太湖水土界面氮磷释放通量的流动培养研究

Study on Ammonium and Phosphate Fluxes at the Sediment-Water Interface of Lake Taihu Using Flow-Through Incubation

运用一种新的水土界面释放通量研究方法——流动培养法,对太湖不同湖区不同季节条件下水土界面氮磷释放通量进行研究。结果表明,太湖水体沉积物是其上覆水体氮磷的内源,不同湖区间铵态氮、磷酸盐交换速率差异显著,其中,受入湖河道污染输入影响较大的梅梁湾北部、竺山湾、西部沿岸带湖区铵态氮释放速率[(103.35±13.17)mg.m-2.d-1]显著高于太湖其他湖区[(11.87±12.03)mg.m-2.d-1]。磷酸盐空间释放规律与铵态氮相似,但释放的高值还出现在西南沿岸带、贡湖湾和东太湖。与静态培养方式下获得的结果相同,流动培养方式下梅梁湾铵态氮和磷酸盐释放速率也表现出季节性和空间差异,即夏季水土界面氮磷释放速率高于春、秋季,且污染严重湖区的释放速率高于其他湖区。由于流动培养的气密性减少了上覆水铵态氮以NH3的形式挥发,使得铵态氮释放速率高于敞口的静态培养方式;而就非挥发性磷酸盐释放速率而言,2种培养方式下得到的结果基本一致。

A study was carried out on seasonal variation of ammonium and phosphate release at the sediment-water interface in Lake Taihu, and particularly in Meiiiang 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 offshore 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.