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Snow is a key component of the cryosphere and has significant impacts on surface energy balance, hydrology, atmospheric circulation, and etc. In addition, numerous studies have indicated that snow impurities, especially nitrate, are sensitive to sunlight and can be photolyzed to emit reactive species including NO2 and HONO, which serve as precursors of O3 and radicals and disturb the overlying atmospheric chemistry. This makes snow a reservoir of reactive species, and this reservoir is particularly important in remote and pristine regions with limited anthropogenic emissions. The magnitude of snow chemical emissions is also influenced by snow physical properties, including snow depth, density and concentrations of light-absorbing impurities (e.g., BC and dust). Exploring and elucidating the emissions and atmospheric consequences of the snow-sourced reactive species require a global or regional model with a snow module. Here, we parameterized atmospheric nitrate deposition and its distributions in snow using a regional chemical transport model, i.e., the WRF-Chem (the Weather Research and Forecasting Model coupled with Chemistry) model, and evaluated the performance of the WRF-Chem model in simulating snow cover, snow depth, and BC, dust and nitrate concentrations with field observations in northern China which is one of the regions with dense and prolong snow cover. The model reasonably reproduces the observed snow cover and depth in northeastern and northwestern China, and the observed snow dust and nitrate concentrations are also reasonably reproduced. These results illustrate the ability of WRF-Chem in simulating snow properties including concentrations of reservoir species in northern China, and in the future, we will incorporate snow nitrate photolysis in the model, exploring the emissions of snow NOx from nitrate photolysis and the impacts on local to regional atmospheric chemistry and air pollutant transformations. [ABSTRACT FROM AUTHOR]

Trace metals (TMs) manganese (Mn), cobalt (Co), and aluminium (Al) have important geochemical and biological roles in the ocean. Here, we present full depth profiles of dissolved (d) and particulate Al, Mn, and Co along the latitude of 40 °S in the South Atlantic Ocean from the GEOTRACES GA10 cruises that operated in austral spring 2010 and summer 2011. The region is characterized by enhanced primary productivity and forms a key transition zone between the Southern Ocean and South Atlantic Subtropical Gyre. The mean concentrations of dAl, dCo, and dMn (±standard deviation) were 3.36 ± 2.65 nmol kg−1, 35.3 ± 17.6 pmol kg−1, and 0.624 ± 1.08 nmol kg−1, respectively. Their distributions in surface waters were determined by external sources and complex internal biogeochemical processes. Specifically, surface ocean dCo was controlled by the interplay between phytoplankton uptake, remineralization and external inputs; dMn was likely determined by the formation and photoreduction of Mn-oxides; and dAl was supplied by atmospheric deposition and removed by scavenging onto particles. Fluvial and sedimentary inputs near the Rio de La Plata estuary and benthic sources from the Agulhas Bank resulted in elevated dTM concentrations in near-shore surface waters. These externally sourced dTMs were effectively delivered to the open ocean by offshore diffusion and/or advection, and potentially facilitated enhanced primary productivity along the transect. The distributions of dTMs at depth were predominantly controlled by the mixing of North Atlantic Deep Water (NADW) and waters of Antarctic origin (e.g., Upper Circumpolar Water (UCDW) and Antarctic Bottom Water (AABW)). The calculated endmember concentrations of dAl and dCo in NADW showed minor decreases in the SASTG following north–south transport, suggesting removal rates of 0.064 nM/year and 0.035–0.075 pM/year, respectively. The endmember concentration of dCo in AABW was maintained at ∼30 pmol kg−1 without evidence for scavenging removal in the Southern Ocean and SASTG (time frame >400 years). The concentrations of dMn in NADW and AABW were between 0.1 and 0.16 nmol kg−1, and any elevated dMn concentrations were ascribed to local external inputs (e.g., from sediments in the Argentine Basin and hydrothermal activity near the Mid-Atlantic Ridge). Hence, four controlling factors (sources, internal cycling, water mass mixing and time) need to be considered when assessing TM distributions in the global ocean, even for TMs that are vulnerable to scavenging removal processes. Because the deep waters formed in high latitude oceans are crucial components of the global thermohaline overturning system, any processes (e.g., glacier melting, upwelling and sinking, and biological activity) that impact the preformed dTM concentrations in high latitude oceans will determine the downstream dTM distributions. Therefore, the sources and sinks of TMs and associated biological activity in high latitude oceans could engender basin to global scale impacts on seawater distributions of Al, Co, and Mn and their stoichiometric relationships with macronutrients, and the global biogeochemical cycles of these scavenged-type TMs. [ABSTRACT FROM AUTHOR]

Summary: Ectomycorrhizal fungi are essential for nitrogen (N) cycling in many temperate forests and responsive to anthropogenic N addition, which generally decreases host carbon (C) allocation to the fungi. In the boreal region, however, ectomycorrhizal fungal biomass has been found to correlate positively with soil N availability. Still, responses to anthropogenic N input, for instance through atmospheric deposition, are commonly negative.To elucidate whether variation in N supply affects ectomycorrhizal fungi differently depending on geographical context, we investigated ectomycorrhizal fungal communities along fertility gradients located in two nemo‐boreal forest regions with similar ranges in soil N : C ratios and inorganic N availability but contrasting rates of N deposition.Ectomycorrhizal biomass and community composition remained relatively stable across the N gradient with low atmospheric N deposition, but biomass decreased and the community changed more drastically with increasing N availability in the gradient subjected to higher rates of N deposition. Moreover, potential activities of enzymes involved in ectomycorrhizal mobilisation of organic N decreased as N availability increased.In forests with low external input, we propose that stabilising feedbacks in tree‐fungal interactions maintain ectomycorrhizal fungal biomass and communities even in N‐rich soils. By contrast, anthropogenic N input seems to impair ectomycorrhizal functions. [ABSTRACT FROM AUTHOR]

Climate change and atmospheric deposition of nitrogen (N) and sulfur (S) impact the health and productivity of forests. Here, we explored the potential impacts of these environmental stressors on ecosystem services provided by future forests in the contiguous U.S. We found that all stand-level services benefitted (+ 2.6 to 8.1%) from reductions in N+S deposition, largely attributable to positive responses to reduced S that offset the net negative effects of lower N levels. Sawtimber responded positively (+ 0.5 to 0.6%) to some climate change, but negatively (− 2.4 to − 3.8%) to the most extreme scenarios. Aboveground carbon (C) sequestration and forest diversity were negatively impacted by all modelled changes in climate. Notably, the most extreme climate scenario eliminated gains in all three services achieved through reduced deposition. As individual tree species responded differently to climate change and atmospheric deposition, associated services unique to each species increased or decreased under future scenarios. Our results suggest that climate change should be considered when evaluating the benefits of N and S air pollution policies on the services provided by U.S. forests. [ABSTRACT FROM AUTHOR]

Elevated atmospheric reactive nitrogen (Nr) emissions and the subsequent nitrogen (N) deposition have negatively impacted the global environment, particularly in China. In order to assess the long-term trends in atmospheric N deposition in the south of China, Taojiang County in Hunan Province was selected as a representative rural area for study. We analyzed interannual variation in atmospheric Nr, including gaseous ammonia (NH3), nitrogen dioxide (NO2), nitrate acid (HNO3) vapor, particulate ammonium (NH4+), and nitrate (NO3−) in air and NH4+-N and NO3−-N in precipitation from 2011 to 2020. The 10-year average atmospheric wet-plus-dry N deposition was 41.9 kg N ha−1 yr−1, which decreased by approximately 24% after 2012, indicating that NH3 and NOx emissions were effectively reduced by emission controls introduced in 2013. Wet deposition accounted for approximately 74% of the total N deposition and was significantly influenced by annual precipitation amount. Reduced N (NH3, pNH4+, and NH4+ in rainwater) was the dominant form, comprising approximately 58% of the total N deposition, while oxidized N (pNO3−, NO2, HNO3, and NO3− in rainwater) accounted for 42% of the total N deposition. Atmospheric HNO3, NO2, and NH3 concentrations and deposition declined by 30–80% over the decade, while particulate NH4+ and NO3− concentrations and deposition remained at relatively stable levels, which suggests that ongoing research and policy should focus on rural particulate pollution. Future strategies must concentrate on the integrated control of NH3 and NOx emissions to mitigate air pollution and protect human health, particularly in rural areas because current abatement efforts are primarily directed toward urban areas and the industrial sector, whereas non-point source NH3 pollution, influenced mainly by agricultural activities, dominates in rural regions. [ABSTRACT FROM AUTHOR]

Microplastic contamination is ubiquitous across the globe, even in remote locations. Still, the sources and pathways of microplastics to such locations are largely unknown. To investigate microplastic contamination in a semi‐remote location, we measured microplastic concentrations in nine oligotrophic lakes within and around the International Institute for Sustainable Development—Experimental Lakes Area in northwestern Ontario, Canada. Our first objective was to establish ambient concentrations of microplastics in bottom sediments, surface water, and atmospheric deposition in semi‐remote boreal lakes. Across all lakes, mean shallow and deep sediment microplastic concentrations, near‐surface water microplastic concentrations from in situ filtering, and dry atmospheric microplastic deposition rates were 551 ± 354 particles kg−1, 177 ± 103 particles kg−1, 0.2 ± 0.3 particles L−1, and 0.4 ± 0.2 particles m−2 day−1, respectively. Our second objective was to investigate whether microplastic contamination of these lakes is driven by point sources including local runoff and direct anthropogenic inputs or nonpoint sources such as atmospheric deposition. Lakes were selected based on three levels of anthropogenic activity—low, medium, and high—though activity levels were minimal across all study lakes compared with highly populated areas. Whereas a positive correlation would indicate that point sources were a likely pathway, we observed no relationship between the level of anthropogenic activity and microplastic contamination of surface water. Moreover, the composition of microplastics in surface water and atmospheric deposition were similar, comprising mostly polyester and acrylic fibers. Together, these results suggest that atmospheric deposition may be the main pathway of microplastics to these remote boreal lakes. Environ Toxicol Chem 2024;43:999–1011. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Atmospheric deposition is a major nutrient influx in ecosystems and high anthropogenic deposition may disrupt ecosystem functioning. Quantification of the deposition flux is required to understand the impact of such anthropogenic pollution. However, current methods to measure nutrient deposition are costly, labor intensive and potentially inaccurate. Ion Exchange Resin (IER) appears a promising cost-and labor-effective method. The IER-method is potentially suited for deposition measurements on coarse time scales and for areas with little rainfall and/or low elemental concentrations. The accuracy of the IER-method is, however, hardly classified beyond nitrogen. We tested the IER-method for bulk deposition and throughfall measurements of macro and micro-elements, assessing resin adsorption capacity, recovery efficiency, and field behavior. We show that IER is able to adsorb 100 % of Ca, Cu, Fe, K, Mg, Mn, P, S, Zn and NO3 and >96 % of P and Na. Loading the resin beyond the capacity resulted mainly in losses of Na, P, NH4 while losses of Ca, Cu, Fe, Mg, Mn and Zn were hardly detected. Heat (40 °C), drought and frost (-15 °C) reduced the adsorption of P by 25 %. Recovery was close to 100 % for NH4 and NO3 using KCl (1 or 2M) while high (83–93 %) recoveries of Ca, Cu, Fe, K, Mg, Mn and S were found using HCl as an extractant (2–4M). We found good agreement between the conventional and the IER-method for field conditions. Overall, IER is a powerful tool for the measurement of atmospheric deposition of a broad range of elements as the measurements showed high accuracy. The IER-method has therefore the potential to expand current monitoring networks and increase the number of sampling sites. [ABSTRACT FROM AUTHOR]

