Environmental Engineering Reference
In-Depth Information
1. Introduction
Aircrafts and airport sources emit a variety of pollutants, but limited studies have
quantified their contributions using comprehensive air quality models. From a
population risk perspective, there are questions about the ideal spatial domain and
resolution for chemistry-transport modeling. Although the largest domain and finest
resolution would be desired in principle, there are logistical and computational
constraints, and it is important to know over what spatial domain most of the
population exposure occurs, and whether this depends on the model resolution.
Even with the application of a complex model such as CMAQ, multiple modeling
choices can be made that will influence the model run-time and complexity, with
unclear implications for health impact estimates. High-resolution modeling (with
smaller or nested grid cells) represents the theoretical optimum but is more
computationally demanding and requires more refined emissions data, and it is
unclear whether such modeling is necessary in a given decision context. The optimal
spatial domain and resolution may differ across pollutants as well as across airports.
2. Modeling Approach
In this study, we consider emissions from commercial aircraft activities from three
airports in the U.S. - Hartsfield-Atlanta International Airport (ATL, Georgia),
Chicago O'Hare International Airport (ORD, Illinois), and T.F. Green Airport
(PVD, Rhode Island). We included 73 commercial aircraft types for ATL, 109 for
ORD, and 144 for PVD. Emissions Dispersion Modeling System (EDMS)
emissions of criteria pollutants and air toxics were generated for each of the
airports. To provide realistic representations of all emissions from aviation and
airport-related sources, we developed EDMS2Inv [1], an interface to the Sparse
Matrix Operator Kernel Emissions (SMOKE) modeling system, to process hourly
emission inventory outputs from EDMS to create emissions inputs to CMAQ. The
CMAQ model application has a varying vertical resolution from the surface to 50
millibars (about 18 km). There are a total of 22 layers, with the first 15 layers
spanning 10,000 ft, where aircraft emissions are provided. There is thus a
significant spatial enhancement in the vertical representation of aviation emissions
in the vicinity of the airports during the Landing and Takeoff (LTO) cycle.
To characterize exposures, we performed MM5-SMOKE-CMAQ modeling
with and without airport emissions at 36 × 36 km and 12 × 12 km resolutions. We
used CMAQ in a one-atmosphere mode, to include treatment of ozone, PM
2.5
and
air toxics. Recent risk prioritization work indicated that health risks would be
dominated by PM
2.5
and that cancer risks from air toxics would be most influenced
by formaldehyde and 1,3-butadiene with contributions from acetaldehyde and
benzene, arguing for their inclusion in this analysis [2]. Additional details of the
