Research Projects

Project at a Glance

Project Status: complete

Title: Rebuild California Air Resources Board field fumigation facility and maintain for experimental use

Principal Investigator / Author(s): Thompson, C Ray

Contract Number: A0-100-32


Research Program Area: Ecosystem & Multimedia Effects

Topic Areas: Ecosystem Impacts, Field Studies


Abstract:

The purpose of this study was to rebuild, improve and refurbish twenty greenhouses plus ancillary equipment that was constructed on the Riverside campus in 1977 for the Air Resources Board. By the time the Agreement was signed, another site, which had been used by DR. O. C. TAYLOR for air pollution studies, became available. This newly abandoned site had a fine instrument shelter, power lines installed to 20 greenhouse sites and was located in a level field which had deep soil.

It was decided to give up the original site, salvage as much equipment as practical and construct larger, more versatile greenhouses at the new site. About the same cost would be involved. The former greenhouses provided a total enclosed area of 3.3 M2 while the new structures have 7.3 M2.

The new structures are of an original design supported by six galvanized steel tubular posts set in concrete footings. The plastic covers are attached to "polyclip" aluminum circles that are held in the extrusion channels with plastic pipe. The covers are made of two vinyl cylinders. The blowers supply test atmospheres at rates in excess of three changes of air per minute. Two activated charcoal filters provide "clean" air to the system. Flowmeters for metering fumigants into the greenhouses and for measuring samples of the test atmospheres are mounted on panels and a "Scanivalve" which allows rapid sequential sampling from each greenhouse is on hand. Two Thermo Electron SO2 analyzers and two Dasibi ozone analyzers were used for measuring these pollutants.

Performance of the gas dispensing and analytical system was checked by measuring both SO2 and ozone in the greenhouses and at the instrument shelter to find out whether absorption or breakdown of the gases occurred in sampling lines. With SO2 and ozone, the recovery was essentially quantitative, even though lengths of Teflon sampling lines were considerably different to the individual greenhouses.

Exclusion of outside air at plant height (60 cm) within the chamber was very good with windspeeds up to about 20 mph. Above this level internal mixing of outside air became apparent and levels of dispensed SO2 and ozone fluctuated widely.

Air temperature comparisons were made inside and outside the greenhouses by shielded thermocouples. Likewise, relative humidity was determined with wet and dry shielded thermocouples. No measurable differences had been observed previously within the chambers between 1/2 and 2.0 m in height. These results show that dry bulb temperatures inside and outside were essentially equal. Leaf and air temperatures were compared between the different chambers and all were essentially equal.

The mechanics of both gas generating systems and the solenoid controls worked with minimal trouble. At present the facility has operated for three months with no down time, and the experiments in progress are on schedule.


 

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