Soil N-fixing bacterial (NFB) community may facilitate the successful establishment and invasion of exotic non-nitrogen (N) fixing plants. Invasive plants can negatively affect the NFB community by releasing N during litter decomposition, especially where N input from atmospheric N deposition is high. This study aimed to quantitatively compare the effects of the invasive Rhus typhina L. and native Koelreuteria paniculata Laxm. trees on the litter mass loss, soil physicochemical properties, soil enzyme activities, and the NFB. Following N supplementation at 5 g N m−2 yr−1 in four forms (including ammonium, nitrate, urea, and mixed N with an equal mixture of the three individual N forms), a litterbag-experiment was conducted indoors to simulate the litter decomposition of the two trees. After four months of decomposition, the litter cumulative mass losses of R. typhina under the control, ammonium chloride, potassium nitrate, urea, and mixed N were 57.93%, 57.38%, 58.69%, 63.66%, and 57.57%, respectively. The litter cumulative mass losses of K. paniculata under the control, ammonium chloride, potassium nitrate, urea, and mixed N were 54.98%, 57.99%, 48.14%, 49.02%, and 56.83%, respectively. The litter cumulative mass losses of equally mixed litter from both trees under the control, ammonium chloride, potassium nitrate, urea, and mixed N were 42.95%, 42.29%, 50.42%, 46.18%, and 43.71%, respectively. There were antagonistic responses to the co-decomposition of the two trees. The litter mass loss of the two trees was mainly associated with the taxonomic richness of NFB. The form of N was not significantly associated with the litter mass loss in either species, the mixing effect intensity of the litter co-decomposition of the two species, and NFB alpha diversity. Litter mass loss of R. typhina was significantly higher than that of K. paniculata under urea. The litter mass loss of the two trees under the control and N in four forms mainly affected the relative abundance of numerous NFB taxa, rather than NFB alpha diversity. [ABSTRACT FROM AUTHOR]

Trace metals from natural and anthropogenic sources impact the atmospheric environment and enter the soil through dry and wet atmospheric deposition, ultimately affecting human health. In this study, we established an emission inventory of Pb, As, Cr, and Cd in East Asia (80° E–140° E, 15° N–50° N) for the year 2017, including dust and anthropogenic sources from both land and marine. We modified the Community Multiscale Air Quality (CMAQ) model to provide gridded data on concentrations, as well as dry and wet atmospheric deposition fluxes of metals, with a focus on mainland China. The emissions of Pb, As, Cr, and Cd in East Asia were 19,253, 3415, 3332, and 9379 tons, respectively, in 2017, with 55%, 69%, 25%, and 58% distributed in the fine mode. The spatial distribution of atmospheric concentrations and dry deposition of trace metals was similar to that of emissions, while the spatial distribution of precipitation-related wet deposition was further east and greater in the south than in the north. In mainland China, the average bulk-deposition fluxes of Pb, As, Cr, and Cd were 1036.5, 170.3, 465.9, and 185.0 μg·m−2·year−1, respectively. Our study provides gridded data on trace metals in mainland China, which can be used for assessing air quality, human exposure risks, and metal inputs to soils. [ABSTRACT FROM AUTHOR]

Atmospheric dielectric barrier discharge (DBD) is a promising approach for large‐area deposition, whose spatiotemporal evolution determines the deposition rate and film chemistry. To investigate the relationship between the discharge and deposition behavior of tetraethoxysilane/oxygen/argon (TEOS/O2 ${\text{O}}_{2}$/Ar) DBD, a one‐dimensional (1D) fluid model was constructed and experimentally verified. The calculation results reveal that TEOS mainly affects the discharge behavior via Penning ionization, while O2 ${\text{O}}_{2}$ mainly affects discharge via attachment reaction. Penning ionization reduces the excited Ar and the attachment reaction reduces the number of discharges in half voltage cycles. As a result, merely increasing the concentration of TEOS or O2 ${\text{O}}_{2}$ may not proportionally increase the deposition rate of relevant reactive species. [ABSTRACT FROM AUTHOR]

Background: Temperate forests of eastern North America will be increasingly affected by chronic atmospheric nitrogen deposition, elevated temperatures, and drought events that will expose trees to moisture‐stressed conditions in non‐nitrogen‐limited soils. Yet, little is known regarding the response of sugar maple‐dominated forests to moisture stress under non‐nitrogen‐limiting conditions. Aims: The objective of this greenhouse study was to analyze the effects of moisture stress on the nutrition and growth of sugar maple seedlings growing on base‐poor forest soils that were strongly fertilized with nitrogen. Methods: One‐year‐old sugar maple seedlings were grown with and without water stress on soils from a sugar maple stand that had been fertilized for 15 years at a rate of 85 kg N ha−1 y−1. Results: Decreased moisture availability decreased total, leaf, root and stem biomass, and root/stem ratio. Leaf concentrations of N, P, Ca, and Mg and root concentrations of K, Ca, and Mg were 6% to 23% significantly lower under stressed versus unstressed conditions despite no changes in N, P, K, and Mg concentrations in the soil. Only soil Ca concentration was negatively affected by the moisture stress treatment. Soil and leaf δ15N and the k‐factor (i.e., isotopic discrimination effect of 15N‐labeled sources of N between roots and soil) that was used to assess N‐use efficiency of sugar maple seedlings did not differ between water stress treatments. Conclusions: Our results indicate that decreasing root biomass of sugar maple seedlings under moisture stress in non‐nitrogen‐limiting situations would decrease their ability to take up nutrients that are necessary for growth and induce lower concentrations in leaves and roots. Expected severe drought events could substantially limit nutrient uptake capacity of sugar maple seedlings on sites that are subject to chronic atmospheric N‐deposition, which would contribute to dieback in sugar maple stands. [ABSTRACT FROM AUTHOR]

The scenarios of deposition on the sea surface around the Korean Peninsula following hypothetical release at Kori NPP were studied by application of the atmospheric transport model FLEXPART. The series of 1460 dispersion scenarios was calculated, covering the time period of 1 year. The total depositions on the surfaces of the East/Japan Sea (EJS), Yellow Sea (YS), East China Sea (ECS), and near-coast zone of 200-km vicinity around the Korean Peninsula, normalized on the total emission inventory were analyzed. The normalized deposition on the total area of 3 seas varied by more than 2 orders of magnitude from 0.003 to 0.59. The fraction of wet deposition in total deposition varied from 0 to 0.99. The selected most heavy deposition scenarios were divided into those dominated by dry deposition and wet deposition. The most conservative release scenarios (7 August 2020 and 2 September 2020) were dominated by wet deposition and were caused by the monsoon rainband and passage of the typhoon. In the scenario of 7 August 2020, 96% of deposition appeared in the near-coast zone. Cluster analysis of dispersion scenarios confirmed strong seasonal dependence of deposition patterns. For EJS and YS, the maximum average deposition was reached in the 'Summer' cluster. For ECS the maximum average normalized deposition was reached in the 'Spring + Fall' cluster ( D r = 0.055 ). Minimum average deposition on all seas was obtained for the 'Winter' cluster. [ABSTRACT FROM AUTHOR]

• pH of precipitation experienced fluctuating decline, continuous improvement, and slight correction. • S deposition was well controlled, while N deposition did not decrease significantly. • Acid rain has changed from sulfuric acid type to mixed sulfuric and nitric acid type. • Atmospheric deposition is an important source of lake S and N and acidifies mountain lakes. • Future acid deposition should focus on the acidifying effect of NH 4 + deposition. The chemical composition of acid rain and its impact on lake water chemistry in Chongqing, China, from 2000 to 2020 were studied in this study. The regional acid rain intensity is affected jointly by the acid gas emissions and the neutralization of alkaline substances. The pH of precipitation experienced three stages of fluctuating decline, continuous improvement, and a slight correction. Precipitation pH showed inflection points in 2010, mainly due to the total control actions of SO 2 and NO x implemented in 2011. The total ion concentrations in rural areas and urban areas were 489.08 µeq/L and 618.57 µeq/L, respectively. The top four ions were SO 4 2−, Ca2+, NH 4 + and NO 3 −, which accounted for more than 90% of the total ion concentration, indicating the anthropogenic effects. Before 2010, SO 4 2− fluctuated greatly while NO 3 − continued to rise; however, after 2010, both SO 4 2− and NO 3 − began to decline rapidly, with the rates of -12.03 µeq/(L·year) and -4.11 µeq/(L·year). Because the decline rate of SO 4 2− was 2.91 times that of NO 3 −, the regional acid rain has changed from sulfuric acid rain to mixed sulfuric and nitric acid rain. The lake water is weakly acidic, with an average pH of 5.86, and the acidification frequency is 30.00%. Acidification of lake water is jointly affected by acid deposition and acid neutralization capacity of lake water. Acid deposition has a profound impact on water acidification, and nitrogen (N) deposition, especially reduced N deposition, should be the focus of future research. [Display omitted] [ABSTRACT FROM AUTHOR]

