Spectroscopy Of PHOsgene for evaluating the injection of ChLorine into the Earth's Stratosphere (SOPHOCLES)

PHOsgene 光谱学用于评估氯碱注入地球平流层的情况 (SOPHOCLES)

• 批准号: NE/X012670/1
• 负责人: Jeremy Harrison
• 金额: $ 10.27万
• 依托单位: University of Leicester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX012670%2F1
• 关键词: Spectroscopy; PHOsgene; evaluating; injection; ChLorine

Long-lived anthropogenic Cl-containing species such as chlorofluorocarbons are a source of stratospheric Cl and deplete the ozone layer. The Montreal Protocol has led to reductions in the concentrations of many such species, and the ozone layer is now recovering. However, very short-lived substances (VSLS) with lifetimes <6 months, e.g. dichloromethane (DCM), provide a direct source of inorganic chlorine (Cly) in the lowermost stratosphere. DCM is widely used as a solvent and in the production of foam agents. If emissions are left unchecked (DCM is not controlled by the Protocol), recovery of the ozone layer will be significantly delayed. DCM currently accounts for ~10% of stratospheric Cly, and its contribution is expected to increase significantly in coming decades along with this growth and as Cl from long-lived gases decreases.Stratospheric Cl input from VSLS is differentiated into two categories: emitted source gases (source gas injection, SGI) and product gases (product gas injection, PGI). Observationally, source gases can be measured directly by aircraft instruments in the upper troposphere, however these don't provide the long-term record needed for monitoring. Satellite measurements can provide global coverage and long-term monitoring of product gases in the UTLS, but not yet any Cl-VSLS source gases. The Atmospheric Chemistry Experiment - Fourier Transform Spectrometer (ACE-FTS) measures a number of Cly species, including one of the most important product gases, phosgene (COCl2).Phosgene is the common intermediate in the atmospheric degradation of the most important Cl-VSLS: DCM, and the less abundant CHCl3 (chloroform) and C2Cl4 (tetrachloroethene). Cl-VSLS PGI estimates are available from model simulations, however the complexity and approximations in faithfully capturing the chemical processes make these extremely challenging. In particular, there is limited information in the literature regarding the yield of phosgene from DCM oxidation in the upper troposphere. ACE-FTS-derived abundances of phosgene in the upper troposphere are higher than calculated by models by a factor of ~3. The positive trend in these ACE-FTS upper tropospheric phosgene concentrations provided the first direct observational evidence of the increase in PGI associated with VSLS.In order to understand the increasing impact of Cl-VSLS on ozone depletion and to make future predictions, it is important to validate and improve model simulations of source VSLS and product gases in the UTLS. To achieve this, we need to reconcile inconsistencies between model and observations. In this project, we aim to obtain a better understanding of these observations and their uncertainties by providing a complete re-evaluation of phosgene spectroscopy through new laboratory measurements. Accurate quantitative laboratory spectroscopy is fundamental for retrieving abundances of trace gas species from atmospheric spectra recorded by satellite instruments. This work will lead to more robust satellite datasets of phosgene observations in the UTLS, and provide a better constraint on the phosgene PGI associated with Cl-VSLS.

长寿的人为含氯物种，如氯氟烃，是平流层氯的来源，并消耗臭氧层。《蒙特利尔议定书》导致许多这类物种的浓度下降，臭氧层现在正在恢复。然而，寿命很短的物质(VSLS)，如二氯甲烷(DCM)，在平流层最低层提供了无机氯(Cly)的直接来源。DCM被广泛用作溶剂和泡沫剂的生产。如果排放得不到控制(DCM不受《议定书》的控制)，臭氧层的恢复将大大延迟。DCM目前约占平流层Cly的10%，随着这一增长，其贡献有望在未来几十年内显著增加，而来自长寿命气体的氯将减少。VSLS输入的平流层氯分为两类：排放源气体(源气体注入，SGI)和产物气体(产物气体注入，PGI)。从观测上看，可以通过对流层上层的航空仪器直接测量源气体，但这些仪器不能提供监测所需的长期记录。卫星测量可以提供全球覆盖和对UTLS产品气体的长期监测，但还不能提供任何氯-VSLS源气体。大气化学实验-傅里叶变换光谱仪(ACE-FTS)测量了一系列Cly物种，包括最重要的产物气体之一光气(COCl2)。光气是大气中最重要的氯-VSLS：DCM的常见中间体，以及含量较低的CHCl3(氯仿)和C2Cl4(四氯乙烯)。CL-VSLS PGI估计可以从模型模拟中获得，然而，准确捕捉化学过程的复杂性和近似性使这些都极具挑战性。特别是，文献中关于对流层上层DCM氧化产生光气的信息有限。由ACE-FTS得到的对流层上层光气丰度比模式计算的光气丰度高约3倍。这些ACE-FTS光气浓度的正趋势首次提供了与VSLS相关的PGI增加的直接观测证据。为了了解ClVSLS对臭氧消耗的影响并做出未来的预测，验证和改进UTLS中源VSLS和产品气体的模式模拟是重要的。为了实现这一点，我们需要调和模型和观测之间的不一致。在这个项目中，我们的目标是通过新的实验室测量对光气光谱进行全面的重新评估，从而更好地了解这些观测结果及其不确定性。准确的定量实验室光谱学是从卫星仪器记录的大气光谱中恢复痕量气体物种丰度的基础。这项工作将产生更可靠的UTLS光气观测卫星数据集，并对与Cl-VSLS相关的光气PGI提供更好的约束。