REACTIVE NITROGEN EMISSIONS AND DEPOSITION FROM UNCONVENTIONAL NATURAL GAS EXTRACTION IN THE MARCELLUS SHALE BASIN

Emissions of nitrogen oxides (NOx = NO + NO2) in the United States (U.S.) from large stationary sources, such as electric generating units, have decreased since 1995 and resulted in the associated decreases in nitrogen (N) deposition, ambient ozone and nitrogen dioxide (NO2) concentrations. However, increasing NOx emissions from emerging industries, such as unconventional natural gas (UNG) extraction, could potentially offset gains in stationary source emission reductions in shale gas producing regions of the U.S. The Marcellus Shale in the northeastern U.S. has seen dramatic increases in the development of wells over the past ten years, and it is currently unknown whether NOx emissions from UNG extraction are having an effect on ecosystems or air quality. \ud In our study, modeling, experimental, and field studies were used to investigate the influence of Marcellus Shale UNG extraction activities on local and regional fluctuations in N emissions, ambient concentrations, and deposition fluxes. In one study, we determined that federal deposition monitoring networks do not effectively capture regional well pad NOx emissions, despite the high well pad density areas of northeastern and southwestern Pennsylvania where NOx emissions densities can reach 21 kg NOx ha-1 year-1. In another study, passive samplers were deployed at a collaborative research well in the Marcellus Formation, the Marcellus Shale Energy and Environment Laboratory (MSEEL) located in Morgantown, West Virginia (WV) to assess spatio-temporal changes in ambient concentrations, deposition, and isotopic composition of key reactive nitrogen species over a transect spanning the research well pad and access road. NO2, nitric acid (HNO3), ozone (O3), and ammonia (NH3) were measured over the entire well cycle from site development through production. Using an isotopic mixing model, we determined that the N deposition attributable to well pad activities ranged from 0.16 to 0.55 kg N ha-1 within 400 m of the well pad. This research demonstrates that even though well pad activities are not effectively being monitored on a regional scale, the activities are having an effect on local N deposition dynamics and are high enough to impact local ecosystems in high well pad density areas