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Excess deposition (including both wet and dry deposition) of nitrogen and sulfur is detrimental to ecosystems. Recent studies have investigated the spatial patterns and temporal trends of nitrogen and sulfur wet deposition, but few studies have focused on dry deposition due to the scarcity of dry deposition measurements. Here, we use long-term model simulations from the coupled Weather Research and Forecasting and the Community Multiscale Air Quality (WRF-CMAQ) model covering the period from 1990 to 2010 to study changes in spatial distribution as well as temporal trends in total (TDEP), wet (WDEP), and dry deposition (DDEP) of total inorganic nitrogen (TIN) and sulfur (TS) in the United States (US). We first evaluate the model's performance in simulating WDEP over the US by comparing the model results with observational data from the US National Atmospheric Deposition Program. The coupled model generally underestimates the WDEP of both TIN (including both the oxidized nitrogen deposition, TNO3, and the reduced nitrogen deposition, NHx) and TS, with better performance in the eastern US than the western US. The underestimation of the wet deposition by the model is mainly caused by the coarse model grid resolution, missing lightning NOx emissions, and the poor temporal and spatial representation of NH3 emissions. TDEP of both TIN and TS shows significant decreases over the US, especially in the east, due to the large emission reductions that occurred in that region. The decreasing trends of TIN TDEP are caused by decreases in TNO3, and the increasing trends of TIN deposition over the Great Plains and Tropical Wet Forests (Southern Florida Coastal Plain) regions are caused by increases in NH3 emissions, although it should be noted that these increasing trends are not significant. TIN WDEP shows decreasing trends throughout the US, except for the Marine West Coast Forest region. TIN DDEP shows significant decreasing trends in the Eastern Temperate Forests, Northern Forests, Mediterranean California, and Marine West Coast Forest and significant increasing trends in the Tropical Wet Forests, Great Plains and Southern Semi-arid Highlands. For the other three regions (North American Deserts, Temperate Sierras, and Northwestern Forested Mountains), the decreasing or increasing trends are not significant. Both the WDEP and DDEP of TS have decreases across the US, with a larger decreasing trend in the DDEP than that in the WDEP. Across the US during the 1990–2010 period, DDEP of TIN accounts for 58–65 % of TDEP of TIN. TDEP of TIN over the US is dominated by deposition of TNO3 during the first decade, which then shifts to reduced nitrogen (NHx) dominance after 2003, resulting from a combination of NOx emission reductions and NH3 emission increases. The sulfur DDEP is usually higher than the sulfur WDEP until recent years, as the sulfur DDEP has a larger decreasing trend than WDEP.

Increasing atmospheric nitrogen deposition can influence food production, environmental quality and climate change from the regional to global scales. As the largest developing country, China is expected to experience a rapid increase in N deposition. However, the lack of information on dry N deposition limits our understanding of the historical trend of the total N deposition, as well as the main drivers of this trend. Here, we use extensive datasets that include both wet and dry N deposition to evaluate the spatiotemporal variation of N deposition and the changes of its components in China during 1980–2015. Three significant transitions in N deposition in China were observed. First, the total N deposition began to stabilize in 2001–2005, mostly due to a decline in wet NH4+ deposition. Subsequently, a shift to approximately equal wet and dry N deposition occurred in 2011–2015, accompanied by increasing dry deposition. Finally, the contribution of reduced N components in the deposition decreased due to increasing NO3− deposition. These transitions were jointly driven by changes in the socioeconomic structure in China and vigorous controls in N pollution. The three observed important transitions challenge the traditional views about the continuous increase in N deposition in China.Nitrogen deposition in China has been almost constant over the past decade, as decreasing wet deposition has balanced increasing dry deposition, according to analyses of extensive datasets on wet and dry nitrogen depositions in China.

Nanoparticle deposition on various substrates has gained significant attention due to the potential applications of nanoparticles in various fields. This review paper comprehensively analyzes different nanoparticle deposition techniques on ceramic, polymeric, and metallic substrates. The deposition techniques covered include electron gun evaporation, physical vapor deposition, plasma enriched chemical vapor deposition (PECVD), electrochemical deposition, chemical vapor deposition, electrophoretic deposition, laser metal deposition, and atomic layer deposition (ALD), thermophoretic deposition, supercritical deposition, spin coating, and dip coating. Additionally, the sustainability aspects of these deposition techniques are discussed, along with their potential applications in anti-icing, antibacterial power, and filtration systems. Finally, the review explores the importance of deposition purities in achieving optimal nanomaterial performance. This comprehensive review aims to provide valuable insights into state-of-the-art techniques and applications in the field of nanomaterial deposition.

