# Appendix K

Recommended ImprovementsAppendix K - 1Appendix K - 2

The Regional Haze Rule requires states to conduct a mid course review in 2012 of progress toward reasonable progress goals for 2018. There a re several technical improvements that are recommended in the emissions inventory and air qual ity models that are used to support regulatory decisions for regional haze. These techn ical improvements are also important for

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

1) Emissions inventory Continued improvements in emission inventories for regulatory sources, particularly emissions profiles for the composition of PM2.5 emissions is necessary.

2) Continued improvements are needed in the integrated one-atmosphere air quality models that are used to project air quality responses to emissi ons reductions. The interactions among primary and secondary pollutants in the atmosphere affect the levels of ozone, PM2.5, and haze in the atmosphere. As understanding of partit ioning between gaseous and aerosol phases improves, models reflecting this understandi ng need to be developed.

3) Sulfate performance for the CMAQ regional air quality model is good ov erall. Sulfate deposition is frequently overestimated in the model s, particularly in the summer months. Overestimation of precipitation volume from convect ive storms is one possible explanation. Improvements in treatment of convective systems in the meteorological models would improve projections of pollutant deposition concent rations. At the coastal sites, when winds are blowing from the Gulf of Mexico or Atlantic Oce an, 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 reviewe d for sulfate formation over water, including availability of precursor species (hydrog en peroxide and ozone), dispersal patterns for moving and fixed SO2 emission sources, and vert ical 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 a nd 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 amm onia available in the atmosphere. Current understanding of seasonal variation in ammonia emis sions from agricultural sources has improved; additional improvements in seasonal alloc ation of annual inventories would further improve model estimates of ammonium nitrate formation.

5) Organic carbon is generally underestimated in the CMAQ in the sum mer months. Improvement in the characterization of primary carb on emissions and partitioning between gas and aerosol phase and formation of secondary or ganic aerosols is needed.

6) Better tools for organic carbon source apportionment need to be developed. In aged aerosol most of primary aerosol has reacted to form some se condary organic aerosol. Improved emissions profiles and stable molecular makers for anthropogenic and biogenic sources and

fossil and modern carbon are critical.Appendix K - 3

7) Consistent measurement techniques are needed betwee n rural and urban monitoring networks so that concentrations of organic carbon and elemen tal carbon can be compared between

sites.

8) To improve understanding of the contribution of fir e from natural forest fires, prescribed burning, land clearing, and agricultural burning, s tates need to improve record keeping. Records should include acres burned, dates, locatio n (latitude/longitude), fuel type, and intensity of burn.

9) Additional improvements to international emissions inventory are needed to improve understanding of boundary conditions for modeling d omains 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 sou rces. Even when highly resolved meteorological data are used, these monthly average inventories do not reflect the episodic variation in emissions, particularly for fire event s, 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. States and RPOs need to improve their ability to trace emissions that originate within US as they ar e transported outside modeling grids 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 a ir quality model performance needs

additional attention.

11) Values of continuous monitoring need to be captured by evaluating model for the diurnal and spatial patterns seen in the monitored data.

12) Confidence in trajectory model for periods greater than 72 hours also needs to be improved. Currently trajectories of longer duration have such large bands of uncertainty as to reduce any conclusions than can be drawn for transport gre ater than 72 hours.