Estimating Emissions of Toxic Hydrocarbons from Natural Gas Production Sites in the Barnett Shale Region of Northern Texas

Oil and natural gas operations have continued to expand and move closer to densely populated areas, contributing to growing public concerns regarding exposure to hazardous air pollutants. During the Barnett Shale Coordinated Campaign in October, 2013, ground-based whole air samples collected downwind of oil and gas sites revealed enhancements in several potentially toxic volatile organic compounds (VOCs) when compared to background values. Molar emissions ratios relative to methane were determined for hexane, benzene, toluene, ethylbenzene, and xylene (BTEX compounds). Using methane leak rates measured from the Picarro mobile flux plane (MFP) system and a Barnett Shale regional methane emissions inventory, the rates of emission of these toxic gases were calculated. Benzene emissions ranged between 51 ± 4 and 60 ± 4 kg h–1. Hexane, the most abundantly emitted pollutant, ranged from 642 ± 45 to 1070 ± 340 kg h–1. While observed hydrocarbon enhancements fall below federal workplace standards, results may indicate a link between emissions from oil and natural gas operations and concerns about exposure to hazardous air pollutants. The larger public health risks associated with the production and distribution of natural gas are of particular importance and warrant further investigation, particularly as the use of natural gas increases in the United States and internationally.

石油与天然气作业规模持续扩张，且正愈发贴近人口密集区域，由此引发公众对接触有害空气污染物的担忧与日俱增。2013年10月的巴内特页岩（Barnett Shale）协同监测行动中，科研人员在油气田下风处采集的全空气样品显示，与背景值相比，多种具有潜在毒性的挥发性有机化合物（VOCs）浓度出现升高。研究测定了己烷、苯、甲苯、乙苯与二甲苯（BTEX化合物）相对于甲烷的摩尔排放比率。基于皮卡拉罗（Picarro）移动通量平面（MFP）系统测得的甲烷泄漏率，以及巴内特页岩区域甲烷排放清单，科研人员计算得到了上述有毒气体的排放速率。苯的排放速率介于51±4至60±4 kg·h⁻¹之间。排放量最高的污染物为己烷，其排放速率介于642±45至1070±340 kg·h⁻¹之间。尽管观测到的烃类浓度升高未超出美国联邦职业场所标准，但研究结果或表明石油与天然气作业排放与公众对有害空气污染物接触的担忧之间存在关联。与天然气生产和分销相关的更广泛公共健康风险尤为值得关注，亟需开展进一步研究——尤其是在美国及全球范围内天然气使用量持续攀升的背景下。