该研究关注了过去二十年中水平钻井和水力压裂技术的进步，这些技术导致了大量以前无法开采的天然气储量被开发，但也引发了对空气质量影响的担忧。实验结果显示，天然气开采释放的挥发性有机化合物（VOCs）可能超过行业估计的1.5到3倍，这些VOCs可能有毒，能产生地面臭氧或二次有机气溶胶，并影响气候。在科罗拉多州丹佛-朱尔斯堡盆地和宾夕法尼亚州马塞勒斯页岩地区的测量显示，天然气排放是多数C2-C8烷烃的主要来源，但对烯烃和芳烃的贡献较小。天然气排放占羟基自由基反应性的约20%，这可能阻碍下游城市符合联邦臭氧标准。健康风险评估表明，尽管在宾夕法尼亚州的天然气井附近没有增加的癌症或慢性非癌风险，但天然气排放对总风险的贡献在井附近是常态的3-6倍。
【摘要】
Advances in horizontal drilling and hydraulic fracturing over the past two decades have allowed access to previously unrecoverable reservoirs of natural gas and led to an increase in natural gas production. Intensive unconventional natural gas extraction has led to concerns about impacts on air quality. Unconventional natural gas production has the potential to emit vast quantities of volatile organic compounds (VOCs) into the atmosphere. Many VOCs can be toxic, can produce ground-level ozone or secondary organic aerosols, and can impact climate. This dissertation presents the results of experiments designed to validate VOC measurement techniques, to quantify VOC emission rates from natural gas sources, to identify source signatures specific to natural gas emissions, and to quantify the impacts of these emissions on potential ozone formation and human health. Measurement campaigns were conducted in two natural gas production regions: the Denver-Julesburg Basin in northeast Colorado and the Marcellus Shale region surrounding Pittsburgh, Pennsylvania. An informal measurement intercomparison validated the canister sampling methodology used throughout this dissertation for the measurement of oxygenated VOCs. Mixing ratios of many VOCs measured during both campaigns were similar to or higher than those observed in polluted cities. Fluxes of natural gas-associated VOCs in Colorado ranged from 1.5-3 times industry estimates. Similar emission ratios relative to propane were observed for C2-C6 alkanes in both regions, and an isopentane:n-pentane ratio ≈1 was identified as a unique tracer for natural gas emissions. Source apportionment estimates indicated that natural gas emissions were responsible for the majority of C2-C8 alkanes observed in each region, but accounted for a small proportion of alkenes and aromatic compounds. Natural gas emissions in both regions accounted for approximately 20% of hydroxyl radical reactivity, which could hinder federal ozone standard compliance in downwind cities. A health risk assessment showed no increase in cancer or chronic non-cancer risk at locations near natural gas wells in Pennsylvania, but the contribution of natural gas emissions to total risk was 3-6 times higher near wells. These results will assist policy makers, natural gas producers, and citizen stakeholders in crafting effective policies to control VOC emissions from natural gas production activities.
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