Application of Emissions Inventory Uncertainty Estimates to State Implementation Planning

摘要

Emissions inventories are the building block for developing State Implementation Plans (SIPs). They are used to establish the baseline for reasonable further progress. An analysis of the emissions inventory is the starting point for developing a set of controls to reach attainment of the standard. Modeling for developing a control plan has three basic inputs - the emissions inventory, the meteorology, and monitoring results. Uncertainty in the emissions inventory will lead to uncertainty in the modeling results and the corresponding controls that are developed based on the modeling. A number of studies have been performed to evaluate emissions inventories based on monitoring data. This paper shows how results from these studies can be combined with photochemical modeling to assess the uncertainty in the model results. First standard photochemical modeling is performed. This includes developing a base case, evaluating model performance, and determining the level of reduction needed to predict attainment of the standard with projected future year emissions. Second, a set of alternate emissions inventories is developed based on the uncertainties from emissions inventory performance evaluation studies. These alternate inventories are then modeled with the base case (instead of the standard base case emissions) to determine the difference in model performance using these alternates, compared to the standard emissions. Next, the alternate emissions are projected to the future and modeled to determine the level of reduction that would be necessary to attain the standard under each alternative. This set of reduction levels is compared to that developed with the standard emissions to determine what difference there is in the level of reductions and the path toward attainment. If the results are similar in terms of estimated reduction levels and/or show the same direction is needed to attain the standard, then the uncertainty in the modeled results are significantly reduced. If, however, different reduction paths are determined, then additional efforts are needed to establish a better set of emissions upon which to base regulatory decisions. The process is illustrated with information used to develop the SIP submitted by the TNRCC for the Houston/Galveston (H/G) nonattainment area.