Within the last five decades, China has seen a 73 percent increase in pollution levels in the hundreds of cities surrounding the main stem (primary downstream section) of the Yangtze River, according to WWF. The discharge of sewage and industrial waste has reached 25 billion tons per year — 42 percent of the country’s total sewage discharge, according to WWF.
One of the major pollution issues facing the Yangtze River is the excessive accumulation of phosphorus (P) in the water. Phosphorus is a common ingredient in agricultural fertilizer, manure, and other organic wastes found in sewage and industrial discharge. Although phosphorus is essential to plant life in small amounts, too much of it in the water (often due to soil erosion) speeds up a type of pollution called eutrophication — explosive growth of algae that depletes the water of oxygen, according to the National Oceanic and Atmospheric Administration (NOAA). Eutrophication can be extremely harmful to river life.
“As with the rest of eastern China, phosphorus inputs via fertilizer runoff, leaching of animal manures, and human wastes have massively eutrophied the Yangtze River and associated water bodies in its flood plain, leading to blooms of algae and cyanobacteria that can pose a health hazard and cause fish kills,” said James Elser, a research professor at Arizona State University. His research involves studying how carbon, nitrogen and phosphorus shape the ecology and evolution of living things.
“Furthermore, massive amounts of P have accumulated as ‘legacy P’ in the Yangtze River catchment, as the amounts of P used as fertilizer in the basin over the past decades greatly exceed the P that has left the basin river outflow and via food shipments,” Elser told Live Science. “This legacy P will leave a long-lasting impact even after China brings its P management to a better level.”
While discussing what can be done to reduce the damage, Elser said that first, the use of P fertilizer on crops needs to be reduced. He added that current application practices in China add more P than is needed by the crop.
“Second, China needs a massive effort in manure management for its livestock operations. Manure is in great excess in many regions of the country and the manure cannot be returned to fields to fertilize them due to excessive transport costs,” he said. “Less meat in the Chinese diet would also reduce the manure production. “
And finally Elser said there needs to be more widespread adoption of wastewater treatment technologies to prevent P losses from cities and towns. “As China develops this infrastructure, recapture of the P in human waste should be incorporated so that P can be re-used rather than just buried in a landfill somewhere,” he concluded.