Mark A. Sutton

Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions

Humans continue to transform the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels, growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. Much anthropogenic nitrogen is lost to air, water, and land to cause a cascade of environmental and human health problems. Simultaneously, food production in some parts of the world is nitrogen-deficient, highlighting inequities in the distribution of nitrogen-containing fertilizers. Optimizing the need for a key human resource while minimizing its negative consequences requires an integrated interdisciplinary approach and the development of strategies to decrease nitrogen-containing waste.

Summary for policy makers

Over the past century humans have caused unprecedented • changes to the global nitrogen cycle, converting atmospheric di-nitrogen (N 2 ) into many reactive nitrogen (N r ) forms, doubling the total fi xation of N r globally and more than tripling it in Europe. Th e increased use of N • r as fertilizer allows a growing world population, but has considerable adverse eff ects on the environment and human health. Five key societal threats of N r can be identifi ed: to water quality, air quality, greenhouse balance, ecosystems and biodiversity, and soil quality. Cost–benefi t analysis highlights how the overall environ• mental costs of all N r losses in Europe (estimated at €70–€320 billion per year at current rates) outweigh the direct economic benefi ts of N r in agriculture. Th e highest societal costs are associated with loss of air quality and water quality, linked to impacts on ecosystems and especially on human health.

The global nitrogen cycle in the twenty- first century

Global nitrogen fixation contributes 413 Tg of reactive nitrogen (Nr) to terrestrial and marine ecosystems annually of which anthropogenic activities are responsible for half, 210 Tg N. The majority of the transformations of anthropogenic Nr are on land (240 Tg N yr−1) within soils and vegetation where reduced Nr contributes most of the input through the use of fertilizer nitrogen in agriculture. Leakages from the use of fertilizer Nr contribute to nitrate (NO3−) in drainage waters from agricultural land and emissions of trace Nr compounds to the atmosphere. Emissions, mainly of ammonia (NH3) from land together with combustion related emissions of nitrogen oxides (NOx), contribute 100 Tg N yr−1 to the atmosphere, which are transported between countries and processed within the atmosphere, generating secondary pollutants, including ozone and other photochemical oxidants and aerosols, especially ammonium nitrate (NH4NO3) and ammonium sulfate (NH4)2SO4. Leaching and riverine transport of NO3 contribute 40–70 Tg N yr−1 to coastal waters and the open ocean, which together with the 30 Tg input to oceans from atmospheric deposition combine with marine biological nitrogen fixation (140 Tg N yr−1) to double the ocean processing of Nr. Some of the marine Nr is buried in sediments, the remainder being denitrified back to the atmosphere as N2 or N2O. The marine processing is of a similar magnitude to that in terrestrial soils and vegetation, but has a larger fraction of natural origin. The lifetime of Nr in the atmosphere, with the exception of N2O, is only a few weeks, while in terrestrial ecosystems, with the exception of peatlands (where it can be 102–103 years), the lifetime is a few decades. In the ocean, the lifetime of Nr is less well known but seems to be longer than in terrestrial ecosystems and may represent an important long-term source of N2O that will respond very slowly to control measures on the sources of Nr from which it is produced.

The European nitrogen assessment : sources, effects and policy perspectives

In what case do you like reading so much? What about the type of the the european nitrogen assessment book? The needs to read? Well, everybody has their own reason why should read some books. Mostly, it will relate to their necessity to get knowledge from the book and want to read just to get entertainment. Novels, story book, and other entertaining books become so popular this day. Besides, the scientific books will also be the best reason to choose, especially for the students, teachers, doctors, businessman, and other professions who are fond of reading.New updated! The latest book from a very famous author finally comes out. Book of the european nitrogen assessment, as an amazing reference becomes what you need to get. Whats for is this book? Are you still thinking for what the book is? Well, this is what you probably will get. You should have made proper choices for your better life. Book, as a source that may involve the facts, opinion, literature, religion, and many others are the great friends to join with.List of contributors Preface Summary for policymakers Technical summary 1. Assessing our nitrogen inheritance Part I. Nitrogen in Europe: The Present Position: 2. The European nitrogen problem in a global perspective 3. Benefits of nitrogen for food fibre and industrial production 4. Nitrogen in current European policies 5. The challenge to integrate nitrogen science and policies Part II. Nitrogen Processing in the Biosphere: 6. Nitrogen processes in terrestrial ecosystems 7. Nitrogen processes in aquatic ecosystems 8. Nitrogen processes in coastal and marine ecosystems 9. Nitrogen processes in the atmosphere Part III. Nitrogen Flows and Fate at Multiple Scales: 10. Nitrogen flows in farming systems across Europe 11. Nitrogen flows and fate in rural landscapes 12. Nitrogen flows and fate in urban landscapes 13. Nitrogen flows from European watersheds to coastal marine waters 14. Atmospheric transport and deposition of nitrogen in Europe 15. Geographic variation in terrestrial nitrogen budgets across Europe 16. Integrating nitrogen fluxes at the European scale Part IV. Key Societal Threats of Nitrogen: 17. Nitrogen as a threat to European water quality 18. Nitrogen as a threat to European air quality 19. Nitrogen as a threat to the European greenhouse balance 20. Nitrogen as a threat to European terrestrial biodiversity 21. Nitrogen as a threat to European soil quality Part V. European Nitrogen Policies and Future Challenges: 22. Costs and benefits of nitrogen in the environment 23. Developing integrated approaches to nitrogen management 24. Future scenarios of nitrogen in Europe 25. Coordinating European nitrogen policies between directives and international conventions 26. Societal choice and communicating the European nitrogen challenge Glossary Index.

