As we strive for a more environmentally friendly world, everything we eat, drink and buy can be viewed from a sustainability perspective. And that includes simple pleasures like wine.
In California, wine means big business, and it’s common for grape growers to coat their grapes with a sulfur-based fungicide to prevent them from becoming infected with the mold that can devastate crops.
But what happens when a downpour comes and washes the sulfur off the grapes?
It turns out that scientists can distinguish agricultural sulfur atmospheric sulfur by the unique chemical fingerprint of agricultural sulfur that can be identified at the atomic level, according to a press release from the University of Colorado at Boulder (CU Boulder).
in a new study“Sulfur Isotopes Reveal Agricultural Changes in the Modern Sulfur Cycle,” recently published in the journal Environmental Research Letters, CU Boulder researchers show that this distinct agricultural sulfur signature can be traced from when it is applied to grapes in vineyards to where it ends up in the environment. Their findings could lead to an improved ability to protect downstream waters and wetlands from its effects, such as the possible stirring up of toxic heavy metals like mercury.
“We found that you could see the effect of vineyard farming in the Napa River when vineyards are only 11% of the land cover of the entire watershed. That’s a very stable fingerprint for us. to plot and then figure out what ultimately happens,” said assistant professor of environmental studies at CU Boulder Eve-Lyn Hinckley, who was the lead author on the publication, according to the press release.
The amount of sulfur released to the downstream environment depends on the year and the weather.
“The amount of sulfur in runoff varies from year to year, depending on the amount of precipitation. In dry years, it remains locally in the soil, in the vines where it is sprayed. We have no evidence that it is harmful to consumers,” Hinckley told EcoWatch in an email.
In 2020, agricultural sulfur, which is used as a fertilizer and is the most common pesticide used by California farmers — especially grape growers — has become the largest anthropogenic source of the element, surpassing even fossil fuels, according to the Press release.
Before the Clean Air Act of 1970, which reduced the prevalence of atmospheric sulfur to pre-industrial levels, so-called “acid rain” was a frequently talked about environmental problem. But Hinckley said grape growers now use far more sulfur than was produced by the atmosphere when acid rain was prevalent in Europe and North America.
In their research, the scientists collected soil and surface water samples from across California’s Napa Valley. By analyzing the composition of sulfur, they were able to find the distinct chemical fingerprint of agricultural sulfur, which is maintained even through the chemical changes it undergoes when interacting with other elements and microorganisms in the environment. .
“It’s very different from the signature we see in atmospheric deposition or geological weathering, which are the other background sources of sulfur,” Hinckley said in the press release.
Agricultural sulfur can be of particular concern when it enters waterways and wetlands.
“Sulphur in runoff can interact with other elements in ecosystems adjacent to or downstream from vineyards. In particular, this is a concern for wetlands and river sediments. reducing conditions may persist and stimulate interactions between sulfur and heavy metals, such as mercury, which are toxic to wildlife and humans,” Hinckley told EcoWatch. ecosystems and human health, it will be useful to distinguish it chemically from other sources, such as marine, geological and atmospheric sulphur.”
When sulfur moves through the environment, it can have toxic results.
“In soil, oxidation of reduced forms of sulfur can lower pH and potentially cause acidification of soils and sediments over time. In wetlands and waterways, sulfate reduction (a process chemical) can stimulate the production of methylmercury, a neurotoxin dangerous to wildlife and humans. We know these effects from long-term studies of the damage caused by acid rain in forest ecosystems. We now need to investigate the fate , transport and consequences of agricultural sulfur use,” Hinckley told EcoWatch.
According to the press release, sulfur has been used in agriculture since Egyptian times, and sulfur dioxide added to wine during the winemaking process – or omitted, making the wine eligible for the “no sulfur added” label – n is not the same as sulfur previously applied to grapes.
“The sulfur that is the subject of our study is added to the field and it is not desirable for the residue to fall on the grapes at harvest. Growers stop applying sulfur before harvest to avoid carryover,” Hinckley told EcoWatch.
Finding ways to refine the use of sulfur in viticulture is important for the wine industry to move towards more environmentally friendly practices.
“There is a lot of interest in sustainable agriculture in the California wine industry. Grape growers want to protect the environment, which is conducive to growing grapes, for years to come,” Hinckley told EcoWatch. “As a result, we have found that many are receptive to discussing ways to optimize the use of sulfur as a pesticide – to use enough to prevent powdery mildew, but not so much that it doesn’t have negative effects on the environment. We now need to have trials that evaluate the optimization of sulfur spraying in wine grapes.”
In order to achieve a more suitable application of sulfur to wine grapes, the technology will have to be more precise.
“Probably the best approach to optimizing sulfur applications is to invest in the development and adoption of technologies that achieve high-precision sulfur spraying – targeted spraying that is sensitive to the threat of powdery mildew, but not diffused to from tractors, as is the case now,” Hinckley said.
Hinckley hopes knowing the amount of agricultural sulfur in the environment will help farmers adjust their application of the fungicide.
“This work could help inform the development of technologies that help farmers choose when and how much to apply, rather than just applying the same amount preemptively all the time,” Hinckley said in the press release.
Hinckley also said consumers can take a more active role in learning about the origin and growing methods of the grapes that were used to make their wine.
“For wine consumers, it’s great to know how these grapes were grown and where they come from. And there are growers out there who are really striving to be as light on the earth as possible, and to work with and adapt to the changes they face with climate change,” Hinckley said in the release. hurry. “The consumer has a role to play in helping to make these decisions.”
Hinckley’s goal is to help farmers work sustainably and in harmony with the environment.
“My goal as a scientist is to always work in partnership with landowners and with farmers. Hopefully we can get to a place where they can continue in a very sustainable way that also protects the surrounding environment,” Hinckley said.
Hinckley thinks that in the future, the application of sulfur to wine grapes will be done with more care and include more monitoring.
“I think the future of sulfur in winemaking will involve regular monitoring for disease and powdery mildew risk, then adaptive spray programs with tractors that can target applications where the vines need it most” , Hinckley told EcoWatch.