The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly influenced by the inputs of reactive nitrogen (Nr) from human activities, including combustion-related ...NOx, industrial and agricultural N fixation, estimated to be 220 Tg N yr-1 in 2010, which is approximately equal to the sum of biological N fixation in unmanaged terrestrial and marine ecosystems. According to current projections, changes in climate and land use during the 21st century will increase both biological and anthropogenic fixation, bringing the total to approximately 600 Tg N yr-1 by around 2100. The fraction contributed directly by human activities is unlikely to increase substantially if increases in nitrogen use efficiency in agriculture are achieved and control measures on combustion-related emissions implemented. Some N-cycling processes emerge as particularly sensitive to climate change. One of the largest responses to climate in the processing of Nr is the emission to the atmosphere of NH3, which is estimated to increase from 65 Tg N yr-1 in 2008 to 93 Tg N yr-1 in 2100 assuming a change in global surface temperature of 5 degree C in the absence of increased anthropogenic activity. With changes in emissions in response to increased demand for animal products the combined effect would be to increase NH3 emissions to 135 Tg N yr-1. Another major change is the effect of climate changes on aerosol composition and specifically the increased sublimation of NH4NO3 close to the ground to form HNO3 and NH3 in a warmer climate, which deposit more rapidly to terrestrial surfaces than aerosols. Inorganic aerosols over the polluted regions especially in Europe and North America were dominated by (NH4)2SO4 in the 1970s to 1980s, and large reductions in emissions of SO2 have removed most of the SO42- from the atmosphere in these regions. Inorganic aerosols from anthropogenic emissions are now dominated by NH4NO3, a volatile aerosol which contributes substantially to PM10 and human health effects globally as well as eutrophication and climate effects. The volatility of NH4NO3 and rapid dry deposition of the vapour phase dissociation products, HNO3 and NH3, is estimated to be reducing the transport distances, deposition footprints and inter-country exchange of Nr in these regions. There have been important policy initiatives on components of the global N cycle. These have been regional or country-based and have delivered substantial reductions of inputs of Nr to sensitive soils, waters and the atmosphere. To date there have been no attempts to develop a global strategy to regulate human inputs to the nitrogen cycle. However, considering the magnitude of global Nr use, potential future increases, and the very large leakage of Nr in many forms to soils, waters and the atmosphere, international action is required. Current legislation will not deliver the scale of reductions globally for recovery from the effects of Nr deposition on sensitive ecosystems, or a decline in N2O emissions to the global atmosphere. Such changes would require substantial improvements in nitrogen use efficiency across the global economy combined with optimization of transport and food consumption patterns. This would allow reductions in Nr use, inputs to the atmosphere and deposition to sensitive ecosystems. Such changes would offer substantial economic and environmental co-benefits which could help motivate the necessary actions.
