Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: 9/9/2008
Publication Date: 11/11/2008
Citation: Gao, S, D. Wang, T. Pflaum, R.Qin, B. Hanson, G. Browne, H. Ajwa, and S. Yates. Dynamic flux chamber systems for fumigant emission measurements. Ann. Int. Res. Conf. on MeBr Alternatives and Emission Reductions, San Diego, Nov. 11-15, 2008. pp. 21-1 to 21-4.
Interpretive Summary: Emission measurement from soil fumigation is an essential component for several projects under the Pacific Area-Wide (AW) Pest Management Program for Integrated Methyl Bromide Alternatives. Dynamic (flow through) flux chambers were needed to accommodate the emission measurement work. The objective of this project was to design and construct Dynamic Flux Chamber Systems (DFCs) to automate sample collection and record critical data using readily available materials. Twenty four DFCSs were built and experienced a few problems in field measurement in 2007. These DFCSs have been upgraded with significant improvement in field operation and data collection. This equipment provides an essential tool for emission measurement in the field.
Technical Abstract: Assessment of effective field practices on emission reductions from soil fumigation relies on continuous and reliable emission data. Dynamic (flow through) flux chambers can provide continuous sampling for fumigants volatilized from the soil surface. The objective of this project was to design and construct Dynamic Flux Chamber Systems (DFCs) to automate sample collection and record critical data using readily available materials.. Twenty four DFCSs were built in 2007 and experienced a few problems in field measurements. These DFCSs consisted of a flow through chamber (FTC) and an automated sampling and data module (ASDM). The FTC has the dimension for covering a surface area of 50.8 x 25.4 cm. A smoke test to visualize the air flow indicated a uniform flow distribution or laminar flow pattern in the chamber at the flow rate of 5-7 L/min for chamber flow and 100-120 mL/min for the sample flow. In field, the air flow through the chamber will be maintained using a vacuum pump powered by a 12-V battery for each chamber. The ASDM consists of a datalogger, three latching solenoid valves, a tube manifold, two electronic flow meters, a diode voltage stabilizer, and a custom-designed circuit for energizing the solenoid valves. The datalogger is programmed to control the sampling schedule and also to record the chamber and sample flow every minute. A third channel of the datalogger recorded times when the valves changed sampling position. The DFCs allow continuous overnight sampling and require less labor during a field trial as compared to using static flux chambers. The upgraded DFCSs are ready for use in field emission measurements.