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LOQ for Air Emissions
Environment Canada has included hexachlorobenzene (HCB) and polychlorinated dibenzo-pdioxins and dibenzofurans (PCDD/PCDF) in the list of Track 1 substances - toxic substances that are persistent, bioaccumulative and anthropogenic. Virtual elimination from the environment of the Track 1 substances is one of the objectives of the Toxic Substance Management Policy. The Level of Quantification (LoQ) is suggested to be used as a baseline to assist in establishing a virtual elimination target. It is determined by assessing the variability (standard deviation) of repeated measurements of analytes at a concentration near the detection limit.
Part I - A study was undertaken to assess the variability of sampling and analysis of dioxin emissions using the recent available data. The variability associated with sampling, analysis and source emission during each test influence the standard deviation derived from the dioxin emission data. A total of 53 sets of low emission data from 36 combustion facilities consisting of 42 sets of sequential tests and 11 sets of dual-train tests were selected. When standard deviations of the emission test are pooled, LoQ (or pooled standard deviation) decreases with the highest mean concentration in the pooled data. On the basis of the linear correlation between LoQ and the highest mean concentration in the pooled data and the upper limit of the acceptable blank level (10 times detection limit), LoQ for PCDD/PCDF is estimated to be 32 pg/m3 TEQ. This value remains constant when the dual-train test data are excluded.
Part II - A study was undertaken to assess the measurement repeatability of HCB and PCDD/PCDF in spiked blank trains and in fly ashes collected from the four facilities: municipal waste incinerator, medical waste incinerator, cement kiln and iron sintering plant. LoQ is determined as ten times of standard deviation of the repeated measurements. A combined standard deviation of the spiked trains and ashes was used. LoQ for HCB measurement is estimated as 6 ng/m3 for an emission sample. Estimated LoQ for PCDD/PCDF measurement is 16 pg/m3 TEQ for an emission sample.
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