Civil and Environmental Engineering, University of Illinois Urbana-Champaign , Urbana, Illinois 61801, United States.
Department of Chemistry, Purdue University , West Lafayette, Indiana 47907, United States.
Environ Sci Technol. 2016 Feb 16;50(4):2075-81. doi: 10.1021/acs.est.5b04712. Epub 2016 Jan 27.
Approximately 150 billion cubic meters (BCM) of natural gas is flared and vented in the world annually, emitting greenhouse gases and other pollutants with no energy benefit. About 7 BCM per year is flared in the United States, and half is from North Dakota alone. There are few emission measurements from associated gas flares and limited black carbon (BC) emission factors have been previously reported from the field. Emission plumes from 26 individual flares in the Bakken formation in North Dakota were sampled. Methane, carbon dioxide, and BC were measured simultaneously, allowing the calculation of BC mass emission factors using the carbon balance method. Particle optical absorption was measured using a three-wavelength particle soot absorption photometer (PSAP) and BC particle number and mass concentrations were measured with a single particle soot photometer. The BC emission factors varied over 2 orders of magnitude, with an average and uncertainty range of 0.14 ± 0.12 g/kg hydrocarbons in associated gas and a median of 0.07 g/kg which represents a lower bound on these measurements. An estimation of the BC emission factor derived from PSAP absorption provides an upper bound at 3.1 g/kg. These results are lower than previous estimations and laboratory measurements. The BC mass absorption cross section was 16 ± 12 m(2)/g BC at 530 nm. The average absorption Ångström exponent was 1.2 ± 0.8, suggesting that most of the light absorbing aerosol measured was black carbon and the contribution of light absorbing organic carbon was small.
每年全球约有 1500 亿立方米的天然气被燃烧或放空，排放温室气体和其他污染物，没有任何能源效益。美国每年大约有 70 亿立方米天然气被燃烧，其中一半来自北达科他州。与伴生气燃烧相关的排放量测量很少，之前在实地也只报道了有限的黑碳（BC）排放因子。对北达科他州 Bakken 地层的 26 个单个燃烧火炬排放羽流进行了采样。同时测量了甲烷、二氧化碳和 BC，利用碳平衡法计算了 BC 质量排放因子。使用三波长粒子 soot 吸收光度计（PSAP）测量了粒子光学吸收，使用单粒子 soot 光度计测量了 BC 粒子数和质量浓度。BC 排放因子跨越 2 个数量级，伴生气中的平均和不确定度范围为 0.14 ± 0.12 g/kg 碳氢化合物，中值为 0.07 g/kg，这代表了这些测量的下限。PSAP 吸收提供的 BC 排放因子估计值给出了上限，为 3.1 g/kg。这些结果低于之前的估计值和实验室测量值。BC 质量吸收截面在 530nm 处为 16 ± 12 m(2)/g BC。平均吸收 Ångström 指数为 1.2 ± 0.8，表明测量到的大部分吸光气溶胶是黑碳，吸光有机碳的贡献很小。