During wildfires and fossil fuel combustion, biomass is converted to black carbon (BC) via incomplete combustion. BC enters the ocean by rivers and atmospheric deposition contributing to the marine dissolved organic carbon (DOC) pool. The fate of BC is considered to reside in the marine DOC pool, where the oldest BC 14C ages have been measured (>20,000 14C y), implying long-term storage. DOC is the largest exchangeable pool of organic carbon in the oceans, yet most DOC (>80%) remains molecularly uncharacterized. Here, we report C measurements on size-fractionated dissolved BC (DBC) obtained using benzene polycarboxylic acids as molecular tracers to constrain the sources and cycling of DBC and its contributions to refractory DOC (RDOC) in a site in the North Pacific Ocean. Our results reveal that the cycling of DBC is more dynamic and heterogeneous than previously believed though it does not comprise a single, uniformly "old" 14C age. Instead, both semilabile and refractory DBC components are distributed among size fractions of DOC. We report that DBC cycles within DOC as a component of RDOC, exhibiting turnover in the ocean on millennia timescales. DBC within the low-molecular-weight DOC pool is large, environmentally persistent and constitutes the size fraction that is responsible for long-term DBC storage. We speculate that sea surface processes, including bacterial remineralization (via the coupling of photooxidation of surface DBC and bacterial co-metabolism), sorption onto sinking particles and surface photochemical oxidation, modify DBC composition and turnover, ultimately controlling the fate of DBC and RDOC in the ocean. [ABSTRACT FROM AUTHOR]

To trace Critical Zone processes and to quantify Li fluxes from one Critical Zone compartment into another, we investigated the Li concentration and isotopic composition (δ7Li) of time-series water samples (including subsurface flow, groundwater and creek water), vegetation, bedrock (including separated minerals from bedrock), and regolith (including exchangeable fraction and clay-sized fraction of regolith) in a temperate forested headwater catchment in the Black Forest, Conventwald, Germany. Our estimation of the Li budget shows that atmospheric deposition and biological processes played minor roles in the Li cycle relative to chemical weathering. All water samples (δ 7Li value of 6.5 to 20.4 ‰) were enriched in 7Li compared to bedrock (-1.3 ‰) and regolith (∼-1.7 ‰), but δ7Li differed between water pathways: δ7Li variations in subsurface flow, creek water and groundwater were controlled by conservative mixing, exchangeable pool buffering and Li incorporation/adsorption, respectively. Fractionated heavy Li isotopes in water samples resulted from the formation of secondary solids which preferentially incorporated 6Li, with the separated clay-sized fraction of the regolith exhibiting more negative δ7Li values (-5.4 to −3.5 ‰) than the bulk regolith (∼-1.7 ‰). However, Li in secondary solids only accounted for 8 ± 6 % of the total Li hosted in bulk regolith, and consequently δ7Li in soil did not differ significantly from δ 7Li in bedrock. This is unexpected considering water is continuously removing 7Li in preference over 6Li from regolith. Mass balance calculations applied at the catchment scale point to an irreconcilable imbalance with our data. On one hand, the regolith's δ7Li values are not negative enough to balance the 7Li export by river water, and on the other hand Li in the riverine dissolved load only accounts for ∼ 30 % of the Li solubilized from regolith. Therefore, we suggest that there might be a "hidden export pathway" for Li at our site, possibly subsurface removal of fine particles enriched in 6Li. In light of increasingly frequent observations of such isotopic imbalances in the Critical Zone this phenomenon deserves increased attention. [ABSTRACT FROM AUTHOR]

Concerns have been raised regarding the degradation of stream water quality due to the excessive influx of atmospheric deposition. This study aimed to reveal the long‐term variation in stream water chemistry in approximately 40 forested small watersheds in the northern Kanto region, based on 3 surveys conducted in 1991–1992, 2006–2007, and 2022. The factors influencing each dissolved element were investigated. Regarding long‐term variations in stream water chemistry, relatively stable concentrations of cations (Ca2+, Mg2+, K+, and Na+) and SiO2 were observed. However, the concentrations of anions (Cl−, NO3−$$ {\mathrm{NO}}_3^{-} $$, and SO42−$$ {\mathrm{SO}}_4^{2-} $$) decreased due to the improvement in the atmospheric environment and the diminishing effect of fertilization. Furthermore, the recent increase in stream water pH was attributed to an increase in bicarbonate (HCO3−$$ {\mathrm{HCO}}_3^{-} $$), compensating for the decrease in anion concentrations relative to cations. Geology was the most significant factor for inter‐watershed variations in cations and SiO2, and this influence remained relatively constant over 30 years. Forest practices, especially fertilization, had a significant effect on Cl− and NO3−$$ {\mathrm{NO}}_3^{-} $$, and contributed to higher concentrations in the fertilized watersheds than in the non‐fertilized watersheds over the 15 years following fertilization. Sulfate deposition was a significant influencing factor for SO42−$$ {\mathrm{SO}}_4^{2-} $$, and the concentration fluctuated under long‐term variations in deposition over the past 30 years. Despite substantial acid deposition in the study area, the absence of stream water acidification could be attributed to the abundant cation supply from bedrock and volcanic ash, which underwent weathering processes. [ABSTRACT FROM AUTHOR]

The stable chromium isotope system has been widely used as a redox proxy to reconstruct the oxygenation history of ocean atmosphere systems. However, the Cr isotope mass balance in modern oceans (i.e., inputs and outputs) remains poorly constrained. To investigate the influence of seawater‐peridotite reaction on the global marine Cr isotope mass balance, we report high‐precision Cr isotope data (δ53Cr) on a series of fresh and altered abyssal peridotites from the Gakkel Ridge and the Southwest Indian Ridge (SWIR). The least altered peridotites give a δ53Cr value of −0.08 ± 0.06‰ (2SD, n = 4) for the oceanic mantle which is consistent with the established δ53Cr of the Bulk Silicate Earth. Compared to fresh peridotites, a subset of altered peridotites exhibit a loss of isotopically light Cr with relatively positive δ53Cr values (up to 0.04‰). These altered peridotites are characterized by significant Cr loss and likely have been subject to serpentinization. By contrast, seafloor weathering has limited influence on the Cr concentrations and isotopic compositions of the altered peridotites. Monte Carlo (MC) simulations of marine alteration suggest a net Cr flux into seawater from altered abyssal peridotites of ∼3.5 × 108 mol/yr, which is on the same order of magnitude as the riverine input flux of 108–109 mol/yr. Furthermore, the MC results suggest that the peridotite‐sourced net Cr flux has a negative δ53Cr signature (−0.33 ± 0.21‰, 2SD). Thus, seawater‐peridotite interactions must be considered when evaluating the modern oceanic Cr isotope mass balance. Plain Language Summary: The stable chromium isotope system is an emerging paleoredox proxy for tracing Earth's atmospheric oxygenation over geological timescales. However, accurately inferring past Earth's atmospheric oxygenation levels using chromium isotopes requires a more precise understanding of the elemental and isotopic cycling of chromium, particularly within the oceans. By studying abyssal peridotites which are rocks found beneath the oceanic crust, we find that specific types of alterations in these rocks, particularly the process of serpentinization, have an impact on the chromium isotopes. These findings provide insights into the mechanisms involved in transporting chromium from the deep Earth mantle to the oceans. We discover that these altered rocks release a flux of isotopically light chromium into the ocean, which is comparable to the amount coming from rivers. Our study sheds new light on the complex interactions between seawater and abyssal peridotites, which potentially exert a profound impact on the global marine Cr isotope mass balance. Key Points: The first data set of stable Cr isotopic compositions for abyssal peridotitesSeafloor weathering has insignificant impact on the Cr isotopic compositions of abyssal peridotitesSeafloor alteration exerts a key control on the Cr isotopic composition of seawater [ABSTRACT FROM AUTHOR]

The present work was carried out to obtain and highlight the fifth comprehensive baseline dataset on atmospheric deposition of trace elements and to assess air quality in Macedonia. In the period from August to September 2020, a total of 72 moss samples were collected in accessible areas in the country. The content of 28 elements (Ag, Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sc, Sr, Ti, U, and Zn) was determined using inductively coupled plasma–mass spectrometry. Based on the data obtained on the content of the elements, a factor analysis was carried out to identify and characterise different sources of pollution. In addition, distribution maps were created for all elements to show the regions most affected by anthropogenic activities. The survey conducted in 2020 has shown that air pollution with potentially toxic elements (PTEs) has slightly decreased compared to the results of the previous survey from 2015. This is due to the fact that, despite the operation of all mining and smelting facilities with the same capacity, government regulations for the installation of cleaning systems and additional regulations to reduce pollution have been introduced in the last five years. Nevertheless, the fact remains that the highest anthropogenic air pollution with PTEs is still caused by the operation of the ferronickel smelter in Kavadarci (Ni and Cr) in the southern part and by the lead and zinc mines in Probištip, Makedonska Kamenica, and Kriva Palanka in the eastern part of the country (Cd, Pb, and Zn). [ABSTRACT FROM AUTHOR]

