Effect of Rainfall on Chromophoric Dissolved Organic Matter (CDOM) and TOC in Springwater

Abstract

Chromophoric dissolved organic matter (CDOM) is a colored dissolved organic matter that consists of a complex mixture of organic matter molecules primarily derived from decaying organic matter and the remains of organisms. CDOM can be used as an indicator of water quality, but further research is necessary to determine the correction factor and parameters that influence it. This study aimed to analyze the effect of rainfall on the absorbance of CDOM and the concentration of total organic carbon (TOC) in spring water. Water samples were taken from Candi Kuning Spring, located in the northern part of Bali Island. During sampling, pH measurements were conducted in-situ. CDOM absorbance was measured using a Shimadzu UV-1800 spectrophotometer by scanning at 200-800 nm with a 0.5 nm step. From this absorbance data, E₂/E₃, S_275-295, S_350-400, and S_R were calculated. TOC was measured by titration. The data showed that an increase in rainfall resulted in a decrease in pH, E₂/E₃, S_275-295, S_350-400, and S_R. A decrease in all of these absorbance parameters indicates an increase in the molecular weight and aromaticity of CDOM. Based on the decrease in TOC concentration with increasing rainfall, it can be concluded that the increase in the molecular weight and aromaticity of CDOM is due to reduced photodegradation during the rainy season.