Contrasting source contributions of Arctic black carbon to atmospheric concentrations, deposition flux, and atmospheric and snow radiative effects

Black carbon (BC) particles in the Arctic contribute to rapid warming of the Arctic by heating the atmosphere and snow and ice surfaces. Understanding the source contributions to Arctic BC is therefore important, but they are not well understood, especially those for atmospheric and snow radiative effects. Here we estimate simultaneously the source contributions of Arctic BC to near-surface and vertically integrated atmospheric BC mass concentrations (MBC_SRF and MBC_COL), BC deposition flux (MBC_DEP), and BC radiative effects at the top of the atmosphere and snow surface (REBC_TOA and REBC_SNOW), and show that the source contributions to these five variables are highly different. In our estimates, Siberia makes the largest contribution to MBC_SRF, MBC_DEP, and REBC_SNOW in the Arctic (defined as > 70° N), accounting for 70 %, 53 %, and 43 %, respectively. In contrast, Asia’s contributions to MBC_COL and REBC_TOA are largest, accounting for 38 % and 45 %, respectively. In addition, the contributions of biomass burning sources are larger (24−34 %) to MBC_DEP, REBC_TOA, and REBC_SNOW, which are highest from late spring to summer, and smaller (4.2−14 %) to MBC_SRF and MBC_COL, whose concentrations are highest from winter to spring. These differences in source contributions to these five variables are due to seasonal variations in BC emission, transport, and removal processes and solar radiation, as well as to differences in radiative effect efficiency (radiative effect per unit BC mass) among sources. Radiative effect efficiency varies by a factor of up to 4 among sources (1465−5439 W g–1) depending on lifetimes, mixing states, and heights of BC and seasonal variations of emissions and solar radiation. As a result, source contributions to radiative effects and mass concentrations (i.e., REBC_TOA and MBC_COL, respectively) are substantially different. The results of this study demonstrate the importance of considering differences in the source contributions of Arctic BC among mass concentrations, deposition, and atmospheric and snow radiative effects for accurate understanding of Arctic BC and its climate impacts.

Assessment of Mercury Concentrations and Fluxes Deposited from the Atmosphere on the Territory of the Yamal-Nenets Autonomous Area

The problem of mercury input and its further distribution in the Arctic environment is actively debated, especially in recent times, due to the observed processes of permafrost thawing causing the enhanced release of mercury into the Arctic atmosphere and further distribution in the terrestrial and aquatic ecosystem. The atmospheric mercury deposition occurs via dry deposition and wet scavenging by precipitation events. Here we present a study of Hg in wet precipitation on the remote territory of the Russian Arctic; the data were obtained at the monitoring stations Nadym and Salekhard in 2016–2018. Mercury pollution of the Salekhard atmosphere in cold time is mainly determined by regional and local sources, while in Nadym, long-range transport of mercury and local fuel combustion are the main sources of pollutants in the cold season, while internal regional sources have a greater impact on the warm season. Total mercury concentrations in wet precipitation in Nadym varied from <0.5 to 63.3 ng/L. The highest Hg concentrations in the springtime were most likely attributed to atmospheric mercury depletion events (AMDE). The contributions of wet atmospheric precipitation during the AMDE period to the annual Hg deposition were 16.7% and 9.8% in 2016/2017 and 2017/2018, respectively. The average annual volume-weighted Hg concentration (VWC) in the atmospheric precipitation in Nadym is notably higher than the values reported for the remote regions in the Arctic and comparable with the values obtained for the other urbanized regions of the world. Annual Hg fluxes in Nadym are nevertheless close to the average annual fluxes for remote territories of the Arctic zone and significantly lower than the annual fluxes reported for unpolluted sites of continental-scale monitoring networks of the different parts of the world (USA, Europe, and China). The increase of Hg deposition flux with wet precipitation in Nadym in 2018 might be caused by regional emissions of gas and oil combustion, wildfires, and Hg re-emission from soils due to the rising air temperature. The 37 cm increase of the seasonally thawed layer (STL) in 2018 compared to the 10-year average reflects that the climatic changes in the Nadym region might increase Hg(0) evasion, considering a great pool of Hg is contained in permafrost.