Mercury (Hg) is a global pollutant whose atmospheric deposition is a major input to the terrestrial and oceanic ecosystems. Gas‐particle partitioning (GPP) of gaseous oxidized mercury (GOM) redistributes speciated Hg between gas and particulate phase and can subsequently alter Hg deposition flux. Most 3‐dimensional chemical transport models either neglected the Hg GPP process or parameterized it with measurement data limited in time and space. In this study, CMAQ‐newHg‐Br (Ye et al., 2018, https://doi.org/10.1002/2017ms001161) was updated to CMAQ‐newHg‐Br v2 by implementing a new GPP scheme and the most up‐to‐date Hg redox chemistry and was run for the northeastern United States over January‐November 2010. CMAQ‐newHg‐Br v2 reproduced the measured spatiotemporal distributions of gaseous elemental mercury (GEM) and particulate bound mercury (PBM) concentrations and Hg wet deposition flux within reasonable ranges and simulated dry deposition flux in agreement with previous studies. The GPP scheme improved the simulation of PBM via increasing winter‐, spring‐ and fall‐time PBM concentrations by threefold. It also improved simulated Hg wet deposition flux with an increase of 2.1 ± 0.7 μgm2 in the 11‐month accumulated amount, offsetting half of the decreasing effect of the updated chemistry (−4.2 ± 1.8 μgm2). Further, the GPP scheme captured the observed Kp‐T relationship as reported in previous studies without using measurement data and showed advantages at night and in rural/remote areas where existing empirical parameterizations failed. Our study demonstrated CMAQ‐newHg‐Br v2 a promising assessment tool to quantify impacts of climate change and emission reduction policy on Hg cycling. Plain Language Summary: Mercury is a toxic global pollutant and can enter the food chain through atmospheric deposition to ecosystems. Atmospheric mercury was defined operationally in the forms of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate bound mercury (PBM). GEM is relatively inert, but GOM and PBM are highly soluble and readily removed from the air via deposition. GEM gets oxidized to GOM and GOM can be transformed to PBM through gas particle partitioning (GPP). CMAQ‐newHg‐Br v2 was updated from its predecessor via implementing the most up‐to‐date Hg redox chemistry and a new GPP scheme. The model improved the simulation of GEM, PBM, and Hg wet deposition. Most notably the model reproduced the observed partitioning coefficient and temperature relationship (Kp‐T) and improved nighttime and less polluted PBM simulations. CMAQ‐newHg‐Br v2 can be used to assess how climate change and emission reduction policy impact environmental Hg cycling. Key Points: CMAQ‐newHg‐Br was updated to version 2 with a new gas‐particle partitioning (GPP) scheme and the most up‐to‐date Hg redox chemistryCMAQ‐newHg‐Br v2 better simulated gaseous elemental mercury (GEM), particulate bound mercury (PBM) and Hg wet depositionThe new GPP scheme captured the observed Kp‐T relation not using measurement data and improved nighttime and less polluted simulations [ABSTRACT FROM AUTHOR]

Long-term deposition of atmospheric pollutants emitted from coal combustion and their effects on the eco-environment have been extensively studied around coal-fired power plants. However, the effects of coal-fired power plants on soil microbial communities have received little attention through atmospheric pollutant deposition and coal-stacking. Here, we collected the samples of power plant soils (PS), coal-stacking soils (CSS) and agricultural soils (AS) around three coal-fired power plants and background control soils (BG) in Huainan, a typical mineral resource-based city in East China, and investigated the microbial diversity and community structures through a high-throughput sequencing technique. Coal-stacking significantly increased (p < 0.05) the contents of total carbon, total nitrogen, total sulfur and Mo in the soils, whereas the deposition of atmospheric pollutants enhanced the levels of V, Cu, Zn and Pb. Proteobacteria, Actinobacteria, Thaumarchaeota, Thermoplasmata, Ascomycota and Basidiomycota were the dominant taxa in all soils. The bacterial community showed significant differences (p < 0.05) among PS, CSS, AS and BG, whereas archaeal and fungal communities showed significant differences (p < 0.01) according to soil samples around three coal-fired power plants. The predominant environmental variables affecting soil bacterial, archaeal and fungal communities were Mo-TN-TS, Cu-V-Mo, and organic matter (OM)-Mo, respectively. Certain soil microbial genera were closely related to multiple key factors associated with stacking coal and heavy metal deposition from power plants. This study provided useful insight into better understanding of the relationships between soil microbial communities and long-term disturbances from coal-fired power plants. [Display omitted] [ABSTRACT FROM AUTHOR]

Atmospheric dust deposition can modulate the earth's climate and atmospheric CO2 through fertilising the ocean (nutrient source) and by accelerating the biological carbon pump through fuelling the ballasting process. To distinguish the biogeochemical effects of Saharan dust with respect to fertilization and ballasting, and to gain a broader perspective on the coccolith calcite Sr/Ca in relation to the drivers of coccolith export production, we determined the coccolith-Sr/Ca from a one-year (2012–2013) time-series sediment trap record in the western tropical North Atlantic (M4—49°N/12°W). High Sr/Ca were linked to enhanced export production in the upper part of the photic zone, most notably under windier, dry, and dustier conditions during spring. Attenuated Sr/Ca in the autumn probably reflect a combination of lower Sr-incorporation by dominant but small-size placolith-bearing species and the presence of "aged" coccoliths rapidly scavenged during a highly productive and usually fast export event, likely added by (wet) dust ballasting. Higher Sr/Ca observed in the large coccolith size fractions support the existing notion that larger-sized coccolithophores incorporate more Sr during calcification under the same environmental conditions. The presence of the abnormally Sr-rich species Scyphosphaera apsteinii is also shown in the separated large fraction of our Sr/Ca seasonal data. [ABSTRACT FROM AUTHOR]

Burning of fossil fuels, application of fertilisers, and livestock farming have greatly increased emissions of reactive nitrogen (N). The consequent increase in atmospheric deposition of N compounds has compromised air, soil and water quality, ecosystems, and human health and wellbeing. Sulphate aerosols also affect climate dynamics by scattering solar radiation, leading to surface cooling and, indirectly, cloud formation and precipitation. During 2021 (the pre-war year), the rates of total N deposition over the lower, middle and upper parts of the Dniester catchment were 21.8 ± 1.7, 17.0 and 19.0 ± 3.1 kgN/ha, respectively. The war in Ukraine brought a 35% decrease in annual total N deposition within the Lower Dniester region as a consequence of economic disruption and population displacement. In contrast, the influx of refugees and business relocation to the middle and upper parts of the basin counteracted the impacts of war, resulting in a slight increase (ca. 4%) or no change in cumulative total N deposition during 2022 compared to the pre-war year. The pre-war rates of sulphate deposition were 2.8 ± 0.1, 2.8 and 3.2 ± 0.1 kgS/ha for the lower, middle and upper basin: these were reduced 11–15%. These findings emphasise that local and regional factors interact. Peace is a prerequisite for reducing N emissions and safeguarding the environment. [ABSTRACT FROM AUTHOR]

Globally increased nitrogen (N) to phosphorus (P) ratios (N/P) affect the structure and functioning of terrestrial ecosystems, but few studies have addressed the variation of foliar N/P over time in subtropical forests. Foliar N/P indicates N versus P limitation in terrestrial ecosystems. Quantifying long‐term dynamics of foliar N/P and their potential drivers is crucial for predicting nutrient status and functioning in forest ecosystems under global change. We detected temporal trends of foliar N/P, quantitatively estimated their potential drivers and their interaction between plant types (evergreen vs. deciduous and trees vs. shrubs), using 1811 herbarium specimens of 12 widely distributed species collected during 1920–2010 across China's subtropical forests. We found significant decreases in foliar P concentrations (23.1%) and increases in foliar N/P (21.2%). Foliar N/P increased more in evergreen species (22.9%) than in deciduous species (16.9%). Changes in atmospheric CO2 concentrations (PCO2$$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$), atmospheric N deposition and mean annual temperature (MAT) dominantly contributed to the increased foliar N/P of evergreen species, while PCO2$$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$, MAT, and vapor pressure deficit, to that of deciduous species. Under future Shared Socioeconomic Pathway (SSP) scenarios, increasing MAT and PCO2$$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$ would continuously increase more foliar N/P in deciduous species than in evergreen species, with more 12.9%, 17.7%, and 19.4% versus 6.1%, 7.9%, and 8.9% of magnitudes under the scenarios of SSP1‐2.6, SSP3‐7.0, and SSP5‐8.5, respectively. The results suggest that global change has intensified and will progressively aggravate N–P imbalance, further altering community composition and ecosystem functioning of subtropical forests. [ABSTRACT FROM AUTHOR]

Obtaining a holistic understanding of the impacts of atmospheric nitrogen deposition on multiple ecosystem services of forest is essential for developing comprehensive and sustainable strategies, particularly in heavy N deposition regions such as subtropical China. However, such impacts remain incompletely understood, with most previous studies focus on individual ecosystem function or service via understory N addition experiments. To address this knowledge gap, we quantified the effects of over‐canopy and understory N additions on multiple ecosystem services based on a 7‐year large‐scale field experiment in a typical subtropical forest. Our results showed continued over‐canopy N addition with 50 kg ha−1 year−1 over a period of 4–7 years significantly increased plant nutrient retention, but did not affect the services of soil nutrient accumulation, water yield, C sequestration (in plants and soil), or oxygen release. There were trade‐offs between the soil and plant on providing the services of nutrient accumulation/retention and C sequestration under over‐canopy N addition. However, without uptake and retention of tree canopy, the trade‐off between soil and plant were more weaken under the understory N addition with 50 kg ha−1 year−1, and their relationships were even synergetic under the understory N addition with 25 kg ha−1 year−1. The results suggest that understory N addition cannot accurately simulate the effects of atmospheric N deposition on multiple services, along with mutual relationships. Interestingly, the services of plant N, P retention, and C sequestration exhibited a synergetic increase under the over‐canopy N addition but a decrease under the understory N addition. Our results also found tree layer plays a primary role in providing plant nutrient retention service and is sensitive to atmospheric N deposition. Further studies are needed to investigate the generalized effects of forest canopy processes on alleviating the threaten of global change factors in different forest ecosystems. [ABSTRACT FROM AUTHOR]

Mercury (Hg) contamination in the environment is a persistent issue as emissions from industry are ongoing and legacy cycling is prolonged. To quantify total mercury (total Hg) and methylmercury (MeHg) concentrations in lake sediments across a wide suite of temperate to subarctic lakes, measurements and modeling were conducted for 320 sites across Canada. Total Hg varied from 7 to 567 ng g−1 dry sediment with a mean (median) value of 148 (128) ng g−1 dry sediment, with lowest concentrations observed in eutrophic lakes of the Prairies and Boreal Plains. Average total Hg concentrations have increased twofold in contemporary sediments relative to their preindustrial pair. MeHg concentrations were generally low, with a mean of 0.8 ng g−1 dry sediment and this form representing on average 0.6% of the total contemporary mercury concentrations. Water column variables related to eutrophication were among the strongest predictors of contemporary total Hg, MeHg, and total Hg enrichment in the sediments. In lakes where sediment radiometric data were collected, contemporary total Hg accumulation rates were strongly related to longitude(+) and Hg atmospheric deposition(+). Latitude(−) and Hg atmospheric deposition(+) were the best predictors of MeHg accumulation rates. Chromophoric dissolved organic matter optical properties were key predictors of both total Hg concentrations and accumulation rates. Our work highlights the paramount importance of lake trophic state and the nature of organic matter as key predictors of lake sediment mercury metrics. [ABSTRACT FROM AUTHOR]

