Wet Nitrogen Deposition Research Articles

Role of advection in atmospheric ammonia: A case study at a Japanese lake basin influenced by agricultural ammonia sources

The dry and wet depositions of atmospheric ammonia (NH3) is one of the important pathways of nitrogen loads to aquatic ecosystems and should be managed to mitigate lake eutrophication. Crop and livestock agriculture, one of the largest emitters of NH3 in Asian countries, are known to cause high spatial and seasonal variation of NH3 and influence the surrounding lake basin areas via its dry and wet deposition. However, the spatial characteristics of the NH3 concentration in basin scale are not completely understood for regulation in NH3 emission because a paucity of monitoring network is currently available for NH3 in many Asian countries. Here we aim to clarify dominant factors of spatial and seasonal variations of the NH3 concentration in a shallow eutrophic lake basin (Lake Kasumigaura basin) surrounded by agricultural areas in eastern Japan. Passive sampling over various land use categories in the basin was conducted at 36 sites in total from October 10, 2018 to January 14, 2020. Mean NH3 concentration in the observational period was in the order of farmland (6.6 ppbv), lake (5.9 ppbv), rural (3.5 ppbv), and forest (2.6 ppbv). Interestingly, the observed NH3 concentration near the livestock houses were higher in winter than summer, which was inconsistent with knowledge of seasonal changes of current NH3 emission inventory based on temperature-driven volatilization process. Comparing monthly NH3 concentrations at farmland and lake sites with various meteorological factors, we suggested the importance of seasonal advection of NH3 from high emission sources to which has been rarely paid attention by the previous past studies. Consequently, a higher nitrogen input by dry deposition of NH3 was preliminarily estimated over the lake than that of wet deposition of total nitrogen. Our finding of a role of seasonal advection in NH3 spatial pattens should be considered for lake ecosystem management since its deposition is known to be closely related to the ecological processes such as phytoplankton blooming.

Long term trends of wet deposition and atmospheric concentrations of nitrogen and sulfur compounds at EMEP site in Armenia

This paper presents the trends of gaseous nitric acid, nitrogen dioxide, sulfur dioxide, ammonia and nitrate, ammonium, sulfate ions in atmospheric air, and nitrate, ammonium and sulfate ions in wet deposition over 2008–2018 in Armenia. Atmospheric nitrogen and sulfur concentrations were monitored by data obtained from filter pack samplers and glass sinter filters at background monitoring station of Armenia (Amberd), which is designated as EMEP (European Monitoring and Evaluation Programme) station. Laboratory analyses were performed by ion chromatography system and UV spectrophotometer. MAKESENS programme was used for detecting and estimating trends in the time series of annual average values of atmospheric concentrations. Long term trends of atmospheric concentrations of nitrogen and sulfur compounds at the Amberd air quality monitoring station were calculated and discussed for the investigated decade. The trends significance levels for all parameters are calculated. It is identified that there are no significant trends for all explored paramenters, except reduced sulfur in aerosols. Possible emission and deposition changes of nitrogen and sulfur compounds in Armenia were explored in order to identify possible transboundary air pollution and its main sources. Deposition data was estimated by EMEP MSC-W model calculations. Investigation of transboundary fluxes of nitrogen and sulfur compounds displays main receptor areas and contributors. Analysis of seasonality in atmospheric pollutants shows strong seasonal behaviour of the measured parameters in wet deposition - higher concentrations during summertime compared with the wintertime. Atmospheric concentrations of nitrate and ammonium ions are lower during summertime compared with the wintertime, while ammonia has low concentrations during wintertime. Atmospheric nitric acid, sulfate ion, sulfur dioxide and nitrogen dioxide revel no significant seasonality.

