Modeled Representation of Visibility Impacts due to Emissions Associated with Oil and Gas

摘要

We evaluate the model estimated impact of emissions from oil and gas (O&G) activities on visibility, focusing on National Parks (NPs) in the Western US. We use a regional photochemical modeling platform representing a best estimation of emissions and meteorology in the year 2011. This platform includes fine spatial (12km by 12km) and temporal (hourly) detail of inputs and includes the most current estimation of emissions associated with O&G activities in the Western US. The O&G emissions inventory was developed and evaluated for model performance by the Intermountain West Data Warehouse -Western Air Quality Study (IWDW-WAQS). By running the model both with and without emissions associated with O&G and comparing the model output of these two runs, we can estimate the modeled impact of O&G emissions on all air quality metrics including visibility. We show how O&G impacts on visibility change between the highest and lowest impaired days and seasons, and we evaluate the relative impact of the different species that make up fine Particulate Matter (PM). We also explore emissions modeling assumptions related to primary PM speciation. Findings suggest that O&G impacts on visibility are mostly localized in the Western US meaning that O&G operations have the largest impact on visibility in NPs that are located close to O&G basins. However, O&G impacts on visibility are widespread in Texas and Oklahoma mostly related to the formation of nitrate during winter months. At eleven class II national parks, which are not subject to the Regional Haze Rule requirements, the O&G production activity contributed more than 0.5 DV to the average 20% worst haze days. Finally, relative to the Federal Land Managers' Air Quality Related Values Group (FLAG) criteria, there are six National Park Service units with greater than 1 deciview (DV) modeled change in visibility due to O&G emissions on more than 50 days of the 2011 modeling year, and 17 NPs where O&G caused more than 0.5 DV of haze on at least 50 days a year.