风浪条件下太湖藻源性“湖泛”的消退及其水体恢复进程

Fade and recovery process of algae-induced black bloom in Lake Taihu under different wind conditions

"湖泛"发生后的稳定持续时间是决定其致灾程度的主要指标,风浪的复氧是破坏其稳定性的主要因素.本文采用室内装置模拟、视觉比较和氧化还原条件分析等方法,研究了不同风浪作用下藻源性"湖泛"的稳定性及水体中主要特征参数恢复过程.结果显示:静风对照下,"湖泛"水体黑色在实验过程中始终未消失,水体DO含量保持在约1.5mg/L以下;小风(～2m/s)和中风(～4m/s)下,"湖泛"大约可持续2d左右,"湖泛"消失时的DO含量约6mg/L;大风(～8m/s)下,仅需要14h就可使"湖泛"黑臭完全消失.并且发现,在"湖泛"消失后,保持原来的风速下至144h,没有再出现黑臭的回复;水体溶解性营养物(NH4+和PO43)含量的降低随风浪大小有明显的响应关系.研究结果为藻源性"湖泛"的应急治理提供了决策依据.

The duration time of the black bloom is a major index which would determine weather the disaster of the black bloom is severe or not. Wind-induced reoxygenation is the main factor which can disrupt the stability of the black bloom. In this study, laboratory simulation, visual comparison, and analysis of oxidation and reduction methods were employed to investigate the stability of algae-induced black bloom and the recovery processes of the water characteristics under different levels of wind conditions. Results showed that under the controlled calm condition, the black bloom system remained at a stable state in the entire experiment period, in which the DO was continuously1.5 mg/L. Under slow wind （S, the wind speed was about 2 m/s） and moderate wind （M, the wind speed was about 4 m/s） conditions, the black bloom disappeared after 2 d and the DO increased to about 6 mg/L when the black color of the water faded. Under high wind （H, the wind speed was about 8 m/s） condition, the black bloom totally disappeared in only 14 h. The results indicated that the black bloom did not re-occur after disappears while the wind conditions were maintained in the left experiment time. It was also shown that the concentrations of water soluble nutrients （NH＋4-N and PO34 -P） were significantly responded to the wind levels. The research results would provide decision basis on the emergency control of the algae-induced black bloom.