Nitrate isotopic composition of sequential Hurricane Harvey wet deposition: Low latitude NOx sources and oxidation chemistry

Abstract Chemical characterization of hurricane wet deposition is integral to understanding how future extreme weather events will impact coastal biogeochemical cycles. Sequential Hurricane Harvey wet deposition samples (n = 7 over 20.5 h) were collected in southeastern Texas, U.S. and the isotopic composition of nitrate and water (δ15N–NO3-, δ18O–NO3- and δ18O–H2O, δ2H–H2O) and the concentrations of ammonium, anions, and dissolved organic carbon were measured. Areas of peak deposition (~1500 mm) received up to 75% of the region's typical average annual inorganic nitrogen wet deposition. After δ15N–NO3- values were corrected for potential fractionation effects, contributions of lightning, natural gas combustion, vehicle exhaust and biogenic sources to NO3− in wet deposition (43.7 ± 31.2%, 7.8 ± 6.1%, 42.6 ± 27.5% and 5.9 ± 5.3%, respectively) were determined using a Bayesian isotope mixing model. Results highlight the significance of natural-sourced nitrogen being deposited to terrestrial systems during hurricane events. The relatively low δ18O–NO3- (36.1 ± 3.0‰) emphasized the role played by hydroxyl and peroxy radicals in HNO3 formation during the tropical summer. An established global NOx oxidation model in combination with δ18O–NO3- approximates the significance of RO2 vs O3 oxidation of NO during the daytime (36.0% vs 64.0%, respectively) and results provide valuable insight to low-latitude atmospheric chemistry.

Sources and trends of oxidized and reduced nitrogen wet deposition in a typical medium-sized city of eastern China during 2010–2016

Fluxes and composition dynamics of atmospheric nitrogen deposition play key roles in better balancing economic development and ecological environment. However, there are some knowledge gaps and difficulties in urban ecosystems, especially for small and medium-sized cities. In this study, both flux and composition (ratio of NH4+-N to NO3−-N, RN) of wet-deposited dissolved inorganic nitrogen (DIN, sum of NO3−-N and NH4+-N) were estimated and sources were identified at a long-term urban observation station in Tongling, a typical medium-sized city in eastern China during 2010–2016, respectively. Results showed that wet-deposited DIN fluxes were 33.20 and 28.15 kgN ha−1 yr−1 in Tongling city during 2010–2011 and 2015–2016, respectively. Compared to these two periods, both DIN and NO3−-N fluxes decreased by 15.2% and 31.8% for a series of NOx abatement measures applied effectively, respectively. At the same time, the NH4+-N flux remained stable and ranged from 19.53 to 20.62 kgN ha−1 yr−1, and the RN increased from 1.7 to 2.2. Seasonally, winds from the southwest and west-southwest with higher frequencies and speeds in spring and summer brought more NH4+-N and DIN wet deposition from an ammonia plant, which could threaten the safety of regional hydrosphere ecosystems. On the whole, the wet-deposited NH4+-N was threatening regional ecosystems of both the hydrosphere and forest. The wet-deposited DIN including NH4+-N in Tongling city stemmed mainly from a combined source of coal combustion and dust from Cu extraction and smelting, ammonia production, and roads. Therefore, production lines should be updated for Cu extraction and smelting industries, thermal power generations and the ammonia plant, old vehicles should be eliminated, and the use of new energy vehicles should be promoted for regional sustainable development and human health in the medium-sized city.

Nitrogen wet deposition in the Three Gorges Reservoir area: Characteristics, fluxes, and contributions to the aquatic environment

Measurements of nitrate nitrogen (NO3−-N), ammonia nitrogen (NH4+-N), and dissolved organic nitrogen (DON) in precipitation were conducted at six different sites in the hinterland of the Three Gorges Reservoir (TGR) area from January 2016 to December 2017. The characteristics and the sources of nitrogen (N) species were identified. N flux of wet deposition in the hinterland of the TGR area were 13.56 ± 2.95 kg N ha−1 yr−1, of which the proportions of NO3−-N, NH4+-N and DON were 60.9%, 25.1% and 14.0%, respectively. N flux in urban area was significantly higher than those in suburban, agricultural, and wetland areas. Industrial activities, biomass burning, and secondary transformation were the main contributors of N in urban area. In agricultural area, biomass burning, crustal, and manure were main sources of N. In suburban area, mixed emissions from industry, agriculture, and crustal sources were primary contributors of N. For wetlands, the major contributions were from industrial sector and biomass burning. Additional, analysis of regional distribution of dissolved N deposition in the TGR area was conducted by combining current study data and previously published data between 2000 and 2017. N flux of wet deposition in the entire TGR area ranged from 12.17 to 51.93 kg N ha−1 yr−1, with an average of 26.81 kg N ha−1 yr−1. Regional N distribution was greatest in the tail region, followed by the head region, and then the hinterland in the TGR area. The amount of N entering the TGR directly through atmospheric wet deposition was 2906 t yr−1, accounting for 2.1% of the total N inputs. N load from wet deposition had exceeded the critical loads from that of the water, forest, and even some farmland ecosystems in the TGR area. Decreasing NH3 emissions from agricultural activities is the key to alleviate the regional N deposition.

