Pesticides and fertilizers have overtaken fossil fuels as the largest human source of sulfur in the environment, a study shows
- Sulfur is one of the key components of acid rain, which can damage ecosystems
- Regulation of fossil fuel emissions has helped reduce this type of damage
- US experts have found that sulfur used in agriculture is now having similar effects
- In Florida, for example, the release of sulfur contributes to the formation of toxic methyl mercury
- This compound can accumulate in the food chain and reach unsafe levels in fish
Agricultural pesticides and fertilizers have overtaken fossil fuels as the largest human source of sulfur in the environment, a study found.
Reactive sulfur is a key component of acid rain – one that used to come primarily from the use of coal-fired power plants.
The acid rain threat was first exposed in the 1970s when experts discovered that it was responsible for damage to ecosystems in the northeastern United States and Europe.
They found that this rain came from fossil fuel emissions from industrial centers up to hundreds of kilometers from affected forests and waterways.
In the United States, the results ultimately led to the introduction of the Clean Air Act in 1990, which and similar pieces of legislation helped reduce sulfur levels in the atmosphere.
However, experts from the University of Colorado have found that the increasing use of sulfur in agriculture is having an impact similar to that of the acid rain of the past.
Agricultural pesticides and fertilizers have overtaken fossil fuels as the largest human source of sulfur in the environment, a study found
SULFUR: THE FACTS
Sulfur is a naturally occurring element.
It is a plant nutrient and can be used to make fertilizers – along with pesticides.
When released into the atmosphere, it can produce sulfuric acid, which contributes to the formation of acid rain – harmful plant life and acidic aquatic ecosystems.
Researchers have found that sulfur releases from agriculture contribute to methylmercury – a neurotoxin that can accumulate throughout the food chain.
"It seemed like the sulfur story was over," said paper writer and environmental scientist Eve-Lyn Hinckley of the University of Colorado at Boulder.
"However, our analysis shows that sulfur applications on farmland in the US and elsewhere are often ten times higher than the maximum sulfur exposure in acid rain."
"Nobody has fully studied the effects of these supplements on the environment and human health."
In their study, Professor Hinckley and colleagues examined the use of sulfur in U.S. agricultural practices in several key crops – including corn in the Midwest, sugar cane in Florida, and grapes in California.
The team found that areas such as New England are showing signs of recovery from the historical deposition of sulfur in the atmosphere, but that sulfate releases from agricultural areas into the environment are increasing.
"Although sulfur is applied to agricultural land to improve crop production and health, it can adversely affect agricultural soils and downstream waters," added Charles Driscoll, New York City's Syracuse University paper writer.
Professor Driscoll added that these effects are "similar to those found in remote forest landscapes under acid rain".
One example that the researchers highlighted is the Everglades Agricultural Area in Florida, where sulfur draining into bodies of water encourages the formation of methylmercury – a powerful neurotoxin that builds up in living organisms.
If methylmercury enters the food chain, it can build up in high concentrations and there is a risk of wildlife and humans being exposed to the toxic metal if such fish are ingested.
In their study, Professor Hinckley and colleagues examined the use of sulfur in US agricultural practices in several major crops. The picture shows the sources and effects of sulfur in agricultural and other areas
Previous research has mainly focused on understanding and managing the use of nitrogen and phosphorus fertilizers that cause potentially harmful algal blooms, resulting in the removal of oxygen from water bodies and the killing of fish.
The team called for more research to study the effects of high sulfur consumption in modern farming practices – both to study the environmental and health effects, and to work with farmers to optimize sulfur consumption.
"Agricultural sulfur doesn't go away," said Professor Hinckley.
"Nevertheless, there is an opportunity to bring science and practice together to create viable solutions that protect the long-term goals for the environment, the economy and human health."
The full results of the study were published in the journal Nature Geoscience.