Abstract: A study was carried out on seasonal variation of ammonium and phosphate release at the sediment-water interface in Lake Taihu,and particularly in Meiliang Bay,using a novel technology of flow-through incubation.Results show that ammonium and phosphate release at the sediment-water interface in Lake Taihu was characterized mostly by its endogenousness,despite of the obvious spatial variation of ammonium and phosphate fluxes from site to site in the lake zones.Due to the pollution input of inflow rivers,the ammonium fluxes in the north of Meiliang Bay,Zhushan Bay and the off-shore area in the west of Lake Taihu [Mean±SD:(103.35±13.17) mg·m^-2·d^-1] were greater than those in other lake zones [(11.87±12.03) mg·m^-2·d^-1].A similar trend was observed with phosphate flux,and in addition,high fluxes were also monitored in Gonghu Bay,East Lake Taihu and off-shore area of the southwest of Lake Taihu.Similar to what was found in a static incubation system,the ammonium and phosphate fluxes measured in the flow-through incubation system at Meiliang Bay also demonstrated seasonal and spatial variations,i.e.higher in summer than in spring and autumn and in more polluted lake zones than in others.Because of the airtight design of the flow-through incubation system,volatilization of ammonia from overlying water was negligible,as compared to the open-top mode of the static incubation system.So the ammonium flux in the flow-through incubation system was much higher than that in the static incubation system,while phosphate fluxes were more or less the same due to its nonvolatility.

Key words: Lake Taihu, sediment, ammonium, phosphate, flux