The exchange of ammonia between the atmosphere and plant communities.

Publisher Summary The chapter reviews the existing data on ammonia exchange, and examines the conclusions and limitations of the different studies. An historic survey presented covers the research interest, starting with the early 19th century uncertainties about the source of plant nutrients, and continuing up to the present-day concern about the ecological effects of atmospheric nitrogen deposition on semi-natural ecosystems. An examination of progress in the measurement of ammonia, data on air concentrations and an examination of evidence for increased emissions and deposition over the past century is also presented. A major part of the chapter is devoted to reviewing the range of approaches and experimental studies on ammonia surface/atmosphere exchange. This is drawn together to provide a synthesis of the factors controlling ammonia exchange and to identify uncertainties and current research priorities.

Measurements and parameterizations of small aerosol deposition velocities to grassland, arable crops, and forest: Influence of surface roughness length on deposition

New micrometeorological measurements of small (0.1-0.2 μ diameter) aerosol particle fluxes using the eddy correlation technique are presented for moorland and also for grassland vegetation, the latter measurements being made both before and after cutting of the grassland to observe the resultant change in particle deposition velocity. These data are considered together with previously reported and reanalyzed micrometeorological measurements, again using the eddy correlation technique, for a number of different surface types, including arable crops and forest. Differences in observed surface deposition velocities, vds, due to the different surface roughnesses are highlighted. It was found that the various data sets showed a wholly consistent behavior when ensemble averages over the typical range of atmospheric stability ranges are considered in order to reduce the scatter inherent in these types of measurements. A working parameterization of surface deposition velocity in terms of the surfaces roughness length, z0, is presented. This is then extended for different atmospheric stabilities, using the parameterization suggested by Lamaud et al. [1994c], to yield vds/u* = k1 + k2 (-300 z/L 2/3, where k1 = k1 = 0.001222 log(z0) + 0.003906, k2 = 0.0009, where z is the measurement height, L is the Obukhov stability length, and u* is the local friction speed. The new data are finally compared to current analytical model descriptions of the deposition process, highlighting deficiencies in our understanding of the surface collection efficiency even for these small particles. Copyright 2002 by the American Geophysical Union.

The relationship between nitrogen deposition, species composition and foliar nitrogen concentrations in woodland flora in the vicinity of livestock farms

Measurements of atmospheric ammonia concentration along a gradient of decreasing concentration, species composition and tissue nitrogen content of a range of plant species were made in woodland in the vicinity of four intensive animal units in Scotland. Ammonia concentrations were large at woodland edges close to the livestock buildings (annual means 20–60 μg m−3) and exceed critical levels for NH3 (8 μg m−3 annual mean). Surveys of species composition of ground flora along an 0.5 km transect from livestock buildings show marked changes within 300 m downwind of the buildings. Species such as Deschampsia flexuosa, Holcus lanatus, Rubus idaeus and Urtica dioica were abundant close to livestock units and their percentage cover decreased rapidly with distance from source, while the more N-sensitive species such as Oxalis acetosella, Galium odoratum, mosses and ferns which are found upwind and outside the influence of the NH3 source, were scarce at all sites receiving >25 kg ha−1 N year−1. Visible injury to pine and spruce needles was observed immediately downwind of the buildings. Foliar nitrogen concentration of a number of species was large close to the buildings and declined with distance. Total nitrogen deposition at the woodland boundaries is estimated to range from 40 to 80 kg N ha−1 year−1 at the 4 sites and exceeds critical loads for acidic coniferous forest, i.e. 15–20 kg N ha−1 year−1 to protect ground flora, and is also often in excess of that (11–50 kg N ha−1 year−1) proposed to protect tree health. Foliar nitrogen content of mosses, (LN, % dry weight) is related to nitrogen deposition (FN, kg N ha−1 year−1) according to LN = 3.81(1-e−0.04FN).

