Atmospheric Trace Gas Flux Meter Using Tunable Diode Lasers

对流层的化学成分由生物和人为微量气体的源和汇以及连接它们的中间光化学变化和质量传输过程决定。最近认识到，在评估人为扰动的影响之前，有必要彻底了解自然大气中的这些过程，这促使人们共同努力研究自然对流层。从这项研究中获得的见解将使人们能够更准确地预测人类活动对环境的影响。这一第一阶段SBIR研究项目的目标是开发测量进出地球表面的大气痕量气体通量的仪器。要研究的方法是基于成熟的涡旋相关技术，并将使用可调谐半导体激光光源和多通道吸收池相结合来检测十亿分之一以下的痕量物种。该仪器将专门设计成与声波风速计对接，以提供快速的时间响应和涡流相关法所需的最小的流场干扰。在第一阶段研究中，将对减压痕量气体采样系统的设计进行评估和测试，并将设计和评估最大化路径长度和最小干扰条纹的多程吸收池。第一阶段工作的结果预计将解决关键的设计问题，并允许在后续阶段开发现场仪器。最终的仪器将适用于包括二氧化硫、一氧化氮、二氧化氮、硝酸、臭氧和过氧化氢在内的痕量气体的通量测量。

The chemical composition of the troposphere is determined by the sources and sinks of biogenic and anthropogenic trace gases and the intervening photochemical transformations and mass transport processes linking them. The recent recognition that a thorough understanding of these processes in the natural atmosphere is necessary before the effects of man-made perturbations may be assessed has prompted a concerted effort to study the natural troposphere. The insight gained from this research will allow more accurate predictions of the impact of man's activities on the environment. The objective of this Phase I SBIR research project is the development of instrumentation to measure fluxes of atmospheric trace gases to or from the earth's surface. The method to be investigated is based on the well established eddy correlation technique and would use a tunable diode laser light source combined with a multiple pass absorption cell to detect trace species at sub-part-per-billion levels. The instrument would be designed specifically to be interfaced with a sonic anemometer to provide fast time response and minimal flowfield interference as required for the eddy correlation method. In the Phase I study, designs for a reduced pressure trace gas sampling system are to be evaluated and tested, and a multiple pass absorption cell which maximizes the path length and minimizes interference fringes will be designed and evaluated. The results of the Phase I effort are expected to resolve critical design issues and permit the development of field instrumentation in succeeding phases. The final instrument will be applicable to flux measurements of trace gases including sulfur dioxide, nitric oxide, nitrogen dioxide, nitric acid, ozone, and hydrogen peroxide.