Atmospheric nitrous oxide (N2O) significantly impacts Earth's climate due to its dual role as an inert potent greenhouse gas in the troposphere and as a reactive source of ozone-destroying nitrogen oxides in the stratosphere. Global atmospheric concentrations of N2O, produced by natural and anthropogenic processes, continue to rise due to increases in emissions linked to human activity. The understanding of the impact of this gas is incomplete as there remain significant uncertainties in its global budget. The experiment described in this thesis, in which a global chemical transport model (MOZART-4), a fine-scale regional Lagrangian model (NAME), and new high-frequency atmospheric observations are combined, shows that uncertainty in N2O emissions estimates can be reduced in areas with continuous monitoring of N2O mole fraction and site-specific isotopic ratios. Due to unique heavy-atom (15N and 18O) isotopic substitutions made by different N2O sources, the measurement of N2O isotopic ratios in ambient air can help identify the distribution and magnitude of distinct sources. The new Stheno-TILDAS continuous wave laser spectroscopy instrument developed at MIT, recently installed at the Mace Head Atmospheric Research Station in western Ireland, can produce high-frequency timelines of atmospheric N2O isotopic ratios that can be compared to contemporaneous trends in correlative trace gas mole fractions and NAME-based statistical distributions of the origin of air sampled at the station. This combination leads to apportionment of the relative contribution from five major N2O sectors in the European region (agriculture, oceans, natural soils, industry, and biomass burning) plus well-mixed air transported from long distances to the atmospheric N2O measured at Mace Head. Bayesian inverse modeling methods that compare N2O mole fraction and isotopic ratio observations at Mace Head and at Diibendorf, Switzerland to simulated conditions produced using NAME and MOZART-4 lead to an optimized set of source-specific N2O emissions estimates in the NAME Europe domain. Notably, this inverse modeling experiment leads to a significant decrease in uncertainty in summertime emissions for the four largest sectors in Europe, and shows that industrial and agricultural N2O emissions in Europe are underestimated in inventories such as EDGAR v4.3.2. This experiment sets up future work that will be able to help constrain global estimates of N2O emissions once additional isotopic observations are made in other global locations and integrated into the NAME-MOZART inverse modeling framework described in this thesis.

Nitrous oxide (N2O) and molecular nitrogen (N2) isotopic compositions and aerosol optical properties were investigated through experiments and observations to elucidate their roles in atmospheric radiative transfer and chemistry. In Earth's atmosphere, the isotopic composition of N2O, a potent greenhouse gas, is a useful tool for investigating its sources and sinks. N2 is the main component of the atmospheres of Earth and Titan, and isotope effects in its photoionization may lead to isotopic fractionation. The optical properties of aerosols, a component of most planetary atmospheres, determine how they affect radiative transfer. A polarimeter was developed to measure aerosol optical properties in situ in an existing apparatus. Three sets of measurements of N2O isotopic composition provide new insight into its budget. First, a time-series from 1940 to 2005 from firn and archived air samples is consistent with the observed N2O increase being largely due to isotopically light N2O emissions from agriculture and reveals seasonal cycles due to the seasonally-varying influences of multiple N2O sources and stratosphere-troposphere exchange. Second, measurements from the tropical free troposphere show coherent vertical variations in N2O isotopic compositions consistent with the persistent influence of a regional surface source, most likely the ocean. Third, samples from the marine boundary layer with anomalously high N2O mixing ratios and perturbed isotopic compositions were used to deduce a source isotopic composition that is perhaps representative of N2O emitted from the South Atlantic Ocean. Isotope effects in the non-dissociative photoionization of N2 -- investigated by measuring the photoionization efficiency spectrum for its three isotopologues -- clarify peak identities and show that these previously ignored isotope effects may be important in planetary atmospheres. The shifts in peak energy due to isotopic substitution show that the controversial peak at 15.68 eV for 14N2 is most likely due to a Rydberg state converging to the v'=2 level of the A2[pi]u N2+ state. A model of Titan's atmosphere shows that isotopic self-shielding in 14N2 photoionization may cause isotopic fractionation between N2 and other N-bearing molecules distinct from that caused by N2 photodissociation, providing a possible mechanism for determining the relative importance of ion versus neutral photochemistry.

