a-Cyclodextrin, and Glycogen as indicators of polymers; 2-
Hydroxybenzoic Acid and 4-Hydroxybenzoic Acid as indicators
of phenolic acids; whilst Phenylethylamine and Putrescine were
considered as indicators of amines/amides. Significant differences
were observed for all absorbance values of the six types of carbon
sources across the four sites. S-ud had the highest mean
absorbance values of carboxylic acids, polymers, and amines/
amides, which were significantly higher than D-t, D-ud and S-t,
with the exception of polymers in S-t. Additionally, the mean
absorbance values of carbohydrates, amino acids, and phenolic
acids were significantly higher in S-t than the other three sites.