Weijiang Chen

Thanks to a variety of clean air and water regulations, China's infamously polluted waterways are looking cleaner.

According to a report published today in Nature Geosciences, phosphorous levels in China's lakes declined by 60% between 2006 and 2014. Phosphorous is a crucial nutrient for plant growth, but it's also a common byproduct of industry and used as a fertilizer. Too much of it can trigger the growth of harmful algae that, when it dies and decomposes, can consume the ecosystem's oxygen and kill all animal life.

Why it matters: Phosphorous pollution is a large source of water quality degradation globally that threatens biodiversity and the health of humans near polluted water. In the U.S., economic losses associated with high phosphorus levels in freshwaters is about $2.2 billion each year.

How they did it: Yan Lin of the Norwegian Institute for Water Research in Oslo and his colleagues took monthly measurements of phosphorous concentrations from 862 lakes across China and looked at the source of phosphorous in each lake separately.

What they found: Phosphorous levels have decreased in lakes in western, eastern, and central China. This corresponds with cleaner industry in the area and better sewage systems in the cities. However, in remote and relatively pristine Northeastern China levels of the mineral have increased, suggesting runoff of naturally-occurring phosphorous in the soil could be increasing due to logging.

Looking forward: Lin told Axios that building good sanitation and sewage infrastructure is the best way to stop phosphorous pollution. Although phosphorous levels in lakes decrease when pollution stops, phosphorous does build up in the soil. Lin notes that in places like Scandinavia and the U.S., lake phosphorous has started to increase despite anti-pollution measures. That's because phosphorous from pollutants builds up in the soil, and can continue to bleed into lakes for years to come. It doesn't mean that anti-pollution measures don't work, says Lin.

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