The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly influenced by the inputs of reactive nitrogen (Nr) from human activities, including combustion-related ...NOx, industrial and agricultural N fixation, estimated to be 220 Tg N yr−1 in 2010, which is approximately equal to the sum of biological N fixation in unmanaged terrestrial and marine ecosystems. According to current projections, changes in climate and land use during the 21st century will increase both biological and anthropogenic fixation, bringing the total to approximately 600 Tg N yr−1 by around 2100. The fraction contributed directly by human activities is unlikely to increase substantially if increases in nitrogen use efficiency in agriculture are achieved and control measures on combustion-related emissions implemented. Some N-cycling processes emerge as particularly sensitive to climate change. One of the largest responses to climate in the processing of Nr is the emission to the atmosphere of NH3, which is estimated to increase from 65 Tg N yr−1 in 2008 to 93 Tg N yr−1 in 2100 assuming a change in global surface temperature of 5 °C in the absence of increased anthropogenic activity. With changes in emissions in response to increased demand for animal products the combined effect would be to increase NH3 emissions to 135 Tg N yr−1. Another major change is the effect of climate changes on aerosol composition and specifically the increased sublimation of NH4NO3 close to the ground to form HNO3 and NH3 in a warmer climate, which deposit more rapidly to terrestrial surfaces than aerosols. Inorganic aerosols over the polluted regions especially in Europe and North America were dominated by (NH4)2SO4 in the 1970s to 1980s, and large reductions in emissions of SO2 have removed most of the SO42− from the atmosphere in these regions. Inorganic aerosols from anthropogenic emissions are now dominated by NH4NO3, a volatile aerosol which contributes substantially to PM10 and human health effects globally as well as eutrophication and climate effects. The volatility of NH4NO3 and rapid dry deposition of the vapour phase dissociation products, HNO3 and NH3, is estimated to be reducing the transport distances, deposition footprints and inter-country exchange of Nr in these regions. There have been important policy initiatives on components of the global N cycle. These have been regional or country-based and have delivered substantial reductions of inputs of Nr to sensitive soils, waters and the atmosphere. To date there have been no attempts to develop a global strategy to regulate human inputs to the nitrogen cycle. However, considering the magnitude of global Nr use, potential future increases, and the very large leakage of Nr in many forms to soils, waters and the atmosphere, international action is required. Current legislation will not deliver the scale of reductions globally for recovery from the effects of Nr deposition on sensitive ecosystems, or a decline in N2O emissions to the global atmosphere. Such changes would require substantial improvements in nitrogen use efficiency across the global economy combined with optimization of transport and food consumption patterns. This would allow reductions in Nr use, inputs to the atmosphere and deposition to sensitive ecosystems. Such changes would offer substantial economic and environmental co-benefits which could help motivate the necessary actions.
Black carbon (BC) in the atmosphere contributes to the human health effects of particulate matter and contributes to radiative forcing of climate. The lifetime of BC, particularly the smaller ...particle sizes (PM2.5) which can be transported over long distances, is therefore an important factor in determining the range of such effects, and the spatial footprint of emission controls. Theory and models suggest that the typical lifetime of BC is around one week.
The frequency distributions of measurements of a range of hydrocarbons at a remote rural site in southern Scotland (Auchencorth Moss) between 2007 and 2010 have been used to quantify the relationship between atmospheric lifetime and the geometric standard deviation of observed concentration. The analysis relies on an assumed common major emission source for hydrocarbons and BC, namely diesel-engined vehicles. The logarithm of the standard deviation of the log-transformed concentration data is linearly related to hydrocarbon lifetime, and the same statistic for BC can be used to assess the lifetime of BC relative to the hydrocarbons. Annual average data show BC lifetimes in the range 4–12 days, for an assumed OH concentration of 7 × 105 cm−3. At this site there is little difference in BC lifetime between winter and summer, despite a 3-fold difference in relative hydrocarbon lifetimes. This observation confirms the role of wet deposition as an important removal process for BC, as there is no difference in precipitation between winter and summer at this site. BC lifetime was significantly greater in 2010, which had 23% less rainfall than the preceding 3 years.
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► Hydrocarbon and black carbon concentrations are log-normally distributed. ► Standard deviation of log(concentration) of hydrocarbons correlates with lifetime. ► Black carbon lifetimes, by analogy, are between 4 and 12 days at this site. ► Black carbon lifetime is determined by rainfall, and similar in summer and winter.
An agricultural ammonia (NH
3) emission inventory in the North China Plain (NCP) on a prefecture level for the year 2004, and a 5 × 5 km
2 resolution spatial distribution map, has been calculated for ...the first time. The census database from China's statistics datasets, and emission factors re-calculated by the RAINS model supported total emissions of 3071 kt NH
3–N yr
−1 for the NCP, accounting for 27% of the total emissions in China. NH
3 emission from mineral fertilizer application contributed 1620 kt NH
3–N yr
−1, 54% of the total emission, while livestock emissions accounted for the remaining 46% of the total emissions, including 7%, 27%, 7% and 5% from cattle, pigs, sheep and goats, and poultry, respectively. A high-resolution spatial NH
3 emissions map was developed based on 1 × 1 km land use database and aggregated to a 5 × 5 km grid resolution. The highest emission density value was 198 kg N ha
−1 yr
−1.