Structure, phase evolution, and properties of Ta films deposited using hybrid high-power pulsed and dc magnetron co-sputtering

Crystalline phase and microstructure control are critical for obtaining desired properties of Ta films deposited by magnetron sputtering. Structure, phase evolution, and properties of Ta films deposited by using hybrid high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) under different fractions of DCMS power where Ta ion to Ta neutral ratios of the deposition flux were changed are investigated. The results revealed that the number of Ta ions arriving on the substrate/growing film play an important role in structure and phase evolution of Ta films. It can effectively avoid the unstable arc discharge under low pressure and show a higher deposition rate by hybrid high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) compared with only high power impulse magnetron sputtering (HiPIMS). Meanwhile, the high hardness α-Ta films can be directly deposited by hybrid co-sputtering compared to those prepared by direct current magnetron sputtering (DCMS). In the co-sputtering technology, pure α-Ta phase film with extremely fine, dense and uniform crystal grains were obtained, which shows smooth surface roughness (3.22 nm), low resistivity (38.98 μΩ·cm) and abnormal high hardness (17.64 GPa).

Long term variation in chemical composition of precipitation and wet deposition of major ions at Minicoy and Portblair : Islands in Arabian Sea and Bay of Bengal

Lkkj & bl ’kks/k Ik= esa vjc lkxj ds feuhdkW; rFkk caxky dh [kkM+h ds iksVZCys;j }hi ds nks LFkkuksa ds o"kZ 1981 ls 2002 rd ds 22 o"kkZsa ds jklk;fud feJ.k ds dsoy vknzZ&o"kZ.k vk¡dM+kas dk fo’ys"k.k fd;k x;k gSA fofo/k vk;fud ldsUnzh;dj.k ds chp ds lglaca/kksa dks Li"V djus dk iz;kl fd;k x;k gSA ’kjn_rq ds nkSjku gqbZ o"kkZ ds ty esa lYQsV] ukbVªsV vkSj gkbMªkstu vk;uksa dh vf/kdre lkUnzrk ikbZ xbZ gS A _rq okj oxhZdj.k ds nkSjku ekWulwu _rq esa lHkh vk;uksa ds vknZz o"kZ.k vfHkokg ds vf/kdre gksus dk irk pyk gS A nksuksa gh LFkkuksa ij vEyh; fu{ksi.k esa c<+ksrjh dh izo`fr ns[kh xbZ gS A futZu}hi ij Tokykeq[kh dh fØ;k’khyrk iksVZCys;j ds o"kkZty esa jklk;fud feJ.k dks izHkkfor djrh gS A lYQsV vk;u ¼½ dk okf"kZd vknzZ o"kZ.k feuhdkW; esa 15-6 fd-xzk- izfr gsDVs;j izfr o"kZ rFkk iksVZCys;j es 25-5 fd-xzk- izfr gsDVsvj izfr o"kZ ik;k x;k gS rFkk ukbVªsV vk;u ¼½ dh fu{ksfir ek=k feuhdkW; esa 38-0 fd-xzk- izfr gsDVs;j izfr o"kZ vkSj iksVZCys;j esa 74-6 fd-xzk- izfr gsDVs;j izfr o"kZ rd ikbZ xbZ gS A /kuk;u vk;uksa esa lksfM;e vk;u ¼Na+½ rFkk dSfY’k;e vk;u ¼Ca2+½ ds rRo vf/kd ek=k esa tek gksrs gSa ftuesa eSXusf’k;e vk;u ¼Mg2+½ds lkFk&lkFk iksVkf’k;e vk;u ¼K+½ Hkh feys gksrs gSa A The data on chemical composition of wet only precipitation from two island stations Minicoy in Arabian Sea and Portblair in Bay of Bengal, representing 22 year period, 1981-2002 have been analyzed. An attempt has been made to explain the correlation between various ionic concentrations. The maximum concentrations of sulfate, nitrate and hydrogen ions in rainwater are observed during winter season. When classified by season the wet deposition flux for all the ions is greatest in the monsoon season during which precipitation is substantially high. A tendency for increase in acidic deposition is observed at both the stations. The volcanic activity at Barren island appears to influence the chemical composition of rainwater at Portblair. The annual wet deposition of SO42- ranged from 15.6 kg ha-1 yr-1 at Minicoy to 25.5 kg ha-1 yr-1 at Portblair, and the corresponding amounts of NO3- deposited ranged from 38.0 kg ha-1 yr-1 at Minicoy to 74.6 kg ha-1 yr-1 at Portblair. Of the cations Na+ and Ca2+ are the elements deposited in largest quantities followed by Mg2+ and K+.

