air quality management information system |
for urban and industrial applications
Environmental Impact Assessment
EIA, legal framework and procedure is mainly define in (85/337/EC);
that EIA Directive of 1985 has been amended three times, in 1997, in 2003 and in 2009:
For impacts in terms of emissions and air quality, other relevant Directives include
(2008/50/EC), the consolidated Airquality Framework Directive;
EIA in AirWare:
Relevant project that can be addressed with AirWare involve everything that will lead to
changes in local emissions; this can be new or modified emission sources,
or policies (like speed limits or traffic control) that will affect emissions patterns.
The basic methodology is straight forward:
- Establish a baseline, calibrate and validate the model tools for the baseline;
- Describe the project including a number of variants or alternatives in
terms of emission (or target) scenarios and mitigation strategies,
- Simulate the impacts in terms of
- Ambient pollutant concentrations with full spatial coverage at high resolution,
- Compliance with air quality standards for various aggregation periods,
- Population exposure, with emphasis on sensitive groups or locations,
including the assessment of indoor air quality,
- Environmental and economic damages (including structures, assets) with a range of valuation methods;
- Evaluate the alternatives (usually a multi-criteria ranking).
Multi-Model based assessment:
Results depend also on the choice of model. Therefore, the basic methodology uses
several models: the widely used and often stipulated regulatory Gaussian model AERMOD (USEPA)
for a first screening, at typical resolution of 500 to 100 m, and for a few years
of hourly simulations; this determines the basic compliance or expected exceedances.
Where the resulting "worst case" estimates indicate possible violations of air
quality standards (NOx/NO2), we re-run the scenario at high resolution and subsequent
aggregation to the required resolution, replacing point estimates with areal averages.
AERMOD simulates conservative NOx, most air quality standard are defined for NO2:
for NO2, AERMOD/OLM version is used for a "compatible" yet simple NO2 estimate;
in parallel, for the days of predicted exceedances, we run AERMOD for
24 hours to obtain detail hourly results for sensitivity analysis
(meteorology, resolution, spacing of receptor points, source characteristics such as stack heights).
To get more "physically based" estimates of NO2 and particulates, the 3D Eulerian photochemical model
CAMx (driven by MM5 prognostic meteorology) is run in a nested grid
setup for a few days "around" the period of predicted violations,
also exploring different grid resolutions; and alternative option is the Eulerian model is CMAQ.
Where major sources representing traffic
(represented by low lying area sources) are involved, TRAFFIC, a kernel/convolution
based model for line sources with a mixing zone approach is also used for comparison;
For major point sources and dynamic meteorological conditions, CAMx/PIG is used;
for mobile point sources (harbors, airports) or high-resolution near-field analysis,
we can also run a version of INPUFF to avoid the extreme values predicted as steady-state
solution by AERMOD under low wind conditions. A more complex alternative Lagrangian model
system would be CALPUFF/CALMET.
Finally, for complex terrain and "near-field"
violations (typically from low level emissions) we run TIMES, a 3D dynamic CFD model
with a very high spatial resolution and explicit representation of 3D terrain and obstacles.
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