The first high-resolution spatial distribution of ammonia emissions for the North China Plain showed rates up to 200 kg NH
3–N ha
−1 yr
−1.
This review considers the ways in which atmospheric organic nitrogen has been measured and linked to potential sources. Organic N exists in gas, particle and dissolved phases and represents a large ...(ca. 30%) fraction of total airborne nitrogen, but with large variability in time and space. Although some components (e.g. amines) have been the subject of several studies, little information is available for the many other components of organic N that have been identified in individual measurements. Measurements of organic N in precipitation have been made for many decades, but both sampling and chemical analytical methods have changed, resulting in data that are not directly comparable. Nevertheless, it is clear that organic N is ubiquitous and chemically complex. We discuss some of the issues which have inhibited the widespread adoption of organic N as a routine analyte in atmospheric sampling, and identify current best practice. Correlation analysis is the most widely used technique for attributing likely sources, examining the co-variation in time and/or space of organic N with other components of precipitation or particulate matter, yet the shortcomings of such simple approaches are rarely recognised. Novel measurement techniques which can identify, if not yet quantify, many of the components of particulate or dissolved organic N greatly enhance the data richness, thereby permitting powerful statistical analyses of co-variation such as factor analysis, to be employed. However, these techniques also have their limitations, and whilst specific questions about the origin and fate of particular components of atmospheric organic N may now be addressed, attempts to quantify and attribute the whole suite of materials that comprise atmospheric organic N to their sources is still a distant goal. Recommendations are made as to the steps that need to be taken if a consistent and systematic approach in identifying and quantifying atmospheric organic N is to progress. Only once sources have been recognised can any necessary control measures to mitigate adverse effects of atmospheric organic N on human health or ecosystem function be determined.
► There are no global patterns in the organic fraction of atmospheric nitrogen. ► Biogenic and anthropogenic components contribute to complex composition. ► Composition complexity confounds attempts to identify all but simple sources. ► Novel analytical techniques and statistical approaches hold promise for the future. ► Systematic and consistent sampling and analysis of atmospheric organic N are needed.
This paper reviews current understanding of the sources and sinks of ozone in the troposphere, recent studies of long-term trends, and the factors which have to be taken into consideration when ...constructing and interpreting future models of ozone concentration. The factors controlling surface O
3 concentrations are discussed initially to provide a basis for the ensuing discussion, followed by a summary of the evidence for recent trends in ground-level ozone concentrations, i.e. over the past 3 decades, which have shown a significant increase in the annual average in ‘background’ air typical of the unpolluted northern hemisphere. Closer to precursor sources, although urban winter concentrations have increased, rural peak spring and summer concentrations during ozone ‘episodes’ have decreased markedly in response to emissions reductions. In order to determine whether such trends are meaningful, the statistical techniques for determining temporal trends are reviewed. The possible causes of long-term trends in ozone are then discussed, with particular reference to the use of chemistry-transport models to interpret past trends. Such models are also used to make predictions of future trends in surface ozone concentrations, but few are comprehensive in integrating future climate changes with changes in land use and in emissions of ozone precursors. Guidance is given on the likely effects of climate/precursor/chemistry interactions so that model predictions can be judged.
The cycling of organic nitrogen through the atmosphere Jickells, T.; Baker, A. R.; Cape, J. N. ...
