Kentucky Energy and Environment Cabinet 

Kentucky Division for Air Quality 

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Appendix K 

Recommended 

Improvements 

 

Appendix K - 1 

Kentucky Regional Haze SIP
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Appendix K - 2 

Kentucky Regional Haze SIP
Recommended Improvements

The Regional Haze Rule requires states to conduct a mid course review in 2012 of progress

toward reasonable progress goals for 2018. There are several technical improvements that are

recommended in the emissions inventory and air quality models that are used to support

regulatory decisions for regional haze. These technical improvements are also important for

states’ efforts to demonstration attainment of the ozone and PM2.5 health standards. 

1. Emissions inventory. We need to continue to improve emission inventories for regulatory

sources, particularly emissions profiles for the composition of PM2.5 emissions. 

2. Continued improvements are needed in the integrated one-atmosphere air quality models that

are used to project air quality responses to emissions reductions. The interactions among

primary and secondary pollutants in the atmosphere affect the levels of ozone, PM2.5, and

haze in the atmosphere. As our understanding of partitioning between gaseous and aerosol

phases improves, this understanding needs to be reflected in the models.

3. Sulfate performance for the CMAQ regional air quality model is good overall. Sulfate

deposition is frequently overestimated in the models, particularly in the summer months. 

Overestimation of precipitation volume from convective storms is one possible explanation. 

Improvements in treatment of convective systems in the meteorological models would

improve projections of pollutant deposition concentrations. At the coastal sites, when winds

are blowing from the Gulf of Mexico or Atlantic Ocean, CMAQ under estimates measured

sulfate at the monitors. Improvements to emissions inventories for commercial shipping in

the Gulf and Atlantic were made in 2006; additional refinements to emissions estimates are

needed. As well CMAQ’s processes should be reviewed for sulfate formation over water,

including availability of precursor species (hydrogen peroxide and ozone), dispersal patterns

for moving and fixed SO2 emission sources, and vertical and horizontal within clouds over

water. The accuracy of meteorological modeling of flux at the land-water interface is also an

area for additional attention. 

4. Nitrate is overestimated by the CMAQ model in the winter and underestimated in the

summer, although summer monitored values of nitrate are very low. In the southeastern US,

nitrate formation is driven largely by level of ammonia available in the atmosphere. Our

understanding of seasonal variation in ammonia emissions from agricultural sources has

improved; additional improvements in seasonal allocation of annual inventories would

improve model estimates of ammonium nitrate formation.

5. Organic carbon is generally underestimated in the CMAQ in the summer months. 

Improvement in the characterization of primary carbon emissions and partitioning between

gas and aerosol phase and formation of secondary organic aerosols is needed. 

6. We need better tools for organic carbon source apportionment. In aged aerosol most of

primary aerosol has reacted to form some secondary organic aerosol. Improved emissions

profiles and stable molecular makers for anthropogenic and biogenic sources and fossil and

modern carbon are critical. 

7. Consistent measurement techniques are needed between rural and urban monitoring networks

Appendix K - 3 

Kentucky Regional Haze SIP
so that concentrations of organic carbon and elemental carbon can be compared between

sites. 

8. To improve our understanding of the contribution of fire from natural forest fires, prescribed

burning, land clearing, and agricultural burning, states need to improve record keeping. 

Records should include acres burned, dates, location (latitude/longitude), fuel type, and

intensity of burn.

9. Additional improvements to international emissions inventory are needed to improve our

understanding of boundary conditions for our modeling domain and of the contributions from

international emissions to pollutant concentrations at the VISTAS Class I areas. Currently

monthly average inventories are used for non-US sources. Even when highly resolved

meteorological data are used, these monthly average inventories do not reflect the episodic

variation in emissions, particularly for fire events, that are important at the receptors. In the

current modeling we cannot distinguish Us from non-US sources of pollutant concentrations

at the boundaries of the model domain. We need to improve our ability to trace emissions

that originate within US as they are transported outside our modeling grid so that when they

re-circulate back into the modeling domain they retain their identify as US emissions rather

than non-US boundary conditions. 

10. The effect of meteorological model performance on air quality model performance needs

additional attention.

11. We need to capture the value of the continuous monitoring by evaluating model for the

diurnal and spatial patterns seen in the monitored data.

12. We need to improve confidence in trajectory model for periods greater than 72 hours. 

Currently trajectories of longer duration have such large bands of uncertainty as to reduce

any conclusions than can be drawn for transport greater than 72 hours.

Appendix K - 4 

Kentucky Regional Haze SIP