Piercing the haze

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Science  14 Sep 2018:
Vol. 361, Issue 6407, pp. 1060-1063
DOI: 10.1126/science.361.6407.1060

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Ammonia—the colorless, sharp-smelling, and eye-watering gas—is getting a closer look from researchers because of its role in producing deadly air pollution. In developed nations, most ammonia comes from farms that use chemical fertilizers or produce heaps of animal manure. In the atmosphere, it combines with other pollutants to form the tiny, dangerous particles that make up smog. Despite its abundance, however, ammonia is poorly understood. In part, that's because it is notoriously difficult to track. Ammonia molecules are "sticky" and eagerly combine with other compounds, making it difficult for monitoring instruments to capture them. But new ground-, air-, and space-based sensors are helping bring the sources, movements, and fate of ammonia into clearer focus. The improved monitoring comes as some nations, including the United Kingdom, are moving to slash ammonia emissions. But others, including the United States, have not made limiting ammonia a priority, opting instead to target other key smog ingredients. But the focus on ammonia is likely to intensify. Global emissions of the gas have doubled over the past 70 years and are forecast to continue to rise, in large part because of growing demand for chemical fertilizers. That has put pressure on researchers and regulators to better understand the implications.

  • * Jason Plautz is a journalist in Denver.