Note: All depletion estimate calculations were done on an oil weight basis, which were obtained
during sample preparation. Oil weights used were the TPH-oil ((g/gram TPH) * grams dry
weight = g oil) for the samples.
Importantly, any compound or group of compounds can be normalized relative to a recalcitrant
biomarker. For statistical analyses of data, TPH, summed PAHs, and aliphatic and aromatic
fractions were all normalized using a recalcitrant biomarker.
3.6.7 Normalization with Respect to Climate
By expressing changes in the composition of petroleum relative to the recalcitrant biomarker
decalin, we normalized degradation rates with respect to concentration differences and thereby
reduced concentration variability at each site. However, each site was treated for different
lengths of time and at different conditions. To account for this, we normalized the treatment time
based on temperature at the site. Due to issues common at remote field demonstration sites, we
were unable to collect reliable soil field temperature data. As an alternative, we used air
temperature data available from the National Oceanographic and Atmospheric Administration
(www.cdc.noaa.gov). Barrow and Annette Island data were obtained from this database, but
Galena data were not available. To substitute for Galena data, we used Fairbanks temperature
data for the Galena site. The latitude and air temperatures at Galena and Fairbanks are similar.
Using 0C as the base temperature, growing degree-days (GDD) were calculated as
GGD = ∑((daily average high + daily average low)/2)-0. The GDD for the treatment time at each
site was summed from the initiation of the demonstration to the final sample time.
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