Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2000
Publication Date: 8/1/2002
Citation: Allaire, S.E., Yates, S.R., Ernst, F.F., Gan, J. 2002. A Dynamic Two-Dimensional System for Measuring Volatile Organic Compound Volatilization and Movement in Soils. Journal of Environmental Quality. 31(4)1079:1087. Interpretive Summary: A experimental laboratory device was constructed to allow the study of the movement and dissipation of soil fumigants in soil. The device consists of two square plates separated by a thin zone containing the soil medium. Numerous injection/sampling ports were placed on one of the steel plates to allow the sampling of the soil fumigant gas concentration. The loss of chemical from the soil surface can be measured using flux chamber(s) attached to the top of the device. The system is unique in that it allows experiments to be conducted under conditions that commonly occur in the field.
Technical Abstract: 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 bed'furrow 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 ion) were sym metric around the bed within 10 percent. The system saves labor cost and time. This versatile system can be modified and used to compare management practices, estimate concentration'time indexes for pest control, study chemical movement, degradation, and emissions, and test mathematical models.