Effect Of Sediment Re-Suspension On Phosphorus Adsorption And The Thransformation Of Different Phosphorus Forms

Sediment re-suspension has significant effect on phosphorus migration and transformation. However, the information about phosphorus migration and transformation and the effect on the development process of waterbody eutrophication are limited under the conditions of sediment re-suspension. So it is necessary to study the law of phosphorus migration and transformation under the conditions of sediment re-suspension. It is important to explain the mechanism on the development process of waterbody eutrophication under the conditions of sediment re-suspension induced by disturbance. In the article, the phosphorus migration in overlaying water and the transformaiton of phosphorus forms in the sediments under sediment re-suspendion were investigated and the transformation possability of different phosphorus forms was analyzed. The transformation mechanism of different phosphorus forms was discussed, too.These will provide beneficial references to explain the mechanism on the evolution of phosphorus and the development process of waterbody eutrophica- tion under the conditions of sediment re-suspension induced by disturbance. The overlying water in this project was different from that in the previous study and the scale of experiment time was extended, so the aim was to try to probe the environmental effects of sediment re-suspension on the migration and transformation of phosphorus in the waterbody. The results showed that phosphorus migration in overlaying water is obviously affected by sediment re-suspension ways, frequency, disturbance time, environment factors. Sediment re-suspendion induced by aeration to sediment and disturbance could promote the dissolved inorganic phosphorus(DIP) from overlying water to sediment. The enhancement on phosphorus migration from overlying water to sediment increases with the increase of the frequency of sediments re-suspension. The migration of dissolved phosphorus from water to sediment is evidently promoted by continuing disturbance and interval disturbance, compared with the control experiment. Continuing disturbance could enhance the release of particulate phosphorus(PP) and can maintain the concentrations of PP and total phosphorus(TP) in high levels. However, PP was released from the sediment in the first 12 hours for interval disturbance, and reduced evidently in overlying water, and the concentration of PP and TP was maintained in low levels, compared with the initial state. The enhancement on phosphorus migration from overlying water to sediment was reduced with pH increase under sediment re-suspension. The enhancement at winter temperature on DIP from overlying water to sediment was better than that at summer temperature. Summer temperature could promote TP migration to sediment, compared with winter temperature. Under the conditons of sediment re-suspension, the amount of phosphorus was released from sediment to distilled water was larger than to river water. Different initial phosphate concentration in overlying water has evidently effect on DIP migration.It was found that the capability of phosphorus adsorption onto sediments after re-suspended was increased obviously, compared with the initial state. Smax of sediment after aeration was 1.12~1.29 times of that of initial state. the capability of phosphorus adsorption onto the sediment after aeration was larger than the sediment by disturbance and the long-term phosphorus storage was enhanced evidently. The amount of potentially mobile phosphorus(PMP) was decreased marked, compared with that of the initial state and the control experiment. By sediments re-suspension, EPC0 was decreased obviously, compared with that of raw sediments. Remarkable negative correlation was shown between the EPC0 of re-suspended sediments and its TP, BAP, BD-P concentrations. It was doubt that the features of phosphorus forms in re-suspended sediments could be changed obviously, compared with that of raw sediments and the sediments in control experiment.This paper also studied the transformation of sedimentary phosphorus forms under sediment re-suspension. Sediment re-suspension could promote the transformation of phosphours from potentially mobile forms to refractory forms. The percentage of PMP to TP was increased obviously in the sediment not re-suspendsion, compared with that of initial state, indicating that phosphorus was transformed into potentially mobile phosphorus at the first step in migration of phosphorus from overlying water to sediments. Sediment re-suspension would enhance the transformation from potentially mobile phosphorus to refractory forms and from bioavailable phosphorus(BAP) to nonbioavailable phosphorus in sediment with the increase of sediment re-suspension frenquency. With the time of sediment re-suspension increase, the amount of BD-P, Al-P, Ca-P was increased evidently, while the amount of NH4Cl-P was reduced. In addition, the features of BD-P in re-suspended sediments could be changed obviously, compared with that of the sediments in control experiment. After sediment re-suspension, the content of BAP was reduced, while the amount of BAP was increased in the sediment in the control experiment, compared with that of initial state. The formation mechanism of algae available phosphorus(AAP) and Olsen-P was similar. When phosphorus in overlying water was incorporated into the sediments, the changes of phosphorus forms are outstanding for PMP, while the refractory forms are kept constant. The formaiton mechanism of PMP is phisical and chemical transformation. The formaiton of BAP is affected by the amount and features of PMP.Finally, sediment re-suspension could reduce the content of phosphorus in the overlying water and could enhance the long-term phosphorus storage in the sediments. Therefore, it is suggested that the development of eutrophication of the waterbody could be delayed.