Wet Nitrogen Deposition Research Articles

The composition, seasonal variation, and potential sources of the atmospheric wet sulfur (S) and nitrogen (N) deposition in the southwest of China.

The composition, seasonal variation, and potential sources of sulfate (S) and nitrogen (N) deposition in precipitation in the southwest of China from 2003 to 2013 were investigated. The results showed that the concentration of SO4 (2-), NO3 (-), and NH4 (+) in rainwater were 10.57-1360, 7.16-523.71, and 7.54-1020 μeq l(-1), with an annual volume-weighted mean (VWM) concentration of 103.99, 46.73, and 97.30 μeq l(-1), respectively. The annual wet deposition of SO4 (2-), NO3 (-), and NH4 (+) was 21.66, 8.16, and 17.49 kg S (N) ha(-1), respectively. The temporal variations of the ions showed that the abrupt decreasing breakpoints were in 2008 for SO4 (2-) and in 2009 for NO3 (-) and NH4 (+), and increasing trends were observed after 2010 for the three ions. These trends reflected the effect of economy recession and the policy of controlling SO2 and NOx emissions. The acid rain type of precipitation was shifted from sulfur to a mixed one. The ions of SO4 (2-), NO3 (-), and NH4 (+) presented high values in winter and spring and low values in autumn and summer. A highly positive linear correlation between SO4 (2-) and NO3 (-) (R(2) = 0.71), SO4 (2-) and NH4 (+) (R(2) = 0.74), and NO3 (-) and NH4 (+) (R(2) = 0.84) existed while a strong negative correlation was found between the three main ionic concentrations and precipitation. The SO4 (2-) was mainly from fossil fuel combustion (60.53%), aged sea salt (19.03%), agriculture (11.38%), crust (6.66%), and biomass burning (2.40%); the NO3 (-) was mainly from fossil fuel combustion (75.41%), biomass burning (9.67%), aged sea salt (7.97%), and agriculture (6.96%); and the NH4 (+) was mainly from agriculture (86.38%), fossil fuel combustion (10.52%), and aged sea salt (3.09%).

Wet deposition of atmospheric inorganic nitrogen at five remote sites in the Tibetan Plateau

Abstract. Since the mid-20th century, nitrogen (N) deposition has shown an increasing trend in the Tibetan Plateau (TP), where alpine ecosystems are sensitive to elevated N deposition. However, the quantitative characterization of N deposition in the TP remains unclear, due in most part to the lack of in situ measurement. Using the Tibetan Observation and Research Platform network, we conducted short-term in situ measurements of major ions (NO3−, Cl−, SO42−, NH4+, Na+, K+, Ca2+, and Mg2+) wet deposition at five remote sites in the TP during 2011–2013. At Southeast Tibet Station, Nam Co Station, Qomolangma Station, Ngari Station, and Muztagh Ata Station, the NH4+–N wet deposition was 0.63, 0.68, 0.92, 0.36, and 1.25 kg N ha−1 yr−1, respectively; the NO3−–N wet deposition was 0.28, 0.24, 0.03, 0.08, and 0.30 kg N ha−1 yr−1, respectively; and the inorganic N wet deposition was 0.91, 0.92, 0.94, 0.44, and 1.55 kg N ha−1 yr−1, respectively. The inorganic N wet deposition mainly occurred in the form of NH4+–N during summer at all sites. Results of enrichment factor analysis and principal component analysis demonstrated that both NH4+–N and NO3−–N wet deposition in the TP were mainly influenced by anthropogenic activities. Backward trajectory analysis showed that the inorganic N deposition at Muztagh Ata Station was mainly transported from central Asia and the Middle East through westerlies. At Southeast Tibet Station, Nam Co Station, Qomolangma Station, and Ngari Station, the inorganic N deposition was mainly contributed by anthropogenic sources in south Asia, and was mainly transported by the Indian monsoon. Combining site-scale in situ measurements of inorganic N wet deposition in this and previous studies, the average wet deposition of atmospheric NH4+–N, NO3−–N, and inorganic N in the TP was estimated to be 1.06, 0.51, and 1.58 kg N ha−1 yr−1, respectively. The average NH4+–N : NO3−–N ratio in precipitation in the TP was approximately 2 : 1. Results from the present study suggest that earlier estimations based on chemical transport model simulations and/or limited field measurements likely overestimated substantially the regional inorganic N wet deposition in the TP. To clarify the total N deposition in the TP more clearly, it is essential to conduct long-term monitoring of both wet and dry deposition of atmospheric N in various climate zones in the TP in the future.

