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Published in:
01-09-2015 | Thematic Issue
Phosphorus release characteristics of sediments in Erhai Lake and their impact on water quality
Published in: Environmental Earth Sciences | Issue 5/2015
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Abstract
In view of the problems of high P concentration in the sediments and low P concentration in the overlying waters of Erhai Lake (EH), an indoor static incubation experiment was performed to determine the P release characteristics of sediments at different depths. The differences in the P forms of the sediments before and after the incubation experiment were compared, and the impact of such forms on the characteristics of the P release of sediments at different depths and that of P release on the water quality of EH were also investigated. Results were as follows: (1) Dissolved organic P (DOP) is the main form of P released at the sediment–water interface of EH, which is approximately six times that of soluble reactive P (SRP), which indicates that the DOP release of sediments may have a more important impact on P composition and the content of the overlying water of EH than SRP. The release flux of the DOP of sediments at the surface layer is higher than that at the bottom layer. The vertical distribution of the release flux of SRP is characterized by an increase at the surface layer and a decline at the lower layer. (2) Different P release potentials exist for different forms of P in the sediments of EH. Among the different P forms, the loosely absorbed inorganic P (NH4Cl-rp) is the main source of SRP that is released from the sediments into the overlying waters. (3) The release flux of total P (TP) at the sediment–water interface of EH amounts to 114.2 t/a, which accounts for 87.2 % of the total external P input in the lake. Although the amount of the P release of sediments under indoor static simulation conditions is higher than that under real conditions, the trend of the P release of the sediments of EH is accurate. According to this result, the contribution of the sediment P release to the TP concentration of the overlying water is up to 31 %, reaching a concentration of 9.4 µg/L. The annual P release of the sediments of EH influences the P concentration in the overlying water. The contribution of the sediment P release to the TP concentration of overlying water in the northern part of EH is obviously higher than to that of the other parts. The water quality of this kind of lake can be improved by controlling the P release of sediments, particularly the release of OP.