Characteristics of Dissolved Organic Matter in Sediments of Typical Lakes in Southeastern Hubei Province, China

Abstract

This study aimed to reveal the distribution characteristics and sources of dissolved organic matter (DOM) in sediments of typical lakes in the southeastern of the Hubei province and provide a reference for pollution control of eutrophic lakes. The sediments of four typical lakes (Liangzi, Baoan, Daye, and Qingshan) in the southeastern of the Hubei Province were investigated in May 2019. Ultraviolet-visible (UV-Vis) absorption spectroscopy and excitation-emission matrixes characteristics of DOM were obtained by UV-Vis spectrophotometry and three-dimensional fluorescence spectroscopy. Moreover, the DOM fluorescence components were resolved by parallel factor analysis (PARAFAC). The results showed that: (1) The absorption coefficient a350 in surface sediments followed the order: Baoan Lake (16.99 ± 3.82 m−1) > Qingshan Lake (15.37 ± 3.8 m−1) > Liangzi Lake (12.54 ± 5.58 m−1) > Daye Lake (12.43 ± 1.43 m−1). Specifically, with increasing depth in the sediment cores, a350 increased and then gradually decreased in Daye Lake and Baoan Lake, but fluctuated in Liangzi Lake and Qingshan Lake with a roughly decreasing trend. (2) Two humic-like components (C1, C2) and one protein-like component (C3) were identified via PARAFAC. This analysis also showed that the surface sediment fluorescent dissolved organic matter (FDOM) was dominated by protein-like, while the sediment core FDOM was dominated by humic-like in Liangzi Lake. The proportion of humic-like in FDOM was higher than protein-like in surface sediments and sediment cores of Baoan, Daye, and Qingshan Lakes. (3) The DOM of surface sediments in the Liangzi Lake comprised mostly autochthonous components, mainly produced by the vital activities of aquatic organisms. The DOM of surface sediments in Baoan Lake and Qingshan Lake showed weak humic and moderate autochthonous characteristics. The humification of DOM in sediment cores of Liangzi, Baoan, and Qingshan Lakes gradually decreased from depth to the surface. The DOM in surface sediments of Daye Lake had strong humic and moderate autochthonous characteristics. (4) In general, the DOM of lake sediments in southeastern Hubei Province has dual-contribution characteristics representing terrigenous and endogenous sources. In the restoration and treatment of lake ecology, both internal and terrestrial pollution should be considered. At the same time, it is noteworthy that cyanobacteria depletion and aquatic residues caused potential internal pollution.

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

“…The mean value of M was 3.37 ± 1.34 (Figure 4b), which gradually decreased in the depth range of 0-6 cm, but fluctuated more sharply in the depth range of 6-34 cm and reached a maximum value of 5.6 at 20 cm depth. Most of the M values in the deep sediments were greater than 3.5 at 6-24 cm, indicating that the proportion of fulvic acid in the sediment DOM was higher than that of huminic acid at this depth, while the opposite was true at other depths [5]. The mean value of SR was 0.92 ± 0.53 (Figure 4c), and the variation in the surface layer of sediment was not obvious.…”

“…where A(λ) represents the corrected absorption coefficient at λ (m −1 ); λ is the wavelength, (nm); and a(700) represents the absorption coefficient at 700 nm [5]. A(350), the absorption coefficient at 350 nm, was chosen to represent the relative concentration of DOM [29,30].…”

“…S (275-295) is the spectral slope of the DOM absorption curve at 275-295 nm, and M is the ratio of the absorption coefficients of DOM at 250 nm and 365 nm [32]. When M > 3.5, the proportion of fulvic acid in DOM is higher, and when M < 3.5, the proportion of humic acid in DOM is higher [5].…”

“…"-" indicates that there is no relevant data in the article. Most of the data for this table was taken from [5].…”

“…Endogenous sources are closely related to aquatic biological activities and are generated by the secretions and metabolic products of algae, bacteria, microorganisms, and other aquatic organisms and show a dominance of protein-like substances [4]. When the exogenous pollution of a lake is effectively controlled, the effects of endogenous pollution will be further highlighted, which in turn will aggravate the eutrophication of the lake [5]. In addition, elevated concentrations of nutrients such as nitrogen and phosphorus are generally considered to be the root cause of cyanobacterial bloom outbreaks and the main factor for eutrophication in water [6].…”