Temporal and spatial patterns of nitrogen wet deposition in different weather types in the Pearl River Delta (PRD), China

The temporal and spatial patterns of nitrogen wet deposition were investigated in the Pearl River Delta (PRD) under different weather types. The study was carried out in 27 monitoring sites with reliable meteorological data from 2010 to 2017. Large spatial variation data showed that both annual volume weighted mean (VWM) concentrations and fluxes were higher in the central PRD while lower in the outer area. The annual mean concentrations and fluxes were in the range of 0.8–1.3 mg N L−1 and 10.9–20.6 kg N ha−1 yr−1, respectively. The monthly mean concentrations and fluxes ranged from 0.1 to 0.2 mg N L−1 and 0.4 to 2.4 kg N ha−1, respectively. Further the study data revealed that the ratio of NH4+/NO3− was 1.1 which was much lower than the ratio reported in other regions like Northern China, Sichuan Basin, the US and Europe. The flux of NH4+ in urban sites was comparable to rural sites, implying that potential non-agricultural NH3 emissions were likely to be high in the PRD. The top three weather types were E, C and SE, with the total contribution of more than a half to the flux. Multiple linear regression was used to set up an equation to predict the variation of annual fluxes under the changes in weather conditions. The result hints that the variation on annual fluxes in the PRD tends to be stable in the next 30 years. Considering the increasing impact on the ecosystem, more effort should be exerted to reduce nitrogen wet deposition in the future.

Hydrochemical Characteristics and Ion Sources of Precipitation in the Upper Reaches of the Shiyang River, China

The Shiyang River Basin is located at the edge of the monsoon wind system of South and Southeast Asia. The hydrochemical characteristics of precipitation are influenced by both monsoon and arid regions. The regression analysis method, comparative analysis, neutralization factor (NF), enrichment factor (EF) and HYSPLIT4 were used to analyze the precipitation samples collected from the upper reaches of the Shiyang River from October 2016 to October 2017. In order to study the hydrochemical characteristics and ion sources of precipitation in this basin. The results, as discussed in this paper, show that the precipitation in the upper reaches of the Shiyang River is mildly alkaline all year round while the neutralization ability of Ca2+ and NH4+ in precipitation is strong. The ion concentration was higher in the dry season than that in the wet season, but the concentration of NH4+ was higher in summer. Furthermore, as the altitude increased, the electrical conductivity (EC) of the precipitation decreased gradually. Influenced by precipitation and rainy days, the wet deposition of nitrogen (N) and sulfur (S) was higher in the wet season than that during the dry season, and the wet deposition gradually increased with the elevation. In precipitation, the earth’s crust is a major source of Ca2+, K+ and Mg2+, the ocean is a major source of Cl−, the ocean and the earth’s crust are the sources of Na+, human activities are the main sources of SO42−, NO3− and NH4+, the amount of F− is very small, its sources are natural and human activities. Water vapor in precipitation mainly comes from westerly air mass circulation and monsoon circulation while the particles come mainly from the earth’s crust.

Agriculture driven nitrogen wet deposition in a karst catchment in southwest China

