Agriculture is the largest human source of sulfur in the environment

Fertiliser and pesticide used in agriculture are the largest source of sulfur in the environment. Amounts are 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, says a new study.

Sulfur is a naturally occurring element and an important plant nutrient, helping with the uptake of nitrogen. But sulfur is also highly reactive, meaning it will quickly undergo chemical transformations once its stable form surfaces – affecting the health of ecosystems and reacting to form heavy metals that pose a danger to wildlife and people.

The possible negative risks of the rising sulfur levels include increasing levels of mercury in wetlands, soil degradation and a higher risk for asthma for populations in agricultural areas, explains a statement.

“Sulfur in agriculture is used in many different forms, and we haven’t studied broadly how those different forms react in the soil,” said Eve-Lyn Hinckley, lead author of the study at the University of Colorado Boulder. “No one has looked comprehensively at the environmental and human health consequences of these [agricultural] additions.”

Historically, coal-fired power plants were the largest source of reactive sulfur to the biosphere – leading to acid rain in the 1960s and 1970s, and the degradation of forest and aquatic ecosystems across the northeastern U.S. and Europe. Research on this issue prompted the Clean Air Act and its amendments, which regulated air pollution and drove sulfur levels from atmospheric sources down to pre-industrial levels.

The researchers examined trends in sulfur applications across multiple important crops in the U.S.: corn in the Midwest; sugarcane in Florida; and wine grapes in California. Their models of sulfur in surface waters showed that in areas that are recovering from the impacts of acid rain, the amount of sulfur is again increasing.

The researchers predict that increasing levels of sulfur will continue in many croplands around the world, including places like China and India that are still working to regulate fossil fuel emissions.

Hinckley emphasized that simply documenting the impacts of increased sulfur on the environment and human health isn’t enough – increased monitoring and research should include farmers, regulatory agencies and land managers to increase collaboration and collective action on the issue.

“We have an imperative to understand the impact that we’re having on the environment,” said Hinckley. “And then we need to work together towards solutions to mitigate those effects.”

Photo credit: Natural England/ Flickr Creative Commons

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