Dissolved organic carbon concentration and its seasonal variation in the Huguangyan Maar Lake of Southern China

The dissolved organic carbon (DOC) in the surface water of Huguangyan Maar Lake was continuously monitored based on once per week sampling frequency of 4 locations from June 2018 to May 2019. The DOC concentrations and its seasonal variation were discussed by correlating with the rainfall, water temperature, and pH of lake water. The results showed that the weekly DOC varied from 8.15 to 32.65 mg/L with an annual average concentration of 17.96 mg/L. There was a significant difference in the average DOC concentrations between the rainy and dry seasons as the monthly average DOC concentration was 21.72 mg/L for the wet season compared to the dry season concentration of 14.21 mg/L. The rainfall shows a significant effect on the DOC concentration of lake water, as DOC concentration was much high during the wet season. There were no significant spatial variations in the average monthly concentration among the four sampling locations except occasional variation during the wet season. The reason for the wet season DOC differences among four sampling locations is likely due to the uneven runoff and underground water inputs and the relatively slow circulation of lake water. Finally, the seasonal fluctuation of DOC concentration in this closed lake water suggests that dissolved soil organic matter inputs through the rainfall related to surface runoff and subsurface infiltration from the surrounding watershed land is important to the primary production and organic matter deposition in the lake sediments.