations are influenced by anomalous cyclonic circulations developing over the Gulf of Alaska forced by eastward Rossby waves. The coincidence rate of these propagations with atmospheric rivers is, respectively, 85.31% in autumn, 91.35% in winter, 73.94% in spring, and 64.52% in summer. Overall, the observed propagations from extreme IVT to EPEs yield insights into the mechanism of atmospheric moisture transport and the predictability of precipitation. Plain Language Summary: Owing to different synoptic systems such as atmospheric rivers, low‐level jets, and tropical cyclones, there exist profound propagations from extreme integrated vapor transport to extreme precipitation. Focusing on North America, this paper is concentrated on the complex network underlying extreme integrated vapor transport and extreme precipitation events. It is found that the Rocky Mountains play an important part in shaping the propagations from extreme integrated vapor transport to extreme precipitation events. In particular, along the west coast of North America, extreme integrated vapor transport originating from the eastern North Pacific tends to be blocked by the Rocky Mountains, causing rising/cooling and leading to extreme precipitation. Overall, along the Rocky Mountains, there exist eight communities of extreme precipitation. Key Points: There exists a complex network on propagations from extreme integrated vapor transport to extreme precipitation events in North AmericaIn the west coast of North America, the propagations typically originate from eastern North Pacific and make landfalls in 4 daysThe coincidence rate of propagations with atmospheric rivers is, respectively, above 90% and 60% in boreal winter and summer [ABSTRACT FROM AUTHOR]

Major explosive volcanic eruptions were important triggers of abrupt climate changes during the Holocene and crucial sources of Hg to the atmosphere, yet there remains limited understanding regarding the long‐range transportation of this volcanic Hg and its imprint in natural archives. Here, we present a reconstruction of Holocene global volcanism based on the anomalies in Hg concentrations, accumulation fluxes, and Hg/C ratios in three high‐resolution peat profiles spanning Eurasia. Our reconstruction reveals that the two Tibetan peat profiles recorded 33 major explosive volcanic eruptions (with 11 eruptions being synchronously detected), which correspond with a French Pyrenees peat record and sulfate anomalies in polar ice cores. Additionally, the major explosive volcanic eruptions recorded in the TP peat profiles coincided with abrupt decreases in solar irradiance during the Holocene, suggesting these eruptions might have had a greater global climate impact. Our results suggest the atmospheric transport of volcanic Hg within the Northern Hemisphere and underscore the significant role played by major explosive volcanic eruptions in precipitating abrupt global climate and environmental changes during the Holocene. This study has implications for deciphering the configuration of volcanic eruption seasons, locations, and magnitudes during the Holocene and aligning the chronology of peat deposits with ice cores. Plain Language Summary: Major explosive volcanic eruptions, one of the principal geogenic sources of Hg to the atmosphere, are widely acknowledged as significant drivers of abrupt global environmental and climate changes during the Holocene. While the magnitudes and timing of these eruptions have been well documented in ice core records, the long‐range transportation of the volcanic materials (such as Hg and SO2) and their terrestrial dispersion remain largely unknown. In this study, we present a reconstruction of Holocene global volcanism based on the anomalies in Hg concentrations, accumulation fluxes, and Hg/C ratios in three high‐resolution peat profiles, with two collected from the Tibetan Plateau and one from the French Pyrenees. Our reconstruction reveals that the Tibetan peat profiles recorded 33 major volcanic eruptions, which correspond with a French peat record and the sulfate anomalies in polar ice cores. Additionally, we demonstrate that certain major explosive volcanic eruptions likely triggered several abrupt decreases in solar irradiance during the Holocene. Our findings suggest the convective atmospheric transport of volcanic Hg within the Northern Hemisphere extratropical region and underscore the significant role played by major explosive volcanic eruptions in precipitating abrupt global climate and environmental changes during the Holocene. Key Points: Eleven major explosive volcanic eruptions during the Holocene were synchronously recorded in two peat profiles in the Tibetan PlateauThe recorded major explosive volcanic eruptions coincide with nine abrupt decreases in solar irradiance during the HoloceneThe Hg anomalies in peat profiles have the potential to be chronology markers that were linked with volcanic eruptions [ABSTRACT FROM AUTHOR]

