[Fluorescence Spectral Characteristics of Dissolved Organic Matter in Songhua Lake Sediment]

Dissolved organic matter (DOM) has a significant impact on the main pollution indicators of the lake (e.g., COD), and sediment is the main source of pollution in the lake. Research on the fluorescence spectral characteristics of DOM in sediments is important to reveal the mechanism of lake pollution. In this study, sediments were collected from 20 sites in Songhua Lake. The DOM components in the sediment were analyzed using the excitation emission matrix-parallel factor analysis (EEM-PARAFAC) technique, and the properties of the sediment DOM were clarified via spectroscopy. Additionally, the relationship between DOM and eutrophication of the water column was explored. The results showed that four components were identified from the sediment DOM of Songhua Lake:humic-like C1 (330/415 nm), C2 (255/440 nm), C3 (365/470 nm), and protein-like C4 (280/355 nm). The high HIX and low BIX indicated that the source of sediment DOM was mainly terrestrial and included some biological sources. The spatial distribution of the fluorescence intensity of the four components was relatively similar, showing that the fluorescence intensity was higher in the upstream (S1-S7) than that in the downstream (S8-S20). The massive deposition of suspended particulate matter (SPM) carried by the three rivers (Huifa River, Songhua River, and Jiao River) was the main reason for this spatial distribution. Eutrophication status in the water column of Songhua Lake was similar to the fluorescence intensity distribution of sediment DOM. Meanwhile, there was a strong correlation between eutrophication level and sediment DOM fluorescence intensity in the downstream water column of Songhua Lake.