藻类打捞对太湖聚藻区湖泛发生的影响

藻类打捞是多年来控制太湖沿岸藻源性湖泛的主要措施,为科学地指导藻类的打捞、防止湖泛的发生,采用能够模拟太湖风浪与沉积物再悬浮的大型装置,模拟湖泛易发的藻类聚集量下不同打捞频率(1次/d～1次/6 d)对湖泛发生时水体主要视觉指标和敏感指标〔ρ(DO)、E_h、ρ(Fe2+)、ρ(TFe)、ρ(∑S2-)等〕的影响. 结果表明:1次/d和1次/2 d的高打捞频率能够有效预防湖泛的发生,当第4天对照组发生湖泛时,1次/d和1次/2 d打捞频率下ρ(DO)为0.60和0.06,E_h为48和37,ρ(Fe2+)是对照组的79.3%和90.7%,ρ(TFe)是对照组的64.8%和72.3%,ρ(∑S2-)是对照组的62.03%和64.56%；1次/3 d频率虽不能控制湖泛的发生,但能有效推迟湖泛发生时间约2~3 d；而1次/4 d～1次/6 d的低打捞频率既不能预防也不能推迟湖泛的发生. 研究显示,在2.5 kg/(m2·d)鲜藻聚集速率下,1次/2 d的打捞频率是在控制湖泛发生前提下的最经济打捞频率. 

Effects of Algae Salvage on Black Blooms in Algae Accumulation Area in Taihu Lake

Algae salvage has been used as the main measure to control the algae-induced black blooms along the bank of Taihu Lake over the past few years. A series of large devices were used to study the most effective and economical salvage frequency to control black blooms in the algal accumulation prone area. Different salvage frequencies (once/d to once/6 d) were simulated under the most common algal amounts during black blooms. The influence of salvage on visual variations and typical characteristics (e.g., DO, E_h, Fe, S2-) of the overlying water was studied. The results showed that the occurrence of black blooms could be prevented under the salvage frequencies of once/day or once/2 d. Under these two salvage frequencies, ρ(DO) were 0.60 and 0.06, E_h were 48 and 37, ρ(Fe2+) were 79.3% and 90.7%, ρ(TFe) were 64.8% and 72.3%, ρ(∑S2-) were 62.03% and 64.56% that of the control treatment respectively, when black blooms occurred in the control treatment on the fourth day. Although the salvage frequency of once/3 d did not prevent the occurrence of black blooms, it still postponed the occurrence for about 2-3 d. Low salvage frequencies of once/4 d-once/6 d neither prevented nor postponed the occurrence of black blooms. The differences of typical characteristics during black blooms and the salvage effects between once/d and once/2 d of salvage were compared. The results showed that once/2 d is the most economical salvage frequency to prevent the occurrence of black blooms under 2.5 kg/(m2·d) fresh matter accumulation rate.