Objectives: Dental clinics are one of the major producers of mercury-containing waste due to the use of dental amalgam. The atmospheric transport and persistence of mercury and its compounds in the environment, coupled with their high potential for bioaccumulation and detrimental effects on human health and ecosystems, underscore the necessity for effective management of mercury waste. Due to the lack of comprehensive and integrated guidelines for the effective management of dental amalgam waste in Iran, the objective of this study was to adapt a guideline for the management of amalgam waste in dental settings within the country. Materials and Methods: The method used was based on the adaptation principles presented by the Ministry of Health and Medical Education, and included searching and reviewing guidelines related to the management of amalgam waste in developed countries, extracting recommendations, revising the recommendations considering the local infra-structures and conditions, and receiving expert opinions and reaching consensus according to the RAND/UCLA Appropriateness Method. Results: The final guideline includes 34 recommendations in 5 areas: management of the amalgam scraps, considerations for dental equipment, management of the extracted teeth containing amalgam restorations, management of the amalgam capsules, and considerations for placement and replacement of the amalgam restorations. Conclusion: The use of this guideline in medical universities, public and private dental clinics, along with the supervisory role of the Ministry of Health and Medical Education, can be a way to minimize the environmental hazards of mercury. [ABSTRACT FROM AUTHOR]

Chinese baijiu as one of the famous distilled liquor in which fermented in open environments, with various microorganisms (i.e., bacteria, fungi, and yeast) involved in their brewing process, and created corresponding unique flavor. However, the sources of environmentally enriched microbial communities associated with liquor fermentation are still being characterized yet. Given the dependence of microbial growth and reproduction on environmental ecology, it is important to understand the correlation between baijiu fermentation microbial community and surrounding environmental ecology (i.e., temperature, humidity, wind, and precipitation). This study systematically overviewed the sources of microorganisms in the Jiang-flavor-Baijiu fermentation system. The results showed that microorganisms in baijiu brewing (i.e., mold, lactic acid bacteria, and yeast) mainly originated from surrounding environmental matrices, including the air (i.e., Yeast , Streptomyces and Bacillus), soil (i.e., Xanthomonas , Methanococcus and Comamonas) and water (i.e., Flavobacterium , Acinetobacter , and Pseudomonas) via atmospheric transport, raw material transfer and surface runoff. In addition, the unique baijiu fermentation microbial community diversity depends on local geology and meteorological conditions, highlighting that the structural stability and diversity of the microorganisms in the Baijiu brewing process dominated by local environmental ecology. We also explored the regional environmental conditions on the microbial community and found that the unique Jiang-flavor-Baijiu fermentation microbial community diversity depends on local geology and meteorological conditions. The Jiang-flavor-Baijiu workshop is located in the basin of the middle-and low latitude mountainous areas, with sufficient solar irradiation and rainfall, high air humidity, and low wind speed that favor the growth and propagation of Baijiu fermentation microorganisms. Therefore, the obtained conclusions provide new insights unraveling the key factor controlling the unique flavor of Chinese Baijiu, where protecting the ecology of baijiu brewing-regions is fundamental for maintaining the long-term quality of baijiu. [ABSTRACT FROM AUTHOR]

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. Analyses of atmospheric samples at a high-altitude site show that methylated forms of arsenic, emitted via biological processes, represent an important share of arsenic deposition. These forms are transported from both marine and terrestrial systems. [ABSTRACT FROM AUTHOR]

