Quantifying Uncontrolled Landfill Gas Emissions from Two Florida ...
Quantifying Uncontrolled Landfill Gas Emissions from Two Florida ...
Quantifying Uncontrolled Landfill Gas Emissions from Two Florida ...
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The R 2 value was used to assess the accuracy of each concentration measurement <strong>from</strong> this<br />
project. Table 5-3, taken <strong>from</strong> the Boreal Laser, Inc. <strong>Gas</strong>Finder 2.0 Operation Manual, presents<br />
a range of R 2 values, and the corresponding accuracy of the measurement.<br />
Table 5-3. Accuracy of Concentration Measurements for Different R 2 Value<br />
R 2<br />
Measurement<br />
Accuracy (%)<br />
> 0.95 ± 2<br />
0.9 ± 5<br />
0.7 ± 10<br />
0.5 ± 15<br />
0.4 ± 20<br />
0.3 ± 25<br />
0.15 ± 50<br />
0.1 ± 70<br />
< 0.05 ± 100<br />
The R 2 value of each data point (measured methane concentration) was analyzed to assess<br />
whether or not it met the DQI criterion for accuracy of ±20 percent, which corresponds to an R 2<br />
value of greater than 0.4. A total of 21,467 data points were analyzed, and 16,509 met the DQI<br />
criteria for accuracy, for a total completeness of 77 percent. This value did not meet the project<br />
DQI criteria of 80-percent completeness.<br />
The precision of the OP-TDLAS methane concentration measurements was assessed by<br />
comparing consecutive methane concentration values measured along the same beam path.<br />
Methane path-averaged concentration data values were collected with the OP-TDLAS instrument<br />
and input into the VRPM algorithm<br />
5.2.2 DQI Check for Analyte PIC Measurement with OP-FTIR<br />
The precision and accuracy of the analyte path-integrated concentration (PIC) measurements<br />
collected with the OP-FTIR instrument was assessed by analyzing the measured nitrous oxide<br />
concentrations in the atmosphere. A typical background atmospheric concentration for nitrous<br />
oxide is about 315 ppb. However, this value may fluctuate due to seasonal variations in nitrous<br />
oxide concentrations or elevation of the site.<br />
The precision of the analyte PIC measurements was evaluated by calculating the relative<br />
standard deviation of each data subset. A subset is defined as the data collected along one<br />
particular path length during one particular survey in one survey sub-area. The number of data<br />
points in a data subset depends on the number of cycles used in a particular survey.<br />
The accuracy of the analyte PIC measurements was evaluated by comparing the calculated<br />
nitrous oxide concentrations <strong>from</strong> each data subsets to the typical background concentration of<br />
5-3