ESTIMATION OF DISSOLVED ORGANIC CARBON IN RIVER FLOWS AND IDENTIFICATION OF THE RELATIONSHIPS BETWEEN PEAT HUMIC FRACTIONS AND PHYSICOCHEMICAL QUALITIES

Abstract

Peatlands are wetlands that contain higher amounts of carbon, some of which is often released with water in dissolved form, especially when land use change occurs. However, peatland carbon is mostly stabilized in humic fractions where it forms complexes with metallic elements. This study sought to measure the levels of dissolved organic carbon (DOC) in rivers and analyze the link between physicochemical parameters and humic fractions along the Buhandanda and Lushala peat profiles. Inductively-Coupled Plasma Optical Emission Spectrometry, chemical fractionation followed by sulfochromic oxidation, and dosing by indirect chemical oxidation were used to determine major geochemical elements (MGE), humic fractions (HS), and DOC, respectively. Average MGE concentrations were 4.1±1.4, 3.6±0.5, 2.8±0.6, 1.8±0.7, 1.1±0.4, 0.3±0.1, 0.1±0.0, 0.5±0.3, 0.1±0.0, 0.03±0.0, 0.03±0.0 and 1.9±0.9, 3.6±0.8, 2.5±0.6, 2.0±0.5, 1.1±0.4, 0.3±0.0, 0.09±0.01, 0.18±0.1, 0.06±0.04, 0,02±0.0 for Ca, Fe, Si, Al, S, Ti, K, Mg, Mn, Na for Lushala and Buhandanda, respectively. Fulvic acid (FA) fractions were constantly higher than humic acid (HA) from 0 to 80 cm and lower beyond on Buhandanda peaty profile. FA was also higher than HA for Lushala peat except for depths 20, 90, 140, and 200 cm. Humin (HU) was the highest fraction on the two peatlands. Humification index (HI) and degree of transformation (DT) of HS had values of the same order of magnitude (from 0.32 to 2.43). No association was found between physicochemical properties and HS, except for FA and Fe, Ca, S, Mg, Mn, Se on Lushala peat. DOC showed a downward trend from entry to exit of peatlands. The two sites were not statistically different. Mountainous peat can contain high levels of MGE and loses a tiny fraction of its carbon with runoff waters.