[Dissolved Organic Matter Component and Source Characteristics of the Metropolitan Lakes and Reservoirs in a Typical Karst Region].

Abstract

In order to explore dissolved organic matter (DOM) components and their origins in metropolitan lakes and reservoirs in the karst region, the typical Hongfeng Lake, Baihua Lake, Songbaishan Reservoir, and Aha Reservoir were investigated in Guiyang City. Surface water parameters, including dissolved organic carbon (DOC), chlorophyll a (Chla), and optical parameters (a₂₅₄, a₂₈₀, a₃₅₀, E2:E3, S_275-295, FI, β:α, BIX, and HIX) were analyzed. Fluorescence peaks (B, T, A, M, C, D, and N) and three-dimensional matrix fluorescence with parallel factor analysis (EEM-PARAFAC) were employed to explain distinct DOM abundances and proportions. Meanwhile, Spearman's correlation coefficients and principal component analysis (PCA) were used to decipher parameter types and primary environmental processes. The results showed that aquatic ρ(DOC) and ρ(Chla) ranged between 4.24-11.9 mg·L^-1 and 0.32-19.7 μg·L^-1, respectively. High humic-like (a₂₅₄) and protein DOM (a₂₈₀) were observed in the Songbaishan Reservoir, resulting in higher DOM molecular weight when compared to that in other lakes and reservoirs. Surface water DOM mainly contained visible-light humic-like (23.8%-46.9%) and terrestrial fulvic-like components (17.6%-28.4%). High FI, β:α, and BIX but low HIX values in this study suggested that endogenous inputs largely contributed to aquatic DOM. Aquatic DOM component and source characteristics were significantly correlated with each other. Furthermore, inputs of humic-like DOM and microbial metabolism, as well as coupled carbonate dissolution and photosynthesis, drove dynamic DOM behaviors in the karst lakes and reservoirs.