For the month of December, the concentration figures we report for both fencelines are based on analysis of the raw FTIR spectral files utilizing the same background spectral files which had been used for the November report. No attempts were made to identify newer background spectra, to modify the analytical "script files", or to otherwise improve upon detection limits. The decision to proceed in this manner was made in the interest of expediency. At the time this report is being prepared (July '98) we are now several months behind in our analysis of the raw data coming to us. Currently, our plan is to simply "run the numbers" for the next several month's data in an effort to get caught up.
For the December data, overall detection limits are seen to suffer (increase) accross the board on both fencelines. This seems to correlate with an overall decrease in spectral quality during the month. It is unclear to what extent, if at all, updating the background reference files would have helped in this regard.
The emissions picture presented by the December data is very much like that from November. The pollutant gases which are encountered most often on both fencelines are MTBE and methyl pentane. As in November, these gases are seen to be present more often on the South fenceline, although at lower concentrations than on the North. Also, on the North fenceline, the vast majority of "hits" for these compounds continue to appear in the early morning hours, whereas no such clearly-defined pattern is apparent on South.