Spatial and Seasonal Variation of Polycyclic Aromatic Hydrocarbons (Pahs) Deposition Flux and Sources in Shanghai

Spatial and temporal variations of PAHs deposition flux and sources may significantly facilitate risk evaluations of super magacity in China. A study on polycyclic aromatic hydrocarbons of wet deposition and dry deposition in Shanghai was conducted from January to December, 2019. 17 sites were investigated located in four representative functional areas, covering iron and steel industry (BS), petrochemical industry (JS), central city (CC) and agricultural area (CM). The results showed that atmospheric PAHs level in shanghai was the lowest in autumn and the highest in winter. As industrial area, BS and JS demonstrated higher PAHs deposition fluxes than those in CC and CM sites. Triangle map indicated that the PAHs distribution in winter and spring samples were more homogeneous, suggesting possible common origins, whereas that of summer and autumn seemed to be more dispersed. Isomar ratio and positive matrix factorization model were employed to identify the potential sources of PAHs in specific functional areas. BS was dominated by a high percentage (46%) of coal combustion. In JS site, the petroleum volatilization source percentage was 47.6%. The highest biomass burning (55.3%) contributions were in CM. Vehicle emission (49.3%) was identified as the predominant source of PAHs in CC. This study highlighted that local emission sources have a greater influence on PAHs deposition to specific functional regions in Shanghai.

Multiphase processes in the EC-Earth Earth System model and their relevance to the atmospheric oxalate, sulfate, and iron cycles

Understanding how multiphase processes affect the iron-containing aerosol cycle is key to predict ocean biogeochemistry changes and hence the feedback effects on climate. For this work, the EC-Earth Earth system model in its climate-chemistry configuration is used to simulate the global atmospheric oxalate (OXL), sulfate (SO42−), and iron (Fe) cycles, after incorporating a comprehensive representation of the multiphase chemistry in cloud droplets and aerosol water. The model considers a detailed gas-phase chemistry scheme, all major aerosol components, and the partitioning of gases in aerosol and atmospheric water phases. The dissolution of Fe-containing aerosols accounts kinetically for the solution’s acidity, oxalic acid, and irradiation. Aerosol acidity is explicitly calculated in the model, both for accumulation and coarse modes, accounting for thermodynamic processes involving inorganic and crustal species from sea salt and dust. Simulations for present-day conditions (2000–2014) have been carried out with both EC-Earth and the atmospheric composition component of the model in standalone mode driven by meteorological fields from ECMWF’s ERA-Interim reanalysis. The calculated global budgets are presented and the links between the 1) aqueous-phase processes, 2) aerosol dissolution, and 3) atmospheric composition, are demonstrated and quantified. The model results are supported by comparison to available observations. We obtain an average global OXL net chemical production of 12.61 ± 0.06 Tg yr−1 in EC-Earth, with glyoxal being by far the most important precursor of oxalic acid. In comparison to the ERA-Interim simulation, differences in atmospheric dynamics as well as the simulated weaker oxidizing capacity in EC-Earth result overall in a ~30 % lower OXL source. On the other hand, the more explicit representation of the aqueous-phase chemistry in EC-Earth compared to the previous versions of the model leads to an overall ~20 % higher sulfate production, but still well correlated with atmospheric observations. The total Fe dissolution rate in EC-Earth is calculated at 0.806 ± 0.014 Tg Fe yr−1 and is added to the primary dissolved Fe (DFe) sources from dust and combustion aerosols in the model (0.072 ± 0.001 Tg Fe yr−1). The simulated DFe concentrations show a satisfactory comparison with available observations, indicating an atmospheric burden of ∼0.007 Tg Fe, and overall resulting in an atmospheric deposition flux into the global ocean of 0.376 ± 0.005 Tg Fe yr−1, well within the range reported in the literature. All in all, this work is a first step towards the development of EC-Earth into an Earth System Model with fully interactive bioavailable atmospheric Fe inputs to the marine biogeochemistry component of the model.

