消浪工程对太湖底泥再悬浮及营养盐释放的影响

为了解863消浪工程对太湖底泥再悬浮及营养盐释放的抑制作用,于2005年7月15～17日在工程区投放悬浮物捕获器测定沉积物的再悬浮通量，并分层采集水样进行水体营养盐浓度的垂向分布研究。16日平均风速3 m/s时,测得的再悬浮通量上层最大值为7.22 g/d·m2,下层最大值为41.8 g/d·m2；17日平均风速5 m/s时,测得的再悬浮通量上层最小值24.7 g/d·m2,下层最小值为48.4 g/d·m2，沉积物再悬浮通量与风浪扰动强度关系密切。对比消浪工程区内外沉积物的再悬浮通量表明，消浪工程能够显著减弱风浪对底泥的扰动,抑制沉积物再悬浮,减轻营养盐的内源释放通量。实验结果还表明，太湖水体悬浮物浓度越高,悬浮物的有机质含量就越低,相应地，单位悬浮物中磷的含量也越低。随着风浪扰动的持续和增强,尽管能够将更多的沉积物间隙水中的溶解性磷带入水体，但是，野外观测中发现水体溶解性的磷含量并未相应增高甚至降低，这可能是由于水体中悬浮物浓度越高，对水体溶解性磷的吸附能力也越高,从而使得水中溶解性磷的含量增高不显著甚至降低。

EFFECTS OF WAVE DISSIPATION ENGINEERINGS ON SEDIMENT RESUSPENSION AND NUTRIENT RELEASE IN LAKE TAIHU

In order to evaluate the effects of wave dissipation engineerings on reducing sediments resuspension and internal nutrient release in Lake Taihu, sediment traps were settled on July 15 to 17, 2005 in the wave dissipation engineering area to measure resuspension flux of sediments. Water of different layers was sampled so as to know the vertical distribution of nutrient concentration. The maximum value of the upper resuspension flux was 7.22 g /d·m2 and the maximum value of the lower resuspension flux was 41.8 g /d·m2 on July 16 when the wind speed was 3 m/s; The minimum value of the upper resuspension flux was 24.7 g/ d·m2 and the minimum value of the lower resuspension flux 48.4 g/ d·m2 on July 17 when the wind speed was 5 m/s. Sediments resuspension flux has a close relation to wind wave disturbance. When comparing the resuspension fluxes in and out of the engineering area, it was obvious that wave dissipation engineering has weakened the wind wave disturbance to sediments, with an effect to prevent sediment resuspension, and therefore a lower nutrient resuspension flux was observed. Organic matter in suspended solid also reduced with the increase of suspended solid materials. Accordingly, phosphorus in suspended solid per unit will decrease too. Dissolved phosphorus did not increase in the observation,though sustained wind wave disturbance may bring much dissolved phosphorus from sediments into overlying water. Suspended solids can absorb dissolved phosphorus in the water. As a result, dissolved phosphorus will not increase dramatically with drastic sediments resuspension.