TRACING DISSOLVED ORGANIC MATTER FLUORESCENCE IN WULIXIA KARST RESERVOIR - A CASE STUDY IN GUANGXI, CHINA

The geochemistry characteristics of DOM in water can be qualitatively and quantitatively analyzed. In this respect, water sample from Wulixia Reservoir in Guangxi, China was collected on December 2016, April 2017 and June 2017, respectively. Our findings showed that the average CDOM absorption coefficient a(355) was 0.52 m^-1. The value of a(355) in summer is slightly higher than that in other periods. Relatively high S_{275 ~ 295} value and M value indicate that the dissolved organic matter in the research area was dominated by small molecular weight substances with low humic acid share and more rich acid. A total of 3 fluorescence components (C1, C2, C3) with the maximum of single or multiple excitation and emission wavelengths are identified in the study area by the PARAFAC model. Among them, C1 belongs to the fulvic acid substance, the C2 belongs to the humic acid substances, C1 and C2 usually represent the hardly degradable DOM, and C3 belongs to the protein such as tryptophan, suggesting that tryptophan was derived from algae and microorganism degradation. Among the 3 components in December, the corresponding excitation and emission wavelengths are C1 (250,325/425 nm), C2 (260,370/470 nm) and C3 (260/370 nm), and the excitation and emission wavelengths of the 3 components in June are C1 (250,300/390 nm), C2 (270,350/450 nm) and C3 (280/340 nm). A comprehensive analysis of the DOM fluorescence spectrum parameters showed that the higher BIX, β:α, FI values and lower HIX values had a good indication for the source of DOM in the study area. Talked together, DOM is influenced by terrigenous matter and endogenous substances, indicating that microorganisms and algae are the main source of these endogenous substances affecting the transform from dissolved inorganic carbon to organic carbon.