Understanding the Burst of Hydroxyl Radicals (OH) in Newly Formed Cloud Droplets

气溶胶颗粒和气溶胶-云相互作用仍然是全球气候模拟和预测工作中受限制最少的方面之一。为了帮助加深目前的理解，PI试图描述气溶胶颗粒中的反应机制，这些气溶胶颗粒最近被证明会产生最具氧化性的物种--羟基自由基(OH)的光诱导初始爆发。重点将放在痕量金属和有机过氧化物上，后者代表了在这一背景下要研究的一类新分子。环境气溶胶分析、实验室模拟和室内实验的结果将为氢氧化氢生产的参数化提供信息，以便纳入更大规模的气候模式。该项目旨在增进对大气中云滴中羟基的产生机制的了解。这项工作的动机是PI观察到当气溶胶暴露在近紫外线辐射下时，OH产生的初始和实质性的爆发。识别云滴中新的氢氧源对影响全球气候和人类健康的许多化学和物理大气过程具有重要的和潜在的变革性影响。三管齐下的实验方法包括测量(I)收集和化学分析的各种环境气溶胶中的OH产生；(Ii)使用一系列合成的(氢)过氧化物、痕量金属以及不同的pH、电导率和波长进行对照实验室实验；以及(Iii)小室产生的气溶胶粒子。寻求开发一种新的半便携式仪器(直接到液体的氢氧化氢分析仪)，使气溶胶生长到液滴，然后在几十分钟到几小时的时间尺度上收集和分析氢氧化氢的形成。实验方法的所有组成部分的结果的化学动力学模型将被用来得出速率常数和参数化，以便在更大规模的模型中实施。两名研究生将通过这个项目接受培训，来自代表人数不足的人群的一些本科生将从PI校园的现有项目中招募。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。

Aerosol particles and aerosol-cloud interactions remain one of the least constrained aspects in global climate modeling and prediction efforts. To help increase current understanding, the PI seeks to characterize reaction mechanisms in aerosol particles that have shown recently to produce light-induced initial bursts of the most oxidizing species, hydroxyl radical (OH). Focus will be on trace metals and organic peroxides, latter of which represent a new class of molecules to be studied in this context. Results from ambient aerosol analyses, laboratory simulations and chamber experiments will inform parametrization of OH production for incorporation into larger scale climate models. The project aims at increasing understanding of mechanisms of atmospheric production of OH in cloud droplets. The work is motivated by the PI’s observation of an initial and substantial burst in OH production when exposing aerosols to near-UV radiation. Identifying new OH sources in cloud droplets has important and potentially transformative implications on many chemical and physical atmospheric processes that affect global climate and human health. The three-pronged experimental approach consists of measuring OH production in (i) collected and chemically analyzed ambient aerosols of various types; (ii) controlled laboratory experiments using a series of synthesized (hydro)peroxides, trace metals, and varying pH, conductivity, and wavelength; and (iii) chamber generated aerosol particles. A new semi-portable instrument (direct-to liquid OH analyzer) is sought to be developed that allows aerosols to grow to droplets that are collected and analyzed for OH formation on the time scale of tens of minutes to hours. Chemical kinetic modeling of results from all components of the experimental approach will be used to derive rate constants and parametrization for implementation in larger scale models. Two graduate students will receive training through this project, and a number of undergraduate students from underrepresented populations will be recruited from existing programs on the PI’s campus.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.