Browsing by Subject "Air"

Now showing 1 - 6 of 6
  • Thumbnail Image
    ItemOpen Access
    Estimation of in-canopy ammonia sources and sinks in a fertilized Zea mays field.
    (Environ Sci Technol, 2010-03-01) Bash, JO; Walker, JT; Katul, GG; Jones, MR; Nemitz, E; Robarg, WP
    An analytical model was developed to describe in-canopy vertical distribution of ammonia (NH(3)) sources and sinks and vertical fluxes in a fertilized agricultural setting using measured in-canopy mean NH(3) concentration and wind speed profiles. This model was applied to quantify in-canopy air-surface exchange rates and above-canopy NH(3) fluxes in a fertilized corn (Zea mays) field. Modeled air-canopy NH(3) fluxes agreed well with independent above-canopy flux estimates. Based on the model results, the urea fertilized soil surface was a consistent source of NH(3) one month following the fertilizer application, whereas the vegetation canopy was typically a net NH(3) sink with the lower portion of the canopy being a constant sink. The model results suggested that the canopy was a sink for some 70% of the estimated soil NH(3) emissions. A logical conclusion is that parametrization of within-canopy processes in air quality models are necessary to explore the impact of agricultural field level management practices on regional air quality. Moreover, there are agronomic and environmental benefits to timing liquid fertilizer applications as close to canopy closure as possible. Finally, given the large within-canopy mean NH(3) concentration gradients in such agricultural settings, a discussion about the suitability of the proposed model is also presented.
  • Thumbnail Image
    ItemOpen Access
    Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies.
    (The New phytologist, 2014-05) Zaehle, Sönke; Medlyn, Belinda E; De Kauwe, Martin G; Walker, Anthony P; Dietze, Michael C; Hickler, Thomas; Luo, Yiqi; Wang, Ying-Ping; El-Masri, Bassil; Thornton, Peter; Jain, Atul; Wang, Shusen; Warlind, David; Weng, Ensheng; Parton, William; Iversen, Colleen M; Gallet-Budynek, Anne; McCarthy, Heather; Finzi, Adrien; Hanson, Paul J; Prentice, I Colin; Oren, Ram; Norby, Richard J
    We analysed the responses of 11 ecosystem models to elevated atmospheric [CO2 ] (eCO2 ) at two temperate forest ecosystems (Duke and Oak Ridge National Laboratory (ORNL) Free-Air CO2 Enrichment (FACE) experiments) to test alternative representations of carbon (C)-nitrogen (N) cycle processes. We decomposed the model responses into component processes affecting the response to eCO2 and confronted these with observations from the FACE experiments. Most of the models reproduced the observed initial enhancement of net primary production (NPP) at both sites, but none was able to simulate both the sustained 10-yr enhancement at Duke and the declining response at ORNL: models generally showed signs of progressive N limitation as a result of lower than observed plant N uptake. Nonetheless, many models showed qualitative agreement with observed component processes. The results suggest that improved representation of above-ground-below-ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of eCO2 effects. Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C-N budgets. The two FACE experiments are insufficient to fully constrain terrestrial responses to eCO2 , given the complexity of factors leading to the observed diverging trends, and the consequential inability of the models to explain these trends. Nevertheless, the ecosystem models were able to capture important features of the experiments, lending some support to their projections.
  • Thumbnail Image
    ItemOpen Access
    Identifying and Evaluating Air Filtration Methods for Personal Protection from Airborne Particulate Matter
    (2011-04-29) Ramadan, Ramsey
    Air pollution is a major environmental health risk in both developing and developed countries. According to the World Health Organization (WHO), air pollution is responsible for more than two million deaths worldwide every year. The WHO recognizes that particulate matter (PM) is the most dangerous among the various air pollutants and affects more people than any other. Exposure to fine particulate matter is dominated by emissions from anthropogenic point sources such as from vehicles, industry and power plants; for larger, coarse particulate matter the major sources are from road dust, construction and wind-blown dust from agricultural areas. Most approaches to reduce exposure involve controls on the emitting sources. Though this approach reduces the health risks, it cannot sufficiently protect our sensitive populations from point source PM, especially fine PM. Air filtration devices such as personal face mask filters are rapidly implementable solutions to reduce fine PM exposure at the point of contact. Most personal face mask filters are designed as single-use devices for the medical and chemical industries; whereas an air filter designed for the general population must allow for multiple uses and protection from PM. Given a set of criteria, the conceptual personal filtration device was evaluated in a case study of China where, if the devices were adopted by the population, health costs associated with fine PM exposure are estimated to be reduced by up to 87% ($ 223 billion).
