China is making significant headway in preventing toxic algal blooms, by decreasing a pollutant — phosphorus — in its lakes.
Phosphorus, a mineral and an ingredient in farm fertilizer runoff that can prompt algae to multiply, dropped 60 percent in Chinese lakes from 2006 to 2014, according to a new study that analyzed 862 lakes across the country. By showing where Chinese water pollution policies succeeded and where they fell short, this study offers a blueprint for other industrializing and developing nations, where algal blooms threaten drinking water, kill aquatic life and pose dangers to children, pets and livestock.
The researchers point to the Chinese government’s efforts to reduce water pollution as the main catalyst for the decline.
“We wanted to check the long term trend of phosphorus concentrations of Chinese water bodies in terms of the five-year plans in China,” said Yan Lin, a scientist at the Norwegian Institute for Water Research and an author of the study published in Nature Geoscience.
Every five years, China reviews and revises its national plan to control water pollution. According to Lin’s study, 34 laws or regulations targeting domestic and industrial wastewater discharges have been issued from the China State Council and the Ministry of Environmental Protection since 2006. The Chinese Central Government has also invested upwards of $116 billion on these controls.
Lin’s team examined phosphorous levels in four parts of the country — eastern, middle, western and northeastern China — taking population density, economic development and geographic characteristics into how they demarcated the regions.
Each area saw unique changes based on implemented government policies.
“In the most populated areas, in eastern and middle China, the most successful measures have been improved sanitation in the urban and rural residential areas,” Lin said. Household waste is a major contributor of phosphorus to the environment. Washing machine detergents, dishwasher soap and personal care products contain phosphorous that readily seeps into water supplies.
While improved sanitation reduced phosphorous in western China too, the study argued further gains could have been achieved with policies aimed at agriculture and aquaculture. Most phosphorus in that area comes from big crop and livestock farms as well as the phosphate chemical industry, such as companies that mine phosphate deposits for sale on the global fertilizer market.
Any policies that keep phosphorus in the soil and soil on the ground will decrease phosphorus runoff into aquatic systems, said Jessica Corman, an ecologist at the University of Wisconsin-Madison who was not involved in the study. Human activities like deforestation, overgrazing and overcropping can loosen soil and make it prone to erosion by wind and rain. Erosion can then carry phosphorus in the soil into nearby water bodies.
Farmers should only use fertilizer when they need it, and be efficient in their use to avoid waste, Corman said.
But it’s difficult to make sure all farmers are following specific policies, Lin said.
“There are guidelines for farmers on how to do fertilization. However, it is hard to control every single farmer as strictly as point sources like wastewater treatment plants. It is impossible to check every single farmer’s practices,” said Lin. “We suggest that different regions in China should have more flexibilities to develop their own strategies.”
Meanwhile, northeastern China is bucking the national trend. Phosphorous levels increased in the region over the study period, but researchers are unsure why. Many lakes in northeastern China have low nutrient levels, so the increase in phosphorus could be part of a natural shift.