Deposition Of Atmospheric Ammonia Research Articles

Atmospheric ammonia deposition and its role in a cool-temperate fragmented deciduous broad-leaved forest

Forest fragmentation can increase dry deposition of atmospheric ammonia (NH3) volatilized from agricultural areas, and consequently increase spatial variability of Nr deposition within the forest (“elevated reactive nitrogen (Nr) deposition”). However, little is known about this effect and its impact on forest production in a deciduous broad-leaved forest in Asian countries. Here, we performed the field observations of atmospheric concentration and deposition of inorganic Nr gases and particles in a Japanese fragmented forest from May 2018 to April 2019. Leaf traits and growth of Japanese oak tree and understory vegetation were also measured. Atmospheric concentration and deposition of dissolved inorganic Nr (DIN) to tree canopies were measured via filter sampling and throughfall methods, respectively. Canopy retention/exchange was also estimated as a part of dry deposition using the canopy budget model. The results demonstrated that annual dry deposition of NH3 to tree canopies (4.4 kgN ha−1 y−1) was dominant in the annual total DIN deposition (7.1 kgN ha−1 y−1) at the forest edge, including the elevated Nr deposition of approximately 2 kgN ha−1 y−1. Additionally, agricultural activities such as fertilization in the area surrounding the forest likely enhanced the potential of canopy retention of NH4+, readily absorbed by tree canopy. The growth rates of tree and understory vegetation (dwarf bamboo) were higher at the edge than that at the interior, emphasizing a need for further investigation to quantify the effect of low Nr deposition (<3–5 kgN ha−1 y−1) on forest production, along with the conventional experimental studies under a high Nr deposition.

The Haber Bosch–harmful algal bloom (HB–HAB) link

Large-scale commercialization of the Haber–Bosch (HB) process is resulting in intensification of nitrogen (N) fertilizer use worldwide. Globally N fertilizer use is far outpacing that of phosphorus (P) fertilizer. Much of the increase in N fertilizers is also now in the form of urea, a reduced form of N. Incorporation of these fertilizers into agricultural products is inefficient leading to significant environmental pollution and aquatic eutrophication. Of particular concern is the increased occurrence of harmful algal blooms (HABs) in waters receiving nutrient enriched runoff. Many phytoplankton causing HABs have physiological adaptive strategies that make them favored under conditions of elevated N : P conditions and supply of chemically reduced N (ammonium, urea). We propose that the HB-HAB link is a function of (1) the inefficiency of incorporation of N fertilizers in the food supply chain, the leakiness of the N cycle from crop to table, and the fate of lost N relative to P to the environment; and (2) adaptive physiology of many HABs to thrive in environments in which there is excess N relative to classic nutrient stoichiometric proportions and where chemically reduced forms of N dominate. The rate of HAB expansion is particularly pronounced in China where N fertilizer use has escalated very rapidly, where soil retention is declining, and where blooms have had large economic and ecological impacts. There, in addition to increased use of urea and high N : P based fertilizers overall, escalating aquaculture production adds to the availability of reduced forms of N, as does atmospheric deposition of ammonia. HABs in both freshwaters and marginal seas in China are highly related to these overall changing N loads and ratios. Without more aggressive N control the future outlook in terms of HABs is likely to include more events, more often, and they may also be more toxic.

Point Source Ammonia Emissions are Having a Detrimental Impact On Prairie Vegetation

Prairie grasslands are very species rich but have declined in their extent considerably due to land-use change and exploitation. Many remaining prairie fragments are situated within an agricultural matrix and can be subjected to high levels of atmospheric ammonia deposition from animal units. Three prairie fragments in Minnesota that were located in close proximity to feedlots were selected, and 500-m transects were studied at an increasing distance from the feedlot. Changes in soil pH, soil nitrate concentration, and soil ammonium concentration with increasing distance from the source were variable between the sites, possibly due to differences in the processing of nitrogen in the soil and the degree of nitrogen limitation. Species richness showed significant negative relationships with ammonia deposition and soil nitrate concentration, whereas aboveground biomass showed a positive relationship with ammonia deposition. Both the richness and biomass of nongraminoid species declined with increasing soil nitrate concentration, whereas graminoid biomass was positively related to ammonia deposition and was negatively associated to richness. Bromus inermis, a non-native perennial grass, was the main species that increased at high deposition. The results of this study have important implications for the conservation and restoration of prairie grasslands.