  • Thumbnail Image
    ItemOpen Access
    United States and Canada Air Quality Management Standard Implementation Plan
    (2023-04-27) Koehn, Shelley
    Organizations can use internal management standards to set guidelines and expectations for various program areas, including stretch goals to push themselves to be leaders in a given space. Company A, a global manufacturing company, is working through creating and implementing a new Air Quality Management Standard, which supports its internal organizational goals to have a best-in-class Environmental, Health, and Safety (EHS) program. This project involved gathering necessary background information via pilot site reviews, document comparison, and internal interviews in order to prepare an Air Quality Management Standard Implementation Plan for Company A’s United States and Canada region. In addition, the overall Standard creation process was evaluated, and the project lead to the creation of a recommendation memo outlining strategy tools that could increase the efficiency and clarity of future Standard rollouts within Company A’s EHS group. This memo could also be applied to the five-year update process for the existing 50+ EHS Standards.
  • Thumbnail Image
    ItemOpen Access
    United States Environmental Protection Agency Clean Air Research Program Accomplishments Report
    (2009-04-24T13:28:14Z) Hagan, Nicole
    Millions of dollars are spent annually on research to advance the scientific basis for setting air quality standards and implementing programs to protect public health and the environment. It is necessary for the U.S. Environmental Protection Agency’s Office of Research and Development (ORD) to document and evaluate their accomplishments in order to communicate the value of their research to the public and government leaders. This report is intended to highlight the major research accomplishments of EPA’s Clean Air Research Program since 2002. Among the most notable achievements are near roadway studies, understanding emissions from wild and prescribed fires, advancing characterization of emissions, improving source apportionment and characterization, and control of secondary PM2.5 from coal combustion. Significant progress has also been made in understanding secondary organic aerosol formation, development of a new secondary organic aerosol model, updating emissions inventories, and improving measurement and modeling techniques. Additionally, health research has investigated target doses of pollutants to various human lung sites, identified risk factors for susceptible subpopulations, uncovered biological mechanisms for cardiopulmonary effects, identified new target tissues from air pollution exposure, and explored co-pollutants and other mediating factors. Research generated by ORD directly affects the National Ambient Air Quality standards setting process through health and environmental research, supports the evaluation of environmental conditions with monitoring and modeling research, provides information to states for regulation and management via technical products and support, and allows EPA to track progress. This report, in addition to summarizing the major research accomplishments of ORD, evaluates the research accomplishments against the framework for air quality management, detailing which efforts directly support the framework and how future research will support the framework. With the support of research generated by the Clean Air Research Program, EPA can continue to protect human health and the environment from the adverse effects of air pollution.
  • Thumbnail Image
    ItemOpen Access
    Where does the carbon go? A model-data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free-air CO2 enrichment sites.
    (The New phytologist, 2014-08) De Kauwe, Martin G; Medlyn, Belinda E; Zaehle, Sönke; Walker, Anthony P; Dietze, Michael C; Wang, Ying-Ping; Luo, Yiqi; Jain, Atul K; El-Masri, Bassil; Hickler, Thomas; Wårlind, David; Weng, Ensheng; Parton, William J; Thornton, Peter E; Wang, Shusen; Prentice, I Colin; Asao, Shinichi; Smith, Benjamin; McCarthy, Heather R; Iversen, Colleen M; Hanson, Paul J; Warren, Jeffrey M; Oren, Ram; Norby, Richard J
    Elevated atmospheric CO2 concentration (eCO2) has the potential to increase vegetation carbon storage if increased net primary production causes increased long-lived biomass. Model predictions of eCO2 effects on vegetation carbon storage depend on how allocation and turnover processes are represented. We used data from two temperate forest free-air CO2 enrichment (FACE) experiments to evaluate representations of allocation and turnover in 11 ecosystem models. Observed eCO2 effects on allocation were dynamic. Allocation schemes based on functional relationships among biomass fractions that vary with resource availability were best able to capture the general features of the observations. Allocation schemes based on constant fractions or resource limitations performed less well, with some models having unintended outcomes. Few models represent turnover processes mechanistically and there was wide variation in predictions of tissue lifespan. Consequently, models did not perform well at predicting eCO2 effects on vegetation carbon storage. Our recommendations to reduce uncertainty include: use of allocation schemes constrained by biomass fractions; careful testing of allocation schemes; and synthesis of allocation and turnover data in terms of model parameters. Data from intensively studied ecosystem manipulation experiments are invaluable for constraining models and we recommend that such experiments should attempt to fully quantify carbon, water and nutrient budgets.