Agriculture, not fossil fuels, now top source of sulfur, study finds

Fossil fuels are no longer the top source of sulfur released into the environment by humans, a new study found. 

Agriculture has now gained that dubious distinction, according to a press release from the National Science Foundation.

The study, published in Nature Geoscience, “identifies fertilizer and pesticide applications to croplands as the largest sources of sulfur in the environment -- up to 10 times higher than the peak sulfur load seen in the second half of the 20th century, during the days of acid rain,” the National Science Foundation said in the press release. 

Coal-fired power plants historically were the largest source of reactive sulfur. This led to acid rain in the 1960s. Forests and aquatic ecosystems also suffered from degradation in the northeastern U.S. and Europe. 

"This is a very different problem than in the acid rain days," Eve-Lyn Hinckley, the study’s lead author, said in the press release. "We've gone from widespread atmospheric deposition over remote forests to targeted additions of reactive sulfur to regional croplands. These amounts are much higher than what we saw at the peak of acid rain."

Researchers at the University of Colorado Boulder are recommending expanded monitoring of sulfur and its impacts, including damage to wetlands and soil and higher risks of asthma, the foundation said.