The effects of modern pesticides on a Roman bowl from the late Iron Age

Harsh pesticides have corroded an ancient Roman bowl, destroying a piece of history.

Researchers from the University of Oxford School of Archeology have examined the effects of pesticides on the ancient artifact. The analysis was published in Springer Nature.

Discovery and preservation

In November 2016, a person using a metal detector came across this copper bowl while in a grassy area at a farm in Kent, United Kingdom. After being discovered, the bowl was protected in its original place so that a team would be able to study it a month later. The research team was from Canterbury Archaeological Trust and Dover Archaeological Group. They did not find any cremation or burial around the bowl to associate with its discovery.

The researchers removed the bowl from the original place it was found and took it to the Conservation Science Investigations (CSI): Sittingbourne laboratory for preservation and to eventually display at Sandwich Guildhall Museum in Kent.

Time period

The bowl was made of copper and dated back to 43 to 410 AD.

It was found “mid-way between the important Roman settlements at Richborough and Canterbury, close to two large Roman villas and Roman watermills.” The bowl was buried at a depth of 15.7 inches (40 cm) in clay soil that also contained chalk inclusions. The researchers discovered that the bowl was placed specifically in a ditch that was previously unknown to archeology.

Pieces of pottery and coins found at the site allowed them to date the time period to around the time of the Late Iron Age.

Condition of the bowl

Although the bowl was in particularly good condition, both the internal and external surface showed signs of deterioration containing green and brown- colored corrosion. The researchers took samples from these discolorations.

Within the corrosion, they found basic copper chlorides atacamite and paratacamite. In the brown corrosion, the team found diethyltoluamide (DEET), a chemical component and active ingredient used in insect-repellent.

Inside the green portion of the corrosion, the research team found chlorobenzenes, which are “common soil contaminants in rural areas from the use of pesticides.” They noted that many of these pesticides were banned more than 50 years ago.

Minerals found in the corrosion

During the process of conservation, archeologists took samples from where the bowl showed corrosion, on the brown and green spots from inside and outside the artifact. It was collected for analysis.

The team found minerals within the corrosion in the bowl. The minerals in the green corrosion were atacamite and quartz, and inside the brown corrosion, they discovered only the mineral quartz.

Pollutants can threaten preservation

Overall, this study shows the changes in the environment by human interaction over many years. It also proves that toxins added to the environment, such as chlorobenzenes, can cause corrosion at a quicker rate, often ruining historical material that can be ruined through environmental contamination and pollutants.

“Chlorobenzenes are synthetic compounds released in the environment through agricultural and industrial activities. Our study provides the first evidence that chlorobenzenes are associated with accelerated corrosion mechanisms linked to archaeological material and demonstrates that they are a threat to the preservation of archaeological metals in the ground,” the study said.

This study shows how pesticides affect our environment, but also the ancient artifacts, destroying a piece of history.