Assessment of Natural Radioactivity, Heavy Metals and Partic-Ulate Matter in Air and Soil Around a Coal-Fired Power Plant—An Integrated Approach

A comprehensive study of the environmental radioactivity covered in a distance up to 20 km from a point source—two stacks of a coal-fired power plant. Airborne particulate matter was collected, and the element composition on the 30 cm soil profile was determined. The range of activity concentrations of 226Ra, 232Th and 40K from the studied areas varies from 8 Bq/kg to 41 Bq/kg, 5 to 72 Bq/kg and 62 to 795 Bq/kg, respectively. The activities values are increased by 44% for 226Ra, 37% for 40K, and 75% for 232Th in the prevailing wind direction. For some elements, the respective concentration in the soil is above the maximum permissible level for all types of soil use, particularly for the arsenic concentration. The deposition flux ranged from 0.36 to 5.70 (g m−2 per month) in the first sampling campaign and from 0.02 to 3.10 (g m−2 per month) for the second sampling campaign. Maps on the spatial distribution of gamma dose rates, radionuclides activity concentrations, deposition flux and trace metals in topsoil were developed for the study region. These maps are in accordance with higher values in specific locations in the vicinity of the coal-fired power plant, showing the influence of point sources, and for locations within 6 and 20 km from the stacks, particularly in the prevailing wind direction.

High resolution aerosol concentration data from the Greenland NorthGRIP and NEEM deep ice cores

Records of chemical impurities from ice cores enable us to reconstruct the past deposition of aerosols onto the polar ice sheets and alpine glaciers. Through that, they allow us to gain insight into changes of the source, transport and deposition processes that ultimately determine the deposition flux at the coreing location. However, the low concentrations of the aerosol species in the ice and the resulting high risk of contamination poses a formidable analytical challenge, especially if long, continuous and highly resolved records are needed. Continuous Flow Analysis, CFA, the continuous melting, decontamination and analysis of ice-core samples has mostly overcome this issue and has quickly become the de-facto standard to obtain high-resolution aerosol records from ice cores after its inception at the University of Bern in the mid 90s. Here we present continuous records of calcium (Ca2+), sodium (Na+), ammonium (NH4+), nitrate (NO3−1) and electrolytic conductivity at 1 mm depth resolution from the NGRIP (North Greenland Ice Core Project) and NEEM (North Greenland Eemian Ice Drilling) ice cores produced by the Bern Continuous Flow Analysis group in the years 2000 to 2011. Both of the records have previously been used in a number of studies but have never been published in the full 1 mm resolution. Alongside the 1 mm datasets we provide decadal averages, a detailed description of the methods, relevant references, an assessment of the quality of the data and its usable resolution. Along the way we will also give some historical context on the development of the Bern CFA system.

Seasonal Variations in Dissolved Organic Carbon in the Source Region of the Yellow River on the Tibetan Plateau

Rivers as the link between terrestrial ecosystems and oceans have been demonstrated to transport a large amount of dissolved organic carbon (DOC) to downstream ecosystems. In the source region of the Yellow River (SRYR), climate warming has resulted in the rapid retreat of glaciers and permafrost, which has raised discussion on whether DOC production will increase significantly. Here, we present three-year data of DOC concentrations in river water and precipitation, explore the deposition and transport processes of DOC from SRYR. Results show that annual mean concentrations of riverine DOC ranged from 2.03 to 2.34 mg/L, with an average of 2.21 mg/L. Its seasonal variation is characterized by the highest concentration in spring and summer (2.65 mg/L and 2.62 mg/L, respectively), followed by autumn (1.95 mg/L), and the lowest in winter (1.44 mg/L), which is closely related to changes in river runoff under the influence of precipitation and temperature. The average concentration of DOC in precipitation (2.18 mg/L) is comparable with riverine DOC, while the value is inversely related to precipitation amount and is considered to be the result of precipitation dilution. DOC deposition flux in precipitation that is affected by both precipitation amount and DOC concentration roughly was 86,080, 105,804, and 73,072 tons/yr from 2013 to 2015, respectively. DOC flux delivered by the river ranged from 24,629 to 37,539 tons/yr and was dominated by river discharge. Although permafrost degradation in SRYR is increasing, DOC yield is not as significant as previously assumed and is much less than other large rivers in the world.