Advection of NH&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; over a pasture field and its effect on gradient flux measurements

Abstract. Deposition of atmospheric ammonia (NH3) to semi-natural ecosystems leads to serious adverse effects, such as acidification and eutrophication. A step in quantifying such effects is the measurement of NH3 fluxes over semi-natural and agricultural land. However, measurement of NH3 fluxes over vegetation in the vicinity of strong NH3 sources is challenging, since NH3 emissions are highly heterogeneous. Indeed, under such conditions, local advection errors may alter the measured fluxes. In this study, local advection errors (ΔFz,adv) were estimated over a 14 ha grassland field, which was successively cut and fertilised, as part of the GRAMINAE integrated Braunschweig experiment. The magnitude of ΔFz,adv was determined up to 810 m downwind from farm buildings emitting between 6.2 and 9.9 kg NH3 day−1. The GRAMINAE experiment provided a unique opportunity to compare two methods of estimating ΔFz,adv: one inference method based on measurements of horizontal concentration gradients, and one based on inverse dispersion modelling with a two-dimensional model. Two sources of local advection were clearly identified: the farm NH3 emissions leading to positive ΔFz,adv ("bias towards emissions") and field NH3 emissions, which led to a negative ΔFz,adv ("bias towards deposition"). The local advection flux from the farm was in the range 0 to 27 ng NH3 m−2 s−1 at 610 m from the farm, whereas ΔFz,adv due to field emission was proportional to the local flux, and ranged between −209 and 13 ng NH3 m−2 s−1. The local advection flux ΔFz,adv was either positive or negative depending on the magnitude of these two contributions. The modelled and inferred advection errors agreed well. The inferred advection errors, relative to the vertical flux at 1 m height, were 52% on average, before the field was cut, and less than 2.1% when the field was fertilised. The variability of the advection errors in response to changes in micrometeorological conditions is also studied. The limits of the 2-D modelling approach are discussed.

The potential for spatial planning at the landscape level to mitigate the effects of atmospheric ammonia deposition

Ammonia (NH3) is emitted mainly from agricultural practices, with NH3 concentrations decreasing rapidly away from sources. As a consequence there is a high spatial variability in nitrogen deposition and its consequent ecological effects in agricultural landscapes that is in addition to differences in sensitivity between habitat types. This variability points to the potential to include spatial planning measures as part of strategies to protect sensitive vegetation from ammonia deposition. National abatement policies typically include uniform recommendations for technical abatement measures, such as ploughing in manures after land spreading. In this study, the complementary potential of spatial planning to reduce effects on target locations is analysed through model scenarios for an example landscape in central England. Scenarios included defining buffer zones of low-emission agriculture and establishing tree belts surrounding either emission sources or priority areas for the protection of semi-natural habitats. The analysis showed that tree belts can reduce deposition to sensitive areas, with trees surrounding the sensitive habitats being more effective than trees around the sources. Low emission buffer zones around sink areas also result in useful reductions in N deposition. Smaller nature reserve sites benefit to a greater degree from such spatial planning measures, as large reserves can provide their own buffer zone to some degree. Similarly, relocating point sources or using planning policies to ensure the location of large NH3 point sources are at least 2–3 km from the sensitive habitats results in substantial reductions in N deposition.

A coupled dispersion and exchange model for short-range dry deposition of atmospheric ammonia

The MODDAS-2D model (MOdel of Dispersion and Deposition of Ammonia over the Short-range in two dimensions) is presented. This stationary model couples a two-dimensional Lagrangian stochastic model for short-range dispersion, with a leaf-scale bi-directional exchange model for ammonia (NH3), which includes cuticular uptake and a stomatal compensation point. The coupling is obtained by splitting the upward and downward components of the flux, which can be generalized for any trace gas, and hence provides a way of simply incorporating bi-directional exchanges in existing deposition velocity models. The leaf boundary-layer resistance is parametrized to account for mixed convection in the canopy, and the model incorporates a stability correction for the Lagrangian time-scale for vertical velocity, which tends to increase the Lagrangian time-scale in very stable conditions compared with usual parametrizations. The model is validated against three datasets, where concentrations of atmospheric NH3 were measured at several distances from a line source. Two datasets are over grassland and one is over maize, giving a range of canopy structure. The model correctly simulates the concentration in one situation, but consistently overestimates it at further distances or underestimates it at small distances in the two other situations. It is argued that these discrepancies are mainly due to the lack of length of one of the line sources and non-aligned winds. Analysis shows that the surface exchange parameters and the turbulent mixing at the source level are the predominant factors controlling short-range deposition of NH3. Copyright © 2006 Royal Meteorological Society

