The dangers of green algae

What is cyanobacteria

Cyanobacteria, also known as blue-green algae, are the most primitive and ancient algae. Cyanobacteria appeared on the earth 3.5 billion to 3.3 billion years ago. Now there are more than 1,500 known species. They are widely distributed all over the world, but they are mainly produced in freshwater. A few can live in hot springs between 60°C and 85°C, and some species grow with fungi, mosses, ferns and gymnosperms. In some nutrient-rich water bodies, some cyanobacteria often multiply in large numbers in summer and form a layer of blue-green and fishy-smelling foam on the water surface, which is called "album bloom", exacerbating the deterioration of water quality and causing serious harm to fish and other aquatic animals. , as well as humans and livestock, it will cause great harm, and in severe cases, it will cause the death of fish.

Experts say algae in Taihu Lake may last for four to five months (picture) June 1, 2007 15:19 Jinyang.com-Yangcheng Evening News

Wuxi Water Supply Corporation Nanquan Water Source Plant Workers are fishing for cyanobacteria in the waters near the water intake. According to Xinhua News Agency

Wuxi’s water quality has improved after taking a series of measures, but no one seems to be able to give a timetable

On May 29, a sudden drinking water The crisis has swept almost the entire city of Wuxi, and the culprit is Taihu cyanobacteria. Although Wuxi City was well prepared, it was unable to prevent the crisis.

Tiny blue algae is a "frequent visitor" that infests Wuxi citizens every year, but why does it arrive so early and so fiercely this year? The Wuxi Municipal Government took a lot of measures to remedy the situation afterwards, without causing chaos or panic. However, why the beautiful and fertile Taihu Lake became a smelly lake is a question that people have to ponder...

When the crisis comes We were mentally prepared, but the outbreak was too serious to control

In fact, the crisis swept over from the afternoon of the 29th. According to the staff at the water intake of Wuxi Nanquan Water Source Plant, on the morning of the 29th, under high temperature conditions, a large-scale blue-green algae outbreak suddenly occurred in the Wuxi Basin of Taihu Lake. The drinking water supply to the city's citizens was also quickly contaminated by blue algae. Although salvage was carried out at the site, the blue algae outbreak was too severe to be controlled. Water contaminated by blue algae enters water plants and then flows through pipes into thousands of households.

According to relevant personnel, the Wuxi Taihu Basin is affected by wind direction, temperature, water flow, etc., and blue algae outbreaks have occurred almost every year in recent years. But it usually passes in a day or two. This is the first time such a concentrated and large-scale outbreak has occurred. This really caught both the government and citizens a bit off guard. Taihu Lake is Wuxi’s only source of drinking water, so the direct consequence of cyanobacteria is that the drinking water safety of citizens has been greatly affected.

The reporter witnessed the smell of "quilts" covered with lake water at the water intake site.

The reporter saw in the urban drinking water intake area of ??Wuxi City yesterday afternoon that a thick layer of water was floating on the water. Blue algae and fishy smell blow in the wind. The reporter threw a stone at random and felt that it settled very slowly. Cyanobacteria cover the water body like a thick quilt. At the nearby water company, relevant testing personnel are continuously taking samples to test the water quality. However, relevant experts said that unless the wind direction changes or heavy rainfall occurs immediately, it is difficult for the situation to fundamentally improve within a day or two.

According to reports, the smell and color of water contaminated by cyanobacteria are prominent, and the biochemical standards of water quality have not changed.

Government measures: 190 million tons of Yangtze River water was injected into Taihu Lake

Many citizens are very concerned about the improvement of drinking water. Some citizens said that it can be overcome in the short term, but if it is not relieved in the long term , I really don’t know what to do with my life.

Relevant parties such as Jiangsu Province, Wuxi City, and the Taihu Basin Management Bureau of the Ministry of Water Resources organized a large number of experts to actively study countermeasures to eliminate blue algae. The current main measure is to increase the water diversion capacity of "Diversion from the Yangtze River to Taihu" (diversion of water from the Yangtze River to supplement water from Taihu Lake), and the increase of the water diversion capacity of "Diversion from the Yangtze to Taihu". The flow rate has been increased from the original 170 cubic meters per second to 240 cubic meters per second. . At present, 367 million cubic meters of clear water from the Yangtze River have been diverted and 190 million cubic meters have entered the lake. By diverting the Yangtze River to the Taiyuan River, Taihu Lake water has been effectively replenished. The water quality of the Xidong Water Plant, which is responsible for water supply for 20% of Wuxi residents, is currently stable.

