Sediment Quality in an Anthropogenically Disturbed Shallow Lake: A Case Study of Baiyangdian Lake

We determined the total nitrogen (TN), total phosphorus (TP), total carbon (TC), and organic matter concentrations in sediments from surface water, waterways, ditches, swamps, and ponds of Baiyangdian Lake (BYDL), and investigated the spatial distribution, properties, and sources of the sediments. The TN, TP, TC, and OM concentrations in the sediments averaged 3677.21 ± 3686.15 mg/kg, 2038.25 ± 1190.87 mg/kg, 45,742.76 ± 29,535.23 mg/kg, and 12.05% ± 6.80%, respectively, and the concentrations were higher in the surface sediment (0–10 cm) than in the deeper sediment. We found that the TN and TP single evaluation indices at 0–10 cm averaged 5.61 and 2.18, respectively, indicating severe TN and TP pollution. The comprehensive pollution index averaged 4.80, and more than 87% of the sampling points were severely polluted. The organic and organic nitrogen (N) indices showed that 92.82% and 93.65% of the sites were polluted with organic matter and organic N, respectively. According to the C/N and C/P ratios, the organic matter and in the surface sediments was mainly from cellulose plant debris and phytoplankton. Of the correlations between the sediment properties, OM and TN were most strongly correlated, which indicates that the OM mineralization was closely related to the N source and migration. The findings of this study serve as crucial baseline data for the governance of BYDL, providing a vital data foundation for the systematic management of its water eco-environment.