太湖藻源性“湖泛”形成机制的气象因素分析

Analysis of Meteorological Factors of Forming Feculent and Anaerobic Water Aggregation Induced by Algal Bloom in Taihu Lake

将蓝藻水华引发的太湖水域黑臭水团现象称为藻源性"湖泛",并将其形成过程分为藻源形成、厌氧反应产物"泛"起、黑臭水团聚积3个阶段.针对2007年5月和2008年5月2次藻源性"湖泛"形成过程中气象要素演变的共同特征,结合水动力模型研究发现,适宜的气象条件提供了必要的热力与动力环境,是诱发"湖泛"形成的必要因素之一.第1阶段持续3 d以上高温、微风、风向基本一致的气象条件,有利于藻华在湖岸局部地区大量聚集、死亡、下沉、腐烂,发生厌氧反应,构成"湖泛"发生的物质基础;第2阶段冷空气过境,气温迅速降低、风速短时增大、持续1 d以上时间风向偏转接近180°,有利于厌氧反应产物"泛"至水表,形成黑臭水团,构成"湖泛"形成的触发机制;第3阶段持续高温、微风,有利于黑臭水团在水面较长时间存在,构成"湖泛"形成的维持机制.基于气象因素的可预报性,此研究为实现太湖"湖泛"的早期预警与防治提供了理论依据.

The water quality pollution problem about feculent and anaerobic water aggregation（FAWA） induced by algal bloom in Taihu Lake,which is often called ‘hufan’in Chinese,was studied.Its forming process is divided into 3 phases,i.e.,material elements forming of FAWA,anaerobic products to be brought to the water surface and the maintaining of FAWA in the water surface.The conventional observational data from Wuxi meteorological station was analyzed.The result shows that there are similar meteorological characteristics of two FAWA phenomena in Taihu Lake in May,2007 and May,2008.A numerical simulation was performed to prove the analysis results.It indicates that propitious meteorological condition is one of the necessary forming factors of FAWA,which provides thermal and dynamical environment for FAWA.During the first phase,the weather conditions,such as high air temperature,gentle breeze and nearly invariable wind direction,maintain for more than 3 days and cause algal bloom to aggregate,then die,sink and anaerobic decay near lake bank.All these provide the precondition for FAWA.During the second phase,when the cold air mass passes across the Taihu basin,almost counter-direction wind,which maintains for more than 1 day with higher speed and lower air temperature,makes anaerobic products to be brought to the water surface by uplifted current.This is the trigger mechanism of FAWA.During the last phase,continual high air temperature and gentle breeze is favorable for FAWA in the water surface.Because meteorological factors are predictable,this research provides a way and basis for the further study of warning and controlling approaches of FAWA.