Airborne microplastics are emerging pollutants originating from disposable tableware, packaging materials, textiles, and other consumer goods. Microplastics vary in shape and size and exposed to external factors break down into even smaller fractions. Airborne microplastics are abundant in both urban and natural environments, including water bodies and glaciers, as particles can travel long distances. The potential toxicity of airborne microplastics cannot be underestimated. Microparticles, especially those < 10 µm, entering the human body through inhalation or ingestion have been shown to cause serious adverse health effects, such as chronic inflammation, oxidation stress, physical damage to tissues, etc. Microplastics adsorb toxic chemicals and biopolymers, forming a polymer corona on their surface, affecting their overall toxicity. In addition, microplastics can also affect carbon dynamics in ecosystems and have a serious impact on biochemical cycles. The approaches to improve sampling techniques and develop standardized methods to assess airborne microplastics are still far from being perfect. The mechanisms of microplastic intracellular and tissue transport are still not clear, and the impact of airborne microplastics on human health is not understood well. Reduced consumption followed by collection, reuse, and recycling of microplastics can contribute to solving the microplastic problem. Combinations of different filtration techniques and membrane bioreactors can be used to optimize the removal of microplastic contaminants from wastewater. In this review we critically summarize the existing body of literature on airborne microplastics, including their distribution, identification, and safety assessment. [ABSTRACT FROM AUTHOR]

Four severe nuclear accident scenarios have been identified for operating nuclear power plants (ONPPs). However, there is a research gap in predicting the mid–long-term radiation doses for these scenarios. This study aims to address this gap by proposing a novel approach for predicting the mid–long-term radiation dose in the case of a hypothetical short-term station blackout (STSBO) scenario, one of the aforementioned scenarios. Firstly, the Weather Research and Forecasting (WRF) model was coupled with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) (WRF-HYSPLIT) model to establish an atmospheric transport and diffusion model for airborne radionuclides, and the regularity of the atmospheric transport and diffusion for the airborne radionuclides was determined. Subsequently, the Residual Radioactive Material Guidelines (RESRAD) OFFSITE (RESRAD-OFFSITE) code was utilized to establish a radiation dose model for predicting the mid–long-term radiation dose resulting from the airborne radionuclides, and the evolution of the mid–long-term radiation dose was analyzed. Finally, the proposed approach was applied to an ONPP, and the results were used to predict the mid–long-term public radiation dose. The results indicated that the total radiation dose would be lower than the dose limit recommended by the International Commission on Radiological Protection (1 mSv/yr) from the second month to the 100th year after the hypothetical STSBO nuclear accident, and the total radiation dose would decrease slowly over time. Recommendations are made for offsite emergency response measures. These research findings can assist ONPPs in analyzing their environmental impacts in the event of an STSBO scenario. [ABSTRACT FROM AUTHOR]

Semi-volatile organic contaminants (SVOCs) are known for their tendency to evaporate from source regions and undergo atmospheric transport to distant areas. Cold condensation intensifies dry deposition, particle deposition, and scavenging by snow and rain, allowing SVOCs to move from the atmosphere into terrestrial and aquatic ecosystems in alpine and polar regions. However, no standardized methods exist for the sampling, laboratory processing, and instrumental analysis of persistent organic pollutants (POPs) in snow. The lack of reference methods makes these steps highly variable and prone to errors. This study critically reviews the existing literature to highlight the key challenges in the sampling phase, aiming to develop a reliable, consistent, and easily reproducible technique. The goal is to simplify this crucial step of the analysis, allowing data to be shared more effectively through standardized methods, minimizing errors. Additionally, an innovative method for laboratory processing is introduced, which uses activated carbon fibers (ACFs) as adsorbents, streamlining the analysis process. The extraction method is applied to analyze polychlorobiphenyls (PCBs) and chlorinated pesticides (α-HCH, γ-HCH, p,p′-DDE, o,p′-DDT, HCB, and PeCB). The entire procedure, from sampling to instrumental analysis, is subsequently tested on snow samples collected on the Svalbard Islands. To validate the efficiency of the new extraction system, quality control measures based on the EPA methods 1668B and 1699 for aqueous methods are employed. This study presents a new, reliable method that covers both sampling and lab analysis, tailored for detecting POPs in snow. [ABSTRACT FROM AUTHOR]

