Abstract
The concentration of dissolved carbohydrate (DCHO) in water of a mountain bog pool was determined by three different methods from May to November, 1990. The phenol sulfuric acid (PSA) method consistently gave the highest concentration (1.22-4.01, average 2.15 mgC⋅l-1). The concentration of DCHO by the 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) method ranged 0.75-2.18 mgC⋅l-1 (average, 1.36 mgC⋅l-1). The ratio of MBTH-DCHO/DOC indicates that DCHO constituted a rather constant fraction of the DOC pool. Eight neutral monosaccharides were determined by gas chromatography (GC). GC-DCHO (sum of the 8 saccharides) ranged 0.28-1.99 mgC⋅l-1 (average, 0.99 mgC⋅-1). Glucose (25%), galactose (22%) and mannose (15%) were dominant. GC-DCHO agreed well with MBTH-DCHO from late May to early August, and was smaller than MBTH-DCHO in autumn.
Based on the specificity of the colorimetries given by previous authors, we adopted the results from the MBTH method as a measure of the total DCHO pool size. From these results, the PSA method appears to have overestimated the DCHO in bog water. On the other hand, to clarify the composition of DCHO is of great advantage to the GC method, though the method requires time, and its application is limited to the neutral sugars.
