Heterogeneous Chemical Reactions in the Upper Troposphere and Lower Stratosphere

通过实验室研究，这些研究人员将系统地寻找对流层上层和平流层下层新的重要非均相反应；即除公认发生在南极春季的非均相反应外的非均相反应。他们将测量水冰(ICE)、三水硝酸(NAT)和过冷硫酸/水(SA/W)溶液表面选定的痕量物种的表面覆盖率和组成。这些表面将暴露于示踪大气物种，一次一个，一次两个，在某些情况下一次三个，以便研究反应增强的表面吸附以及单一物种的表面覆盖。该计划是在类似于对流层上层和平流层下层的实验条件下研究这些表面成分。这些实验将使用以下表面科学技术：X射线光电子能谱(XPS)用于确定表面的元素组成和氧化态，从而确定表面化学物种的成键，俄歇电子能谱(AES)用于确定表面的元素组成，以及四极杆质量谱(QMS)用于识别和监测气相化学物种。结合这些实验，通过使用化学热力学结合利弗莫尔二维大气模型提供的成分和温度数据，这些研究人员将确定各种化学反应在中午和午夜、6月和9月、5至35公里高度和从极地到极地发生非均相催化的热力学位置和时间。通过将这两条新的研究路线结合起来，他们试图确定新的非均相大气反应的候选者和适合这种反应的催化剂。感兴趣的反应物包括大气中的痕量物种，如二氧化硫(S02)、过氧化氢(H202)、氯(Cly)分子和NOY分子。一项具体的研究任务将强调氮N(III)的+3氧化状态，这在城市烟雾中很重要，但在平流层模型和测量中显然并不重要。N(III)物种可能是活性NOx的重要储存库，平流层NOY的汇，活化HCl的催化剂，以及大气中OH自由基的来源。通过这样的实验室研究，他们希望定位大气中N(III)化学的重要位置，并调查在对流层上层和平流层下层存在的条件下发生的以前未确定的多相反应。

Through laboratory studies these researchers will conduct a systematic search for new important heterogeneous reactions in the upper troposphere and lower stratosphere; that is, heterogeneous reactions other than those recognized to occur in the Antarctic spring. They will measure the surface coverages and compositions of selected trace species on the surfaces of water ice (ICE), nitric acid trihydrate (NAT), and supercooled sulfuric acid/water (SA/W) solutions. These surfaces will be exposed to trace atmospheric species one at a time, two at a time and in some cases three at a time in order to investigate reaction-enhanced surface adsorption as well as single-species surface coverages. The plan is to study these surface compositions under experimental conditions similar to those present in the upper troposphere and lower stratosphere. These experiments will employ the surface science techniques of X-ray photoelectron spectroscopy (XPS) for the determination of the elemental composition of the surface and the oxidation states, (and therefore the bonding) of the surface chemical species, Auger electron spectroscopy (AES) for the determination of the elemental composition of the surface, and quadrapole mass spectroscopy (QMS) for identification and monitoring of the gas phase chemical species. In conjunction with these experiments, through use of chemical thermodynamics combined with the composition and temperature data provided by the Livermore two-dimensional atmospheric model, these researchers will determine the locations and times that various chemical reactions are the thermodynamically capable of undergoing heterogeneous catalysis at noon and midnight, during June and September, at altitudes of 5 to 35 km, and from pole to pole. By combining these two novel lines of study they seek to identify candidates for new heterogeneous atmospheric reactions and suitable catalysts for such reactions. Reactants of interest include atmospheric trace species such as sulfur dioxide (S02), hydrogen peroxide (H202), Chlorine (Cly) molecules, and NOy molecules. One specific research task will emphasize the +3 oxidation state of nitrogen N(III), which is significant in urban smog, but is apparently not important in stratospheric models and measurements. N(III) species may be a significant reservoir for active NOx, a sink for stratospheric NOy, a catalyst for activating HC1, and a source of atmospheric OH radical. Through such laboratory studies, they hope to locate where in the atmosphere N(III) chemistry is important and investigate previously unidentified heterogeneous reactions that occur under the conditions present in the upper troposphere and lower stratosphere.