Early effects of atmospheric ammonia deposition on Calluna vulgaris (L.) hull growing on an ombrotrophic peat bog

This paper reports data from a field study investigating the impacts of elevated ammonia (NH3) deposition on Calluna vulgaris growing on an ombrotrophic peat bog in S.E. Scotland. Shoot extension, foliar N concentrations, chlorophyll concentration and chlorophyll fluorescence were measured during the second growing season of exposure to a gradient of ammonia concentrations. Results indicate that NH3 increases growth between 150–200 kg N ha−1y−1 cumulative deposition. Foliar N content increased significantly in response to NH3 cumulative deposition up to 400 kg N ha−1 y−1 whereas chlorophyll a content significantly decreased. Measurements of Fv/Fm suggest that although NH3 exposure altered the growth and reduced chlorophyll a, the efficiency of photosystem II was insensitive to NH3-N deposition at this stage.

A study of atmospheric ammonia by means of modeling analysis in the Kanto region of Japan

Abstract To evaluate the primary factor for the seasonal variation and the level of atmospheric ammonia concentration in the local scale, the emission, transport, and deposition of atmospheric ammonia were analyzed in the Kanto region of Japan, which has an area of about 40,000 km2, by means of an atmospheric transport model. In the analysis of episodes of high concentration, the model reproduced an observed concentration of NH3 and NH4+ particles during a 5-day observation period in the summer of 2002. In the annual simulation, the calculated concentration showed reasonable agreement with the spatial distribution and seasonal variation of the annual observation in 2000. The NH3 concentration strongly reflected the effect of local emission sources because of its short lifespan in the atmosphere. Moreover, it is found from the simulation results that atmospheric ammonia was transported over long distances when it existed as a particulate. The calculated deposition amount of NH3 and NH4+ particles was about the same as the emission amount of NH3 throughout the year. Moreover, the model simulation showed that there was little contribution from sources outside the Kanto region. These findings suggest that the concentration and the deposition in the Kanto region mainly originated from the emission sources in itself.

Gestion de l'azote en syst�me d'�levage d�velopp�. Enjeux scientifiques et environnementauxNitrogen management from intensive livestock production : scientific and environmental issues

Growing environmental concern led to increased public and scientific attention to nitrogen transfers from animal manure and slurry. Major environmental problems arise from the excessive use of nitrogen compounds. Amongst these are (i) acidification of forests and natural ecosystems through atmospheric deposition of ammonia (NH3), (ii) eutrophication of inland waters and coastal seas mainly by organic N and nitrates, (iii) contamination of groundwater by nitrates and (iv) a contribution to the global warming problem by nitrous oxide, N2O. Tracer methods using 15N stable isotope provide and excellent tool for studying such complex transfers during the different stages of animal slurry management including storage, treatment and land spreading. In this article, we present a brief review of isotopic tracer principles and history through a general description of terms, definitions and assumptions follow by the methodologies developed in our laboratory to label the ammoniacal nitrogen fraction of pig slurry using artificial 15N enrichment. The aim of our studies is to gather information concerning nitrogen pig slurry turnover and to focus on those processes, where major progress is made using the stable isotope 15N. Recent research findings are Presented. La connaissance du cycle de l'azote des déjections animales (lisiers) est un enjeu primordial au regard de préoccupations environnementales : accroissement de l'efficacité agronomique et/ou réduction des pollutions atmosphériques. Dans ce contexte, l'utilisation du traceur isotopique 15N permet de quantifier les différents mécanismes (assimilation et réorganisation, minéralisation, volatilisation, nitrification—dénitrification) et d'étudier les voies de transferts possibles. La technique développée consiste notamment à marquer la fraction azote ammoniacal du lisier par ajout direct de sulfate d'ammonium ou d'urée enrichis en 15N. Des essais en laboratoire illustrent les processus de nitrification - dénitrification ainsi que les transferts d'azote sous forme de protoxyde d'azote (N2O). Par ailleurs le suivi du devenir de l'azote après épandage de lisier au champ, permet d'établir un bilan sol—plante—air. Au travers de ces expériences, l'utilisation du marquage isotopique 15N de l'azote des déjections animales apparaît comme un outil de première importance.

