[Impacts of Sediment Disturbance on the Distribution of Suspended Particle Size and Phosphorus].

To clarify the influence of the sediments disturbance on the particle size distribution of suspended solids, and the influence of particle distribution on the forms of dissolved phosphorous in the overlaying water, the sediments and overlying water from Meiliang Bay, Taihu Lake, were used to conduct the indoor simulation experiments to investigate the particle size of suspended solids according to the Ubbelobde particle size criteria and the distribution of phosphorus compounds in the overlying water under the disturbance circumstances. The results indicated that the average proportions of small (0-10 microm), middle (10-20 microm) and large (> or = 20 microm) diameter particles presented different trends of increasing, decreasing and staying stable, respectively. It indicated the possible transformation of particle size of suspended solids from small-middle diameter to large diameter. In addition, the data of DTP/TP and DIP/TP showed a periodical variation with the corresponding periodical variety of particle diameter in suspended solids, while ns obvious variety of DTP and DIP was observed. It suggested that disturbance enhanced the ability of phosphorus immobilization by suspended solids. On the other band, the percentages of DTP in TP and DIP in TP were 19% and 13% under the disturbance, respectively, and they were obviously lower than those (DTP/TP, 80% and DIP/TP, 69% ) in the control. It indicated that tbs transformation of particle size of suspended solids from small-middle diameter to large diameter due to disturbance was in favor of tbe adsorption and sedimentation of dissolved phosphorus. Accordingly, the formation of particle phosphorus was enhanced. Therefore, it delayed the development of eutrophication in the water body.

[Impacts of Multiple Disturbance on Migration and Transformation of Endogenous Phosphorus in Lake].

This work aimed to clarify the influence of multiple disturbance factors on the migration and transformation of endogenous phosphorus. In this experiment, the sediment of Meiliang Bay in Taihu Lake was studied as the major research object. With the help of Rhizon sampling technique, Unisense microelectrode system and so on, this experiment studied the change regularities of dissolved oxygen between sediment and water interface, different forms of phosphorus and iron ions under disturbance. The results indicated that the dissolved oxygen content in sediment decreased in the presence of Corbicula fluminea as compared with the control experiment. Disturbance made the peak area of DIP in interstitial water to migrate from 3-4 cm to 4-5 cm, which suggested that the "active region" of DIP regeneration went deeply into sediment with the appearance of Chironomus plumosus and Corbicula fluminea. Meanwhile, the existence of Corbicula fluminea and algae further reduced DIP in the interstitial water. That was because the released NH4Cl-P was transferred to phosphorus in overlying water and Fe/Al-P. With the increase of disturbance factors, the transformation ratio from NH4Cl-P to Fe/Al-P also increased gradually (from 44% to 59%).

[Development of Sediment Micro-Interface Under Physical and Chironomus plumosus Combination Disturbance].

Synergistic effect of physical and Chironomus plumosus combination disturbance on the characteristics of the micro-environment and micro-interface was investigated by the Rhizon samplers and Unisense micro sensor system. The results showed that the oxygen penetration depth (OPD), total oxygen exchange (TOE), water content and total microbial activity increased under the combination disturbance and bioturbation and were kept at the higher level, compared with the control. These parameters increased with the physical intensity under combination disturbance. However, the content of Fe2+ decreased under the combination disturbance and bioturbation and the decrease was more obvious than that in the control. The changes of the Fe2+, the water content and the total microbial activity were large at 0-4 cm depth in the sediments. Therefore, the area might be the active area for the transformation of internal sedimentary phosphorus forms. The curve fitting was used for the OPD, TOE, the content of Fe2+, the water content and the total microbial activity with the physical intensity under combination disturbance. It was observed that the second-order polynomial equation was suitable for the curve fitting. In addition, jump type synergistic effect was presented in the above mentioned parameters under combination disturbance when the physical intensity was higher than 34 r x min(-1). The remodeling on the sediment micro-interface and micro-environment might be the main inducing mechanism for the transformation of internal phosphorus.