Nitrogen (N) deposition plays a key role in ecosystem function as one of the major N sources for natural vegetation, particularly in karst agricultural areas with thin soil cover, which drive the karst N fate via rainwater. To understand the seasonal and spatial variation in nitrogen deposition and to identify the major sources of nitrate in wet deposition in a karst agricultural area (Houzhai Catchment) in southwestern China, two sites with different land use were selected to assess wet and dry deposition for one year. Houzhai village (HZV) is an area highly influenced by agriculture, whereas Muzhu reservoir (MZR) is a more pristine environment with less anthropogenic influence. Nitrogenous species and dual nitrate isotopes were analyzed. The results showed that agriculture-derived NH4+ was the major contributor of annual total wet N deposition (>55 %). The contribution of NH4+ to wet N deposition was 1.63 times higher than that of NO3− and dissolved organic nitrogen (DON). The annual nitrogen deposition in this study was approximately twice as much as the average wet N deposition over China, while lower dry N deposition relative to other Chinese monitoring sites was observed. The δ15N-NO3− showed a seasonal trend of negative summer values and positive winter values, which were primarily controlled by the variations in NOx emission sources. Seasonal variation in δ18O-NO3− was mainly controlled by NOx oxidation pathways and showed a similar trend to δ15N-NO3−. The contributions from four endmembers (coal combustion, vehicle exhaust, biomass burning, and soil emission) were calculated using a stable isotope mixing model. Contributions show a clear seasonal variation (except vehicle exhaust), with the four sources accounting for 20.0 %, 25.6 %, 22.9 % and 31.5 % respectively (annual mean probability estimate, AMPE) at HZV, and 19.0 %, 27.8 %, 23.2 % and 30.0 % (AMPE) at MZR. Isotopic evidence determined agricultural soil emission is a major contributor to rainwater during the summer growing season, which can significantly impact the agricultural ecosystems.

Seasonal fluxes and sources apportionment of dissolved inorganic nitrogen wet deposition at different land-use sites in the Three Gorges reservoir area.

To identify seasonal fluxes and sources of dissolved inorganic nitrogen (DIN) wet deposition, concentrations and δ15N signatures of nitrate (NO3-) and ammonium (NH4+) in wet precipitation were measured at four typical land-use types in the Three Gorges reservoir (TGR) area of southwest China for a one-year period. Higher DIN fluxes were recorded in spring and summer and their total fluxes (averaged 7.58kgN ha-1) were similar to the critical loads in aquatic ecosystems. Significant differences of precipitation δ15N were observed for NH4+-N between town and wetland sites in spring and between urban and rural sites in summer. For NO3--N, significant differences of precipitation δ15N were observed between town and rural sites in spring and between urban and town sites in autumn, respectively. Quantitative results of NO3--N sources showed that both biomass burning and coal combustion had higher fluxes at the urban site especially in winter (0.18±0.09 and 0.19±0.08kgN ha-1), which were about three times higher than those at the town site. A similar finding was observed for soil emission and vehicle exhausts in winter. On the whole, DIN wet deposition averaged at 12.13kgN ha-1 yr-1 with the urban site as the hotspot (17.50kgN ha-1 yr-1) and regional NO3--N fluxes had a seasonal pattern with minimum values in winter. The contribution to NO3--N wet deposition from biomass burning was 26.1±14.1%, which is the second dominant factor lower than coal combustion (26.5±12.6%) in the TGR area during spring and summer. Hence N emission reduction from biomass burning, coal combustion and vehicle exhausts should be strengthened especially in spring and summer to effectively manage DIN pollution for the sustainable development in TGR area.

Responses of lake phytoplankton communities to changing inorganic nitrogen supply forms

A shift has been predicted in future nitrogen emission scenarios from nitrous oxide to higher proportions of ammonium compounds. To investigate the interaction between increasing nitrogen load and varying nitrate:ammonium ratios (NO3−:NH4+), we performed a mesocosm experiment in an oligotrophic lake in southern Germany. We fertilized mesocosms with both roughly natural and four times the natural nitrogen wet deposition amounts in molar NO3−:NH4+ ratios of 4:1 and 1:4. We observed greater phytoplankton biomass in treatments with a relatively higher ammonium supply, but not in those with nitrate and total nitrogen load. Ammonium significantly increased the total chlorophyll a concentrations, and especially the growth of small nanophytoplankton species. The effects observed indicate that NH4+ was taken up preferentially and that spring phytoplankton in oligotrophic lakes appear to be able to respond to variations in nitrogen forms (available NO3−:NH4+ ratios) by adjusting their community composition. Such communal changes at the base of the food web may affect higher trophic levels. Therefore, the effects of varying available forms of nitrogen should also be considered in primarily phosphorus-limited aquatic systems.

