Spatial–seasonal characteristics and influencing factors of dissolved organic carbon and chromophoric dissolved organic matter in Poyang Lake

As the largest organic carbon pool in water, dissolved organic carbon (DOC) plays a key role in the carbon cycle. In inland rivers and lakes, DOC is closely related to chromophoric dissolved organic matter (CDOM) with optical attenuation. In this study, the spatial distribution and seasonal variations of DOC and CDOM in Poyang Lake in 2014–2016 were investigated. The results demonstrated that the DOC concentration in Poyang Lake had a range of 1.34–5.56 mg/L with an average of 2.12 ± 0.54 mg/L. The absorption coefficient of CDOM at 355 nm had a range of 1.24–5.70 m−1 with an average of 2.71 ± 0.83 m−1. In terms of the spatial distribution, the concentrations of DOC and CDOM in the south of Poyang Lake were higher than those in the north of the lake. In terms of seasonal variations, the concentrations of DOC and CDOM were higher in spring and summer than in autumn and winter. The absorption coefficients of CDOM and DOC concentrations in Poyang Lake exhibited a significant linear correlation. The correlation between DOC and CDOM in some sections of Poyang Lake varied spatially and seasonally. The highest correlation was observed in wetland waters of the southern Poyang Lake in spring, while there was no significant correlation in northern section of the lake in most of the periods. The results revealed that water level, precipitation and the vegetation cover pattern had determining effects on the spatial heterogeneity of DOC and CDOM. The spectral characteristic parameters demonstrated that the main source of the CDOM in Poyang Lake was from terrestrial input.