Chapter 9 Vapor Flux Measurements – Chamber Methods

Authors: Gao, Suduan; Wang, Dong

Submitted to: Vapor Emission to Outdoor Air and Enclosed Spaces for Human Health Risk Assessment: Site characterization, monitoring and modeling
Publication Type: Book / Chapter
Publication Acceptance Date: 4/8/2010
Publication Date: 6/9/2011
Citation: Gao, S., Wang, D. 2011. Chapter 9 Vapor Flux Measurements – Chamber Methods. Vapor Emission to Outdoor Air and Enclosed Spaces for Human Health Risk Assessment: Site characterization, monitoring and modeling. p. 191-207.

Interpretive Summary: Quantifying vapor flux into the atmosphere is essential for understanding the dynamics of many trace gases across the air-earth interface, identifying their sources/sinks or processes/mechanisms controlling emissions, and developing strategic plans for protecting the health of the global ecosystem. Accurate estimates of flux in the open surfaces face many challenges not only because of the heterogeneous nature of various trace gases in their production and transport but also the lack of standardization and challenges lying in the technical approaches for quantifying accurate vapor flux in open fields. This chapter reviews flux estimates for trace gases using chamber methods including static and dynamic flux chambers and discusses the major factors affecting flux estimates. This paper provides basic and necessary information on how to apply chamber methods to obtain the representative flux estimates in open fields.

Technical Abstract: Emissions of many trace gases from the Earth’s surface to the atmosphere have a profound impact on the air quality we breathe as well as the health of the global ecosystem. These trace gases include toxic chemicals and greenhouse gases from both anthropogenic and natural sources. Accurate measurements of their emission flux are essential for better understanding the major sources/sinks or processes/mechanisms controlling emissions and further developing mitigation strategies. This chapter reviews chamber methods for the direct estimate of vapor flux from soil surfaces to the atmosphere in open fields. Two types of commonly deployed chambers, static (or closed, passive) and dynamic (or flow-through, active), are discussed according to their design, operation and major factors affecting flux estimate such as model selection, pressure deficit, flow rate, temperature and water condensation, etc. These “chamber effects” must be minimized to obtain the flux estimates best approximating ambient conditions.