1. Eutrophication and cyanobacterial blooms in water bodies
With the increasing development and utilization of environmental resources by human beings, the high concentration of industrial development and urban population, a large number of industrial wastewater and domestic sewage produced in production and life are eventually discharged into the water body through various channels, so that the pollution load of nitrogen and phosphorus in the water body increases, exceeding the production capacity of the water body itself, so that the water body continues to enrich a large number of nutrients, resulting in the intensification of the eutrophication phenomenon of lake water.
Net map - urban sewage source
In the eutrophication state, the algae or upper aquatic plants in the water body over-multiply, the organic matter increases, and the dissolved oxygen decreases, resulting in the large-scale death of the underlying aquatic organisms, the serious degradation of the ecosystem, and the final deterioration of water quality. Usually, lakes with closed water bodies, poor fluidity and shallow water depth are not conducive to the evacuation of nutrients and are more likely to lead to the occurrence of eutrophication.
At present, most of the lakes in China are in a state of moderate trophic and eutrophication, and lake eutrophication usually causes cyanobacteria to multiply in large quantities on the surface of the water body, forming algae aggregates visible to the naked eye, covering most or all of the waters, that is, cyanobacterial blooms.
Net map - cyanobacteria outbreak in the channel
Second, the causes of cyanobacterial blooms
Water quality conditions are the basis for the growth and development of cyanobacteria, a large number of nitrogen, phosphorus and other nutrients in eutrophication water provide a direct carbon source for the growth and reproduction of cyanobacteria, it is generally believed that eutrophication of water is the direct cause of cyanobacterial outbreaks; and the mineralization and decomposition of organic matter in sediments, anaerobic metabolism intermediates and other types of nutrient salts released into the water have a direct impact on the eutrophication of water and the occurrence of cyanobacterial blooms; under the premise that lake eutrophication cannot be effectively controlled, Meteorological factors may be the main limiting factors leading to cyanobacterial outbreaks, and meteorological conditions often play an accelerating or inhibiting role in cyanobacterial outbreaks. In addition, the occurrence of cyanobacterial blooms is also closely related to other organisms living around it.
Third, the harm of cyanobacterial blooms
Cyanobacterial blooms as a whole show the characteristics of large range, high frequency and high biomass, which directly or indirectly affect human health and cause imbalances in the structure and function of water ecosystems, and the total hazards of incoming water can be roughly classified into the following categories:
(1) Destruction of cultural landscapes
When eutrophication occurs in water bodies, plankton in the water body multiply and breed, consume a large amount of dissolved oxygen in the water body, and at the same time the transparency decreases, the water quality becomes turbid, and accompanied by a fishy odor, resulting in a decrease in the quality of the water body. In addition, algae and other plankton are decomposed by aerobic microorganisms after death, which will further consume dissolved oxygen in the water, or be decomposed by anaerobic microorganisms, and constantly produce toxic gases such as hydrogen sulfide, which will cause a large number of fish and aquatic organisms to die, manifesting as black and odorous water bodies. The sharp changes in the color of the water body and the odor emitted by the decomposition of the algae body will seriously affect the quality and effect of the human settlement environment and the cultural landscape.
The water body is sensory and accompanied by a foul odor
(2) Ecosystem destruction
Cyanobacterial bloom outbreaks will seriously deteriorate the aquatic environment, reduce the biodiversity of aquatic ecosystems, break the original interspecific equilibrium and system homeostasis, degrade aquatic ecosystems, become more vulnerable, accelerate the aging of lakes, and make ecological disasters more frequent. In addition, cyanobacterial blooms will indirectly accelerate the rate of silt deposition in eutrophication lakes and reservoirs, reduce reservoir capacity, raise water levels, and cumulatively affect regional flood control capabilities.
Eutrophication of water bodies leads to the death of fish
(3) Threat to human health
Cyanobacteria itself will release toxins harmful to fish and humans to the water body, and toxins can lead to poisoning by people and livestock or drinking, such as: skin allergies, liver poisoning, etc. These harmful substances are also enriched layer by layer through the food chain and food web, ultimately endangering human health.
(4) Cause economic losses
Cyanobacterial blooms will cause economic losses to the aquaculture industry, etc.; cyanobacterial blooms in urban water bodies will seriously affect the image of the city and the quality of life of residents, reduce the value of ecological landscapes, and increase the cost of treatment; and the outbreak of cyanobacterial blooms in water bodies such as reservoirs will increase the cost of drinking water quality improvement process operation, and will also increase the difficulty of transportation due to pipeline corrosion.