Nur H. Orak

Implications of a statistical occurrence model for mixture toxicity estimation, Orak N.H., Small M.J., 2016  Full paper:

Ambient Air Quality Near a Marcellus Shale Well Pad in Southwestern Pennsylvania


The objective of this study is to investigate the effect of shale gas well pad production activity on local air quality. The U.S. Department of Energy National Energy Technology Laboratory operated a mobile air monitoring laboratory to monitor ambient air quality 600 m-near a Marcellus shale well pad in southwestern Pennsylvania. Continuous air monitoring occurred over a year prior to well pad construction to characterize background conditions, and during drilling, hydraulic fracturing, flowback, and production activities.  High resolution air quality data were collected for the following compounds between 2011 and 2014: volatile organic compounds (VOCs), ozone, methane and carbon isotopes in methane, carbon dioxide (CO2) and carbon isotopes in CO2, coarse and fine particulate matter (PM10 and PM2.5), and organic and elemental carbon in aerosols. Also, meteorological data were collected during the same time intervals. To identify possible sources of pollutants and determine the contribution of sources to samples based on the fingerprints of the sources, we apply the U.S. Environmental Protection Agency (EPA) Positive Matrix Factorization (PMF) software, 5.0. PMF is a multivariate factor analysis tool to decompose factor profiles and contributions.


The results of two PMF solutions for baseline conditions and well pad development phases indicate that there are three potential factor profiles: natural gas, regional transport/photochemistry, and engine emissions. There is a significant contribution of vertical drilling, maintenance, and horizontal drilling stages to natural gas factor. The model outcomes show that there is an increasing contribution to engine emission factor over different well pad drilling through production phases. Moreover, model results suggest that the major contributors of the regional transport/photochemistry factor are vertical drilling, horizontal drilling and flowback stages. A comprehensive analysis of this case study of Western Pennsylvania provides useful information about the potential contaminant sources, which can lead a better risk assessment and management plan. 


A BBN Network for Risk Assessment of Air Pollutants in New York City


Network-Based Framework for Dose-Response Study Design and Interpretation

Past Research