Atmospheric nitrogen deposition in China has attracted public attention in recent years due to the increasing anthropogenic emission of reactive nitrogen (Nr) and its impacts on the terrestrial and aquatic ecosystems. However, limited long-term and multisite measurements have restrained the understanding of the mechanism of the Nr deposition and the chemical transport model (CTM) improvement. In this study, the performance of the simulated wet and dry deposition for different Nr species, i.e., particulate NO3- and NH4+, gaseous NOx, HNO3 and NH3 have been conducted using the framework of Model Inter-Comparison Study for Asia (MICS-Asia) phase III. A total of nine models, including five Weather Research and Forecasting models coupled with the Community Multiscale Air Quality (WRF-CMAQ) models, two self-developed regional models, a global model and a Regional Atmospheric Modeling System coupled with the Community Multiscale Air Quality (RAMS-CMAQ) model have been selected for the comparison. For wet deposition, observation data from 83 measurement sites from the East Asia Acid Deposition Monitoring Network (EANET), Chinese Ecosystem Research Network (CERN), China Agricultural University Deposition Network (CAUDN), National Acid Deposition Monitoring Network (NADMN) and Department of Ecological Environment (DEE) of China have been collected and normalized for comparison with model results. In general, most models show the consistent spatial and temporal variation of both oxidized N (Nox) and reduced N (Nrd) wet deposition in China, with the normalized mean error (NME) at around 50 %, which is lower than the value of 70 % based on EANET observation over Asia. Both the ratio of wet or dry deposition to the total inorganic N (TIN) deposition and the ratios of TIN to their emissions have shown consistent results with the Nationwide Nitrogen Deposition Monitoring Network (NNDMN) estimates. The performance of ensemble results (ENMs) was further assessed with satellite measurements. In different regions of China, the results show that the simulated Nox wet deposition was overestimated in northeastern China (NE) but underestimated in the south of China, namely southeastern (SE) and southwestern (SW) China, while the Nrd wet deposition was underestimated in all regions by all models. The deposition of Nox has larger uncertainties than the Nrd, especially in northern China (NC), indicating the chemical reaction process is one of the most important factors affecting the model performance. Compared to the critical load (CL) value, the Nr deposition in NC, SE and SW reached or exceeded reported CL values and resulted in serious ecological impacts. The control of Nrd in NC and SW and Nox in SE would be an effective mitigation measure for TIN deposition in these regions. The Nr deposition in the Tibetan Plateau (TP) with a high ratio of TIN ∕ emission (∼3.0), indicates a significant transmission from outside. Efforts to reduce these transmissions ought to be paramount due the climatic importance of the Tibetan region to the sensitive ecosystems throughout China.

The Model Inter-Comparison Study for Asia (MICS-Asia) phase III was conducted to promote understanding of regional air quality and climate change in Asia, which have received growing attention due to the huge amount of anthropogenic emissions worldwide. This study provides an overview of acid deposition. Specifically, dry and wet deposition of the following species was analyzed: S (sulfate aerosol, sulfur dioxide (SO2), and sulfuric acid (H2SO4)), N (nitrate aerosol, nitrogen monoxide (NO), nitrogen dioxide (NO2), and nitric acid (HNO3)), and A (ammonium aerosol and ammonia (NH3)). The wet deposition simulated by a total of nine models was analyzed and evaluated using ground observation data from the Acid Deposition Monitoring Network in East Asia (EANET). In the phase III study, the number of observation sites was increased from 37 in the phase II study to 54, and southeast Asian countries were newly added. Additionally, whereas the analysis period was limited to representative months of each season in MICS-Asia phase II, the phase III study analyzed the full year of 2010. The scope of this overview mainly focuses on the annual accumulated deposition. In general, models can capture the observed wet deposition over Asia but underestimate the wet deposition of S and A, and show large differences in the wet deposition of N. Furthermore, the ratio of wet deposition to the total deposition (the sum of dry and wet deposition) was investigated in order to understand the role of important processes in the total deposition. The general dominance of wet deposition over Asia and attributions from dry deposition over land were consistently found in all models. Then, total deposition maps over 13 countries participating in EANET were produced, and the balance between deposition and anthropogenic emissions was calculated. Excesses of deposition, rather than of anthropogenic emissions, were found over Japan, northern Asia, and southeast Asia, indicating the possibility of long-range transport within and outside of Asia, as well as other emission sources. To improve the ability of models to capture the observed wet deposition, two approaches were attempted, namely, ensemble and precipitation adjustment. The ensemble approach was effective at modulating the differences in performance among models, and the precipitation-adjusted approach demonstrated that the model performance for precipitation played a key role in better simulating wet deposition. Finally, the lessons learned from the phase III study and future perspectives for phase IV are summarized.