Determination of Dissolved Organic Carbon Concentrations Using UV-Visible Absorbance for Water Samples in a Rural Watershed, the Republic of Korea

Abstract

Dissolved organic carbon (DOC) in water discharged from agricultural land is one of the indicators of water pollution. As aromatic compounds, which is the main component of DOC, absorb light in the UV-visible region, the intensity of UV-visible absorbance is correlated with DOC concentrations in water. In this study, a regression equation between DOC concentration of reference samples (n = 12, extracts of manure composts) and UV-visible absorbance was established. The applicability of the established equation was tested using water samples (n = 44) collected from a rural watershed in Jeonnam, South Korea. The peak absorbance of DOC in the compost extracts was detected at 275 nm, and was positively correlated (R 2 = 0.99, P < 0.001) with DOC concentrations. Although the DOC concentrations of water samples determined using the equation were lower than those measured by TOC analysis by about 15%, the estimated DOC concentrations were strongly (R 2 = 0.96, RMSE = 0.97, P < 0.001) correlated with measured DOC concentrations. Our study suggests that the DOC concentrations of watershed can be estimated by measuring the UV-visible absorbance method.