Hu L, Millet D B, Kim S Y, Wells K C, Griffis T J, Fischer E V, Helmig D, Hueber J, Curtis A J
Department of Soil, Water, and Climate, University of Minnesota, St. Paul, Minnesota, USA.
School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA.
Atmos Chem Phys. 2013 Mar 15;13(6):3379-3392. doi: 10.5194/acp-13-3379-2013. Epub 2013 Mar 25.
We apply a full year of continuous atmospheric acetone measurements from the University of Minnesota tall tower Trace Gas Observatory (KCMP tall tower; 244 m a.g.l.), with a 0.5° × 0.667° GEOS-Chem nested grid simulation to develop quantitative new constraints on seasonal acetone sources over North America. Biogenic acetone emissions in the model are computed based on the MEGANv2.1 inventory. An inverse analysis of the tall tower observations implies a 37% underestimate of emissions from broadleaf trees, shrubs, and herbaceous plants, and an offsetting 40% overestimate of emissions from needleleaf trees plus secondary production from biogenic precursors. The overall result is a small (16%) model underestimate of the total primary + secondary biogenic acetone source in North America. Our analysis shows that North American primary + secondary anthropogenic acetone sources in the model (based on the EPA NEI 2005 inventory) are accurate to within approximately 20%. An optimized GEOS-Chem simulation incorporating the above findings captures 70% of the variance ( = 0.83) in the hourly measurements at the KCMP tall tower, with minimal bias. The resulting North American acetone source is 11 Tg a, including both primary emissions (5.5 Tg a) and secondary production (5.5 Tg a), and with roughly equal contributions from anthropogenic and biogenic sources. The North American acetone source alone is nearly as large as the total continental volatile organic compound (VOC) source from fossil fuel combustion. Using our optimized source estimates as a baseline, we evaluate the sensitivity of atmospheric acetone and peroxyacetyl nitrate (PAN) to shifts in natural and anthropogenic acetone sources over North America. Increased biogenic acetone emissions due to surface warming are likely to provide a significant offset to any future decrease in anthropogenic acetone emissions, particularly during summer.
我们运用了明尼苏达大学高塔痕量气体观测站（KCMP高塔；海拔244米）全年连续的大气丙酮测量数据，并结合0.5°×0.667°的GEOS - Chem嵌套网格模拟，来对北美地区季节性丙酮源建立新的定量约束。模型中的生物源丙酮排放是根据MEGANv2.1清单计算得出的。对高塔观测数据的反演分析表明，阔叶林、灌木和草本植物的排放被低估了37%，而针叶树的排放以及生物源前体的二次生产则被高估了40%，从而相互抵消。总体结果是，模型对北美地区初级 + 次级生物源丙酮总源的低估幅度较小（16%）。我们的分析表明，模型中基于美国环保署2005年国家排放清单（EPA NEI 2005）的北美初级 + 次级人为源丙酮排放量的误差在约20%以内。纳入上述研究结果的优化后的GEOS - Chem模拟能够捕捉到KCMP高塔每小时测量数据中70%的方差（ = 0.83），偏差极小。由此得出的北美丙酮源为11太克/年，包括初级排放（5.5太克/年）和二次生产（5.5太克/年），人为源和生物源的贡献大致相等。仅北美丙酮源就几乎与化石燃料燃烧产生的大陆挥发性有机化合物（VOC）总源一样大。以我们优化后的源估算值为基线，我们评估了北美地区自然和人为丙酮源变化对大气丙酮和过氧乙酰硝酸酯（PAN）的敏感性。由于地表变暖导致生物源丙酮排放增加，很可能会显著抵消未来人为丙酮排放的任何减少，尤其是在夏季。
