The Spatial Distribution Characteristics of Dissolved Organic Matter (DOM) in Sediments and Water Quality of Wuli Lake, Taihu Lake Basin, China

Abstract

Based on a field investigation conducted in May 2019, the spatial distribution characteristics of dissolved organic matter (DOM) in sediments of Wuli Lake in the Taihu Lake basin were analyzed using ultraviolet-visible (UV-Vis) absorption spectroscopy and three-dimensional fluorescence spectroscopy. The results showed that: (1) The overall water quality of West Wuli Lake was significantly better than that of East Wuli Lake. The water transparency, measured in Secchi depth (SD), of West Wuli Lake was higher than that of East Wuli Lake, while the suspended solids (SS), total nitrogen (TN), total phosphorus (TP) and chlorophyll a (Chl-a) were higher in East Wuli Lake than in West Wuli Lake. (2) The spatial distribution of a(350), M and SR values of DOM in surface sediment in Wuli Lake differed; a(350) values were highest in the northwestern part of Wuli Lake, while M and SR values were highest in the eastern part. The mean value of SR in Wuli Lake was 2.12 ± 0.67, indicating that the DOM contained more authigenic humus; the mean M value was less than 3.5, indicating that the proportion of humic acid was higher than that of fulvic acid. (3) The ranges of the biogenic index (BIX), the humic index (HIX) and the fluorescence index (FI) of surface sediments in Wuli Lake were 0.64~0.85, 3.79~4.84 and 1.72~1.84, respectively, indicating that surface sediments in Wuli Lake were characterized by authigenic sources, and the humic components of DOM in sediments were characterized by a dual contribution from terrestrial and endogenous sources.