Numerical methods and simulation codes are essential for the advancement of our understanding of complex atmospheric processes. As technology and computer hardware continue to evolve, the development of sophisticated code is vital for accurate and efficient simulations. In this paper, we present the recent advancements made in the FLEXible PARTicle dispersion model (FLEXPART), a Lagrangian particle dispersion model, which has been used in a wide range of atmospheric transport studies over the past 3 decades, extending from tracing radionuclides from the Fukushima nuclear disaster, to inverse modelling of greenhouse gases, and to the study of atmospheric moisture cycles. This version of FLEXPART includes notable improvements in accuracy and computational efficiency. (1) By leveraging the native vertical coordinates of European Centre for Medium Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) instead of interpolating to terrain-following coordinates, we achieved an improvement in trajectory accuracy, leading to a ∼8 %–10 % reduction in conservation errors for quasi-conservative quantities like potential vorticity. (2) The shape of aerosol particles is now accounted for in the gravitational settling and dry-deposition calculation, increasing the simulation accuracy for non-spherical aerosol particles such as microplastic fibres. (3) Wet deposition has been improved by the introduction of a new below-cloud scheme, by a new cloud identification scheme, and by improving the interpolation of precipitation. (4) Functionality from a separate version of FLEXPART, the FLEXPART CTM (chemical transport model), is implemented, which includes linear chemical reactions. Additionally, the incorporation of Open Multi-Processing parallelisation makes the model better suited for handling large input data. Furthermore, we introduced novel methods for the input and output of particle properties and distributions. Users now have the option to run FLEXPART with more flexible particle input data, providing greater adaptability for specific research scenarios (e.g. effective backward simulations corresponding to satellite retrievals). Finally, a new user manual (https://flexpart.img.univie.ac.at/docs/ , last access: 11 September 2024) and restructuring of the source code into modules will serve as a basis for further development. [ABSTRACT FROM AUTHOR]

Remote sensing based on satellites can provide long-term, consistent, and global coverage of NO2 (an important atmospheric air pollutant) as well as other trace gases. However, satellites often miss data due to factors including but not limited to clouds, surface features, and aerosols. Moreover, as one of the longest continuous observational platforms of NO2 , the Ozone Monitoring Instrument (OMI) has suffered from missing data over certain rows since 2007, significantly reducing its spatial coverage. This work uses the OMI-based tropospheric NO2 (OMNO2) product as well as a NO2 product from the Global Ozone Monitoring Experiment-2 (GOME-2) in combination with machine learning (eXtreme Gradient Boosting – XGBoost) and spatial interpolation (data-interpolating empirical orthogonal function – DINEOF) methods to produce the 16-year global daily High Spatial–Temporal Coverage Merged tropospheric NO2 dataset (HSTCM- NO2 ; https://doi.org/10.5281/zenodo.10968462 ; Qin et al., 2024), which increases the average global spatial coverage of NO2 from 39.5 % to 99.1 %. The HSTCM- NO2 dataset is validated using upward-looking observations of NO2 (multi-axis differential optical absorption spectroscopy – MAX-DOAS), other satellites (the Tropospheric Monitoring Instrument – TROPOMI), and reanalysis products. The comparisons show that HSTCM- NO2 maintains a good correlation with the magnitudes of other observational datasets, except for under heavily polluted conditions (> 6 × 1015 molec.cm-2). This work also introduces a new validation technique to validate coherent spatial and temporal signals (empirical orthogonal function – EOF) and confirms that HSTCM- NO2 is not only consistent with the original OMNO2 data but in some parts of the world also effectively fills in missing gaps and yields a superior result when analyzing long-range atmospheric transport of NO2. The few differences are also reported to be related to areas in which the original OMNO2 signal was very low, which has been shown elsewhere but not from this perspective, further confirming that applying a minimum cutoff to retrieved NO2 data is essential. The reconstructed data product can effectively extend the utilization value of the original OMNO2 data, and the data quality of HSTCM- NO2 can meet the needs of scientific research. [ABSTRACT FROM AUTHOR]

