Key Points:
- A chemical used in many herbicides to prevent “drifting” has been found to vaporize and drift itself.
- In all herbicide mixtures tested, the chemical amines were found to volatize and spread.
- Herbicides are responsible for the release of about 4 gigagrams of amines annually in the U.S.
The herbicide dicamba is known to drift when applies, causing unintentional damage to neighboring plants. To rectify this, other chemicals, typically amines, are mixed with dicamba to “lock” it in place and prevent it from volatilizing. However, new research says the solution may actually be the problem.
In a new study published in Environmental Science and Technology, researchers from Washington University in St. Louis have demonstrated for the first time that amines themselves volatilize, often more than dicamba itself.
For the study, first author Stephen Sharkey measured the change in the amount of amines present over time when mixed with different herbicides. In all mixtures, the amines volatilized from the herbicide-amine mixtures. Sharkey and colleagues also confirmed that the amines were entering the gas phase from herbicide-amine mixtures by capturing amines from the air to measure.
The team also quantified the amount of amines that were entering the atmosphere, which required a bit of detective work. Sharkey used two separate data sets—estimated rates of herbicide applications and survey data from U.S. farmers that showed which specific amines were used with different herbicides. The results indicate herbicide use—such as dicamba and other herbicides, including 2,4-D and the widely used glyphosate—are responsible for the release of about 4 gigagrams (4,000 metric tons) of amines annually in the U.S.
The findings came somewhat as a surprise to, the researchers say, not only because the chemistry doesn’t immediately suggest that amines volatilize in this way, but also for a more practical reason.
“There has been extensive work looking at the different ways in which amines enter the atmosphere. There has been a lot of effort put into understanding where amines come from, but research into its use with herbicides just wasn’t considered before,” said Kimberly Parker, an assistant professor of energy, environmental and chemical engineering at Washington University in St. Louis.
Information provided by Washington University in St. Louis.