The Qarhan Salt Lake is the largest brine lake on the Qinghai-Tibet Plateau (QTP), which contains some potentially toxic elements (PTEs) due to the increase of human activities. This study endeavor encompassed the collection of 62 sediment samples from eight rivers that recharge the Qarhan Salt Lake, and the measurement of seven PTEs' concentrations (As, Hg, Pb, Cd, Cu, Ni, and Zn). Results indicated that the concentrations of most PTEs were lower than their local soil background values, except for Hg and Cd, which surpassed the background contents by 6.8 and 1.1 times, respectively. The I geo and PLI outcomes demonstrated a relatively low level of Hg contamination. Hg was the most hazardous elements with the mean ecological risk factor of 273.88. The Hazard Index (HI) values for PTEs were computed at 0.20 and 0.46 for adults and children, respectively, indicating that neither group was at a non-carcinogenic risk. Through the utilization of source identification methods, this study identified three predominant sources responsible for PTEs in the area: natural geogenic sources, anthropogenic sources and atmospheric deposition inputs. The findings of this study provide a robust scientific foundation for the management of the ecological environment security of rivers in the QTP. [Display omitted] [ABSTRACT FROM AUTHOR]

We re-examined the effects of acidification on Scandinavian freshwater lakes using paleolimnological reconstructions focused on subfossil chironomids. Our study showed a widespread shift in chironomid community composition occurring at around 1960 and corresponding with the maximum fallout of anthropogenic SO42− deposition. Results also showed that taxonomic turn-over was higher in chironomid records from nitrogen-limited lakes, likely due to the cumulative effects of acidification and eutrophication driven by atmospheric nitrogen deposition. Despite strong evidence of chemical recovery from acidification, all lake records failed to show a return to pre-acidified community compositions and most chironomid communities instead continue to follow the trajectories triggered by acidification. We hypothesized that when SO42− deposition started to decrease after 1980, a period also marked by rapid environmental and climatic changes, the influence of pH and/or other acidification-related variables in structuring chironomid community became less important, thus, giving more relative importance to other drivers, such as brownification and climatic processes. Results, therefore, suggest the key role of acidification in shaping the response of chironomid communities to future environmental changes. Future paleolimnological studies will contribute to better manage aquatic ecosystems recovering from acidification worldwide by allowing managers to quantify the efficacy of different management actions taken to mitigate acidification as well as to redefine appropriate restoration targets. [ABSTRACT FROM AUTHOR]

A prerequisite to applying 10Be in natural archives for solar and geomagnetic reconstructions is to know how 10Be deposition reflects atmospheric production changes. However, this relationship remains debated. To address this, we use two state‐of‐the‐art global models GEOS‐Chem and ECHAM6.3‐HAM2.3 with the latest beryllium production model. During solar modulation, both models suggest that 10Be deposition reacts proportionally to global production changes, with minor latitudinal deposition biases (<5%). During geomagnetic modulation, however, 10Be deposition changes are enhanced by ∼15% in the tropics and attenuated by 20%–35% in subtropical and polar regions compared to global production changes. Such changes are also hemispherically asymmetric, attributed to asymmetric production between hemispheres. For the solar proton event in 774/5 CE, 10Be shows a 15% higher deposition increase in polar regions than in tropics. This study highlights the importance of atmospheric mixing when comparing 10Be from different locations or to independent geomagnetic field records. Plain Language Summary: The cosmogenic radionuclide beryllium‐10 (10Be) deposition in natural archives can be used to reconstruct solar and geomagnetic changes in the past. Understanding how 10Be deposition reflects atmospheric production rate changes is crucial for these applications. However, this relationship remains debated. To address this issue, we use two state‐of‐the‐art global models, GEOS‐Chem 14.1.1 and ECHAM6.3‐HAM2.3, along with the latest beryllium production model (CRAC: Be). When responding to solar modulation, both models indicate that 10Be deposition corresponds proportionally to global production rate changes, with a minor latitudinal bias. However, during geomagnetic modulation, 10Be deposition changes significantly compared to global production rate changes. 10Be deposition also shows varying hemispheric responses to geomagnetic modulation, attributed to the asymmetric production between hemispheres. For the extreme solar proton event in 774/5 CE, 10Be shows a higher deposition flux increase in the polar regions compared to the tropics. These findings underscore the need to account for atmospheric mixing on 10Be deposition from different locations, especially for the changes due to the geomagnetic field variations. Key Points: We used two state‐of‐the‐art global models incorporating the latest beryllium production rates to study the sources of 10Be deposition10Be deposition shows strong regional bias compared to the global signal in response to geomagnetic modulation but not to solar modulation10Be deposition shows varying hemispheric responses to geomagnetic modulation, attributed to the asymmetric production between hemispheres [ABSTRACT FROM AUTHOR]

This study aims to assess ecological risks from heavy metal atmospheric deposition in the Indus River at Kotri Barrage, Sindh, Pakistan. Monitoring occurred at four locations, yielding 40 air samples analyzed for heavy metals via Triple Quadrupole Inductively Coupled Plasma Mass Spectrometry (TQ-ICP-MS). Pollution indicators, including Contaminant Factor (CF), Degree of Contamination (CD), Geo-accumulation Index (Igeo), Enrichment Factor (EF), Pollution Load Index (PLI), Potential Ecological Risk Index (PERI), and Nemerow Integrated Pollution Index (NIPI), quantified contaminant levels. Air monitoring revealed PM2.5 concentrations exceeding regulatory guidelines at all four sites. Heavy metal mean concentrations ranked as follows: Fe > Cr > Pb > Mn > As > Cu > Ni > Cd > Mo > Co, and deposition fluxes followed this order: Fe > Pb > Cr > Mn > As > Cu > Ni > Cd > Mo > Co. Pollution indices indicated moderate to extreme pollution for Fe, Cr, Cd at all sites, and Pb at site D. Emissions from a nearby coal-fired power plant and vehicular sources were identified as primary contributors to high heavy metal deposition. The Ecological Risk Index ranged from 150 to 600, signifying substantial ecological risk linked to Cd. These findings offer crucial insights for governmental agencies and policymakers to address pollution issues arising from heavy metal atmospheric deposition in the Indus River near Kotri Barrage. [ABSTRACT FROM AUTHOR]

Atmospheric nitrogen deposition may affect the biodeterioration process of stone monuments through direct and indirect pathways, but relevant studies are lacking. Therefore, taking the biologically colonized rocks around the Leshan Giant Buddha (World Heritage - Mixed Property) as the research objects, we studied the effects of multiple nitrogen addition levels (0, 9, 18, 36, 72 kg N hm-2 a-1; N0, N1; N2 ; N3; N4) on the bacterial community structure and soil nutrients on the surfaces of stones with four biocolonization types, including naked rock (NR), and lichen (LR), bryophyte (BS) and vascular plant (VS) colonization, to investigate the potential effect of atmospheric nitrogen deposition on the rock weathering of the Leshan Giant Buddha. The results demonstrated that nitrogen addition impacted soil carbon, nitrogen and phosphorus nutrients, as well as bacterial community structure and composition, but the responses to nitrogen input varied among different colonization types. Nitrogen fertilization promoted the accumulation of total organic carbon and total nitrogen in NR and LR, and increased the content of total phosphorus in VS. Bacterial α-diversity decreased with nitrogen addition in NR but increased with nitrogen addition in VS. Nitrogen addition significantly (R > 0.9, p < 0.01) changed the bacterial community composition in the four biocolonization types, and the changes were dominated by species replacement (contributed to 60.98%, 76.32%, 67.27% and 72.14% for bacterial diversity in NR, LR, BS and VS, respectively). Total nitrogen, dissolved organic nitrogen, dissolved organic nitrogen and total phosphorus were the most important ecological factors affecting bacterial community structure in NR, LR, BS and VS, respectively. Nitrogen addition enriched different bacterial taxa in the four biocolonization types. The results of this study provide basic data for the protection of stone monuments and the formulation of sustainable development strategies under a changing climate. [ABSTRACT FROM AUTHOR]

Nutrient budgets help to identify the excess or insufficient use of fertilizers and other nutrient sources in agriculture. They allow for the calculation of indicators, such as the nutrient balance (surplus if positive or deficit if negative) and nutrient use efficiency, that help to monitor agricultural productivity and sustainability across the world. We present a global database of country-level budget estimates for nitrogen (N), phosphorus (P) and potassium (K) on cropland. The database, disseminated in FAOSTAT, is meant to provide a global reference, synthesizing and continuously updating the state of the art on this topic. The database covers 205 countries and territories, as well as regional and global aggregates, for the period from 1961 to 2020. Results highlight the wide range in nutrient use and nutrient use efficiencies across geographic regions, nutrients, and time. The average N balance on global cropland has remained fairly steady at about 50–55 kg ha -1 yr -1 during the past 15 years, despite increasing N inputs. Regional trends, however, show recent average N surpluses that range from a low of about 10 kg N ha -1 yr -1 in Africa to more than 90 kg N ha -1 yr -1 in Asia. Encouragingly, average global cropland N use efficiency decreased from about 59 % in 1961 to a low of 43 % in 1988, but it has risen since then to a level of 55 %. Phosphorus deficits are mainly found in Africa, whereas potassium deficits occur in Africa and the Americas. This study introduces improvements over previous work in relation to the key nutrient coefficients affecting nutrient budgets and nutrient use efficiency estimates, especially with respect to nutrient removal in crop products, manure nutrient content, atmospheric deposition and crop biological N fixation rates. We conclude by discussing future research directions and highlighting the need to align statistical definitions across research groups as well as to further refine plant and livestock coefficients and expand estimates to all agricultural land, including nutrient flows in meadows and pastures. Further information is available from 10.5061/dryad.hx3ffbgkh (Ludemann et al., 2023b) as well as the FAOSTAT database (https://www.fao.org/faostat/en/#data/ESB ; FAO, 2022a) and is updated annually. [ABSTRACT FROM AUTHOR]