The global atmospheric transport of microplastics (MPs) plays a crucial role in the contamination of remote, especially higher-elevation, environments. Precipitation is considered the main source of MP pollution. Meanwhile, plastic waste generated from, for example, tourism activities can be a local source of MP pollution. In this study, we specify which of the mentioned sources of MP, global or local, have a higher impact on the pollution level in the high-elevation oligotrophic lakes of Tatra National Park in Poland. Due to its unique natural value, it is listed by UNESCO as an international biosphere reserve and meets the criteria for Natura 2000 areas. We comprehensively analyzed the morphometric and anthropogenic features of 11 lakes in terms of the contamination level, color, shape, and polymer type of the MPs found in the surface waters. MP fibers were found to be present in all studied lakes, with contamination ranging from 25 to 179 items/m3. Polypropylene, polyethylene terephthalate, and natural or semi-natural cellulose fibers—black or red in color with a length of 0.2–1.0 mm—predominated, which corresponds with other studies conducted on remote mountain ecosystems. We did not find any correlation of the number of MPs with local anthropogenic pressure characteristics. In turn, the significant correlation with lake area, coastline length, lake volume, and catchment area indicated airborne sources, including global transport of MPs to the lakes with reduced water outflow. [ABSTRACT FROM AUTHOR]

Atmospheric inverse modeling is the process of estimating emissions from atmospheric observations by minimizing a cost function, which includes a term describing the difference between simulated and observed concentrations. The minimization of this difference is typically limited by uncertainties in the atmospheric transport model rather than by uncertainties in the observations. In this study, we showcase how a temporally varying, flow-dependent atmospheric transport uncertainty can enhance the accuracy of emission estimation through idealized experiments using an ensemble Kalman smoother system. We use the estimation of European CH4 emissions from the in situ measurement network as an example, but we also demonstrate the additional benefits for trace gases with more localized sources, such as SF6. The uncertainty in flow-dependent transport is determined using meteorological ensemble simulations that are perturbed by physics and driven at the boundaries by an analysis ensemble from a global meteorology and a CH4 simulation. The impact of direct representation of temporally varying transport uncertainties in atmospheric inversions is then investigated in an observation system simulation experiment framework in various setups and for different flux signals. We show that the uncertainty in the transport model varies significantly in space and time and that it is generally highest during nighttime. We apply inversions using only afternoon observations, as is common practice, but also explore the option of assimilating hourly data irrespective of the hour of day using a filter based on transport uncertainty and taking into account the temporal covariances. Our findings indicate that incorporating flow-dependent uncertainties in inversion techniques leads to more accurate estimates of GHG emissions. Differences between estimated and true emissions could be reduced more effectively by 9 % to 82 %, with generally larger improvements for the SF6 inversion problem and for the more challenging setup with small flux signals. [ABSTRACT FROM AUTHOR]