Wet deposition of sulfur and nitrogen at Mt. Emei in the West China Rain Zone, southwestern China: Status, inter-annual changes, and sources

The West China Rain Zone (WCRZ) is of ecological importance and thus, anthropogenic impacts on its vitality are of concern. To ascertain if China's SO2 and NOx emissions reductions in the recent years are reflected in reduced impacts, sulfur and nitrogen wet deposition at Mt. Emei was observed during 2017–2019. The source contributions to sulfur and nitrogen wet deposition were estimated using the positive matrix factorization (PMF) and the source-oriented Community Multi-scale Air Quality (CMAQ) model. The annual Volume Weighted Mean (VWM) pH of precipitation increased from 4.01 to 4.75 in the 1980s–2000s to 5.39 in 2017–2019. However, 12% of the samples during 2017–2019 had pH < 4.50. The VWM SO42− concentration decreased from 80.9 to 26.0 μeq L−1 from 2007–2009 to 2017–2019. The VWM NO3− concentration (18.3 μeq L−1) in 2017–2019 was close to that measured in 2007–2009. Although the dry deposition fluxes onto forest canopy were under-estimated, the mean annual total wet and dry deposition flux of nitrogen (24.3 kg N ha−1 yr−1) was higher than the critical load (CL: 10.0–15.0 kg N ha−1 yr−1), while the flux of sulfur (12.1 kg S ha−1 yr−1) was lower than the CL (16.0–32.0 kg S ha−1 yr−1). The annual wet deposition fluxes of SO42− and NO3− were mainly from industries (54% and 43%, respectively) and power plants (21% and 25%, respectively), and that of NH4+ was mostly from agriculture (88%). Emissions within and outside the Sichuan Basin (SCB) were both important sources of the wet deposition fluxes of sulfur (45% and 39%, respectively) and nitrogen (68% and 29%, respectively), and other unidentified sources accounted for 16% and 3% of the sulfur and nitrogen fluxes, respectively. This study suggests that to protect Mt. Emei's ecosystems, efforts are needed to further control sulfur and nitrogen deposition through reducing emissions within and outside the SCB.

Wet atmospheric deposition of nitrogen and phosphorus and estimation of their contributions to the lake in typical subtropical reservoir basins

Wet atmospheric deposition of nitrogen and phosphorus and estimation of their contributions to the lake in typical subtropical reservoir basins

Effects of wet atmospheric nitrogen deposition on epiphytic lichens in the subtropical forests of Central China: Evaluation of the lichen food supply and quality of two endangered primates.

Over the last few decades, the threat posed to biodiversity and ecosystem function by atmospheric nitrogen (N) deposition has been increasingly recognized. The disturbed nutrient balance and species composition of plants induced by higher N deposition can impact the biodiversity of the organisms that consume the plants. In this research, we implemented several experiments to estimate the effects of increased N deposition on the growth, survival, and nutrients of the dominant epiphytic lichens in the subtropical mountains in Central China to assess the lichen food amount and nutritional quality for two endangered primates endemic to China. Our results indicated that the thallus growth and propagule survival of the lichens were significantly decreased when nitrogen addition changed from 6.25 to 50.0kgN·ha-1·y-1; it was also shown that lichen biomass could be decreased by 11.2%-70.2% when the deposition addition exceeded 6.25kgN·ha-1·y-1. Further, our study revealed that increased nitrogen deposition also reduced the nutritional quality of the lichens via reducing the soluble protein and soluble sugar levels and increasing the fiber content, which would substantially affect the diet selection of the plants consumers in the region, particularly the populations of the two lichen-eating endangered primate species, Rhinopithecus roxellana and R. bieti. Our experimental study suggested that the nitrogen pollution derived from anthropogenic activities could cause cascading effects for the whole forest ecosystem of Central China; thus, more studies about nitrogen deposition in this region are required.

Are typhoon and marine eutrophication the possible missing sources of high dissolved organic nitrogen in wet deposition?

The aim of this study is to elaborate a possible missing source of high-throughput organic nitrogen in rainfall. The authors classified the observed flux data of dissolved organic nitrogen in terms...