Mercury cycles at levels three- to five-fold higher today than the pre-Industrial era, resulting in global contamination of ecosystems. In the western United States (U.S.), mercury mobilization has led to widespread production of methylmercury (MeHg), a potent, bioaccumulating neurotoxin, which has resulted in fish consumption advisories across all states. Mountain regions are particularly sensitive to continued mercury contamination as they receive higher rates of atmospheric deposition, compared to lower elevations, and have aquatic ecosystems on the landscape conducive to MeHg production. In this paper, we focus on the U.S. Rocky Mountain region and synthesize: (1) current knowledge regarding the mercury cycle; (2) impacts of climate change on the mercury cycle connected to hydrology and wildfire; and (3) future research priorities for informing mercury research and regulation. Studies on the interactions between mercury contamination and climate change in mountain ecosystems is still nascent. We use the findings from this synthesis to summarize the following research needs: (1) quantify sources of mercury in wet and dry deposition, as these pathways dictate mercury exposure and toxicity, and are shifting with climate change; (2) investigate MeHg in mountain aquatic ecosystems, which are important pathways of human mercury exposure and provide food resources and habitat to local wildlife; and (3) examine the disproportionate impact of mercury contamination on indigenous communities through community-led research. Although we focus on the Rocky Mountains for this review, the findings are applicable to semi-arid mountain ecosystems globally and must be prioritized to promote the health of ecosystems and people everywhere. [ABSTRACT FROM AUTHOR]

The main objective of this study is to map multi-element geochemical anomalies in soil on a regional scale. We aimed to determine and evaluate the baseline geochemical values and main geochemical trends in soil that may serve as reference values against any future changes. A total of 817 topsoil samples (0–10 cm) were collected in a 5 × 5 km grid and analyzed for 35 elements using ICP-ES after multi-acid digestions (HClO4/HNO3/HCl/HF) and 53 elements using ICP-MS after modified aqua regia digestion (HCl/HNO3/H2O). The analytical results for the two different digestion methods (multi-acid digestion vs. aqua regia) were also compared for each chemical element. Multivariate statistical methods were applied to identify the geochemical trends and main sources of trace elements over the territory of Slovenia. Based on these results, seven natural and one mixed natural/anthropogenic geochemical association were established. The contents and trends of the determined factors are presented according to 8 natural units, 4 drainage areas, and geological units characteristic of Slovenia. The identified anthropogenic geochemical association combines toxic elements (Ag, Bi, Cd, Hg, P, Pb, S, Sn, and Zn). Increased values of these elements can be found in mining areas and metallurgic centers, in Quaternary sediments of the Sava River, and Adriatic Basin as the consequence of past mining activities and in the Julian Alps, where their origin could be connected to the atmospheric deposition. [ABSTRACT FROM AUTHOR]

Plant communities are being exposed to changing environmental conditions all around the globe, leading to alterations in plant diversity, community composition, and ecosystem functioning. For herbaceous understorey communities in temperate forests, responses to global change are postulated to be complex, due to the presence of a tree layer that modulates understorey responses to external pressures such as climate change and changes in atmospheric nitrogen deposition rates. Multiple investigative approaches have been put forward as tools to detect, quantify and predict understorey responses to these global‐change drivers, including, among others, distributed resurvey studies and manipulative experiments. These investigative approaches are generally designed and reported upon in isolation, while integration across investigative approaches is rarely considered. In this study, we integrate three investigative approaches (two complementary resurvey approaches and one experimental approach) to investigate how climate warming and changes in nitrogen deposition affect the functional composition of the understorey and how functional responses in the understorey are modulated by canopy disturbance, that is, changes in overstorey canopy openness over time. Our resurvey data reveal that most changes in understorey functional characteristics represent responses to changes in canopy openness with shifts in macroclimate temperature and aerial nitrogen deposition playing secondary roles. Contrary to expectations, we found little evidence that these drivers interact. In addition, experimental findings deviated from the observational findings, suggesting that the forces driving understorey change at the regional scale differ from those driving change at the forest floor (i.e., the experimental treatments). Our study demonstrates that different approaches need to be integrated to acquire a full picture of how understorey communities respond to global change. [ABSTRACT FROM AUTHOR]

Aquatic communities are increasingly subjected to multiple stressors through global change, including warming, pH shifts, and elevated nutrient concentrations. These stressors often surpass species tolerance range, leading to unpredictable consequences for aquatic communities and ecosystem functioning. Phytoplankton, as the foundation of the aquatic food web, play a crucial role in controlling water quality and the transfer of nutrients and energy to higher trophic levels. Despite the significance in understanding the effect of multiple stressors, further research is required to explore the combined impact of multiple stressors on phytoplankton. In this study, we used a combination of crossed experiment and mechanistic model to analyze the ecological and biogeochemical effects of global change on aquatic ecosystems and to forecast phytoplankton dynamics. We examined the effect of dust (0–75 mg L−1), temperature (19–27°C), and pH (6.3–7.3) on the growth rate of the algal species Scenedesmus obliquus. Furthermore, we carried out a geospatial analysis to identify regions of the planet where aquatic systems could be most affected by atmospheric dust deposition. Our mechanistic model and our empirical data show that dust exerts a positive effect on phytoplankton growth rate, broadening its thermal and pH tolerance range. Finally, our geospatial analysis identifies several high‐risk areas including the highlands of the Tibetan Plateau, western United States, South America, central and southern Africa, central Australia as well as the Mediterranean region where dust‐induced changes are expected to have the greatest impacts. Overall, our study shows that increasing dust storms associated with a more arid climate and land degradation can reverse the negative effects of high temperatures and low pH on phytoplankton growth, affecting the biogeochemistry of aquatic ecosystems and their role in the cycles of the elements and tolerance to global change. [ABSTRACT FROM AUTHOR]

Soil nitrogen (N) availability plays an important role in regulating priming effects (PE). In this study, we aimed to investigate the effects of long-term N fertilization on PE under single and more frequent additions of labile carbon (C) inputs (13C-labeled glucose). The soils collected from a 6-year-long inorganic N fertilization experiment in a subtropical Phyllostachys edulis forest in China were incubated at a constant temperature of 25 °C for 90 days. Regardless of the mode of glucose addition, the cumulative primed C was lower in the previously fertilized soil and showed a positive relationship with soil pH and peroxidase activity. When comparing the amount of cumulative primed C and the remaining added glucose-C after 90 days of incubation, the fertilized soil had a higher net C increase than the control. These results indicate that atmospheric N deposition and N fertilization might reduce the PE caused by labile organic matter inputs, thereby increasing soil organic C sequestration. The effect of N fertilization on PE under a single glucose addition (reduced by 11%) was smaller than that of repeated additions (reduced by 24%). Previously fertilized soil with a single glucose addition exhibited higher microbial P deficiency, which had a negative impact on PE; in contrast, in soil with repeated glucose additions, higher abundance of Gram-positive bacteria contributed to the negative PE. As such, the frequency of glucose addition affects the intensity and regulation of soil PE. Regardless of the N fertilization treatment, soil with a single glucose addition exhibited stronger PE but lower soil net C increases than those with repeated additions, which might be related to higher microbial activities. Collectively, our findings provide insights regarding soil PE in subtropical forests under the combined effects of increasing N deposition and glucose addition. [ABSTRACT FROM AUTHOR]

Aims: Atmospheric trace metal deposition is an important source in agricultural soils and crops, but a large knowledge gap exists between foliar and root uptake of wet/dry deposition. We aim to distinguish the contribution of dry and wet-deposited trace metals to rice plant via foliar and root uptake and to investigate their accumulations during the full growth season. Methods: We performed an atmospheric exposure experiment using customized open top chambers (OTCs) to distinguish the impacts of wet and dry deposition contribution to foliar and root uptake and their mobility in soils. The foliar uptake and then translocation was hypothesized the major pathway of trace metal accumulation in rice grains. Results: Foliar uptake of wet- and dry-deposited Cu, Zn, and Pb played an important role in their accumulations in rice plant, contributing to 44–47%, 23–25%, and 35–37% in rice grains, respectively. The leaf Cu, Zn, and Pb accumulated from atmospheric deposition can be transported upward to rice grains but nodes seem to restrict them downward translocation. Rice leaves cannot directly take up atmospheric As and the deposited As can only accumulate in rice through the root uptake. The trace metals showed high mobility in atmospheric deposition, which significantly increase the bioavailable trace metal fractions in surface soils and soil solutions. Conclusions: This study provides a new insight of similar or even higher contributions of foliar uptake than root uptake of trace metals from atmospheric deposition and that reducing the accumulation of atmospheric trace metals due to deposition on leaves can effectively decrease the accumulation of trace metals in crops. [ABSTRACT FROM AUTHOR]

• 11001 t of N, 68 t of P, and 73528 t of S were delivered in 2021. • Atmospheric deposition contributes 9% for N and 21% for P input to the Middle Route. • There were 988 t of N, 29 t of P and 2,540 t of S accumulated in the main channel. Nutrient levels in the artificial channel constructed for the Middle Route Project are significant indicators of water quality safety and aquatic ecological integrity for this large, inter-basin scheme. However, the distribution and transport of nutrients along the channel were poorly understood. Based on a time-series dataset as well as mass balance and material flow analysis methods, the water and nutrient transport fluxes in the Middle Route of the South-to-North Water Diversion Project were identified in this study. The results indicate that the nutrient concentrations varied considerably with time, but there was no significant difference among the 30 stations of the main channel. Seasonal temperature difference was the major factor in the large fluctuations of water quality indicators over time. The nutrient loadings varied with the water volume outputs from the main channel to the water-receiving cities. Atmospheric deposition was an important source of nutrients in the main channel, accounting for 9.13%, 20.6%, and 0.635% of the nitrogen, phosphorus, and sulfur input from the Danjiangkou Reservoir, respectively. In 2021, a net accumulation of 988 tons of N, 29 tons of P, and 2,540 tons of S, respectively, were present in the main channel. The increase of these external and internal nutrient loadings would cause water quality fluctuation and deterioration in some local sections of the main channel. Our study quantified the spatial and temporal patterns of nutrient transport in the Middle Route and revealed the ecological effects on the aquatic environment, assisting authorities on the project to develop effective water conservation strategies. [Display omitted] [ABSTRACT FROM AUTHOR]