Wind-borne dust supply of iron (Fe) to the oceans plays a crucial role in Earth's biogeochemical cycles. Iron, a limiting micronutrient for phytoplankton growth, is fundamental in regulating ocean primary productivity and in turn the global carbon cycle. The flux of bioavailable Fe to the open ocean affects oscillations in atmospheric CO2 due to its control on inorganic carbon fixation into organic matter that is eventually exported to the sediments. However, the nature of dust-delivered Fe to the ocean and controls on its bioavailability remain poorly constrained. To evaluate the supply of wind-borne bioavailable Fe and its potential impact on Fe-based climate feedbacks over the last 120,000 years, we examine sediment profiles from four localities that define a proximal to distal transect relative to Saharan dust inputs. Bulk δ56Fe isotope compositions (average = -0.05‰) and FeT/Al ratios suggest crustal values, thus pointing to a dominant dust origin for the sediments at all four sites. We observed no variability in grain size distribution or in bioavailable Fe supply at individual sites as a function of glacial-versus-interglacial deposition. Importantly, there is no correlation between sediment grain size and Fe bioavailability. Spatial trends do, however, suggest increasing Fe bioavailability with increasing distance of atmospheric transport, and our sediments also indicate the loss of this Fe and thus potential bioavailability utilization once deposited in the ocean. Our study underscores the significance of Fe dynamics in oceanic environments using refined speciation techniques to elucidate patterns in Fe reactivity. Such insights are crucial for understanding nutrient availability and productivity in various ocean regions, including the Southern Ocean, where wind-delivered Fe may play a pivotal role. It is expected that dust delivery on glacial-interglacial timescales would be more pronounced in these high-latitude regions. Our findings suggest that studies linking Fe availability to marine productivity should benefit significantly from refined Fe speciation approaches, which provide insights into the patterns and controls on Fe reactivity, including atmospheric processing. These insights are essential for understanding the impacts on primary production and thus carbon cycling in the oceans and consequences for the atmosphere. [ABSTRACT FROM AUTHOR]

The North Pacific is known with iron limitation for phytoplankton growth in the subarctic region and nitrogen limitation in the subtropical gyre. Although the growth rate of phytoplankton is determined by the concentration of limiting nutrient, the supply ratio of iron to nitrogen is suggested to be essential to this biogeographic pattern. However, the underlying dynamics determining the ratio remain largely unknown. We investigated mechanisms of dissolved iron (dFe) and nitrate (NO3−) transport to the euphotic zone of the North Pacific using an eddy‐resolvable biogeochemical model. We show that lateral advection and atmospheric deposition are dominant drivers for dFe transport, resulting in high Fe:N supply ratio in both subarctic and subtropical regions. Conversely, significant vertical supplies of NO3− through upwelling and diffusion processes markedly reduce the supply ratio in the subarctic region. These dynamics combined lead to high Fe:N supply ratio in the gyre and low ratio in the subarctic, ultimately driving high nitrogen fixation condition in the gyre and the iron‐limited phytoplankton growth condition in the subarctic region. Plain Language Summary: Iron is a critical trace element for the photosynthesis and nitrogen fixation of phytoplankton in the ocean. In North Pacific Subarctic region, although there is plenty of nitrate, the growth of phytoplankton is limited due to the lack of iron. In the North Pacific Subtropical Gyre (NPSG), nutrient supply to the surface is restricted due to ocean stratification, but diazotrophs can fix nitrogen from the atmosphere. However, their growth is also constrained by iron availability. Understanding how nutrients like iron reach the ocean's surface is vital for predicting the productivity of marine life. Our research employed advanced computer models to explore how dissolved iron is transported in the North Pacific. We discovered that lateral transport by ocean currents, followed by atmospheric deposition, is the primary pathway for iron delivery to the sunlit layer of the NPSG. In the Subarctic Gyre, atmospheric deposition and vertical advection are the major sources of iron. However, we found different transport patterns for nitrate, revealing that physical process‐controlled supply ratio of iron to nitrate may determine where different types of phytoplankton thrive in the surface ocean. This research helps understand the complex processes that supply nutrients to ocean surface. Key Points: Lateral transport and atmospheric deposition dominate supplies of dissolved iron (dFe) to the euphotic zone of the North PacificUpwelling and vertical diffusion control nitrate (NO3−) supply in subarctic regionLateral dFe and vertical NO3− transports determine the stoichiometric supply ratio and shape the biogeographic pattern [ABSTRACT FROM AUTHOR]