Atmospheric deposition of ammonia to semi-natural vegetation in the Netherlands—methods for mapping and evaluation

In this paper an overview is presented of most of the experimental and modelling work conducted in recent years in the Netherlands leading to estimates of deposition of reduced nitrogen to semi-natural vegetation on a 5 km×5 km scale. The average deposition in the Netherlands was 2000 mol ha -1 yr -1 in 1993, about 200 mol ha -1 yr -1 lower than in 1980. Deposition to deciduous forests was on the average 2080 mol ha -1 yr -1, 2430 mol ha -1 yr -1 to coniferous forest, 2210 mol ha -1 yr -1 to heathland and 1460 mol ha -1 yr -1 to other nature areas. The main uncertainty in the deposition estimates is determined by the emission estimates and the surface exchange parametrisation. The dry deposition process description needs to be extended with the dynamics in the bi-directional surface exchange of NH 3. Furthermore, there is lack of independent dry deposition measurements which can be used for model evaluation.

A mechanistic model for estimating ammonia volatilization from slurry applied to bare soil

The loss of ammonia by volatilization after slurry application may lead to large losses of soil-plant nitrogen. It is also a major source of atmospheric ammonia. These fluxes must therefore be accurately measured. However, volatilization depends on many features of the soil, climate and slurry, so that it is difficult to predict, or even to interpret and compare data from different experiments. We have developed a mechanistic model that simulates the influence of the various factors on volatilization, accounting for the transfers and equilibria in the topsoil and between the soil and the atmosphere. The model uses readily available input data, including soil, meteorological and slurry data. It includes energy balance and advection submodels, which make it suitable for field scale applications using simple meteorological data. Sensitivity analysis showed that soil pH has a large influence on volatilization. The model is also sensitive to soil adsorption capacity and some hydraulic characteristics (saturation water conductivity, water content at field capacity). It has been calibrated under real field conditions using experimental data for ammonia fluxes measured over two weeks after slurry application, with a micrometeorological method giving data at 15-min intervals. The soil, climate and slurry factors were also measured. The model provides a fair picture of the ammonia fluxes throughout the volatilization, including the total ammonia volatilized, the decrease in daily loss and their short-term (< 1 h) variations due to the influence of meteorological conditions on soil surface temperature and atmospheric diffusion. Lastly the model has been used to simulate the influence of various meteorological conditions and agricultural techniques on ammonia volatilization. This model will make it easier to interpret data from different experiments and will help to improve the emission submodel of atmospheric ammonia deposition models.

The deposition of atmospheric ammonia and its effects on plants.

Across Europe, total nitrogen deposition is increasing and, of this total, atmospheric ammonia can contribute up to 50-80%. Average deposition of ammonia in the UK is likely to be around 15-20 kg ha-1 yr-1 , while in The Netherlands, which has some of the highest rates of deposition, this value is likely to be between 40 and 50 kg ha-1 yr-1 . It is argued that because of the processes of assimilation and nitrification this ammonia is an acidifying pollutant. Ammonia taken up by plants is most likely to be directly assimilated and this uptake can have a strong effect on the nutrient imbalances of the plant. With root uptake in particular, anions are taken up in preference to cations. However, simple soil/plant nutrient measurements are unlikely to be a definitive means of monitoring ammonia pollution. This is because the processes of ammonia metabolism and acidification affect soil ion activity, mycorrhizas, plant uptake, and foliar leaching. These effects interact with acidity per se, and are compounded by the strong correlative co-deposition of ammonia with sulphur. Evidence for uptake of gaseous and wet deposited ammonia by leaves is presented. The exact mechanism of ammonia toxicity is still not really clear, but could be due to physiological perturbation, rather than to the direct toxicity of the ion. Assimilation of ammonia by leaves releases protons which can cause cellular acidosis, and has important implications for acid-base regulation in cells. This regulation depends on intrinsic features of the plant's metabolism, that is in turn dependent on the ecology of root versus leaf nitrogen nutrition under normal conditions. Certain species are more acidic in a leaf physiological sense and tend to be prone to damage by pollutants. Likewise, acidic habitats are particularly prone to damage through both eutrophication and the different capacities of plants both to utilize and to buffer against this nitrogen enrichment. The current evidence from The Netherlands suggests that the part this plays in perturbing the ecosystem should not be underestimated. Contents Summary 283 I. Introduction 284 II. Emission and deposition of ammonia 284 III. Is ammonia toxic? 288 IV. The eflfects of ammonia deposition 289 V. Throughfall versus foliar uptake 293 VI. Physiological effects on ahove-ground parts 296 VII. Conclusions 301 Acknowledgements 302 References 302.