Inorganic nitrogen wet deposition: Evidence from the North-South Transect of Eastern China

We examined the spatio-temporal variation of dissolved inorganic nitrogen (DIN) deposition in eight typical forest ecosystems of Eastern China for three consecutive years. DIN deposition exhibited an increasing gradient from north to south, with N−NH4+ as the predominant contributor. DIN deposition in precipitation changed after interaction with the forest canopy, and serious ecological perturbations are expected in this region. DIN deposition presented seasonal fluctuations, which might be ascribed to agricultural activity, fossil-fuel combustion and environmental factors (i.e., wind direction, soil temperature). Notably, N fertilizer use (FN), energy consumption (E), and precipitation (P) jointly explained 84.3% of the spatial variation in DIN deposition, of which FN (27.2%) was the most important, followed by E (24.8%), and finally P (9.3%). The findings demonstrate that DIN deposition is regulated by precipitation mainly via anthropogenic N emissions, and this analysis provides decision-makers a novel view for N pollution abatement.

Dissolved organic nitrogen in wet deposition in a coastal city (Keelung) of the southern East China Sea: Origin, molecular composition and flux

In this study, we collected and analyzed rainwater samples from Keelung, Taiwan, which is a coastal city located south of the East China Sea (ECS). From January 2012 until June 2013, 78 rainwater samples were collected over an 18-month period and were analyzed to examine the total dissolved nitrogen (TDN) and major ions in the rainwater. TDN can be divided into dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen (DON). This study, which focused on the composition of DON, is the first study to employ ultrafiltration to separate DON in wet deposition into low molecular weight-DON (LMW-DON) and high molecular weight-DON (HMW-DON). The concentrations of dissolved nitrogen species observed in the research area between November 2012 and April 2013 were relatively high, whereas those observed between May 2013 and October 2012 were relatively low. The patterns of changes over time were similar to those of non-sea-salt (nss) ions. The concentration of nss-ions was high during months in which the total dissolved nitrogen concentration was also high, which occur frequently during the spring and winter. In addition, the concentration of nss-ions was low during months in which the TDN concentration was low, which primarily occurs during the summer. The amounts of DIN and DON accounted for 63 ± 5% and 37 ± 5% of the TDN, respectively, and the percentage of the DIN was higher during the spring and winter. The concentrations of LMW-DON and HMW-DON, which accounted for 84 ± 3% and 16 ± 3% of the DON, respectively, were both high in the winter and low in the summer. The percentage of LMW-DON increased in the summer, possibly because of the numerous oceanic air masses and typhoons. Furthermore, the percentage of HMW-DON increased in the spring, potentially due to biomass burning during agricultural activities. Regarding the wet deposition fluxes, the DIN (197 ± 10.27 mmol m−2 yr−1) and DON (129 ± 6.82 mmol m−2 yr−1) accounted for approximately 64% and 36% of the TDN, respectively, and the LMW-DON (108 ± 5.97 mmol m−2 yr−1) and HMW-DON (19 ± 1.02 mmol m−2 yr−1) accounted for 85% and 15% of the DON, respectively. The wet deposition flux of the nitrogen species observed in the research area was 332 ± 16.0 mmol m−2 yr−1, and the total flux (dry and wet deposition) was approximately 393.4 ± 25.2 mmol m−2 yr−1 (5508 ± 353 mg N m−2 yr−1).

Liu et al. suspect that Zhu et al. (2015) may have underestimated dissolved organic nitrogen (N) but overestimated total particulate N in wet deposition in China

In a recent publication in the journal Science of the Total Environment, Zhu et al. (2015) reported the composition, spatial patterns, and factors influencing atmospheric wet nitrogen (N) deposition based on one year's data from 41-monitoring sites in China. We suspect their results may largely underestimate dissolved organic N (DON) but overestimate total particulate N (TPN) in wet deposition due to the uncertainty resulting from the sampling, storage and analysis methods in their study. Our suspicions are based mainly on our experience from earlier measurements and the literature. We therefore suggest that enhanced data quality control on atmospheric N deposition measurements should be taken into account in future studies.

