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a Département des Sols et de Génie Agroalimentaire, Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, Cité Universitaire, QC, Canada, G1K 7P4
b George E. Brown Jr. Salinity Lab., USDA-ARS, 450 W. Big Springs Rd., Riverside, CA 92507-4617
* Corresponding author (sallaire{at}sga.ulaval.ca)
Received for publication December 4, 2000. There is an important need to develop instrumentation that allows better understanding of atmospheric emission of toxic volatile compounds associated with soil management. For this purpose, chemical movement and distribution in the soil profile should be simultaneously monitored with its volatilization. A two-dimensional rectangular soil column was constructed and a dynamic sequential volatilization flux chamber was attached to the top of the column. The flux chamber was connected through a manifold valve to a gas chromatograph (GC) for real-time concentration measurement. Gas distribution in the soil profile was sampled with gas-tight syringes at selected times and analyzed with a GC. A pressure transducer was connected to a scanivalve to automatically measure the pressure distribution in the gas phase of the soil profile. The system application was demonstrated by packing the column with a sandy loam in a symmetrical bedfurrow system. A 5-h furrow irrigation was started 24 h after the injection of a soil fumigant, propargyl bromide (3-bromo-1-propyne; 3BP). The experience showed the importance of measuring lateral volatilization variability, pressure distribution in the gas phase, chemical distribution between the different phases (liquid, gas, and sorbed), and the effect of irrigation on the volatilization. Gas movement, volatilization, water infiltration, and distribution of degradation product (Br-) were symmetric around the bed within 10%. The system saves labor cost and time. This versatile system can be modified and used to compare management practices, estimate concentrationtime indexes for pest control, study chemical movement, degradation, and emissions, and test mathematical models.
Abbreviations: GC, gas chromatograph VOC, volatile organic compound 3BP, propargyl bromide (3-bromo-1-propyne)
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