(BRAVO) Study: Final Report. - Desert Research Institute

Final Report — September 2004
the i-PPCH tracer that was continuously released from northeast Texas during the last six
weeks of the study. The inversion was conducted using singular value decomposition, which
can invert an under-determined system and dampen instabilities that occur in least square
regressions of ill-conditioned systems, such as the source receptor relationship.
The resulting reconstruction of the locations of the Eagle Pass and northeast Texas
tracer release sites and rates is displayed in Figure 9-10. (The results shown here are based
on analyses using the MM5 wind fields, but similar results were achieved with EDAS/FNL
winds.) Benefiting from a data rich system with about 800 data points and multiple
monitoring sites, the reconstruction was able to properly identify the Eagle Pass tracer release
site location (the red cell with the highest emission rate) and was very close to the northeast
Texas release site location despite the limited amount of usable tracer data there.
Figure 9-10. FMBR reconstructions of the Eagle Pass and northeast Texas tracer release
locations and rates. The colors indicate the estimated tracer emissions from each cell and the
asterisks indicate the actual tracer release locations.
The estimated tracer release rates are compared with the actual rates in Table 9-8.
For the Eagle Pass tracer release, when all tracer concentration data were used, the
reconstructed total tracer release rate of 4.2 kg/day is close to the actual rate of 3.7 kg/day.
The release rate for the northeast Texas tracer was underestimated by about a factor of 6,
though.
Note that the method did not work as well if only the tracer concentrations at Big
Bend were used, particularly for the northeast Texas tracer. For that limited data set, the
estimated location of the Eagle Pass tracer release was still quite good. The northeastern
Texas release location was not identified correctly, though, but rather the reconstruction
indicated tracer releases along the pathway from the actual tracer release location to Big
Bend.
9-26