Balancing Greenhouse Gas Budgets: Accounting for Natural and Anthropogenic Flows of CO2 and other Trace Gases provides a synthesis of greenhouse gas budgeting activities across the world. Organized in four sections, including background, methods, case studies and opportunities, it is an interdisciplinary book covering both science and policy. All environments are covered, from terrestrial to ocean, along with atmospheric processes using models, inventories and observations to give a complete overview of greenhouse gas accounting. Perspectives presented give readers the tools necessary to understand budget activities, think critically, and use the framework to carry out initiatives. Written by a combination of experts across career stages, presenting an integrated perspective for graduate students and professionals alike Includes sections authored by those involved in both early and later IPCC assessments Provides an interdisciplinary resource that spans many topics and methodologies in oceanic, land and atmospheric processes

In 1969 the North Atlantic Treaty Organisation (NATO) established the Committee on Challenges of Modern Society (CCMS). The subject of air pol- tion was from the start, one of the priority problems under study within the fra- work of various pilot studies undertaken by this committee. The organization of a periodic conference dealing with air pollution modeling and its application has become one of the main activities within the pilot study relating to air pollution. The first five international conferences were organized by the United States as the pilot country; the second five by the Federal Republic of Germany; the third five by Belgium; the next four by The Netherlands; and the next five by Denmark; and with this one, the last three by Portugal. th This volume contains the papers and posters presented at the 27 NATO/CCMS International Technical Meeting on Air Pollution Modeling and Its Application held in Banff, Canada, 24-29 October 2004. The key topics at this ITM included: Role of Atmospheric Models in Air Pollution Policy and Abatement Strategies; Integrated Regional Modeling; Effects of Climate Change on Air Quality; Aerosols as Atmospheric Contaminants; New Developments; and Model Assessment and Verification. 104 participants from North and South America, Europe, Africa and Asia attended th the 27 ITM. The conference was jointly organized by the University of Aveiro, Portugal (Pilot Country) and by The University of Calgary, Canada (Host Country). A total of 74 oral and 22 poster papers were presented during the conference.

Understanding, quantifying, and tracking atmospheric methane and emissions is essential for addressing concerns and informing decisions that affect the climate, economy, and human health and safety. Atmospheric methane is a potent greenhouse gas (GHG) that contributes to global warming. While carbon dioxide is by far the dominant cause of the rise in global average temperatures, methane also plays a significant role because it absorbs more energy per unit mass than carbon dioxide does, giving it a disproportionately large effect on global radiative forcing. In addition to contributing to climate change, methane also affects human health as a precursor to ozone pollution in the lower atmosphere. Improving Characterization of Anthropogenic Methane Emissions in the United States summarizes the current state of understanding of methane emissions sources and the measurement approaches and evaluates opportunities for methodological and inventory development improvements. This report will inform future research agendas of various U.S. agencies, including NOAA, the EPA, the DOE, NASA, the U.S. Department of Agriculture (USDA), and the National Science Foundation (NSF).

This eBook presents highlight papers from the 17th International conference of the Recycling of Agricultural, Municipal and Industrial Residues to Agriculture Network (RAMIRAN) that was held in Wexford, Ireland in September 2017. The book contains a broad range of papers around this multidisciplinary theme covering topics including regional and national organic resource use planning, impact of livestock diet on manure composition, fate and utilisation of excreta from grazing livestock, anaerobic digestion, overcoming barriers to resource reuse, hygienic aspects of residue recycling and impacts on soil health. The overarching theme being addressed is the sustainable recycling of organic residues to agriculture, to promote effective nutrient use and minimise environmental impact.