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Cloud Activation Potentials for Atmospheric α-Pinene and β-Caryophyllene Ozonolysis Products
ACS Central Science ( IF 12.7 ) Pub Date : 2017-07-05 00:00:00 , DOI: 10.1021/acscentsci.7b00112
Ariana Gray Bé 1 , Mary Alice Upshur 1 , Pengfei Liu 2 , Scot T. Martin 2, 3 , Franz M. Geiger 1 , Regan J. Thomson 1
Affiliation  

The formation of atmospheric cloud droplets due to secondary organic aerosol (SOA) particles is important for quantifying the Earth’s radiative balance under future, possibly warmer, climates, yet is only poorly understood. While cloud activation may be parametrized using the surface tension depression that coincides with surfactant partitioning to the gas–droplet interface, the extent to which cloud activation is influenced by both the chemical structure and reactivity of the individual molecules comprising this surfactant pool is largely unknown. We report herein considerable differences in the surface tension depression of aqueous pendant droplets that contain synthetically prepared ozonolysis products derived from α-pinene and β-caryophyllene, the most abundant of the monoterpenes and sesquiterpenes, respectively, that are emitted over the planet’s vast forest ecosystems. Oxidation products derived from β-caryophyllene were found to exhibit significantly higher surface activity than those prepared from α-pinene, with the critical supersaturation required for cloud droplet activation reduced by 50% for β-caryophyllene aldehyde at 1 mM. These considerable reductions in the critical supersaturation were found to coincide with free energies of adsorption that exceed ∼25 kJ/mol, or just one hydrogen bond equivalent, depending on the ammonium sulfate and oxidation product concentration in the solution. Additional experiments showed that aldehyde-containing oxidation products exist in equilibrium with hydrated forms in aqueous solution, which may modulate their bulk solubility and surface activity. Equilibration time scales on the order of 10–5 to 10–4 s calculated for micrometer-sized aerosol particles indicate instantaneous surface tension depression in the activation processes leading to cloud formation in the atmosphere. Our findings highlight the underlying importance of molecular structure and reactivity when considering cloud condensation activity in the presence of SOA particles.

中文翻译:

大气α-P烯和β-石竹烯臭氧分解产物的云活化势

二次有机气溶胶(SOA)颗粒形成的大气云滴对于量化未来(可能更温暖)气候下的地球辐射平衡非常重要,但人们对此知之甚少。尽管可以通过与表面活性剂分配到气体-液滴界面相一致的表面张力降低来参数化云的活化作用,但是很大程度上不清楚云活化的程度受构成该表面活性剂池的单个分子的化学结构和反应性的影响。我们在此报告了水性悬垂液滴的表面张力下降存在显着差异,该悬垂液滴包含分别由单萜和倍半萜中含量最高的α-pine烯和β-石竹烯衍生而来的合成制备的臭氧分解产物,排放到地球上广阔的森林生态系统中。发现衍生自β-石竹烯的氧化产物比由α-pine烯制备的氧化产物具有更高的表面活性,并且在1 mM时,云滴活化所需的临界过饱和度对于β-石竹烯醛降低了50%。发现临界过饱和的这些显着降低与超过约25 kJ / mol的吸附自由能或仅一个氢键当量相符,具体取决于溶液中的硫酸铵和氧化产物浓度。其他实验表明,含醛的氧化产物与水溶液中的水合形式平衡存在,这可能会调节其整体溶解度和表面活性。平衡时间标度约为10 发现衍生自β-石竹烯的氧化产物比由α-pine烯制备的氧化产物具有更高的表面活性,并且在1 mM时,云滴活化所需的临界过饱和度对于β-石竹烯醛降低了50%。发现临界过饱和的这些显着降低与超过约25 kJ / mol的吸附自由能或仅一个氢键当量相符,具体取决于溶液中的硫酸铵和氧化产物浓度。其他实验表明,含醛的氧化产物与水溶液中的水合形式平衡存在,这可能会调节其整体溶解度和表面活性。平衡时间标度约为10 发现衍生自β-石竹烯的氧化产物比由α-pine烯制备的氧化产物具有更高的表面活性,并且在1 mM时,云滴活化所需的临界过饱和度对于β-石竹烯醛降低了50%。发现临界过饱和的这些显着降低与超过约25 kJ / mol的吸附自由能或仅一个氢键当量相符,具体取决于溶液中的硫酸铵和氧化产物浓度。其他实验表明,含醛的氧化产物与水溶液中的水合形式平衡存在,这可能会调节其整体溶解度和表面活性。平衡时间标度约为10 对于1 mM处的β-石竹烯醛,云滴活化所需的临界过饱和度降低了50%。发现临界过饱和的这些显着降低与超过约25 kJ / mol的吸附自由能或仅一个氢键当量相符,具体取决于溶液中的硫酸铵和氧化产物浓度。其他实验表明,含醛的氧化产物与水溶液中的水合形式平衡存在,这可能会调节其整体溶解度和表面活性。平衡时间标度约为10 对于1 mM处的β-石竹烯醛,云滴活化所需的临界过饱和度降低了50%。发现临界过饱和的这些显着降低与超过约25 kJ / mol的吸附自由能或仅一个氢键当量相符,具体取决于溶液中的硫酸铵和氧化产物浓度。其他实验表明,含醛的氧化产物与水溶液中的水合形式平衡存在,这可能会调节其整体溶解度和表面活性。平衡时间标度约为10 取决于溶液中硫酸铵和氧化产物的浓度。其他实验表明,含醛的氧化产物与水溶液中的水合形式平衡存在,这可能会调节其整体溶解度和表面活性。平衡时间标度约为10 取决于溶液中硫酸铵和氧化产物的浓度。其他实验表明,含醛的氧化产物与水溶液中的水合形式平衡存在,这可能会调节其整体溶解度和表面活性。平衡时间标度约为10计算出的微米大小的气溶胶颗粒为–5至10 –4 s,表明活化过程中瞬时表面张力下降,从而导致大气中形成云。我们的发现突出了在考虑SOA颗粒存在下的云凝结活性时分子结构和反应性的根本重要性。
更新日期:2017-07-28
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