Spatiotemporal distribution, mobilization kinetics and risk assessment of nickel in sediments of Lake Taihu, China

Excess nickel (Ni) entering lakes can pose adverse effects on aquatic ecosystems and human health. This study aimed to reveal the spatiotemporal distribution, mobilization kinetics, and potential risk of Ni in sediments of a typical multi-ecological lake, Lake Taihu, China.

We conducted seasonal monitoring of the spatial distribution of soluble and labile Ni in sediments using high-resolution dialysis samplers (HR-Peeper) and the diffusive gradient in thin-films technique (DGT), respectively.

We found that the total Ni concentrations in sediments (mean: 37.56 mg kg⁻¹) all exceeded the background value (19.5 mg kg⁻¹). The spatial distributions of soluble and labile Ni showed no notable fluctuations along the vertical profiles of sediments in all seasons. The DGT-induced fluxes model implied that there is a partial Ni resupply capacity in the sediment of all three ecological zones, but it is higher in the algal-type zones than in the macrophyte-type and transition zones. Furthermore, an assessment of the ecotoxicological risk found that the risk quotient values for Ni were less than 1 in all sampling seasons, indicating a low ecotoxicological risk of Ni in the sediments of Lake Taihu.

Our results indicate that the ecological risk in the algal-type lake zones requires special attention. Our findings help towards improving the level of understanding regarding the mobilization process and potential risk of Ni in sediments, which in turn can provide guidance for the prevention and control of sediment Ni pollution in lakes with multiple types of ecological zones.