Philosophical transactions of the Royal Society of London. Series B. Biological sciences,
07/2013, Letnik:
368, Številka:
1621
Journal Article
Recenzirano
Odprti dostop
Atmospheric organic nitrogen (ON) appears to be a ubiquitous but poorly understood component of the atmospheric nitrogen deposition flux. Here, we focus on the ON components that dominate deposition ...and do not consider reactive atmospheric gases containing ON such as peroxyacyl nitrates that are important in atmospheric nitrogen transport, but are probably not particularly important in deposition. We first review the approaches to the analysis and characterization of atmospheric ON. We then briefly summarize the available data on the concentrations of ON in both aerosols and rainwater from around the world, and the limited information available on its chemical characterization. This evidence clearly shows that atmospheric aerosol and rainwater ON is a complex mixture of material from multiple sources. This synthesis of available information is then used to try and identify some of the important sources of this material, in particular, if it is of predominantly natural or anthropogenic origin. Finally, we suggest that the flux of ON is about 25 per cent of the total nitrogen deposition flux.
Over the last two decades significant effort has been dedicated to understanding the fate and transport of pesticides in surface water and groundwater and to use this understanding in the development ...of environmental policy and regulation. However, there have been few studies that have investigated the relationships between pesticides and climate change, and where this work has been undertaken it has principally been in relation to the impacts of climate change on agricultural production rather than in the context of environmental protection. This study addresses that gap by reviewing how climate change may impact the fate and transport of pesticides in surface and groundwaters as a pre-cursor to quantitative studies. In order to structure the review, we have adopted a source–pathway–receptor approach where climate sensitivities of pesticide source terms, environmental pathways and receptors are reviewed. The main climate drivers for changing pesticide fate and behaviour are thought to be changes in rainfall seasonality and intensity and increased temperatures, but the effect of climate change on pesticide fate and transport is likely to be very variable and difficult to predict. In the long-term, indirect impacts, such as land-use change driven by changes in climate, may have a more significant effect on pesticides in surface and groundwaters than the direct impacts of climate change on pesticide fate and transport. The review focuses on climate change scenarios and case studies from the UK; however, the general conclusions can be applied more widely.
Despite over a century of published reports of dissolved organic nitrogen (DON) in precipitation, its implications are still being appraised. The number of studies focusing on atmospheric organic ...nitrogen deposition has increased steadily in recent years, but comparatively little has been done to draw together this disparate knowledge. This is partly a consequence of valid concerns about the comparability of analysis and sampling methodologies. Given the current global trends in anthropogenic nitrogen fixation, an improved qualitative and quantitative understanding of the organic nitrogen component is needed to complement the well-established knowledge base pertaining to nitrate and ammonium deposition. This global review confirms the quantitative importance of bulk DON in precipitation. This cumulative data set also helps to resolve some of the uncertainty that arises from the generally locally and temporally limited scale of the individual studies. Because of analytical and procedural changes in recent decades, assessments are made of the comparability of the data sets; caution is needed in comparisons of individual studies, but the overall trends in the compiled set are more robust. Despite the large number of reports considered, evidence for long-term temporal changes in rainwater organic nitrogen concentrations is ambiguous. With regard to sources, it is likely that some of the organic material observed is not locally generated, but undergoes extensive or long-range atmospheric transport. The compiled data set shows a land-to-sea gradient in organic nitrogen concentration. Possible precursors, reported data on the most likely component groups, and potential source mechanisms are also outlined.
The current critical level for ammonia (CLE
NH3) in Europe is set at 8
μg NH
3 m
−3 as an annual average concentration. Recent evidence has shown specific effects of ammonia (NH
3) on plant community ...composition (a true ecological effect) at much smaller concentrations. The methods used in setting a CLE
NH3 are reviewed, and the available evidence collated, in proposing a new CLE
NH3 for different types of vegetation. For lichens and bryophytes, we propose a new CLE
NH3 of 1
μg NH
3 m
−3 as a long-term (several year) average concentration; for higher plants, there is less evidence, but we propose a CLE
NH3 of 3
±
1
μg NH
3 m
−3 for herbaceous species. There is insufficient evidence to provide a separate CLE
NH3 for forest trees, but the value of 3
±
1
μg NH
3 m
−3 is likely to exceed the empirical critical load for N deposition for most forest ecosystems.
The long-term critical level for NH
3 has been revised down to 1
μg m
−3 for the most sensitive plant species.
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