Researchers said that with the help of billions of dollars in urban sewage pipes and wastewater treatment systems, pollution levels in many lakes in China have fallen over the past decade.
According to a Reuters report, a report in the UK's monthly "Nature ¡¤ Earth Sciences" magazine said that between 2006 and 2014, the phosphorus content of 862 freshwater lakes in China fell by one-third, although still higher than the standard for clean water.
It is reported that phosphorus is vital to life, but too high a content of phosphorus will induce a large amount of toxic algae to grow and suffocate fish and other lives.
Anthropogenic sources of phosphorus include wastewater, animal husbandry, aquaculture, and chemicals.
Lin Yan, a researcher at the Norwegian Water Research Institute, said that "the current decline in pollution levels in the most densely populated areas of the world is due to improved sanitation facilities," such as pipes, sewage treatment plants and better-quality rural toilets.
He told Reuters that the discovery could guide other developing countries in finding vital ways to clean freshwater sources.
The United Nations says that about 2.4 billion people, about one-third of the global population, lack access to basic health services. About 1,000 children die each day from diarrheal diseases caused by water pollution or poor sanitation.
It is reported that this is the first study on the unified measurement of phosphorus content in Chinese lakes. Studies have shown that the median phosphorus content in Chinese lakes dropped from 80 micrograms per liter in 2006 to 51 micrograms per liter in 2014.
But that number is still high: according to European standards, phosphorus levels below 25 micrograms per liter are considered good water.
The report said that the report, written by researchers in China, Canada and Norway, stated that "It takes a long time for Chinese lakes to reach a good ecological state."
It is reported that phosphorus will accumulate in the sediments of the lake and will not fade after the pollution source has dried up.
The report says that although the phosphorus content of lakes in most parts of China is generally declining, it has increased in the relatively less densely populated Northeast China.
Lin Yan pointed out that this rise may be related to climate change, which will lead to more rainstorms and land erosion. A study of rivers and lakes in the United States last year also found that phosphorus levels are increasing, which may be related to more phosphorus being washed into the waters by rainfall changes.