Evaluation of an enclosure method for measuring emissions of volatile organic compounds from quiescent liquid surfaces
An enclosure method for direct measurement of volatile organic emissions from quiescent liquid surfaces was investigated under simulated conditions in the laboratory and in the field at two hazardous waste treatment facilities. In the laboratory study, accuracy and precision of the method was estimated under a variety of environmental and operational conditions including level of emission rates, emission composition, solar intensity, and enclosure sweep flow rate. Precision of the method was determined in the field studies at two sites under a range of environmental conditions including winter versus summer, full sun versus shade, low emission rate versus high emission rate, and polar and nonpolar compounds. The results of the laboratory study show that precision for a single-component emission rate was 3.0% or less measured as pooled relative standard deviation with a sweep flow rate of 5 L/min or above. A consistent negative bias of approximately 50% was found, which was independent of emission rate, solar intensity, or sweep flow rate at or above 5 L/min. The bias was found to vary with compound and between single-compound and multicompound emissions. Precision in the field was found to be approximately 20% expressed as relative standard deviation.