CuO-oxidation products, acid hydrolyzable monosaccharides and amino acids of humic substances occurring in a salt marsh estuary

Abstract

The phenolic oxidation products of lignin and neutral monosaccharides and amino acids released by acid hydrolysis were determined for samples of living and dead Spartina alterniflora (Loisel.), surficial marsh sediment, and the fulvic and humic acids isolated from these source materials, which were collected in a Georgia salt marsh estuary. Humic acids from all sources showed marked similarities in all of the parameters measured and closely resembled the source materials. Fulvic acid, while similar as a group, differed significantly from both the humic acids and the source material. Fungal decomposition of the plants, which is dominant to bacterial decomposition while the plants remain standing in the marsh, selectively degrades polysaccharides rather than indiscriminantly decomposing both lignin and polysaccharide biopolymers. The measured phenols, monosaccharides and amino acids accounted for 50–70% of the total carbon in the fulvic acids and 19–37% of the carbon in humic acids. Amino acids were estimated to account for 35–60% of fulvic acid nitrogen and 15–35% of humic acid nitrogen. There was no evidence that physiological state of the plants altered the intrinsic organic structure of either the fulvic or humic acids.