The composition, spatial patterns, and influencing factors of atmospheric wet nitrogen deposition in Chinese terrestrial ecosystems

Atmospheric nitrogen (N) deposition is an important component of the global N cycle, and is a key source of biologically available N. Understanding the spatio-temporal patterns and influencing factors of N deposition is essential to evaluate its ecological effects on terrestrial ecosystems, and to provide a scientific basis for global change research. In this study, we monitored the monthly atmospheric N deposition in rainfall at 41 stations from the Chinese Ecosystem Research Network through measuring total N (TN), total dissolved N (TDN), ammonium (NH4+–N), and nitrate (NO3−–N). The results showed that the atmospheric wet deposition of TDN, NH4+–N, and NO3−–N were 13.69, 7.25, and 5.93kgNha−1yr−1, respectively. The deposition of TN and total particulate N (TPN) was 18.02 and 4.33kgNha−1yr−1 respectively, in 2013. TPN accounted for 24% of TN, while NH4+–N and NO3−–N made up 40% and 33%, respectively, confirming the assumption that atmospheric wet N deposition would be underestimated without particulate N in rainfall. The N deposition was higher in Central and Southern China, and lower in North-west, North-east, Inner Mongolia, and Qinghai–Tibet regions. Precipitation, N fertilizer use, and energy consumption were significantly correlated with wet N deposition (all p<0.01). Models that included precipitation and N fertilizer can explain 80–91% of the variability in wet N deposition. Our findings reveal, for the first time, the composition of the wet N deposition in China at different scales and highlight the importance of TPN.

Evaluation of the CHIMERE model estimating wet deposition in Spain

An evaluation of how CHIMERE estimates the wet deposition of sulphur and nitrogen (oxidised and reduced) on the Iberian Peninsula was performed. The CHIMERE estimates were compared with monthly data measured in the Spanish EMEP stations covering a period of four years (2005-2008) and with results of the EMEP model. The seasonal and spatial variability have also been studied. The model system formed by WRF and CHIMERE underpredicts the wet deposition of reduced nitrogen, while the results for oxidised nitrogen are better than those of the ECMWF-IFS/EMEP model system. WRF/CHIMERE estimates of wet deposition of sulphur seem to correlate quite well with observations, but there is some slight underprediction. Monthly rainfall estimates by both WRF and ECMWF-IFS meteorological models fit observations quite well, with somewhat worse results in summer and at southeastern stations. The reason why wet deposition estimates are not as good as desirable seems not to be related to how the models simulate precipitation.

Responses of beech and spruce foliage to elevated carbon dioxide, increased nitrogen deposition and soil type.

Although enhanced carbon fixation by forest trees may contribute significantly to mitigating an increase in atmospheric carbon dioxide (CO2), capacities for this vary greatly among different tree species and locations. This study compared reactions in the foliage of a deciduous and a coniferous tree species (important central European trees, beech and spruce) to an elevated supply of CO2 and evaluated the importance of the soil type and increased nitrogen deposition on foliar nutrient concentrations and cellular stress reactions. During a period of 4 years, beech (represented by trees from four different regions) and spruce saplings (eight regions), planted together on either acidic or calcareous forest soil in the experimental model ecosystem chambers, were exposed to single and combined treatments consisting of elevated carbon dioxide (+CO2, 590 versus 374 μL L(-1)) and elevated wet nitrogen deposition (+ND, 50 versus 5 kg ha(-1) a(-1)). Leaf size and foliage mass of spruce were increased by +CO2 on both soil types, but those of beech by +ND on the calcareous soil only. The magnitude of the effects varied among the tree origins in both species. Moreover, the concentration of secondary compounds (proanthocyanidins) and the leaf mass per area, as a consequence of cell wall thickening, were also increased and formed important carbon sinks within the foliage. Although the species elemental concentrations differed in their response to CO2 fertilization, the +CO2 treatment effect was weakened by an acceleration of cell senescence in both species, as shown by a decrease in photosynthetic pigment and nitrogen concentration, discolouration and stress symptoms at the cell level; the latter were stronger in beech than spruce. Hence, young trees belonging to a species with different ecological niches can show contrasting responses in their foliage size, but similar responses at the cell level, upon exposure to elevated levels of CO2. The soil type and its nutrient supply largely determined the fertilization gain, especially in the case of beech trees with a narrow ecological amplitude.

Urbanization in China changes the composition and main sources of wet inorganic nitrogen deposition.