Estimation of Nitrate Concentrations in Groundwater Using a Whole Farm Nitrogen Budget

AbstractContamination of groundwater under agricultural land by NO3 is influenced by the kind of farming system. One possible method of selecting farming systems that result in less NO3 leaching is to calculate whole farm N budgets, that are simplified by assuming soil‐N remains constant from one cycle of a rotation to the next. This method was applied to two model crop rotations using average crop yield data for two regions of Ontario, and to a cash‐crop farm and a dairy farm using information on purchases, sales, and crop yields, for these farms. The model rotations were corn (Zea mays L.)‐soybean [Glycine max (L.) Merr.]‐wheat (Triticum aestivum L.) and corn‐soybean‐wheat‐hay (mixture of timothy, Phleum pratense L. and alfalfa, Medicago sativa L.)‐hay‐hay. Atmospheric deposition (18.4 kg N ha−1 yr) was obtained by literature review. Symbiotic N2 fixation by legume crops with different yields was estimated from regression equations. A net surplus in the N balance was converted to maximum mean NO3‐N concentration in groundwater by assuming a groundwater recharge rate of 160 mm yr−1, and no denitrification. Predicted NO3‐N concentrations in leachate for the model corn‐soybean‐wheat rotation were greater for southwestern Ontario (22.4 mg L−1) than western Ontario (8.5 mg L−1), probably because more fertilizer was recommended in the southwest. Including hay in the model rotation increased the amount of N leached by a factor of two in western Ontario, but only by 9% in the southwest. Predicted NO3‐N concentration in groundwater for the cash crop farm was 6.7 mg L−1, compared with an average measured value of 9.5 mg L−1 in the tile drainage water. For the dairy farm the predicted value was 58 mg L−1 and a measured value was not available. The simplified N balance method provided useful estimates of potential NO3 leaching losses even though it relied on some major assumptions. A major uncertainty was atmospheric deposition of ammonia volatilized from on‐farm sources. Denitrification could be as much as 62 kg N ha−1 yr−1 under continuous production of grain corn, based on differences between N present after harvest and amount of N leached.

Lagoons and ponds

Lagoons and ponds

Deposition of atmospheric ammonia to moorlands

Micrometeorological methods were applied to measure fluxes of atmospheric ammonia (NH 3) to moorlands. Measurements were made in a wide variety of surface conditions and included both Calluna vulgaris (L.) Hull and Eriophorum vaginatum L. dominated sites. NH 3 was found to deposit rapidly to all the sites investigated, providing large deposition velocities ( V d, typically 10–40 mm s −1) and usually minimal surface resistances ( r c). A small number of measurements were made in frozen conditions and suggest a possible exception to this pattern with mean r c of 50–200 s m −1. The effect of vegetation drying was also investigated and a possible increase in r c observed, though this was small (< 10 s m −1). The results are interpreted in terms of the processes controlling exchange; it is shown that NH 3 deposition is predominantly to the leaf surfaces and that the net NH 3 compensation point approaches zero. Annual estimates show that dry deposition of NH 3 is a major source of atmospheric nitrogen to moorland ecosystems. For two typical UK sites subject to background air concentrations, NH 3 dry deposition is of similar magnitude to equivalent NH 4 + inputs in wet deposition. In the vicinity of emission sources, NH 3 dry deposition is expected to dominate inputs of atmospheric nitrogen.

Changes in the composition of rainwater upon passage through the canopies of trees and of ground vegetation in a Dutch oak-birch forest

The composition of canopy throughfall water in an oak-birch woodland, heavily affected by atmospheric deposition of N and S, changed markedly upon contact with the above-ground parts of the ground vegetation, which consisted mainly of bracken. The fluxes of nitrate and H+ decreased, simultaneously with an increase in the flux of bicarbonate, indicative of above-ground uptake of nitrate by the ground vegetation. This above-ground assimilation takes place in spite of abundant availability of inorganic nitrogen in the root zone of the ground vegetation. Fluxes of phosphate were somewhat lower, and those of ammonium somewhat higher in throughfall of the ground vegetation than in that of the tree layer. Although those differences were not statistically significant, they do suggest assimilation of some P and extra net dry deposition of atmospheric ammonia below the tree canopies.

Dry deposition of atmospheric ammonia at Rothamsted in 1976 and 1977

SummarySoils at Rothamsted receive approximately 4 kg NH3-N/ha/year through dry deposition of atmospheric ammonia. The value is low compared with other nitrogen input processes and reflects the low concentrations of ammonia in the atmosphere. Rainfall is a major factor limiting dry deposition as it removes large amounts of ammonia from the atmosphere. Dry deposition of ammonia is a relatively unimportant source of combined soil nitrogen compared with other natural and artificial sources.