Characteristics, sources and environmental implications of atmospheric wet nitrogen and sulfur deposition in Yangtze River Delta

Nitrogen (N) and sulfur (S) deposition rates have changed rapidly in China during recent years. But few studies have simultaneously measured wet N and S deposition rates on different land use types in the same region. In present study, 238 precipitation samples were collected between May 2016 and April 2017 using wet-only auto-samplers, and the wet N and S deposition rates were measured at three sites with different land use types (urban, agriculture, and lake) in the Yangtze River Delta (YRD), Eastern China. The annual wet deposition rates of total N (TN), ammonium (NH4+), nitrate (NO3−), dissolved organic N (DON), water-insoluble particulate N (WIPN), and sulfate (SO42−) were 16.87–26.64, 6.38–10.81, 5.92–11.11, 1.43–1.96, 2.23–2.67, and 9.07–22.53 kg N (S) ha−1 yr−1, respectively. The wet N and S deposition rates were in the order: agriculture > urban > lake sites, and the seasonal variations in wet N and S deposition were similar at all sites. DON and WIPN contributed 6.4–11.8% and 10.7–16.2% of the total wet N deposition, respectively. Chemical N fertilization and fossil fuel were important sources of wet N and S deposition. Annual wet N and S deposition are important nutrient sources that stimulate the eutrophication and soil/water acidification in the YRD. To minimize the environmental cost of wet N and S deposition in the YRD, it is critical to investigate the sources of N and S.

Inorganic nitrogen wet deposition gradients in the Denver-Boulder metropolitan area and Colorado Front Range - Preliminary implications for Rocky Mountain National Park and interpolated deposition maps.

For the first time in the 40-year history of the National Atmospheric Deposition Program/National Trends Network (NADP/NTN), a unique urban-to-rural transect of wet deposition monitoring stations was operated as part of the NTN in 2017 to quantify reactive inorganic nitrogen wet deposition for adjacent urban and rural, montane regions. The transect of NADP stations (sites) was used to collect continuous precipitation depth and weekly wet-deposition samples in the Denver - Boulder, Colorado, urban corridor. Gradients in reactive inorganic nitrogen (Nr) concentrations and wet deposition were identified along the transect, which included Rocky Mountain National Park. Back trajectory modeling and stable isotopes suggested contribution of agricultural ammonia (NH3) to urban Nr wet deposition in Denver, but apportionment of wet-deposited Nr to agricultural versus urban mobile sources was not possible for this study. The results demonstrate the importance of multiple monitoring sites across an urban area in defining fine-scale geographic patterns in atmospheric deposition and its sources. Data from new sites located within 50 km of the urban area demonstrate that the urban influence does not extend as far as the inverse distance weighting would have suggested without such empirical monitoring data. It is important to determine the radius of influence of urban emissions and associated deposition on the interpolated deposition raster, which is constrained by a paucity of monitoring sites east of Denver.

Long-term trends of wet inorganic nitrogen deposition in Rocky Mountain National Park: Influence of missing data imputation methods and associated uncertainty

Excess reactive nitrogen (Nr) deposition is occurring in Rocky Mountain National Park and impacting sensitive ecosystems. In 2006, the National Park Service, State of Colorado, and Environmental Protection Agency established the goal to reduce Nr deposition to below the ecosystem critical load by 2032. Progress is tracked using 5-year averages of annual wet inorganic nitrogen (IN) deposition measured at Loch Vale, Colorado, by the National Atmospheric Deposition Program (NADP). This remote high alpine site is challenging to operate, and large fractions of the annual precipitation, at times >40%, had invalid IN concentrations. Annual wet IN deposition is calculated using the NADP protocol, which replaces missing concentrations with the annual precipitation-weighted mean (PWM) concentration of valid samples. This protocol does not account for seasonal variations in IN concentrations and the inverse relationship between concentration and precipitation amounts. Invalid samples occurred more frequently in the winter and at high and low precipitation amounts, and the NADP protocol generally overestimated annual deposition rates, by as much as 20%. Here, a new method for imputing missing weekly IN concentrations that accounts for their seasonal and precipitation dependence is introduced. Using a bootstrapping analysis shows that the new method reduced the errors in the annual deposition rates by about 30% compared to the NADP protocol and the biases were near zero. The overall trend in the wet IN deposition rates was found to be flat from 1990 to 2017, but the nitrate contribution decreased about 33%, which was offset by a nearly equal increase in ammonium wet deposition. These trends are consistent with known changes in nitrate and ammonium precursor emissions. The long-term trends in the annual IN deposition rates were similar using both data imputation methods, but the 2013–2017 average was about 10% smaller using the new method.