Nowadays, nitrogen (N) deposition has become a growing global concern due to urbanization activities increasing the large amount of reactive N in the atmosphere. However, it remains unclear whether urbanization affects the composition and main sources of N deposition in rapidly urbanizing areas such as in China. One-year measurement of wet inorganic N deposition was conducted using ion-exchange resin (IER) columns in the range of 260 km from urban to rural areas in the Pearl River Delta (PRD) region, south China. An increasing pattern of wet inorganic deposition along the urbanization gradient was observed and it increased in the order: rural (15.26 ± 0.20 kg N ha(-1) year(-1)) < suburban/rural (21.45 ± 3.73 kg N ha(-1) year(-1)) < urban (31.16 ± 0.44 kg N ha(-1) year(-1)) < urban/suburban sites (34.15 ± 5.73 kg N ha(-1) year(-1)). Nitrate N (NO3 (-)-N) accounted for 53.5-79.1 % of total wet inorganic N deposition, indicating a significant negative correlation with distance from the urban core. Based on moss δ(15)N-values the main source of NO3 (-)-N was considered to be emitted from vehicles. Our results demonstrate that urbanization has large impacts on the regional pattern of wet inorganic N deposition. Thus, controlling NOx emission, especially vehicle emission will become an effective strategy for N pollution abatement in China.

Atmospheric wet deposition of sulfur and nitrogen in Jiuzhaigou National Nature Reserve, Sichuan Province, China

In the last two decades, remarkable ecological changes have been observed in Jiuzhaigou National Nature Reserve (JNNR). Some of these changes might be related to excessive deposition of sulfur (S) and nitrogen (N), but the relationship has not been quantified due to lack of monitoring data, particularly S and N deposition data. In this study, we investigated the concentrations, fluxes, and sources of S and N wet deposition in JNNR from April 2010 to May 2011. The results show that SO42−, NO3−, and NH4+ concentrations in the wet deposition were 39.4–170.5, 6.2–34.8, and 0.2–61.2μeqL−1, with annual Volume-Weighted Mean (VWM) concentrations of 70.5, 12.7, and 13.4μeqL−1, respectively. Annual wet deposition fluxes of SO42−, NO3−, and NH4+ were 8.06, 1.29, and 1.39kgS(N)ha−1, respectively, accounting for about 90% of annual atmospheric inputs of these species at the monitoring site. The results of Positive Matrix Factorization (PMF) analysis show that fossil fuel combustion, agriculture, and aged sea salt contributed to 99% and 83% of annual wet deposition fluxes of SO42− and NO3−, respectively. Agriculture alone contributed to 89% of annual wet deposition flux of NH4+. Although wet deposition in JNNR was polluted by anthropogenic acids, the acidity was largely neutralized by the Ca2+ from crust and 81% of wet deposition samples had a pH higher than 6.00. However, acid rain mainly caused by SO42− continued to occur in the wet season, when ambient alkaline dust concentration was lower. Since anthropogenic emissions have elevated S and N deposition and caused acid rain in JNNR, further studies are needed to better quantify the regional sources and ecological effects of S and N deposition for JNNR.

Changes in wet nitrogen deposition in the United States between 1985 and 2012

The United States (US) is among the global hotspots of nitrogen (N) deposition and assessing the temporal trends of wet N deposition is relevant to quantify the effectiveness of existing N regulation policies and its consequent environmental effects. This study analyzed changes in observed wet deposition of dissolved inorganic N (DIN = ammonium + nitrate) in the US between 1985 and 2012 by applying a Mann–Kendall test and Regional Kendall test. Current wet DIN deposition (2011–2012) data were used to gain insight in the current pattern of N deposition. Wet DIN deposition generally decreased going from Midwest > Northeast > South > West region with a national mean rate of 3.5 kg N ha−1 yr−1. Ammonium dominated wet DIN deposition in the Midwest, South and West regions, whereas nitrate and ammonium both contributed a half in the Northeast region. Wet DIN deposition showed no significant change at the national scale between 1985 and 2012, but profound changes occurred in its components. Wet ammonium deposition showed a significant increasing trend at national scale (0.013 kg N ha−1 yr−2), with the highest increase in the Midwest and eastern part of the South region. Inversely, wet nitrate deposition decreased significantly at national scale (−0.014 kg N ha−1 yr−2), with the largest reduction in the Northeast region. Overall, ratios of ammonium versus nitrate in wet deposition showed a significant increase in all the four regions, resulting in a transition of the dominant N species from nitrate to ammonium. Distinct magnitudes, trends and patterns of wet ammonium and nitrate deposition suggest the needs to control N emissions by species and regions to avoid negative effects of N deposition on ecosystem health and function in the US.

