Man-made Environmental Issues–Hypoxia
What is meant by ‘hypoxia’? Explain with reference to the severity of the problem in your own country. In China, as the economy develops rapidly, the environment is going worse and worse because of various pollutions. Hypoxia is one of these. It has been a serious environmental issue that mainly caused by human activities for many decades and may have severe effects to people’s life if people still find no effective ways of dealing with it. Hypoxia occurs when water in a lake, river, or a sea contains low level of dissolved oxygen that cannot sustain the survival of most aquatic animals.
It can be caused by many reasons combined. Generally, physical and biological processes and human activities can both result in oxygen depletion, but the process would be far longer when the former one serve as the dominant cause. Hypoxia mainly occurs in estuarine and coastal areas in wet seasons, between May and September. The poor capability of vertical mixing in shallow water leads to the existence of a strong stratification which influence the normal biological processes in water significantly, such as photosynthesis and respiration action.
Therefore, the regular nutrient pattern would be changed, and phytoplankton would overgrowth to diminish the oxygen in water, giving rise to the hypoxia. Nevertheless, despite of natural processes, human activities are the chief culprit of water hypoxic pollution. Lots of industrial effluents and leachate from fertilized field that contains abundant chemical elements such as nitrogen and phosphorus flux into rivers or seas and caused a phenomenon called eutrophication, which means nutrient enrichment.
Those chemical wastes feed phytoplankton in water as a nutrient and enable them to grow rapidly, eventually sucking out the oxygen and killing most fish in water. Due to the geographic factors, rivers and lakes that surround factories and farmlands are most likely to have a problem of hypoxia. Taking the Pearl River as an example, this is where hypoxia was first investigated in 1970s. Because its drainage basin passes through many urbanized and industrialized cities in China, large amount of sewage water entered and resulted in hypoxia.
In fact, hypoxia occurs worldwide, and China is one of the most effected countries. In China, the South China Sea and the East China Sea have been influenced by hypoxia most significantly. This is because most polluted Chinese rivers or lakes are all flow into these two seas eventually. Including two of the Five Great Freshwater Lakes in China, Boyanghu and Dongtinghu, 67 lakes, 51. 2% of the total lakes, have been influenced by water eutrophication and hypoxia. Among these, Dianchi in Yunnan is the most eutrophic lake in the world.
As for algae blooming, although every lake has the chance for being troubled by this, there are still some lakes have had a severe algae bloom that influenced people’s life. In 2004, massive runoff contained nitrogen and phosphorus entered Qiantang River and caused eutrophication in which has the highest flow velocity in China. In 2007, a Cyanophyta bloom occurred in Taihu, shut down many drinking water treatment plants and created a sever water crisis in Wuxi. Moreover, Chaohu, which is the fifth largest lake in China, has been made one of the most eutrophic freshwater lakes by huge nutrient loading and algae bloom since 1990s.
Along the lake, approximately 2. 3 million people and more than 3000 thousand factories in Anhui Province were affected by low-quality water sources. (Xiao-e et al. 2008) Prediction has been made that in 2030, there would be 30 billion ton of polluted water to be treated, and the treatment rate is 60%. (Xiao-e et al. 2008) Most middle-sized lakes would be polluted at that time. It is obvious that hypoxia and eutrophication are considerably harmful for people as well as the water ecosystem.
Long time of hypoxia can lead to huge damage of the aquatic ecosystem by breaking the intrinsic balance of the water area, and gradually degenerate its function. One straightforward negative effect is the death of aquatic animals. Large scale of phytoplankton develops on the water surface and forms a “green scum”, which reduces and even ceases the sunlight exposure, a necessary condition for photosynthesis to happen. Such water environment is not adapted by most aquatic lives, and many of them will die on account of the low level of needful oxygen.
This not only influences the fishery industry, which will further suppress the economic development in that certain area, but also lowers and poisons the water quality and thus induce a shortage of drinking water. On the other hand, short supply of drinking water has been a troublesome issue for many years in quite a few regions in China. In the Yangtze River Delta, an economic zone, plenty of liquid waste discharge has made 80% of the rivers cannot meet the standard of drinking water quality. In addition, in Zhejiang Province, 36 of 88 counties are still suffering from the pain of drinkable water shortage. (Xiao-e et al. 2008) Unfortunately, Chinese government has not given an effective scheme on how to reduce and prevent the water eutrophication and hypoxia.
Even though people did have some arrangements of dealing with the occurrent eutrophication such as chemical approaches and biological measures, no one has thought about the sustainable development about the water ecosystem. Considering the future ecosystem, people should get more general knowledge about water pollution and how terrible it will be if the ecosystems are destroyed. Domestic and agricultural waste water are two factors of eutrophication and hypoxia.
Cutting down or prohibiting the use of phosphor-contained detergent and air condition additive would both be beneficial on treating water eutrophication. Farmers are supposed to be informed to use more chemical-free fertilizer such as excreta of livestock and decomposer of plants and crops. Furthermore, the main source of polluted discharge, industry effluent, ought to be limited and regulated. Every factory should have their own channels for wasted water, and this sewage water should be decomposed or purified to recycle, instead of fluxing into the rivers and lakes directly.
These solutions are merely the basic treatments of hypoxia, and it need people’s corporation to persist putting these into practice. Hypoxia is indeed a severe environmental issue throughout the world; it pollutes the water, breaks the equilibrium of water ecosystem, and degrades water quality. However, if people can have efficient methods of diminishing it and put them into effect collaboratively, hypoxia will definitely be solved ultimately. At that time, China Rivers and Lakes will be more beautiful than before. References