Zhu Zhongxian, deputy secretary-general of the Wuxi Municipal Government, said at a press conference yesterday afternoon that through the measures taken in the past two days, the water quality in the water source areas has improved to some extent. Yesterday, the temperature in Wuxi dropped below 30 degrees Celsius and experienced a rainfall, which had a certain inhibitory effect on mitigating the re-emergence of blue algae. Judging from the testing results, the level of cyanobacteria outbreak in Taihu Lake yesterday was slightly better than the day before, but it is still difficult to say when it will end. All relevant parties are actively taking measures. Wuxi City is considering adopting artificial rainfall enhancement methods to alleviate the problem when necessary.

The reporter saw yesterday afternoon in waters where blue algae outbreaks were concentrated that Wuxi City had organized some ships to salvage floating blue algae. Zhou Shengdong, director of the Water Quality Monitoring Center of Wuxi Water Supply Corporation, said that at present, the main method of the Water Supply Corporation is to put in a large amount of activated carbon and potassium permanganate to purify water quality. However, due to poor water quality, the phenomenon of yellow and smelly tap water is still serious.

According to the requirements of the Wuxi Municipal Party Committee and Municipal Government, Wuxi Water Supply Corporation has established a 24-hour water quality monitoring post to conduct continuous water quality monitoring.

Nine bullets increased rain and lowered temperatures in Wuxi yesterday

According to the "Yangtze Evening News" report, yesterday, in order to alleviate the blue-green algae crisis, Wuxi City anxiously waited for two days for "God's beauty" in the afternoon. At 1:25, artificial rainfall was implemented simultaneously in three places near the water intake of the water source plant, which effectively resolved the high temperature weather in Wuxi for several days and alleviated the pollution of Wuxi's tap water caused by blue algae.

At 1:25 pm, three artificial rain-enhancing rocket launch vehicles located on both sides of Meiliang Lake pressed the launch button at the same time, and nine rain-enhancing rockets flew into the clouds. A few minutes later , the original small raindrops in the northern part of Taihu Lake increased significantly. After the operation, the maximum precipitation detected by the Taihu Lake Automatic Station reached 7.1mm. At the same time, the temperature also dropped by about 8℃ compared with the day before.

As of press time, since the ground low pressure has not yet moved out of Wuxi, the operation team is still on standby, waiting for new favorable opportunities.

Experts worry: It may threaten Shanghai if it lasts for four to five months

This newspaper reported that Hu Weiping, a researcher at the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences and director of the Taihu Lake Ecosystem Research Station, said that in view of the At present, algae in Taihu Lake are distributed throughout the lake, and the water temperature of Taihu Lake will continue to rise in the next few months as the temperature rises. If the water level maintains the current situation, the scale of Taihu Lake algae will further expand and will last for four to five months. Therefore, Necessary measures need to be taken to reduce the harm of algae.

After a large-scale outbreak of cyanobacteria in Taihu Lake in Jiangsu, whether the water systems in Shanghai and the Yangtze River Delta region will be affected has attracted widespread attention. Lu Jianjian, a professor at the School of Resources and Environmental Sciences of East China Normal University, said that the currently polluted waters are in the West Taihu Lake area. Since there are thousands of control gates in the entire Taihu Lake Basin to maintain the relative independence of each water area, the impact on Shanghai will not be significant for the time being. However, if governance is not effective, The pollution of East Taihu Lake may affect the water quality safety of Shanghai.

(Yao Zong)

Why did cyanobacteria attack Wuxi

It is understood that cyanobacteria are easily caused when the water temperature in Taihu Lake exceeds 30 degrees Celsius. The direct causes of this concentrated blue-green algae outbreak are high temperatures and low water levels in Taihu Lake.

Relevant experts told reporters that the water body in the Taihu Lake Basin in Wuxi does not flow easily, and the southeast wind often blows every summer, causing pollutants on the surface of Taihu Lake to gather in this water area, and it is easy to cause blue algae when encountering high temperatures.

Qin Boqiang, a researcher at the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, said that the cyanobacteria outbreak occurred in Wuxi and its roots are around Taihu Lake. In recent years, among the sources of total nitrogen and total phosphorus in Taihu Lake, the proportion of industrial pollution has decreased, while the proportion of agricultural pollution and urban domestic pollution has increased. The problem of eutrophication of Taihu Lake water is still very serious.