Relationship between site-specific nitrogen concentrations in mosses and measured wet bulk atmospheric nitrogen deposition across Europe

To assess the relationship between nitrogen concentrations in mosses and wet bulk nitrogen deposition or concentrations in precipitation, moss tissue and deposition were sampled within a distance of 1 km of each other in seven European countries. Relationships for various forms of nitrogen appeared to be asymptotic, with data for different countries being positioned at different locations along the asymptotic relationship and saturation occurring at a wet bulk nitrogen deposition of ca. 20 kg N ha−1 yr−1. The asymptotic behaviour was more pronounced for ammonium-N than nitrate-N, with high ammonium deposition at German sites being most influential in providing evidence of the asymptotic behaviour. Within countries, relationships were only significant for Finland and Switzerland and were more or less linear. The results confirm previous relationships described for modelled total deposition. Nitrogen concentration in mosses can be applied to identify areas at risk of high nitrogen deposition at European scale.

Assessing the Impact of Locally Produced Aerosol on the Rainwater Composition at the Gosan Background Site in East Asia

It is often assumed that atmospheric observations at remote sites represent long-range transport of airborne material, and local influences are overlooked. We evaluated the impact of local input on the rainwater composition at Gosan Station, a strategic site for monitoring the continental outflow from Asia. We analyzed a 14-year record of rainwater chemical composition archived by the Korea Meteorological Administration and detected local terrestrial contribution for nitrate, sulfate and ammonium. We also measured the chemical composition of rainwater sampled simultaneously at multiple locations within the premises of the Gosan Station, from which local influence with meter-scale spatial heterogeneity could be discerned. We estimate that the local input accounted for at least ~10% of the wet deposition of nitrogen and ~12% of the wet deposition of sulfur during the 14 years. This highlights the significance of the local influence, which should be carefully assessed when interpreting atmospheric observations at this site.

Atmospheric wet deposition of nitrogen and sulfur in the agroecosystem in developing and developed areas of Southeastern China

Atmospheric nitrogen (N) and sulfur (S) deposition is a significant and growing issue for ecological environment in many parts of the world such as China. However, the study on atmospheric deposition, especially N deposition, is still at the initial stage and usually neglected in agro-ecosystems. To assess the characteristics of N and S wet deposition in agro-ecosystems, we selected Yingtan Station (YTS) located in the developing area and Changshu Station (CSS) in the developed area as typical, agricultural study sites in Southeastern China during 2010–2011. In the two areas, the total N and S wet deposition were in ranges of 30.49–37.37 kg ha−1 year−1 N and 56.02–59.06 kg ha−1 year−1 S, respectively, surpassing their corresponding critical loads in China. The annual means of NH4+–N, NO3−–N and dissolved organic N (DON) deposition contributed 49.6%, 26.4% and 24.0% of the total deposition, respectively. Similar total N and S deposition data were observed in the two sites, but their N species, especially DON, were different due to different numbers of slaughter pigs and types of N fertilizers applied. In conclusion, DON was identified as an important contributor to the total N deposition and should also be monitored in the future. Such high N and S deposition would deteriorate agroecosystems in Southeastern China. Related political measures on livestock industries, managements of motor vehicles and technologies of coal and oil combustion should be improved timely and implemented effectively for reducing the regional N emission and deposition in the future.

Spatial and decadal variations in inorganic nitrogen wet deposition in China induced by human activity

Atmospheric nitrogen (N) deposition, an important component in the global N cycle, has increased sharply in recent decades in China. Here, we constructed national-scale inorganic N wet deposition (Ndep) patterns in China based on data from 280 observational sites and analysed the effects of anthropogenic sources and precipitation on Ndep. Our results showed that the mean Ndep over China increased approximately 25%, from 11.11 kg ha−1 a−1 in the 1990s to 13.87 in the 2000s. Ndep was highest over southern China and exhibited a decreasing gradient from southern to western and northern China. The decadal difference in Ndep between the 1990s and 2000s was primarily caused by increases in energy consumption and N fertiliser use. Our findings conformed that anthropogenic activities were the main reason for the Ndep increase and provide a scientific background for studies on ecological effects of N deposition in China.

