A Synthesis Inversion to Constrain Global Emissions of Two Very Short Lived Chlorocarbons: Dichloromethane, and Perchloroethylene
A Synthesis Inversion to Constrain Global Emissions of Two Very Short Lived Chlorocarbons: Dichloromethane, and Perchloroethylene
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DOI：
10.1029/2019jd031818
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发表时间：
2020-06-27
影响因子：
4.4
通讯作者：
Lunder, Chris
中科院分区：
文献类型：
--
作者：
Claxton, Tom;Hossaini, Ryan;Lunder, Chris
二氯甲烷（CH 2Cl 2）和四氯乙烯（C2Cl 4）是具有人为来源的氯化极短寿命物质（Cl-VSLS）。最近的研究突出表明，这类化合物，特别是二氯甲烷，对平流层氯收支的影响越来越大，因此对臭氧消耗的影响也越来越大。在这里，进行了多年全球尺度的合成反演，以优化CH 2Cl 2（2006-2017）和C2Cl 4（2007-2017）的排放。该方法结合了全球监测网络的长期地表观测，三维化学传输模型（TOMCAT）的输出，以及关于先前工业排放的新的自下而上的信息。我们的后验结果显示，全球CH（2）Cl（2）排放量从2006年的637 +/- 36 Gg yr（-1）增加到2017年的1，171 +/- 45 Gg yr（-1），亚洲排放量分别占这些总量的68%和89%。就绝对值而言，在研究期间，亚洲CH（2）Cl（2）排放量每年增加51千兆克，而欧洲和北美的排放量则有所下降，这表明自2000年代中期以来，排放量分布发生了大陆规模的变化。对于C2Cl 4，我们估计全球排放量将从2007年的141 +/- 14 Gg yr（-1）减少到2017年的106 +/- 12 Gg yr（-1）。随时间变化的后验发射比前验发射提供了显著的改进。利用后验辐射导致模拟的对流层CH（2）Cl（2）和C（2）Cl（4）丰度和趋势与观测结果（包括反演的独立观测）吻合良好。由于包括不确定的Cl汇，C（2）Cl（4）寿命缩短，导致全球C（2）Cl（4）排放量增加约1.5倍，这在某些地方提高了模型测量的一致性。我们的研究结果的敏感性，在反演过程中的假设，包括CH（2）Cl（2）海洋排放，进行了讨论。简明的语言摘要1987年蒙特利尔议定书禁止生产分散使用的主要臭氧消耗气体，如氯氟烃，由于它们的作用，在平流层臭氧层的消耗。因此，随着来自禁用物质的平流层氯慢慢减少，预计臭氧层将在未来几十年内恢复。然而，不受《蒙特利尔议定书》控制的氯化极短寿命物质（Cl-VSLS）是一种很小但不断增长的大气氯来源，可能会减缓臭氧的恢复。因此，重要的是，这些化合物的排放量，其空间分布，并随时间的变化进行量化。在这里，我们结合了Cl-VSLS的观测结果，其排放量的先验估计以及化学传输模型，以在2006年至2017年期间逐区域生成一组优化的排放估计。我们发现，工业排放的二氯甲烷，最丰富的Cl-VSLS，增加了类似的84%，在此期间，主要是由于亚洲排放量的增加，而欧洲和北美的排放量减少。在2007-2017年期间，全氯乙烯（一种含量较低的Cl-VSLS）的排放量有所下降，特别是在欧洲和北美。我们表明，我们的新的排放量估计导致更好的协议与观测数据相比，以前的估计。
Dichloromethane (CH2Cl2) and perchloroethylene (C2Cl4) are chlorinated very short lived substances (Cl-VSLS) with anthropogenic sources. Recent studies highlight the increasing influence of such compounds, particularly CH2Cl2, on the stratospheric chlorine budget and therefore on ozone depletion. Here, a multiyear global-scale synthesis inversion was performed to optimize CH2Cl2(2006-2017) and C2Cl4(2007-2017) emissions. The approach combines long-term surface observations from global monitoring networks, output from a three-dimensional chemical transport model (TOMCAT), and novel bottom-up information on prior industry emissions. Our posterior results show an increase in global CH(2)Cl(2)emissions from 637 +/- 36 Gg yr(-1)in 2006 to 1,171 +/- 45 Gg yr(-1)in 2017, with Asian emissions accounting for 68% and 89% of these totals, respectively. In absolute terms, Asian CH(2)Cl(2)emissions increased annually by 51 Gg yr(-1)over the study period, while European and North American emissions declined, indicating a continental-scale shift in emission distribution since the mid-2000s. For C2Cl4, we estimate a decrease in global emissions from 141 +/- 14 Gg yr(-1)in 2007 to 106 +/- 12 Gg yr(-1)in 2017. The time-varying posterior emissions offer significant improvements over the prior. Utilizing the posterior emissions leads to modeled tropospheric CH(2)Cl(2)and C(2)Cl(4)abundances and trends in good agreement to those observed (including independent observations to the inversion). A shorter C(2)Cl(4)lifetime, from including an uncertain Cl sink, leads to larger global C(2)Cl(4)emissions by a factor of similar to 1.5, which in some places improves model-measurement agreement. The sensitivity of our findings to assumptions in the inversion procedure, including CH(2)Cl(2)oceanic emissions, is discussed.Plain Language Summary The 1987 Montreal Protocol banned production for dispersive uses of major ozone-depleting gases, such as chlorofluorocarbons, due to their role in depletion of the stratospheric ozone layer. In consequence, the ozone layer is expected to recover in coming decades, as stratospheric chlorine from banned substances slowly declines. However, chlorinated very short lived substances (Cl-VSLS), not controlled by the Montreal Protocol, represent a small, but growing, source of atmospheric chlorine that could potentially slow ozone recovery. It is thus important that the magnitude of emissions of these compounds, their spatial distribution, and changes with time are quantified. Here, we combined observations of Cl-VSLS, prior estimates of their emissions, and a chemical transport model to produce an optimized set of emission estimates on a region-by-region basis between 2006 and 2017. We show that industrial emissions of dichloromethane, the most abundant Cl-VSLS, increased by similar to 84% within this period, predominately due to an increase in Asian emissions, while European and North American emissions decreased. Over 2007-2017, emissions of perchloroethylene, a less abundant Cl-VSLS, decreased, particularly in Europe and North America. We show that our new emission estimates lead to better agreement with observational data compared to previous estimates.