Reducing ammonia emissions contributes to PM2.5 reduction

Ammonia and nitrogen oxide emissions are leading to PM2.5 pollution around the world. (Photo provided by the research team)

Reducing ammonia emissions may help mitigate air pollution more efficiently than focusing on nitrogen oxides alone, according to a joint study headed by Gu Baojing, a researcher with The College of Environmental and Resource Sciences, Zhejiang University.

The research, published in the journal Science, analyzed ammonia's contribution to global PM2.5 pollution and its impacts on human health, an area that hadn't been addressed before.

It found that in most countries, ammonia emissions are a larger contributor to PM2.5 pollution than nitrogen oxide emissions, providing a new perspective that supports ammonia mitigation as a cost-effective strategy for reducing air pollution and its impacts on health.

Ammonia and nitrous oxides, two main types of active nitrogen in the atmosphere, are indicative of PM2.5 levels. While nitrogen oxides predominantly come from urban production, ammonia is mostly generated from agricultural production.

Research shows that in the past, the role of ammonia in PM2.5 formation had been gravely underestimated. When calculating the significance of pollutants, scientists would conduct analyses according to mass ratio, effectively ignoring ammonia, whose mass takes up less than 10 percent of the total mass of PM2.5. "For this reason, we suggest the adoption of mole ratio (ratio between the amounts in moles of any two compounds involved in a chemical reaction), and our data model shows that when nitrogen emissions are zero, PM2.5 will drop by about 40 percent," said Gu.

The impacts of nitrogen on climate change coincide with factors such as population density and weather conditions. Thus, it is imperative that scientists find a universal way of evaluating the health effects of nitrogen and prove that global PM2.5 pollution could be mitigated through the targeted management of nitrogen.

Gu believes that PM2.5 pollution could be significantly alleviated if we put more effort in controlling ammonia emissions while maintaining current regulations on nitrous oxides emissions. "Urban-rural coordination is badly needed to address air pollution. Specifically, we could promote large-scale plantation to optimize fertilization, which will see fertilizer consumption and ammonia emissions reduced by about one-third and a half respectively. "

Gu also suggested raising livestock around farmland so that organic fertilizers can be used as soon as they are produced, preventing the release of ammonia that occurs when manures are stored up for a long time.

Content created in partnership with Science and Technology Daily.