Abstract
The aim of this study is to examine and interpret the spatial distribution of sedimentary humic substances in Lake Dalinouer. Humic substances in sediments were analyzed separately in different fractions: humins (HM), humic acid (HA), fulvic acid (FA), and different forms of organic carbon. The results showed that total organic carbon (TOC) contents varied from 7.25 to 65.54 g kg−1 with a mean of 36.37 ± 17.74 g kg−1. It was found that high TOC concentrations were at lake’s center and low TOC concentrations occurred at the estuary of inflows. Different redox conditions caused by water depth were of the most important factors which might influence TOC contents. Concentrations of HM, HA, and FA in sediments were detected in range of 6.40–58.16 g kg−1, 0.27–3.50 g kg−1, and 0.27–4.26 g kg−1, respectively. Of them, HM was the dominant form and accounted for 74–94% of TOC and 80–90% of humus. Organic Sediment Index (OSI) was used to assess the organics accumulation, and the value of OSI ranged from 0.001 to 0.30, which indicated that Lake Dalinouer was relatively clean. The relative high degree of humidification was found in the eastern of lake, where it should be taken into consideration seriously.
Highlights
Natural organic matter (NOM) is present throughout the ecosystem and plays a critical role within several natural and anthropogenic processes, such as the global carbon geochemical cycle and the transport of organic and inorganic pollutants across the environmental compartments [1,2,3]
The source of organic matter presents in soils, and sediments are mainly plants and animals residues, which, after extensive postdepositional microbiological and chemical transformations, become a natural polymeric material known as humic substances (HS) [3, 4]
The results of the present study showed a high spatial heterogeneity of organic nitrogen, total organic carbon, and the different fractions of humus in Lake Dalinouer
Summary
Natural organic matter (NOM) is present throughout the ecosystem and plays a critical role within several natural and anthropogenic processes, such as the global carbon geochemical cycle and the transport of organic and inorganic pollutants across the environmental compartments [1,2,3]. Humic substances, account for 60–75% of the total NOM [4], being recognized as the most persistent reservoir of sedimentary organic carbon with a mean residence time of several hundred years, and involved in the control of CO2 emission to the atmosphere, being a relevant carbon sink [1, 5, 6]. These fairly stable and extremely complex copolymers have received a great deal of interest due to their active participation in biogeochemical processes.
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