New methodology for Ozone Depletion Potentials of short-lived compounds : n-propyl bromide as an example
New methodology for Ozone Depletion Potentials of short-lived compounds : n-propyl bromide as an example
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短寿命化合物的臭氧消耗潜势的新方法：以正丙基溴为例
DOI：
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发表时间：
2001
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影响因子：
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通讯作者：
R. Kotamarthi
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作者：
D. Wuebbles;K. Patten;Matthew T. Johnson;R. Kotamarthi
作为《蒙特利尔议定书》管制物质替代品的一些化合物在大气中的寿命极短，从几天到几个月不等。一个重要的例子是正丙基溴(也称为1-溴丙烷、CH2BrCH2CH3或简称1-C3H7BrO或NPB)。这种化合物可用作溶剂，由于它与羟基发生反应，在大气中的使用寿命不到20天。因为NPB含有溴，任何到达平流层的量都有可能影响平流层臭氧的浓度。对于这类短期化合物，需要修改臭氧消耗潜势的定义，以考虑到排放的地点和时间。像对待寿命较长的气体那样，在所有纬度和经度都统一排放这些化学物质是不够的。因此，对于短期化合物，政策制定者将需要一个ODP值表格，而不是过去研究中通常提供的单一数值。这项研究使用MOZART2三维化学输送模型，并结合我们的计算成本较低的二维模型的研究，来考察NPB对平流层臭氧的潜在影响。这项研究的多个方面审查了关于NPB排放后到达平流层的溴量的关键问题。就短期替代化合物臭氧效应而言，我们在这项研究中最重要的发现总结如下。NPB的降解产生了大量的溴丙酮，这增加了NPB向平流层输送的溴的量。然而，这种影响在很大程度上不是由于溴丙酮本身，而是由于无机溴，它是从对流层氧化NPB、溴丙酮和其他降解产物产生的，并在模型的干和湿沉积过程上方输送。MOZART2 NPB的结果表明，为了得出我们的最终结果，对二维结果进行了最小的修正：对于陆地上假设的全球排放，NPB的化学寿命为19天，臭氧消耗潜力范围为0.033至0.040；对于北半球工业化地区的假设排放，分别为19天和0.021至0.028；对于热带东南亚的假设排放，分别为9天和0.087至0.105。
A number of the compounds proposed as replacements for substances controlled under the Montreal Protocol have extremely short atmospheric lifetimes, on the order of days to a few months. An important example is n-propyl bromide (also referred to as 1-bromopropane, CH2BrCH2CH3 or simplified as 1-C3H7Br or nPB). This compound, useful as a solvent, has an atmospheric lifetime of less than 20 days due to its reaction with hydroxyl. Because nPB contains bromine, any amount reaching the stratosphere has the potential to affect concentrations of stratospheric ozone. The definition of Ozone Depletion Potentials (ODP) needs to be modified for such short-lived compounds to account for the location and timing of emissions. It is not adequate to treat these chemicals as if they were uniformly emitted at all latitudes and longitudes as normally done for longer-lived gases. Thus, for short-lived compounds, policymakers will need a table of ODP values instead of the single value generally provided in past studies. This study uses the MOZART2 three-dimensional chemical-transport model in combination with studies with our less computationally expensive two-dimensional model to examine potential effects of nPB on stratospheric ozone. Multiple facets of this study examine key questions regarding the amount of bromine reaching the stratosphere following emission of nPB. Our most significant findings from this study for the purposes of short-lived replacement compound ozone effects are summarized as follows. The degradation of nPB produces a significant quantity of bromoacetone which increases the amount of bromine transported to the stratosphere due to nPB. However, much of that effect is not due to bromoacetone itself, but instead to inorganic bromine which is produced from tropospheric oxidation of nPB, bromoacetone, and other degradation products and is transported above the dry and wet deposition processes of the model. The MOZART2 nPB results indicate a minimal correction of the two-dimensional results in order to derive our final results: an nPB chemical lifetime of 19 days and an Ozone Depletion Potential range of 0.033 to 0.040 for assumed global emissions over landmasses, 19 days and 0.021 to 0.028, respectively, for assumed emissions in the industrialized regions of the Northern Hemisphere, and 9 days and 0.087 to 0.105, respectively, for assumed emission in tropical Southeast Asia.