The mercury concentration in the tree ring may allow the tree to become a “witness” to illegal gold mining activities in the Amazon

For hundreds of years, Amazon has been misused for money. Today, precious metals are required in the same way, but the remaining small gold particles are much more difficult to find. Mining often occurs in artisans and small-scale mining operations that release mercury (HG) into the atmosphere, pollute the environment, and harm human health.

An international team of researchers are currently examining tree rings of species endemic to the Peruvian Amazon to determine whether the tree can be used to indicate where and when atmospheric mercury was released.

“We demonstrate that Ficus Incipida Tree Core can be used as a biomonitor to characterize the spatial and potential footprint of mercury emissions from gold mining in neotropical artisans,” said Dr. Jacqueline Gerson, assistant professor of biological and environmental engineering at Cornell University, and said Dr. Jacqueline Gerson, the first author of Frantel Science’s Research Science Research.

“By archiving records of mercury concentrations within tree ballwoods, trees can provide a wide range of biomonitoring and rather inexpensive networks.”

Mercury is in the air

For gold extraction, miners add mercury to soil containing small gold particles. Mercury binds to the gold particles that create amalgam. Amalgam has a much lower melting point than gold, so to extract it, the amalgam is burned. This process releases gaseous mercury into the atmosphere.

Three neotropical tree species with previously recorded annual tree rings were examined to test their potential as biomonitors: wild figs (Ficus incipida), common neotropics trees, Brazilian nuts (Bertholletia excelsa), and tornilo (Cedrelinga catenaformis).

Neotropical science year with an unbiased annual climate, not all trees form rings, and the presence of tested species exhibited them. Tree core samples were collected at two sites at three sites within 5 kilometres of mining activities, up to mining towns where amalgams are frequently burned. One of the mining sites was next to a protected forest.

“There are many variables driving individual tree Hg concentrations, making it difficult to determine a particular driver,” explained Gerson. “All of the trees in the study were of the same species and were exposed to the same Hg concentration in the atmosphere from the same location. So we sample multiple trees and then use the average.”

Mercury concentrations in ballwood were highest in two sampling sites close to mining activities, and lower at mining impact sites adjacent to protected forests and mining towns.

“Higher atmospheric HG concentrations are generally associated with nearby mining sites,” Gerson explained. “In Peru’s Amazon, where mining is the main source of HG, it is easy to draw the association between higher HG concentrations and proximity to mining sites.”

Especially since 2000, Hg concentrations near towns have risen where Mercury’s gold amalgam was burned. “This appears to be due to the expansion of gold mining activities around this time,” Gerson said.

Spy Network

This study proved that trees can be used as biomonitoring networks for gas emissions, but this study has some limitations. Most notably, the exact distance to the mining town was unknown due to the illegal nature of these operations. This may have affected the concentration of HG found in trunk wood.

“Ficus Insipida can be used as a cheap and powerful tool to investigate the large spatial trends in HG emissions in neotropical science,” concluded Gerson.

“The use of ballwood enables regional surveillance efforts.” This is particularly important in relation to the United Nations Mercury Convention, an international treaty aimed at reducing the emissions of mercury and mercury compounds and mitigating health and environmental risks.