The deposition of different atmospheric mercury (Hg) species into oceans determines the atmospheric Hg lifetime and the production of neurotoxin methylmercury. Yet, the relative contribution of atmospheric Hg(II) and Hg(0) is largely unconstrained. Here, we report the concentrations of total Hg and methylmercury, as well as Hg isotope composition in living corals collected from the tropical South China Sea (SCS). The results show that the Hg in corals is mainly present as inorganic Hg, exhibiting slightly negative δ202Hg and small yet significant Δ199Hg and Δ200Hg. These isotope features closely resemble those of pelagic waters, suggesting that shallow‐water corals that are widely distributed in oligotrophic waters could be used to trace atmospheric Hg deposition pathways. A mixture model based on coral Δ200Hg indicates that approximately 49% of the seawater Hg in the tropical SCS, a region characterized by high rainfall, originates from atmospheric gaseous Hg(0), much larger than previous estimates. Plain Language Summary: Mercury (Hg) is a toxic heavy metal pollutant that has significant impacts on the environment. The ocean plays a crucial role in the global Hg cycle, with atmospheric Hg deposition being a major source of Hg in seawater. By elucidating the sources, transport, and transformations of Hg in the marine environment, we can develop effective strategies for its mitigation and environmental management. However, our current understanding of how atmospheric mercury enters the open sea is limited, due to challenges in directly measuring trace amounts of mercury in seawater. The widely distributed shallow‐water coral could be an important supplement. Here we present the first‐ever examination of mercury isotope compositions in coral polyps and their symbiotic zooxanthellae from the tropical South China Sea to investigate atmospheric Hg sources into the open ocean. The result shows that the ratio of atmospheric divalent Hg(II) to elemental Hg(0) deposition derived from coral isotopes is only about one quarter of the estimate based on current observations. Our study presents a novel approach to constrain atmospheric Hg deposition pathways into the ocean and challenges the prevailing viewpoint that Hg in tropical oceans mainly originates from precipitation. Key Points: First study of Hg isotope compositions in coral polyps and their symbiotic zooxanthellaeShallow‐water coral tissue can serve as an archive for Hg isotopic compositions of the surface seawaterCoral Δ200Hg reveals that ∼49% of seawater Hg in the tropical South China Sea is derived from atmospheric gaseous elemental Hg [ABSTRACT FROM AUTHOR]

The Congo River supplies vast quantities of trace metals (TMs) to the South Atlantic Ocean, but TM budgets for the Congo plume derived using radium isotopes for GEOTRACES cruise GA08 suggest additional input other than the river outflow. Considering the tight correlations between most dissolved TMs and salinity in the plume and the high rainfall during the wet season over the Congo shelf, we hypothesized that wet atmospheric deposition is a TM source to the Congo plume. Observed TM concentrations in rainwaters across the Congo shelf were mostly comparable to values from previous work in the North Atlantic and Mediterranean Sea. Wet deposition contributed the equivalent of 43% dCd, 21% dCu, 20% dPb and 68% dZn of the Congo River fluxes. Our findings show an important role of wet deposition in supplying TMs to the South Atlantic overlapping with the region that receives substantial TM fluxes from the Congo River. Plain Language Summary: The Congo River has the second largest freshwater discharge volume globally and creates an extensive near‐equatorial plume into the Atlantic Ocean. The Congo plume constitutes an important source of trace metals (TMs) to the ocean, which impacts biogeochemical cycles in the tropical and subtropical ocean. However, existing work suggests a discrepancy within the TM budgets in the Congo plume and points to unknown source other than the Congo River or shelf sediments. Most TM concentrations across the Congo plume remain tightly correlated with salinity, suggesting that any additional sources are likely also freshwater‐derived or enter the ocean at the river mouth coincidently with direct riverine TM inputs. Here, TM concentrations in ocean, river and rainwater collected during the GEOTRACES GA08 cruise are combined to suggest that wet deposition augmented some Congo TM fluxes to the ocean. Fluxes of anthropogenic Cd, Cu, Pb and Zn to the Congo shelf from wet deposition are of the same order of magnitude as the Congo River. Concentrations of these elements in rainwater are similar to prior observations reported for the North Atlantic and Mediterranean Sea, suggesting that a large fraction of the global range of rainwater concentrations over the ocean has been captured in our observations. Key Points: The Congo River is an important source of trace metals (TMs) to the South Atlantic Ocean revealed by data from GEOTRACES cruise GA08Wet deposition (rainfall) is identified as an additional TM source to the Congo plume by concurrently considering river and rain dataRainfall supplies anthropogenic dTMs (Cd, Cu, Pb and Zn) with fluxes equivalent to 20%–68% of those from the Congo River on the Congo shelf [ABSTRACT FROM AUTHOR]

This study addresses the atmospheric deposition of trace elements investigated in Albania, Croatia and Macedonia in 2010 as part of the European Moss Study. This study provides data on the concentration of ten metals (Cd, Cr, Cu, Ni, Pb, V, Zn, Fe, Al, and Li) in naturally growing mosses. In general, all concentration data follow a lognormal distribution. Cd, Cr, Ni, and Zn show strong fluctuations in the moss samples from Albania and Macedonia, and Pb, Fe, and Al in the mosses from Croatia. The concentrations of Cd, Cu, and Zn were higher in the samples from Croatia than in those from Albania and Macedonia; the concentrations of Cr, Ni, V, Fe, Al, and Li were higher in the samples from Albania than in those from Croatia and Macedonia; and a higher concentration of Pb was found in the samples from Macedonia. The observed relationship between the concentration of lithogenic elements (Al, Fe, and V) and the air quality index (AQI) confirms that moss species have a high capacity to retain atmospheric deposition particles. The anthropogenic emission sources of these elements from local and long-range transport were considered to be the most important factors affecting air quality in the studied areas. [ABSTRACT FROM AUTHOR]

African desert dust is emitted and long-range transported with multiple effects on climate, air quality, cryosphere, and ecosystems. On 21–23 February 2021, dust from a sand and dust storm in northern Africa was transported to Finland, north of 60°N. The episode was predicted 5 days in advance by the global operational SILAM forecast, and its key features were confirmed and detailed by a retrospective analysis. The scavenging of dust by snowfall and freezing rain in Finland resulted in a rare case of substantial mineral dust contamination of snow surfaces over a large area in the southern part of the country. A citizen science campaign was set up to collect contaminated snow samples prepared according to the scientists' instructions. The campaign gained wide national interest in television, radio, newspapers and social media, and dust samples were received from 525 locations in Finland, up to 64.3°N. The samples were utilised in investigating the ability of an atmospheric dispersion model to simulate the dust episode. The analysis confirmed that dust came from a wide Sahara and Sahel area from 5000 km away. Our results reveal the features of this rare event and demonstrate how deposition samples can be used to evaluate the skills and limitations of current atmospheric models in simulating transport of African dust towards northern Europe. [ABSTRACT FROM AUTHOR]

Atmospheric deposition of particulate organic nitrogen (ONp) is a significant process in the global nitrogen cycle and may be pivotally important for N-limited ecosystems. However, past models largely overlooked the spatial and chemical inhomogeneity of atmospheric ONp and were thus deficient in assessing global ONp impacts. We constructed a comprehensive global model of atmospheric gaseous and particulate organic nitrogen (ON), including the latest knowledge on emissions and secondary formations. Using this model, we simulated global atmospheric ONp abundances consistent with observations. Our estimated global atmospheric ON deposition was 26 Tg N yr−1, predominantly in the form of ONp (23 Tg N yr−1) and mostly from wildfires (37%), oceans (22%) and aqueous productions (17%). Globally, ONp contributed as much as 40% to 80% of the total N deposition downwind of biomass-burning regions. Atmospheric ONp deposition thus constituted the dominant external N supply to the N-limited boreal forests, tundras and the Arctic Ocean, and its importance may be amplified in a future warming climate. [ABSTRACT FROM AUTHOR]

For over 75 years, the National Oceanic and Atmospheric Administration's Air Resources Laboratory (NOAA ARL) has been at the forefront of federal meteorological and climate research. As the Special Projects Section (SPS) of the U.S. Weather Bureau (USWB), the laboratory pioneered the development of atmospheric trajectory modeling, initially used in studies related to nuclear weapons following World War II. Model development was guided by observations following weapons tests, assisted by later experiments using a wide variety of atmospheric tracers. Today's familiar Gaussian plume dispersion model, previously in nascent form, was developed and promoted with ARL research, as was the much later and widely used HYSPLIT model. Much of ARL's early research was focused on the challenges presented by the complex terrain surrounding nuclear installations, often addressed with high-spatial-resolution meteorological measurements, atmospheric tracers, and site-specific models. ARL has since extended boundary layer research to increasingly complex landscapes, such as forests, agricultural lands, and urban areas, and has expanded its research scope to air quality, weather, and climate applications based on the knowledge and experience developed throughout its long history. Examples of these research endeavors include the establishment of the U.S. Climate Reference Network, fundamental contributions to the development of the National Air Quality Forecast Capability, and foundational participation in the National Atmospheric Deposition Program. ARL looks forward to continuing to refine scientific understanding from field experiments, including coupling ground-based experimentation with modeling, and sustained observations, in order to facilitate the transfer of knowledge into practical applications of societal relevance. [ABSTRACT FROM AUTHOR]

