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

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 EastWuli Lake. The water transparency, measured in Secchi depth (SD), ofWest 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 ofWuli Lake, while M and SR values were highest in the eastern part. The mean value of SR inWuli Lake was 2.12 similar to 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 similar to 0.85, 3.79 similar to 4.84 and 1.72 similar to 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.

Automated summary

Based on UV-Vis absorption spectroscopy and three-dimensional fluorescence spectroscopy, the spatial distribution characteristics of dissolved organic matter (DOM) in sediments of Wuli Lake in the Taihu Lake basin were analyzed. The findings showed that the overall water quality of West Wuli Lake was better than that of East Wuli Lake, with higher water transparency and lower levels of suspended solids, total nitrogen, total phosphorus, and chlorophyll a. The distribution of a(350), M, and SR values of DOM in surface sediment differed across Wuli Lake, with a(350) values highest in the northwestern part and M and SR values highest in the eastern part. The biogenic index, humic index, and fluorescence index of surface sediments in Wuli Lake suggested a dual contribution of terrestrial and endogenous sources.