title: Depth-dependent variations of sedimentary dissolved organic matter composition in a eutrophic lake: Implications for lake restoration.
abstract: Dissolved organic matter (DOM) plays a significant role in regulating nutrients and carbon cycling and the reactivity of trace metals and other contaminants in the environment. However, the environmental/ecological role of sedimentary DOM is highly dependent on organic composition. In this study, fluorescence excitation emission matrix-parallel factor (EEM-PARAFAC) analysis, two dimensional correlation spectroscopy (2D-COS), and ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) were applied to investigate the depth-dependent variations of sediment-leached DOM components in a eutrophic lake. Results of EEM-PARAFAC and 2D-COS showed that fluorescent humic-like component was preferentially degraded microbially over fulvic-like component at greater sediment depths, and the relative abundance of non-fluorescent components decreased with increasing depth, leaving the removal rate of carbohydrates > lignins. The predominant sedimentary DOM components derived from FT-ICR-MS were lipids (>50%), followed by lignins (∼15%) and proteins (∼15%). The relative abundance of carbohydrates, lignins, and condensed aromatics decreased significantly at greater depths, whereas that of lipids increased in general with depth. There existed a significant negative correlation between the short-range ordered (SRO) minerals and the total dissolved organic carbon concentration or the relative contents of lignins and condensed aromatics (p < 0.05), suggesting that SRO mineral sorption plays a significant role in controlling the composition heterogeneity and releasing of DOM in lake sediments. Higher metal binding potential observed for DOM at deeper sediment depth (e.g., 25-30 cm) supported the ecological safety of sediment dredging technique from the viewpoint of heavy metal de-toxicity.
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: hcxu@niglas.ac.cn.
authors.forename: Huacheng
authors.initials: H
authors.lastname: Xu
authors.affiliation: School of Freshwater Sciences, University of Wisconsin-Milwaukee, 600 East Greenﬁeld Avenue, Milwaukee, WI 53204, USA.
authors.forename: Laodong
authors.initials: L
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: hljiang@niglas.ac.cn.
authors.forename: Helong
authors.initials: H
authors.lastname: Jiang
mesh_terms: D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D052918:Environmental Restoration and Remediation; D005068:Eutrophication; D005163:Factor Analysis, Statistical; D019015:Geologic Sediments / Q000032:analysis / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D060106:Lakes / Q000032:analysis / Q000737:chemistry*; D012995:Solubility; D014131:Trace Elements / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006812:Humic Substances; D014131:Trace Elements; D014874:Water Pollutants, Chemical
keywords: EEM–PARAFAC and 2D–COS; FT–ICR–MS; Lake restoration; SRO mineral sorption; Sedimentary DOM