Keywords:
AIR TOXICS, HOMELAND SECURITY, CMAQ, AIR QUALITY MODELING, HUMAN EXPOSURE MODELING, SUBGRID AIR POLLUTANT VARIABILITY, ATMOSPHERIC CHEMISTRY, FINE PARTICULATES,
Project Information:
Progress
:During FY-03, this task was retitled "Community-scale modeling for air toxics and homeland security", replacing the original title of "Fine-scale modeling." This new title reflects an effort to coordinate closely with the air toxics task (Task 15170) by developing a fine-scale modeling tool in concert with the NATA assessment that is being performed at a grid resolution of 36 km. This new title also indicates support to the homeland security modeling effort. Collaborators on this task include NOAA's Atmospheric Transport and Diffusion Division, University of Houston, EPA Region 3, OAQPS, HEASD, and the CMAQ model development, model evaluation, air toxics, and physical modeling teams within AMD.
During FY-00, the design of a prototype system to link air quality modeling with human exposure modeling was initiated. This initial design included efforts to extend the grid resolution of CMAQ to a 1.33 km mesh and to identify, develop and test options for linking CMAQ output with human exposure models. The Philadelphia metropolitan area was selected to test this approach. A simple exposure paradigm was set up to begin exploring linkage; one element of this paradigm included the capability to generate gridded population data from census tracts. Computational Fluid Dynamics (CFD) and physical modeling studies at the AMD Fluid Modeling Facility provide a resource for developing parameterizations for modeling dispersion in complex urban morphologies. Collaboration with NOAA-ATDD was begun to use a chemistry version of a Large Eddy Simulation (LES) model to produce information on the chemical variability of several reactive toxic species such as formaldehyde. Preliminary plans and results of the initial modeling design were presented at several conferences.
During FY-01, work focused on enhancing the meteorological and chemical model formulations to accomodate a grid resolution of 1.33 km, on designing the linkage between CMAQ and NERL's Stochastic Human Exposure-to-Dose (SHEDS) model, and on developing methods for treating subgrid scale dispersion and chemical variability. Investigations included initial introduction and testing of recent urban canopy parameterization schemes in the meteorological model that drives CMAQ.
During FY-02, urban canopy parameterizations were implemented in the MM5 meteorological processor and test simulations were perfomed with CMAQ. An APM based on preliminary results of CMAQ modeling of PM and air toxics at neighborhood scales for simulations of the Philadelphia domain was prepared.
During FY-03, the task expanded to include support for homeland security and to focus efforts on development of a fine-scale modeling prototype to support a human exposure modeling assessment of toxic compounds for the Philadelphia metropolitan area. This redirection capitalized on the availability of computer resources, the expansion of the CMAQ to include additional air toxics compounds, and the ability to make long-term (annual) simulations for specific air toxics compounds, such as formaldehyde, acetaldehyde, acrolein, benzene, and methylene chloride. Annual simulations of these compounds for a 4 km mesh centered over Philadelphia will provide valuable information on concentration distributions for variable spatial resolutions using a chemical transport model. Also during FY-03, physical modeling of emissions from the World Trade Center disaster site continued in earnest. This effort entails the use of a 1-to-600 scale model of lower Manhattan inserted in the Division's meteorological wind tunnel. Results from this effort will be used to characterize the dispersion of compounds emitted following the collapse of the World Trade Center. Results will also be used to improve numerical modeling of flow and dispersion in complex urban settings. During FY-03, collaboration was initiated with Los Alamos to use a numerical model, called QUIC, to estimate dispersion aro
Relevance
:Current state-of-the-science air quality models do not provide an explicit and proven link between modeled concentration fields and human exposure. Tools are needed for assessing human exposure to air toxics and for estimating the dispersion of airborne substances in Homeland Security situations. These tools are needed at community-scale resolutions, especially across urban areas where the distribution of concentrations (across space and time) can be highly complex. Even where observational data exist for human exposure assessments, the temporal sampling and the spatial extent of the monitoring network are usually too sparse to resolve the concentration fields. Until recently, chemical grid models did not speciate individual toxic compounds, and the concentration fields were limited to relatively coarse spatial resolutions (on the order of 20 km). Traditional Gaussian plume models, however, do not account for complex chemistry and fail to adequately account for background contributions. Methods to bridge modeling and monitoring approaches in order to determine concentration variations arising from the juxtaposition of concentrations from the regional and urban sources are needed.
This task is essentially a methods development project to rationally link emissions-based modeling with ambient and exposure monitors to provide concentration fields needed as critical inputs to models of human exposure (and epidemiological studies). The initial effort is characterized as a proof of concept-requirements analysis study. The project will include, but not be limited to, deriving various functional linkages between the Models-3/CMAQ emissions-based modeling system concentration fields of key air toxic and particulate matter parameters with ambient fixed site and personal exposure monitoring data, and incorporating into the methodologies, flow visualization, computational fluid dynamics modeling and statistical techniques. The project will further develop and derive functional relationships that provide a mapping across space and time between the modeled and monitored fields. The investigation will consider the method's strengths and weaknesses, sensitivities to model grid resolution, under different emissions scenarios, for different and full range of averaging time periods from hourly to annual fields. The effort will include methods for modeling exposures for a variety of human activity patterns.
Clients
:Joe Tikvart - OAR/OAQPS, Sally Shaver, Dennis Pagano, EPA-Region 3
Project IDs:
ID Code
:15172
Project type
:OMIS