Atmospheric dry and bulk nitrogen deposition to forest environment in the North China Plain

Atmospheric nitrogen (N) deposition fluxes has dramatically increased in past few decades and has aroused great concerns of its impacts on forest ecosystems. However, complete quantitative information on dry and wet deposition of various reactive nitrogen (Nr) species is very limited for forest environments. Therefore, two-year (2014–2015) measurements of gaseous NH3, NO2, and HNO3 and particulate NH4+ and NO3− (pNH4+ and pNO3-) in air and/or precipitation were conducted in Jigong Mountain National Nature Reserve in the North China Plain (NCP). Our results showed that ambient concentrations of all Nr species were highest in winter and lowest in summer except for NH3; conversely, bulk deposition fluxes of each Nr species generally peaked in summer and were lowest in winter. Annual mean bulk Nr deposition fluxes was 15.5 kg N ha−1 yr−1 (7.9 kg N ha−1 yr−1 for NH4+ and 7.6 kg N ha−1 yr−1 for NO3−), with higher monthly fluxes occurring in spring and summer. Average annual dry Nr deposition fluxes was 44.3 kg N ha−1 yr−1 (30.1 kg N ha−1 yr−1 for reduced N (NH3 plus pNH4+) and 14.2 kg N ha−1 yr−1 for oxidized N (the sum of HNO3, NO2 and pNO3-). Total Nr deposition fluxes (dry plus bulk) reached 59.8 kg N ha−1 yr−1 with more contributions from reduced N than from oxidized N (64% vs 36%). When consider the N critical load (10–20 kg N ha−1 yr−1) in forest ecosystem, potential negative effects may cause by N deposition in the NCP which should be paid more attention.

A database of atmospheric nitrogen concentration and deposition from the nationwide monitoring network in China

Atmospheric nitrogen (N) deposition has increased substantially across China since 1980; however, data for N deposition fluxes since the 2000s has been very limited. Understanding and mitigating the impacts of N deposition requires long-term quantification of dry as well as wet deposition of key reactive nitrogen (Nr) species. Here we present a dataset for inorganic N concentrations and deposition for the period 2010–2015 in China, compiled from the nationwide deposition monitoring network. The dataset comprises information from 32 monitoring sites on concentrations and bulk deposition (wet plus part of dry deposition) fluxes of NH4+-N and NO3−-N, air concentrations and dry deposition fluxes of the major Nr species NH3, NO2, HNO3, and particulate NH4+ and NO3−. This unique database is available inter alia to advance understanding of the spatial patterns of inorganic N concentrations and deposition in China and its associated effects, constrain primary Nr (e.g., NH3, NOx) emission inventories, and validate outputs of atmospheric chemistry and transport models.

Nitrogen dry deposition to Lake Superior and Lake Michigan

Abstract Nitrate (NO3−) levels in Lake Superior have increased from historic levels of about 5 μM to its current concentration of about 25 μM. The atmosphere makes a substantial contribution to the nitrogen budgets for Lake Superior and Lake Michigan. This study provides a more well-defined estimate of nitrogen dry deposition rates derived from the measurement of over-water concentrations, and in situ meteorological measurements, which were input into the Resistance Model. We obtained a nitrogen dry deposition rate of [(3.41 ± 2.26) × 107 kg N/yr; (5.90 ± 3.91) kg N/ha/yr] over Lake Michigan, and [(1.54 ± 1.06) × 107 kg N/yr; (1.87 ± 1.27) kg N/ha/yr] over Lake Superior. Nitric acid (HNO3), which originates from the combustion of fossil fuels, contributes 84% of the total nitrogen dry deposition to Lake Michigan; and 66% to Lake Superior. Ammonia (NH3), which originates from agricultural activities and gasoline combustion, is the second highest contributor of nitrogen dry deposition to both lakes: contributing 13% to Lake Michigan and 32% to Lake Superior. The nitrogen dry deposition is approximately 68% of the nitrogen wet deposition over Lake Superior, and approximately 80% of wet deposition over Lake Michigan. The over-water dry deposition velocity of HNO3 and NH3 were also evaluated. We obtained morning deposition velocities of 0.099 cm/s for NH3 and 0.095 cm/s for HNO3; and afternoon values of 0.137 cm/s for NH3 and 0.132 cm/s for HNO3. Another key finding is that the atmospheric concentrations of nitrogen compounds near Lake Michigan and Lake Superior have decreased since 2003.