Wednesday, 13 January 2016: 4:30 PM
Room 356 ( New Orleans Ernest N. Morial Convention Center)
In 2011 the state of Maryland enacted a moratorium on natural gas extraction from horizontal drilling and hydraulic fracturing citing concerns about human health and environmental impacts of these operations. While conventional natural gas extraction (vertical wells with limited or no hydraulic fracturing required) has been common practice for over a century, the combination of horizontal drilling with large scale hydraulic fracturing to access natural gas in shale formations is a relatively new technology and therefore much is uncertain with regard to environmental impacts. Shale gas development generates emissions of particulate matter (PM), volatile organic compounds (VOCs) and oxides of nitrogen (NOx) during well pad construction, drilling, and hydraulic fracturing. Leaks of natural gas from exploration and production activity result in release of methane and VOCs to the atmosphere. Methane is a potent greenhouse gas and implications for climate change from large scale shale gas development are uncertain. Two counties in the western Maryland panhandle, Garrett and Allegany, are underlain by the gas-rich Marcellus and Utica shale formations. Areas to the north, west, and south in Pennsylvania and West Virginia have experienced extensive shale gas development over the past decade. To determine the air quality conditions in western Maryland during the moratorium, ambient air monitoring was conducted using NETL's Mobile Air Monitoring Laboratory at a rural location near Oakland in Garrett County during two monitoring periods: May – August 2014 (spring/summer) and November 2014 through February 2015 (fall/winter). The measured species included methane, oxides of nitrogen (NOx), fine and coarse particulate matter (PM2.5 and PM10), volatile organic compounds (VOCs), and ozone. To discern the contribution from oil and natural gas emissions sources in the surrounding areas in Pennsylvania and West Virginia, methane and ethane concentration trends were examined. The methane data included the isotopic composition such that contributions from biogenic, surface-related sources and thermogenic (derived from deep underground, i.e. natural gas) methane sources could be distinguished from typical background atmospheric methane. The average methane concentration for both monitoring periods was 2.0ppm, a typical background atmospheric methane concentration. Concentrations were consistently near background, but on occasions of higher concentration (7 short-lived peaks during the spring/summer period and 17 during the fall/winter period), inspection of the isotopic composition revealed influence from a thermogenic source as the probable cause. Significant differences in the presence of VOCs and their concentrations were observed between the spring/summer and fall/winter measurement periods. In general, higher average and maximum concentrations were observed during the winter measurement period. This is likely due to wintertime meteorology and the occurrence of overnight temperature inversions that trap and concentrate VOCs in the atmospheric boundary layer. Of the measured VOCs, alkanes (ethane, propane, butane, pentane) were detected most frequently and at the highest concentrations and are constituents of natural gas. Detailed analysis of the methane and VOCs data as well as observed trends of PM, NOx, and ozone are presented. The methane and ethane data will be further analyzed and presented to quantify the impact of shale gas development in neighboring counties on the Oakland, Maryland monitoring location.
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