Study Finds Dangerous Levels of Phosphorus in Freshwater Worldwide
The amount of phosphorus entering global freshwater sources has reached dangerous heights, according to a new study released by the Water Resources Research journal last Wednesday.
The study examined the phosphorus load to freshwater from 2002 to 2010 and found that human activity contributed to 1.47 Tg/yr of freshwater phosphorus pollution — roughly 1.62 million U.S. tons annually. It also analyzed the grey water footprint (GWF), or “the amount of freshwater needed to assimilate (‘dilute’) the pollutants load” in the infiltrated environment.
The most common anthropogenic sources of phosphorus are fertilizers, manure, and organic wastes, according to the Water Research Center, an organization dedicated to providing information on water evaluation in Pennsylvania. Phosphorus also derives naturally from the environment, such as when rocks weather and release phosphate ions into the environment.
While phosphorus is essential for the development of lake ecosystems, too much phosphorus can lead to eutrophication, an exacerbated lack of oxygen molecules in freshwater environments. Eutrophication occurs when there is an excess of nutrients, such as nitrogen or phosphorus, and can lead to issues such as decreased diversity, toxic algal blooms, and habitat destruction, according to the Water Research Center.
China was the leading driver of phosphorus load to freshwater, according to the study, followed by India and the U.S. Additionally, the domestic sector contributed to 54 percent of the load, followed by agriculture at 38 percent and industry at eight percent.
The GWF increased by 15 percent within the study period, with the highest GWFs in areas with a dense population and/or intensive agriculture. A water pollution level (WPL) below one means that there is enough capacity to dilute the nutrient pollution; however, the study found that only three of the 20 studied river basins had a WPL below one.
The study was led by co-authors Mesfin M. Mekonnen and Arjen Y. Hoekstra, researchers from the University of Twente in The Netherlands.