我国雷州半岛典型农田大气氮沉降研究

近一个半世纪以来，粮食和能源需求导致活性氮创造的急剧增加，从而导致各种活性氮的排放及其沉降的增加。氮沉降引起土壤酸化，水体富营养化，及敏感生态系统植物多样性的丧失等不良生态效应。因此定量不同生态系统氮沉降量对于确定该地区生态系统安全及氮循环有重要意义。南方地区氮沉降已有较多研究，主要集中于湿沉降的研究，选取雷州半岛地区典型农田综合研究了大气氮素的干湿沉降。结果表明：大气活性氮浓度NH₃、HNO₃、NO₂、pNH₄⁺和pNO₃^-浓度分别为5.62、0.88、3.16、3.30、2.02 μg N/m³。采用欧洲氮沉降监测网的氮干沉降速率估算了大气氮干沉降量为17.6 kg N hm^-2 a^-1。大气降雨NO₃^--N浓度为 （0.86±0.36） mg N/L， NH₄⁺-N浓度为（1.11±0.68） mg N/L，大气降雨无机氮含量冬季最高，夏季最低。大气无机氮年湿沉降总量为25.3 kg N/hm²。湿沉降NH₄⁺-N和NO₃^--N， 干沉降NH₃、HNO₃、NO₂、pNH₄⁺、pNO₃^-分别占沉降量的30.8%、28.0%、23.7%、5.4%、2.8%、3.9%、5.4%。湿沉降NH₄⁺和干沉降NH₃在氮沉降中占主导地位显示氮肥施用导致的NH₃挥发对大气活性氮浓度及氮沉降的显著贡献。鉴于研究可观的氮沉降量（总沉降量42.9 kg N hm^-2 a^-1），其向农田的养分的输入不容忽视； 氮沉降对该地区水体，自然生态系统的环境影响需要受到重视。;Reactive nitrogen (Nr) creation has increased sharply over the past 150 years because, as the world population has increased, food and energy consumption have also increased continuously. Consequently, Nr emissions and nitrogen deposition have increased rapidly since the Industrial Revolution. Nitrogen deposition causes a series of environmental problems, including soil acidification, water eutrophication, loss of plant diversity in sensitive ecosystems and indirect N₂O emissions. The Leizhou Peninsula is famous for cash crop cultivation. Because of the specific meteorological characteristics of this area, for example, the high air temperature, high annual rainfall and strong winds, quantifying nitrogen deposition may be very important for evaluating nitrogen cycling in cropland and other related environmental impacts. Previous studies undertaken in this area have considered wet nitrogen deposition. In our study, we investigated total wet and dry nitrogen deposition in a typical cropland in Zhanjiang. The atmospheric concentrations of NH₃, HNO₃, NO₂, pNH₄⁺ and pNO₃^- were 5.62, 0.88, 3.16, 3.30 and 2.02 μg N/m³, respectively, over the duration of the sampling period. The peak NH₃ concentration was observed in summer, and was attributed to NH₃ emission simulation from different NH₃ emission sources (especially N fertilization), induced by high temperatures. pNH₄⁺ and pNO₃^- concentrations were higher in winter due to the low winter rainfall, as were inorganic nitrogen concentrations in precipitation. Atmospheric Nr concentrations were much higher than those reported by the European and American Nr monitoring networks, but much lower than those reported in the North China Plain. Dry nitrogen deposition is difficult to estimate directly because of the complicated meteorological and surface conditions. In this study, we tried to choose reasonable deposition velocities from those summarized in the literature from other studies. The American Clean Air Status and Trend's Network only has data for HNO₃, pNO₃^-, and pNH₄⁺ deposition velocities, and so could not be used in this present study. However, we were able to use the deposition velocities adopted by the European monitoring network. These were considered appropriate because we used the same equipment as was used to monitor nitrogen deposition in the European NitroEurope network. The NH₃, HNO₃, NO₂, pNO₃^- and pNH₄⁺ deposition velocities from this network were 0.53cm/s, 0.8 cm/s, 0.12 cm/s, 0.25 cm/s and 0.25 cm/s, respectively, while the dry nitrogen deposition rate was 17.6 kg hm^-2 a^-1. The average NO₃^--N concentration in precipitation samples was (0.86 ± 0.36) mg N/L, while the average NH₄⁺-N concentration was (1.11 ± 0.68) mg N/L. Inorganic nitrogen concentrations in precipitation samples were higher in winter and lower in summer because of the variation in rainfall between the different seasons. The total wet nitrogen deposition was 25.3 kg N hm^-2 a^-1. Wet NH₄⁺-N and NO₃^--N, and dry NH₃, HNO₃, NO₂, pNH₄⁺ and pNO₃^- contributed 30.8%, 28.0%, 23.7%, 5.4%, 2.8%, 3.9% and 5.4% to the total nitrogen deposition, respectively. The large contributions from wet NH₄⁺-N deposition and dry NH₃ deposition in this study indicated that fertilization played a large role in airborne NH₃ and nitrogen deposition. Comparison of the inorganic nitrogen concentrations in rainfall in other regions of China shows that the NH₄⁺-N concentrations and NO₃^--N concentrations in the Leizhou Peninsula were much lower than those for the North China plain, but that they were consistent with the inorganic nitrogen concentrations reported for southern and eastern China. The total nitrogen deposition recorded during this study was 42.9 kg N hm^-2 a^-1. Wet nitrogen deposition rates showed a close relationship with rainfall events, showing that wet nitrogen deposition changes with the rate of rainfall in different years. Dry deposition velocities of Nr species should be measured directly, or by using inferential methods, to decrease uncertainty in dry nitrogen deposition studies. Further, there should be some concern about cropland nutrient management and the related impacts on water, forest and grassland because of the high rates of background nitrogen deposition in this area.

