Development and Deployment of a Novel Peroxy Radical Detector

该项目的重点是开发和测试一种新的仪器，用于测量大气中过氧基的浓度。新方法将使用一种新的乙醛/一氧化氮化学放大方法，大大改进传统的化学放大技术，即使用一氧化碳(CO)来测量过氧自由基。该仪器的原型已经开发出来，并在马萨诸塞大学阿默斯特分校的实验室进行了成功的测试。过氧基很重要，因为它们与大气中的一氧化氮反应形成臭氧，臭氧是一种强有力的温室气体和空气污染物，对人类和植物的健康和生态造成不利影响。基于乙醛的放大因子预计相对稳定，预计不会随着相对湿度的变化而显著变化，一氧化碳因子也是如此。该方法还将由于添加取样洗涤器而导致的壁损率的差异而使过氧基能够形成，所述取样洗涤器由对氢过氧基(HO2)比对RO2(过氧基，其中R是有机取代基)更具反应性的材料制成。已经确定了几种候选材料，并将在该项目中进行彻底的调查。在现场测试之前，该仪器将测试过氧乙酰硝酸盐、硝酸根和其他可能的干扰物的干扰，并使用多个校准源进行校准，以确保测量不会受到与任何特定校准方法相关的系统误差的影响。将在阿默斯特的室外空气中进行为期一周或更长时间的初步现场测试，定期自动添加二氧化氮和二氧化氢。新仪器的部署将于2015年至2017年夏季在具有不同环境条件的森林地点进行，例如氮氧化物浓度和/或生物挥发性有机碳氢化合物排放类型的差异。在这些部署期间，其他几个科学团队将携带他们的仪器参加过氧基测量方法的相互比较。该项目解决了与气候变化和空气污染科学相关的关键知识差距。

This project is focused on the development and testing of a new instrument for measuring atmospheric concentrations of peroxy radicals in the atmosphere. The new method will use a novel acetaldehyde/nitric oxide chemical amplification approach to greatly improve upon the traditional chemical amplification technique that uses carbon monoxide (CO) for measuring peroxy radicals. A prototype version of the instrument has been developed and successfully tested it in the laboratory at the University of Massachusetts, Amherst. Peroxy radicals are important because they react with nitric oxide in the atmosphere to form ozone, a potent greenhouse gas and an air pollutant with adverse health and ecological impacts on humans and plants.The acetaldehyde-based amplification factor is predicted to be relatively stable and is not expected to vary significantly with relative humidity, as does the CO factor. The method also will enable the peroxy radicals to be speciated due to differences in wall loss rates resulting from the addition of a sampling scrubber made of a material that is much more reactive to the hydroperoxy radical (HO2) than to RO2 (peroxy radical where R is an organic substituent). Several candidate materials have been identified and will be thoroughly investigated in the project. Prior to field-testing, the instrument will be tested for interferences by peroxyacetyl nitrate, nitrate radical, and other possible interferents and calibrated using multiple calibration sources to provide confidence that the measurements are not compromised by systematic errors associated with any particular calibration method. A preliminary field test will be conducted in outdoor air in Amherst over a period of a week or more, with periodic automated standard additions of nitrogen dioxide and HO2. Deployments of the new instrument will take place during the summers of 2015 to 2017 at forest sites that with different environmental conditions, such as differences in nitrogen oxide concentrations and/or types of emissions of biogenic volatile organic hydrocarbons. During these deployments, several other scientific teams will bring their instruments to participate in an intercomparison of peroxy radical measurement methods. This project addresses key knowledge gaps relevant to climate change and air pollution science.