In China, nitrogen leaves pollution haze

STANFORD (US) — In China, the amount of nitrogen from industry, cars, and fertilizer that fell on land and in water increased by 60 percent each year from 1980 to 2010, a new study reports.

It’s no secret that China is faced with some of the world’s worst pollution. Until now, however, information on the magnitude, scope, and impacts of human-caused nitrogen emissions was lacking.

Xuejun Liu and Fusuo Zhang at China Agricultural University in Beijing led the study, which is part of an ongoing collaboration aimed at reducing agricultural nutrient pollution while increasing food production in China—a collaboration that includes Peter Vitousek, a biologist at Stanford University and Pamela Matson, a Woods Institute senior fellow and dean of the School of Earth Sciences.


For the study, researchers analyzed all available data on bulk nitrogen deposition from monitoring sites throughout China during the past 30 years. In that time, the country has become by far the largest creator and emitter of nitrogen globally.

Its use of nitrogen as a fertilizer increased about threefold from the 1980s to 2000s, while livestock numbers and coal combustion increased about fourfold, and the number of automobiles about twentyfold (all of these activities release reactive nitrogen into the environment).

Increased levels of nitrogen have led to a range of deleterious impacts, including decreased air quality, acidification of soil and water, increased greenhouse gas concentrations, and reduced biological diversity.

“All these changes can be linked to a common driving factor: strong economic growth, which has led to continuous increases in agricultural and non-agricultural reactive nitrogen emissions and consequently increased nitrogen deposition,” the authors write in the study published in the journal Nature.

Researchers found highly significant increases in bulk nitrogen deposition since the 1980s in China’s industrialized North, Southeast, and Southwest. Nitrogen levels on the North China Plain are much higher than those observed in any region in the United States and are comparable to the maximum values observed in the United Kingdom and the Netherlands when nitrogen deposition was at its peak in the 1980s.

China’s rapid industrialization and agricultural expansion have led to continuous increases in nitrogen emissions and nitrogen deposition. China’s production and use of nitrogen-based fertilizers is greater than that of the United States and the European Union combined. Because of inefficiencies, more than half of that fertilizer is lost to the environment in gaseous or dissolved forms.

China’s nitrogen deposition problem could be brought under control, the study’s authors write, if the country’s environmental policy focused on improving efficiency in agricultural use of nitrogen and reducing nitrogen emissions from all sources, including industry and transit.

Source: Stanford University