Agriculture replaces fossil fuels as largest human source of sulfur in
the environment

Date:
August 10, 2020
Source:
University of Colorado at Boulder
Summary:
New research identifies fertilizer and pesticide applications to
croplands as the largest source 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.



FULL STORY ==========================================================================
A new paper out today in Nature Geoscience identifies fertilizer and
pesticide applications to croplands as the largest source 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.


==========================================================================
As a result, University of Colorado Boulder researchers recommend greatly expanded monitoring of sulfur and examining possible negative impacts
of this increase, including increasing levels of mercury in wetlands,
soil degradation and a higher risk for asthma for populations in
agricultural areas.

"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, assistant professor of environmental studies and fellow at the Institute of Arctic and Alpine
Research (INSTAAR) at the University of Colorado Boulder. "No one has
looked comprehensively at the environmental and human health consequences
of these [agricultural] additions." Sulfur is a naturally occurring
element and an important plant nutrient, helping with the uptake of
nitrogen. It's mined from underground through fossil fuel extraction
and for the creation of fertilizers and pesticides. 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.

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.

"This is a very different problem than the acid rain days," said Hinckley.

"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." Unknown risks


==========================================================================
A majority of the research that examines excess nutrient use in
agriculture has been in respect to nitrogen and phosphorus. Scientists
have known for a long time that these two chemicals can cause detrimental effects on the environment, including increased greenhouse gas emissions
and algae blooms in downstream waters.

Sulfur has long been applied to agricultural lands to improve the
production and health of crops, serving as both a fertilizer and
pesticide.

"We're moving it through our environment and ecosystems at a much faster
rate than it would otherwise," said Hinckley.

Some agricultural industries around the world have even been putting
more sulfur directly on their fields. So far, only isolated studies
have given scientists a glimpse into the effects of excess sulfur on
soil health and surrounding waters.

In the Florida Everglades, long-term research by the U.S. Geological
Survey linked large applications of sulfur to sugarcane to the
production of methyl mercury in the Everglades -- a potent neurotoxin
that accumulates as it moves up the food chain, affecting each predator
more than the prey it consumes. This threatens a variety of local wildlife
that eat fish, as well as humans.



==========================================================================
So 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." Co-authors of this paper
include John Crawford, postdoctoral scholar at INSTAAR and researcher in
the Sustainability Innovation Lab at Colorado (SILC) at the University
of Colorado Boulder; and Charles T. Driscoll and Habibollah Fakhraei
of the Department of Civil and Environmental Engineering at Syracuse University. Fakhraei has since taken a position at Southern Illinois University.


========================================================================== Story Source: Materials provided by
University_of_Colorado_at_Boulder. Original written by Kelsey
Simpkins. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Eve-Lyn S. Hinckley, John T. Crawford, Habibollah Fakhraei,
Charles T.

Driscoll. A shift in sulfur-cycle manipulation from atmospheric
emissions to agricultural additions. Nature Geoscience, 2020; DOI:
10.1038/s41561- 020-0620-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200810113214.htm

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