Development of Atmospheric Chemistry Instrumentation

这项资助提供了四个研究方向：(1)测试独立的校准方法，以扩大自由基探测器（PERCA，见下文）的应用范围，以更广泛的碳氢化合物过氧化自由基，以及探测器本身的改进；(2)进一步优化现有的用于涡旋相关测量的快速臭氧监测仪；(3)研制了测定大气中二氧化氮和硝酸过氧乙酰基（PAN）的气相色谱仪；(4)开发用于测量分子物种对光的响应（“j值”）的系统。PERCA是“使用化学扩增的过氧自由基检测器”的缩写。测量的主要对象是由氢原子附着于氧分子（化学式：H0）而形成的瞬时化学物质。在两种大气条件下，这些分子在阳光下不断产生，也在化学反应中不断被破坏。然而，可以维持一分钟的浓度，足以使H0在氧化其他微量物质（如一氧化氮）方面发挥重要作用。因此，重要的是能够测量这些低水平的HO及其碳氢化合物衍生类似物，以便构建整个大气化学系统的有效数学表示。PERCA现已投入使用，但需要进一步的校准研究，以便将其应用于更大范围的过氧自由基。一种快速臭氧监测仪现已投入使用，但所提出的优化是为了开发一种更简单、重量更轻的设备，更适合于飞机测量通过大气的臭氧向上或向下的通量。PAN/NO色谱仪是现场测量这两种氮化合物的设备。PAN是大气中活性氮的“储存库”物种，具有有害的生物学特性。二氧化氮是大气光化学系统中光能的主要载体。测量“j值”的系统将用于将大气光化学变化的进程与可变光强的驱动力联系起来。

This grant provides for four lines of research: (1) The testing of independent calibration methods to broaden the application of a free radical detector (the PERCA; see below) to a wider range of hydrocarbon peroxy radicals, along with improvements in the detector itself; (2) the further optimization of an existing fast ozone monitor for eddy correlation measurements; (3) the development of a gas chromatograph for measuring atmospheric nitrogen dioxide and PAN (peroxyacetyl nitrate); (4) the development of systems for measuring the response of molecular species to exposure to light ("j values"). PERCA is the acronym for a "peroxy radical detector using chemical amplification." The principal object of measurement is the transient chemical species formed by the attachment of a hydrogen atom to an oxygen molecule (formula: H0 ). Under 2 atmospheric conditions these molecules are constantly being produced in the presence of sunlight, and also constantly being destroyed in chemical reactions. A minute concentration may be sustained, however, sufficient to confer on H0 an important 2 role in oxidizing other trace species, e.g., nitric oxide (NO). It is therefore important to be able to measure these low levels of HO and of its hydrocarbon-derived analogues in order to 2 construct valid mathematical representations of the total atmospheric chemical system. The PERCA is now operational, but further calibration studies are needed in order to extend its use to a wider range of peroxy radicals. A fast ozone monitor is now operational, but the proposed optimization is directed to the development of a simpler device of lighter weight better adapted to aircraft measurements of upward or downward fluxes of ozone through the atmosphere. The PAN/NO chromatograph is a device for field measurement of 2 these nitrogen compounds. PAN is a "reservoir" species for active nitrogen in the atmosphere and it has deleterious biological properties. Nitrogen dioxide is a principal carrier of light energy in atmospheric photochemical systems. The system for measuring "j values" will find use in correlating the progress of atmospheric photochemical changes with the driving force of variable light intensity.