The transport and deposition of atmospheric particulate matter have attracted significant attention recently due to the increasing frequency of extreme disaster events, such as dust storms, volcanic eruptions, and extensive forest fires. The size distribution of the transported material and the conditions of the land–air interface are dominant factors in comprehending the detrimental potential of atmospheric particulate matter. However, it is still a challenge to understand the mechanism of dust deposition, especially over complex terrain. In an effort to investigate the deposition characteristics of particles over complex terrain, a series of experiments were conducted in a multifunctional environmental wind tunnel. The results show that the wind speed directly above the top of the mild slope model is significantly greater than that in the steep slope model, which indicates that a steep slope has a greater blocking effect on wind fields. At low wind speeds, the average wind speed at the top of the mild slope model is 17.8% higher than that at the top of the steep slope model, and at high wind speeds the average wind speed at the top of the mild slope model is 8.6% higher than that at the top of the steep slope model. The influence trend of the steep slope model and the combination model is basically the same, with both decreasing first and then increasing with the direction of wind velocity. The amount of surface deposition is greatly affected by the location of the feeding point and the microscale characteristics of the surface. In the steep slope model, the deposition is mainly distributed on the windward side, while the leeward side has a small amount of deposition. In the mild slope model, particles are deposited not only on the windward side, but also on the leeward side. The average rate of decline in deposition flux in the steep slope model is 88.4% and 75.1% in the mild slope model. The use of the combination model reduces the particle concentration at the back end compared with the single model. In three different models, the deposition on the windward side was shown to be significantly greater than that on the leeward side of the model. Our work increases understanding of the deposition of coarse dust particles over complex terrain and provides basic data for improving the accuracy of large-region particle transport and deposition simulations. [ABSTRACT FROM AUTHOR]

The toxic heavy metal mercury (Hg) has significantly enhanced the global Hg cycle influenced by human activities over the last century. In this study, we presented a high-resolution Hg deposition history between ∼ 1780 and 2015 AD in a sediment core from Xincun Lagoon, located in the southeastern Hainan Island, South China, and analyzed it in conjunction with geochemical elements, grain-size distribution, organic matter, and HYSPLIT backward trajectory simulation. The objective was to investigate the influencing factors affecting historical Hg deposition in relatively remote regions and assess the extent of the effects of natural background and human activities. The results showed that the Hg in the sediment was deposited primarily through atmospheric deposition, which was closely related to regional and even global human activities. Anthropogenic Hg contamination increased gradually from the 1830s to 1850s, possibly due to Hg emissions from Opium Wars I and II occurring in southeastern China. High broad peaks of anthropogenic Hg were observed during the 1910s to 1950s and in the 1980s, likely associated with the two world wars and modern Chinese wars. In addition, a further sharp increase in anthropogenic Hg from the mid-1970s to the present occurred, likely originating from the intense industrial activities in China triggered by the reform and opening-up policy of China in 1978 and some countries in Southeast Asia. [ABSTRACT FROM AUTHOR]

This study analyzed the contents of Cd, Co, Cr, Cu, Ni, Pb, Zn, Hg and As in 39 surface soil samples in the lower reaches of Huangshui River basin. The results showed that the proportions of Cd, Co and Cr exceeding the standard values in all samples were 17.95%, 17.95% and 12.82%, respectively. The geo-accumulation index analysis showed that 58.33% of Cd was above moderate pollution level. 64.10% of Cr was at the level of moderate pollution and above. Improved Nemerow index evaluation showed that all soil samples had ecological risk of heavy metal pollution, and 64.10% of the samples were in moderate or above pollution level. The results of potential ecological risk index showed that Cd posed a higher ecological risk than other heavy metals. There were 2.6% of the samples with high risk, and the proportions of considerable, moderate and low ecological risks were 12.8%, 2.6% and 82%, respectively. Correlation analysis and PMF analysis showed that the heavy metals in soil were mainly from atmospheric deposition, agricultural and traffic activities, industrial emissions and natural sources. The health risk of soil heavy metals is low, and the health risk caused by any exposure pathway is acceptable. In contrast, Cr, As and Pb were the most important factors contributing to non-carcinogenic risk, and As, Cd and Cr were the main carcinogenic risk factors. Children have higher health risks than adults, and the main route of exposure is ingestion. [ABSTRACT FROM AUTHOR]

An important transport process for particles and gases from the atmosphere to aquatic and terrestrial environments is through dry and wet deposition. An open-source, modular, off-grid, and affordable instrument that can automatically collect wet deposition samples allows for more extensive deployment of deposition samplers in fieldwork and would enable more comprehensive monitoring of remote locations. Precipitation events selectively sampled using a conductivity sensor powered by a battery-based supply are central to off-grid capabilities. The prevalence of conductive precipitation, initially containing high solute levels and progressing through trace level concentrations to ultrapure water in full atmospheric washout, depends on the sampling location but is ubiquitous. This property is exploited here to trigger an electric motor via limit switches to open and close a lid resting over a funnel opening. The motors are operated via a custom-built and modular digital logic control board, which have low energy demands. All components, their design and rationale, and assembly are provided for community use. The modularity of the control board allows operation of up to six independent wet deposition units, such that replicate measurements (e.g., canopy throughfall) or different collection materials for various targeted pollutants can be implemented as necessary. We demonstrate that these platforms are capable of continuous operation off-grid for integrated monthly and bimonthly collections performed across the Newfoundland and Labrador Boreal Ecosystem Latitudinal Transect (47° to 53° N) during the growing seasons of 2015 and 2016. System performance was assessed through measured power consumption from 115 volts of alternating current (VAC; grid power) or 12 volts of direct current from battery supplies during operation under both standby (40 or 230 mA, respectively) and in-use (78 or 300 mA, respectively) conditions. In the field, one set of triplicate samplers was deployed in the open to collect incident precipitation (open fall) while another set was deployed under the experimental forest canopy (throughfall). The proof-of-concept systems were validated with basic measurements of rainwater chemistry including: i) pH ranging from 4.14 to 5.71 in incident open fall rainwater; ii) conductivity ranging from 21 to 166 uS/cm; and iii) dissolved organic carbon (DOC) concentrations in open fall and canopy throughfall of 16 ± 10 mg/L and 22 ± 12 mg/L, respectively; with incident fluxes spanning 600 to 4200 mg C m-2 a-1 across the transect. Ultimately, this demonstrates that the customized precipitation sampling design of this new platform enables more universal accessibility of deposition samples to the atmospheric observation community-for example, those who have made community calls for targeting biogeochemical budgets and/or contaminants of emerging concern in sensitive and remote regions. [ABSTRACT FROM AUTHOR]

Deposition of mineral dust plays an important role in upper‐ocean biogeochemical processes, particularly by delivering iron to iron‐limited regions. Here we examine the impact of dynamically changing iron deposition on tropical Pacific Ocean biogeochemistry in fully coupled earth system model projections under several emissions scenarios. Projected end‐of‐21st‐century increases in central tropical Pacific dust and iron deposition strengthen with increasing emissions/radiative forcing, and are aligned with projected soil moisture decreases in adjacent land areas and precipitation increases over the equatorial Pacific. Increased delivery of soluble iron results in a reduction in, and eastward contraction of, equatorial Pacific phytoplankton iron limitation and shifts primary production and particulate organic carbon flux projections relative to a high emissions projection (SSP5‐8.5) wherein soluble iron deposition is prescribed as a static climatology. These results highlight modeling advances in representing coupled land‐air‐sea interactions to project basin‐scale patterns of ocean biogeochemical change. Plain Language Summary: We use an Earth System Model (ESM) to explore climate‐driven changes in the deposition of dust and iron from the atmosphere to the ocean under a range of climate change scenarios. These simulations use a "dynamic" approach for iron deposition which means iron deposition is affected by changing atmospheric dust loads and factoring in wind and precipitation which affect dust and iron transfer from the atmosphere to the ocean. Under increasing climate change scenarios, GFDL's ESM4.1 projects drier soil conditions, as well as more dust in the atmosphere and precipitation over the Pacific Ocean toward the end of the 21st century. Elevated levels of future iron delivery to the ocean reduce iron limitation of phytoplankton growth in the central Pacific. As a result, we find higher levels of phytoplankton production in the central, equatorial Pacific but lower levels downstream in the western and off‐equatorial Pacific because other nutrients necessary for growth are depleted by reduced upwelling and enhanced production in the eastern Pacific. This geographic pattern also appears in the change in carbon sinking from the surface ocean to depth. Overall, these results highlight how ESM advances can improve our understanding of climate change impacts on marine ecosystems. Key Points: Dynamically modeled atmosphere‐to‐ocean soluble iron deposition permits deposition driver variability to affect upper ocean biogeochemistryTropical Pacific iron deposition increases with radiative forcing, affecting phytoplankton nutrient limitation, production, and POC fluxDeposition increases align with soil moisture decreases in adjacent land areas, and precipitation increases over the equatorial Pacific [ABSTRACT FROM AUTHOR]

While nitrate (NO 3 -) serves as a vital nutrient for soil organisms, the lack of knowledge on its sources and cycling in Antarctic soils does not allow to predict the possible effects of climate and environmental changes on the functioning of terrestrial ecosystems. Thus, the NO 3 - and its stable isotopes of Δ17O NO3 , δ15N NO3, and δ18O NO3 were analyzed in Antarctic soils, collected in coastal ice-free areas of East Antarctica and the tip of the northern Antarctic Peninsula. The soil NO 3 - concentrations and isotopic values of Δ17O NO3 , δ15N NO3, and δ18O NO3 were comparable across the latitudinal gradient except for soils collected beneath moss cushions in the Fildes Peninsula. The proportional calculation of Δ17O NO3 indicated that 93–97% of soil NO 3 - derived from nitrification process, whereas atmospheric deposition probably contributed to the NO 3 - budget for a fraction <10 %. The linear relationship between δ18O NO3 and δ15N NO3 suggested the occurrence in Antarctic soils of denitrification process and active cycling between NO 3 - and nitrite (NO 2 -). The NO 3 - assimilation in soil likely occurred, but at minimal rates. These findings provide new insights in the biogeochemical cycle of nitrogen (N) in Antarctic terrestrial ecosystems and seem to indicate that despite climatic and environmental changes along the wide latitudinal gradient, the sources and cycling of NO 3 - maintain a rather consistent pattern along coastal ice-free areas. The noteworthy increase of NO 3 - concentrations and δ15N NO3 , δ18O NO3 , and Δ17O NO3 values in soils collected under moss in the Fildes Peninsula could also suggest that the warming and the increased availability of liquid water will likely favor the developments of soil biotic communities and changes in the biogeochemical cycle of N in Antarctic terrestrial ecosystems. [ABSTRACT FROM AUTHOR]