蓝藻大量堆积、死亡与黑水团形成的关系

经过多年治理,太湖水环境状况得到一定程度的改善,但大部分湖区仍处于富营养化状态,夏季水华很严重,在适宜的环境条件下会诱发黑水团。2011年8月28日至9月27日在太湖梅梁湖杨湾水域进行为期1个月的原位蓝藻堆积围隔试验,分析蓝藻大量堆积、死亡过程中水体关键环境要素的变化趋势,并基于试验结果初步分析了其与黑水团形成之间的关系。结果表明,蓝藻积聚死亡会导致水体处于缺氧状态,水体溶解氧浓度基本在0.2mg/L上下波动;同时,水体主要营养盐浓度会在短时间内迅速上升,TN、NH4+-N和TP浓度最高值分别为初始值的16、48和46倍。高温时段打捞水体表面积聚的蓝藻是防止蓝藻死亡进一步恶化环境的有效措施。蓝藻死亡的同时会促进致黑物质的产生,丰富的有机污染底泥的参与对于黑水团的形成有决定作用,但形成典型的黑水团需要一定水平的风浪扰动。

Relationship between Accumulation and Dying of Cyanobacteria and Black Spot

Though water environmental of Taihu Lake was improved through many years integrated management,most of the area was eutrophicated.Under proper condition,black spot might be induced because large area algal bloom was still possible.Based on in situ enclose,impacts of large amount of blue-green algae accumulation on water environment was analyzed as well as its relationship with black spot forming.The results showed that,anoxia or hypoxia would be induced and the mean concentration of DO was 0.2 mg /L during the later period of the experiment.TN,NH 4+-N,and TP concentrations increased rapidly in short time when large mounts of blue-green algae dead,with the peak concentration of 16,48 and 46 times higher than the background values.Algal salvage was an effective measure to avoid water environment degrading.The caused black matters could also be induced because of algal death.Abundant polluted sediment was key factor in forming black spot,while wind-wave disturbance was necessary in order to induce typical black spot.