Humans are overloading the world’s freshwater bodies with phosphorus | Science News

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Humans are overloading the world’s freshwater bodies with phosphorus

Poorly treated sewage and fertilizer runoff are main sources of the nutrient

By
11:00am, February 7, 2018
algal bloom

FEELING GREEN  Freshwater bodies on more than a third of Earth’s land area (excluding Antarctica) are maxed out on phosphorus, which can help create algal blooms such as this one.

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Human activities are driving phosphorus levels in the world’s lakes, rivers and other freshwater bodies to a critical point. The freshwater bodies on 38 percent of Earth’s land area (not including Antarctica) are overly enriched with phosphorus, leading to potentially toxic algal blooms and less available drinking water, researchers report January 24 in Water Resources Research.

Sewage, agriculture and other human sources add about 1.5 teragrams of phosphorus to freshwaters each year, the study estimates. That’s roughly equivalent to about four times the weight of the Empire State Building. The scientists tracked human phosphorus inputs from 2002 to 2010 from domestic, industrial and agricultural sources. Phosphorus in human waste was responsible for about 54 percent of the global load, while agricultural fertilizer use contributed about 38 percent. By country, China contributed 30 percent of the global total, India 8 percent and the United States 7 percent.

Overloaded

A new study estimates the water pollution level, or WPL, for phosphorus from human sources in the world’s major river basins, which include lakes and streams, from 2002 to 2010. WPL is an index of how much water a basin needs to dilute incoming phosphorus relative to how much water the basin receives. In 38 percent of these basins, WPL is greater than one, indicating an excess of phosphorus.

Citations

M.M. Mekonnen and A.Y. Hoekstra. Global anthropogenic phosphorus loads to freshwater and associated grey water footprints and water pollution levels: a high-resolution global study. Water Resources Research. Vol. 53, January 24, 2018, p.1. doi: 10.1002/2017WR020448.

Further Reading

C. Gramling. Rising CO2 in lakes could keep water fleas from raising their spiky defenses. Science News. Vol. 193, February 17, 2018, p. 14.

A. Witze. Lakes worldwide feel the heat from climate change. Science News. Vol. 191, May 13, 2017, p. 18.

C. Martin. Invasive species, climate change threaten Great Lakes. Science News. Vol. 191, March 18, 2017, p. 30.

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