Wet and dry atmospheric depositions of inorganic nitrogen during plant growing season in the coastal zone of Yellow River Delta.

The ecological problems caused by dry and wet deposition of atmospheric nitrogen have been widespread concern in the world. In this study, wet and dry atmospheric depositions were monitored in plant growing season in the coastal zone of the Yellow River Delta (YRD) using automatic sampling equipment. The results showed that SO4 2− and Na+ were the predominant anion and cation, respectively, in both wet and dry atmospheric depositions. The total atmospheric nitrogen deposition was ~2264.24 mg m−2, in which dry atmospheric nitrogen deposition was about 32.02%. The highest values of dry and wet atmospheric nitrogen deposition appeared in May and August, respectively. In the studied area, NO3 −–N was the main nitrogen form in dry deposition, while the predominant nitrogen in wet atmospheric deposition was NH4 +–N with ~56.51% of total wet atmospheric nitrogen deposition. The average monthly attribution rate of atmospheric deposition of NO3 −–N and NH4 +–N was ~31.38% and ~20.50% for the contents of NO3 −–N and NH4 +–N in 0–10 cm soil layer, respectively, suggested that the atmospheric nitrogen was one of main sources for soil nitrogen in coastal zone of the YRD.

Influence of precipitation events on phytoplankton biomass in coastal waters of the eastern United States

AbstractPrecipitation over the ocean surface in the vicinity of industrialized and populated coastlines can increase the ocean nitrate concentration and consequently enhance ocean primary productivity. Using satellite data and a meteorological reanalysis product, we evaluated the impact of precipitation events on the chlorophyll a concentration in coastal and offshore waters located downwind of the eastern United States. We found that in low‐nutrient areas (defined as having nitrate concentrations &lt; 1 μM) precipitation events were associated with increased levels of chlorophyll a (up to approximately 15%), but in high‐nutrient areas (nitrate concentrations &gt; 1 μM) they were associated with decreased levels. These contrasting responses of chlorophyll a concentration to precipitation were attributed to the correlation of precipitation with wind speed and to other factors (nutrients and light) limiting phytoplankton growth. Increases in wind speed accompanied by precipitation events typically deepen the mixed layer, which can entrain additional nutrients into the mixed layer but simultaneously reduce light availability. We suggest that in nutrient‐depleted areas (south of 36°N) the added nutrients were a dominant factor increasing the chlorophyll a concentration, whereas in the nutrient‐replete areas (north of 36°N), where phytoplankton growth was light limited, reduced light availability was the dominant factor determining reduced chlorophyll a concentration. Our results indicate that an increase in wind speed accompanied by precipitation events was a major contributor to the observed changes in chlorophyll a concentration during wet days, whereas the wet deposition of pollutant nitrogen slightly increased the chlorophyll a concentration (&lt; 5%) only in nutrient‐depleted areas.

