Seasonal characteristics of phosphorus sorption by sediments from plain lakes with different trophic statuses

Abstract

Phosphorus (P) sorption in sediments plays a significant role in trophic status of a lake. This study investigated the characteristics of P sorption in sediments from three lakes with different trophic statuses (moderately eutrophic, lightly eutrophic and moderately trophic) through kinetic, batch equilibrium and thermodynamic experiments. Results show that pseudo-second-order kinetics best describe P sorption in sediments from the three lakes. Fitting by modified Langmuir and Freundlich isotherms indicates that the moderately trophic lake sediment has higher sorption capacity (maximum of 0.848 mg g−1 at 35°C) than the sediments of the other two lakes at different temperatures (5, 15, 25 and 35°C). Thermodynamic results indicate that the processes of P sorption of the three sediments are spontaneous, entropy-driven and endothermic reactions. The risk of P release in sediments was analysed according to the calculated results of isotherms combined with the change in P fraction. Sediments from the moderately eutrophic lake act as a source in summer. The lightly eutrophic and moderately trophic lakes act as sources in spring and winter, and a pool in summer and autumn, respectively. Furthermore, the amounts of reductant-soluble P, calcium-bound P and iron-bound P are significantly related to the sorption capacity of sediments from the three lakes (p < 0.05). The different sediments have different P release risk, and P fraction in sediment is one of the significant factors of P sorption.

Sorption Properties of the Bottom Sediment of a Lake Restored by Phosphorus Inactivation Method 15 Years after the Termination of Lake Restoration Procedures

“…The largest amount of phosphates was adsorbed by sediments from the surface layer (5-10 cm) at Station 2, at 356.39 mg P kg −1 dw, while the weakest sediment sorptive abilities with respect to phosphorus were shown by sediment taken at St. 1, at 202.47 mg P kg −1 dw (Figures 2-4). These values are within the range recorded for the sediments of other Olsztyn lakes [44] or around the world [45][46][47][48][49][50]. The pH level during experiments was favorable for P adsorption processes onto sediment.…”

“…They often increased with sediment depth (Table 1). Assessed ∆G ads values were similar in range to values observed in [46,48]. The negative ∆G ads values noted during experiments confirm that P sorption was a spontaneous reaction [46] and the order of magnitude of ∆G ads was typical for physical adsorption processes.…”

Contribution to the Study of Phosphorus Adsorption Kinetics on the Superficial Sediments of a Recently Development Artificial Estuary: Vridi Channel (Côte d'Ivoire)

“…Moreover, the adequacy of this model in this study would show that chemisorption is the dominant mechanism during phosphates retention on these substrates. The suitability of this model to describe kinetics on complex materials would be explained essentially by the real heterogeneity of the complexation sites taken into account by the model [21,25,[39][40]. This is in agreement with the nature of these superficial sediments.…”

“…In the second phase, the slow phosphates adsorption on these sediments would be characteristic of their retention after diffusion in mesopores and micropores. This would be a gradual adsorption [15,21,25].…”