EAGER: Airborne Investigation of the Chlorine Mediated Mineral Dust Sea Spray Aerosol (MDSA) Mechanism in the Western Atlantic

这个急切的项目的目标是研究一种化学机制，这种机制可以利用热带大西洋上空撒哈拉尘埃中自然产生的氯和海雾气溶胶中的铁来氧化和消除大气中的甲烷。最近有人提出，在大气中人工引入氯以消除甲烷，可能是减轻温室气体排放对气候影响的一个可行的选择。虽然有限的实验室研究显示了这种去除甲烷的机制的潜力，但基本上对这种方法的可行性及其造成有害影响的潜力知之甚少。MDSA(矿物粉尘-海洋喷雾气溶胶)机制依赖于甲烷和氯(CH4Cl)反应对氯化氢的循环。建立该工艺在不同大气条件下对铁和氯的催化效率是本项目的主要目标。2024年6/7月期间，将在巴巴多斯附近与美国海军和美国国家海洋和大气局资助的动力气象学项目“鹊子”(湿气和气溶胶梯度/逆温演化物理)联合开展为期6周的飞机活动。将测量气溶胶含量和粒度分布，大气中一氧化碳、二氧化碳、甲烷、水蒸气和氯化氢的浓度，以及三维风速、风向和温度。将收集空气样本，以便随后分析CO和CH4中的增量13C，因为这些数据将验证从大气甲烷中提取氯-氢的机制的存在，据信在夏季会产生高度枯竭的13CO。该项目旨在评估向大气中添加氯以去除甲烷的可行性，对减缓气候变化具有很高的社会相关性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this EAGER project is to investigate a chemical mechanism that can utilize naturally generated chlorine from sea-spray aerosol and iron from Saharan dust over the tropical Atlantic Ocean to oxidize and remove methane from the atmosphere. It recently has been suggested that the artificial introduction of chlorine into the atmosphere to remove methane might be a viable option for mitigating the climate impacts of greenhouse gas emissions. While limited laboratory studies have shown the potential for such a mechanism to remove methane, there is essentially little understanding of the viability of the method and its potential for causing harmful impacts.The MDSA (mineral dust-sea spray aerosol) mechanism depends on the recycling of hydrogen chloride by the methane and chlorine (CH4 + Cl) reaction. Establishing the catalytic efficiency of the process with respect to iron and chlorine under different atmospheric conditions is the key goal of this project. An aircraft campaign will be conducted near Barbados over a 6-week period during June/July 2024 in conjunction with MAGPIE (Moisture and Aerosol Gradients/Physics of Inversion Evolution), a dynamical meteorology project funded by the US Navy and NOAA. Measurements will be made of aerosol load and size distribution, and concentrations of atmospheric carbon monoxide, carbon dioxide, methane, water vapor, and hydrogen chloride, as well as 3-D wind speed and direction and temperature. Air samples will be collected for subsequent analysis of delta 13C in CO and CH4 as this data will validate the existence of the chlorine-hydrogen abstraction mechanism from atmospheric methane, believed to yield highly depleted 13CO in the summertime. This project to evaluate the viability of adding chlorine to the atmosphere to remove methane has high societal relevance for mitigating climate change.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.