Can Earth’s Fresh Water Survive the Phosphorus Overload?
Man-made phosphorus pollution is reaching dangerously high levels in freshwater basins around the world, according to new research.
Phosphorus is a common component of mineral and manure fertilizers because it boosts crop yields. However, a large portion of phosphorus applied as fertilizer is not taken up by plants, and either builds up in the soil or washes into rivers, lakes and coastal seas, according to the study’s authors.
The results of a new study show global human activity emitted 1.62 million U.S. tons of phosphorus per year into the world’s major freshwater basins, four times greater than the weight of the Empire State Building.
The study also assessed whether human activity had surpassed the Earth’s ability to dilute and assimilate excess levels of phosphorus in fresh water bodies. The authors found phosphorus load exceeded the assimilation capacity of freshwater bodies in 38 percent of Earth’s land surface, an area housing 90 percent of the global human population. There is simply not enough fresh water in many areas to assimilate the phosphorus.
The study’s results indicate freshwater bodies in areas with high water pollution levels are likely to suffer from eutrophication, or an excess level of nutrients, due to high phosphorus levels. Eutrophication due to phosphorus pollution causes algal blooms, which can lead to the mortality of fish and plants due to lack of oxygen and light. It also reduces the use of the water for human purposes such as consumption and swimming.
Breaking down phosphorus load
The authors of the new study examined agricultural activity to calculate the total amount of man-made phosphorus entering Earth’s surface water from 2002 to 2010. They gathered data on how much fertilizer is applied per crop in each country, and estimated domestic and industrial phosphorus production by looking at protein consumption per capita per country.
The largest contribution to the global Phosphorus load came from domestic sewage at 54 percent, followed by agriculture at 38 percent and industry at 8 percent.
The authors found the phosphorus load from agriculture grew by 27 percent over the study period, from 525 gigagrams (579,000 U.S. tons) in 2002 to 666 gigagrams (734,000 U.S. tons) in 2010.
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SOURCE: The American Geophysical Union. Via Water Online.