More acid rain in East Asia’s future

Large increases in Asian industrial emissions of nitrogen oxides in the next 30 years could lead to a tripling of the acid rain there due to these pollutants.

Worldwide, more than 40 trillion grams (40 teragrams) of nitrogen per year enter the atmosphere as part of nitrogen oxides and other nitrogen-containing gases, says Meredith Galanter, an atmospheric scientist at Princeton University. Natural sources of these so-called NOx compounds, such as lightning and emissions from soils, each contribute about 10 percent of that amount. But 22.4 teragrams of nitrogen–more than half the annual global total–results from the burning of fossil fuels, she notes. Other sources include agricultural burning.

Although NOx emissions from Europe and North America are leveling off, Asian output is poised to skyrocket due to industrialization. Asian emissions of nitrogen now total just over 10 teragrams per year, but models suggest that the continent’s contribution could rise to 31.9 teragrams by the year 2030, says Galanter. That would bring worldwide emissions to more than 77 teragrams, she adds.

NOx compounds substantially contribute to acid rain, which is increasing in eastern Asia. Almost a quarter of China’s current NOx emissions fall back on countries in the region as acid rain, says Tracey Holloway, who is also an atmospheric scientist at Princeton.

More than 27 percent of the NOx-caused acid rain that falls in Japan and 26 percent of that falling on Taiwan is due to Chinese emissions, Holloway notes. In North Korea and South Korea, China’s nearest downwind neighbors, 53 and 39 percent of the acid rain, respectively, traces back to China.

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