陕西省不同生态区大气氮素干湿沉降的时空变异

PDF HTML阅读 XML下载 导出引用 引用提醒 陕西省不同生态区大气氮素干湿沉降的时空变异 DOI: 10.5846/stxb201211011517 作者: 作者单位: 西北农林科技大学资源环境学院,西北农林科技大学资源环境学院,陕西省长安区气象局,中国农业大学,陕西省气象局,西北农林科技大学资源环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（40675006） Spatial-temporal variability of dry and wet deposition of atmospheric nitrogen in different ecological regions of Shaanxi Author: Affiliation: College of Resources and Environmental Sciences,Northwest A F University,Yangling Shaanxi,College of Resources and Environmental Sciences,Northwest A F University,Yangling Shaanxi,Weather Bureau of Changan District,Xi’an,China Agricultural University,Weather Bureau of Shaanxi Province,Xi’an,College of Resources and Environmental Sciences,Northwest A F University,Yangling Shaanxi Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为研究陕西省不同生态区大气氮素干湿沉降的时空变化规律，于2009年11月至2010年10月对4个生态区5个监测点的干湿沉降输入量进行为期1a的观测。结果表明：监测期内，榆林、洛川、西安、杨凌和安康地区总N沉降量分别为4.7、11.9、25.8、31.9和19.2 kg/hm2，其中N湿沉降量分别为2.9、10.4、24.8、27.7和16.3 kg/hm2，占总沉降的62%-96%，N干沉降量分别为1.8、1.5、1.0、4.1和2.9 kg/hm2，占4%-38%，且湿沉降与降雨量之间呈正相关关系，干沉降与之相反；各地区NH4+-N沉降量分别为2.0、6.4、17.0、17.2和11.9 kg/hm2，占总沉降的44%-66%，NO3--N沉降量分别为2.6、5.5、8.8、14.7和7.3 kg/hm2，占34%-56%，除榆林地区外，其他地区以NH4+-N沉降为主。 Abstract:The objective of this experiment was to study the spatial-temporal variability of dry and wet deposition of atmospheric nitrogen in different ecological regions of Shaanxi Province. Measurements were made at five monitoring sites in four different ecological regions from November 2009 to October 2010. The amounts of total inorganic nitrogen (TIN) deposition were 4.7 kg/hm2 at Yulin, 11.9 kg/hm2 at Luochuan, 25.8 kg/hm2 at Xi'an, 31.9 kg/hm2 at Yangling, and 19.2 kg/hm2 at Ankang. Wet deposition accounted for 62 to 96% of the TIN deposition, ranging from 2.9 kg/hm2 at Yulin, 10.4 kg/hm2 at Luochuan, 24.8 kg/hm2 at Xi'an, 27.7 kg/hm2 at Yangling, and 16.3 kg/hm2 at Ankang. Dry deposition accounted for 4 to 38% of the TIN deposition, ranging from 1.8 kg/hm2 at Yulin, 1.5 kg/hm2 at Luochuan, 1.0 kg/hm2 at Xi'an, 4.1 kg/hm2 at Yangling, and 2.9 kg/hm2 at Ankang. Wet deposition and rainfall were positively correlated, whereas dry deposition and rainfall were negatively correlated. Ammonium nitrogen (NH4+-N) deposition amounts were 2.0 kg/hm2 at Yulin, 6.4 kg/hm2 at Luochuan, 17.0 kg/hm2 at Xi'an, 17.2 kg/hm2 at Yangling, and 11.0 kg/hm2 at Ankang. These amounts accounted for 44 to 66% of the TIN deposition. Nitrate nitrogen (NO3--N) amounts were 2.6 kg/hm2 at Yulin, 5.5 kg/hm2 at Luochuan, 8.8 kg/hm2 at Xi'an, 14.7 kg/hm2 at Yangling, and 7.3 kg/hm2 at Ankang. These amounts made up 34 to 56% of the TIN deposition. Nitrogen deposition is mainly in the form of NH4+-N in all regions except Yulin. 参考文献 相似文献 引证文献

Inertia in an ombrotrophic bog ecosystem in response to 9 years' realistic perturbation by wet deposition of nitrogen, separated by form

Wet deposition of nitrogen (N) occurs in oxidized (nitrate) and reduced (ammonium) forms. Whether one form drives vegetation change more than the other is widely debated, as field evidence has been lacking. We are manipulating N form in wet deposition to an ombrotrophic bog, Whim (Scottish Borders), and here report nine years of results. Ammonium and nitrate were provided in rainwater spray as NH4 Cl or NaNO3 at 8, 24 or 56kgNha(-1) yr(-1) , plus a rainwater only control, via an automated system coupled to site meteorology. Detrimental N effects were observed in sensitive nonvascular plant species, with higher cumulative N loads leading to more damage at lower annual doses. Cover responses to N addition, both in relation to form and dose, were species specific and mostly dependent on N dose. Some species were generally indifferent to N form and dose, while others were dose sensitive. Calluna vulgaris showed a preference for higher N doses as ammonium N and Hypnum jutlandicum for nitrate N. However, after 9years, the magnitude of change from wet deposited N on overall species cover is small, indicating only a slow decline in key species. Nitrogen treatment effects on soil N availability were likewise small and rarely correlated with species cover. Ammonium caused most N accumulation and damage to sensitive species at lower N loads, but toxic effects also occurred with nitrate. However, because different species respond differently to N form, setting of ecosystem level critical loads by N form is challenging. We recommend implementing the lowest value of the critical load range where communities include sensitive nonvascular plants and where ammonium dominates wet deposition chemistry. In the context of parallel assessment at the same site, N treatments for wet deposition showed overall much smaller effects than corresponding inputs of dry deposition as ammonia.