Regional estimation of pollutant gas dry deposition in the UK: model description, sensitivity analyses and outputs

A “big-leaf” resistance analogy model for dry deposition of sulphur dioxide, nitrogen dioxide, ammonia and nitric acid is described with a stomatal compensation point included to allow bi-directional exchange of ammonia. The model derivation is constrained by measurement data and it is parameterized for UK conditions. Monthly average dry deposition estimates are provided at the 5 km×5 km spatial scale. The model uses data available nationally at the appropriate spatial and temporal scales, such as gas concentration, land use, wind speed, temperature, rainfall and vapour pressure. A method is presented to overcome the lack of suitable solar radiation data. The effect of uncertainty in model inputs and in model parameterization is explored using sensitivity analyses. SO2 deposition is sensitive to variation in gas concentration, wind speed and wet surface uptake parameters. NO2 deposition is sensitive to parameters and inputs regulating stomatal behaviour, including solar radiation and temperature, as well as to gas concentration. The use of monthly or annual average NO2 concentrations may underestimate deposition substantially in some areas. HNO3 dry deposition is sensitive to wind speed and concentration. NH3 dry deposition to moorland and forest land uses, where the majority of deposition occurs, is sensitive to concentration, wind speed and choice of canopy resistance parameters. For arable and grassland areas, with both deposition and emission of NH3, the model is sensitive to all the model inputs and parameter choices. A full uncertainty analysis requires further work on the reliability of input variables and model parameter choices but these results quantitatively focus on the important areas of the model for each gas. Estimated dry deposition to the UK (excluding Northern Ireland) of SO2 is 135 Gg S yr−1 for 1996, for NH3 is 97 Gg N yr−1, for NO2 is 26 Gg N yr−1 and the preliminary estimate for HNO3 is 42 Gg N yr−1. For sulphur and reduced nitrogen, estimated dry deposition accounts for 40% of total deposition, including wet and cloud droplet deposition. NO2 dry deposition only accounts for 15% of total oxidised nitrogen deposition, but another 25% may come from the dry deposition of HNO3, giving a similar 40% overall by dry deposition. The sensitivity of the model to parameter values and the comparisons of modelled output with measurements show that parameter choices may be valid only at the scale of European countries rather than the whole continent.

Plant-atmosphere exchange of ammonia

The results of recent controlled environment and micrometeorological measurements of NH3 fluxes are presented to highlight the processes controlling NH3 plant-atmosphere exchange. The presence of NH+4 in leaf tissues results in the existence of an NH3 ‘compensation point’ concentration for substomatal tissues (xs), so that both emission and deposition are possible from stomata. In addition, NH3 may deposit efficiently on to leaf cuticles, short-circuiting any stomatal emission, so that a ‘canopy compensation point’ (Xc) may be defined that is smaller than Xs. Ammonia is generally deposited to nitrogen limited ecosystems, indicating a small Xs and small leaf cuticle resistance (Rw). In contrast, fluxes over croplands are typically bidirectional and may reflect a larger Xs as a consequence of greater N supply. The paper discusses the processes defining (humidity, acidic pollutants) and Xs (plant phenology, species, N nutrition) and proposes a new resistance approach, which integrates Xs and Rw into one model. Estimating long term bidirectional NH3 fluxes is still uncertain, though it is now possible to apply a single model concept to a range of ecosystem types and satisfactorily infer NH3 fluxes over diurnal time scales.

Grazing-induced reduction of natural nitrous oxide release from continental steppe

Atmospheric concentrations of the greenhouse gas nitrous oxide (N2O) have increased significantly since pre-industrial times owing to anthropogenic perturbation of the global nitrogen cycle, with animal production being one of the main contributors. Grasslands cover about 20 per cent of the temperate land surface of the Earth and are widely used as pasture. It has been suggested that high animal stocking rates and the resulting elevated nitrogen input increase N2O emissions. Internationally agreed methods to upscale the effect of increased livestock numbers on N2O emissions are based directly on per capita nitrogen inputs. However, measurements of grassland N2O fluxes are often performed over short time periods, with low time resolution and mostly during the growing season. In consequence, our understanding of the daily and seasonal dynamics of grassland N2O fluxes remains limited. Here we report year-round N2O flux measurements with high and low temporal resolution at ten steppe grassland sites in Inner Mongolia, China. We show that short-lived pulses of N2O emission during spring thaw dominate the annual N2O budget at our study sites. The N2O emission pulses are highest in ungrazed steppe and decrease with increasing stocking rate, suggesting that grazing decreases rather than increases N2O emissions. Our results show that the stimulatory effect of higher stocking rates on nitrogen cycling and, hence, on N2O emission is more than offset by the effects of a parallel reduction in microbial biomass, inorganic nitrogen production and wintertime water retention. By neglecting these freeze–thaw interactions, existing approaches may have systematically overestimated N2O emissions over the last century for semi-arid, cool temperate grasslands by up to 72 per cent.