Tropical storm Leslie's high winds damaged 150-year-old trees in a downtown St. John's park, creating a windfall for researchers studying lead levels in the city.

Many trees — some of the oldest in the city — were knocked down in historic Bannerman Park. City crews have been cleaning up and removing the remains since Leslie blew through last Tuesday with winds up to 132 km/h.

A number of old trees were knocked over when tropical storm Leslie hit St. John's Sept. 18. (CBC)

However, what was a loss has turned into a gain for local researchers at a project that has launched several studies looking at lead levels in the area. In one such study, LeadNL has been looking at trees in the park to measure how lead levels have changed in the atmosphere.

Principal investigator and geography professor Trevor Bell says researchers were only taking small samples of trees because they didn't want to cut one down.

Then Leslie did the job for them.

"It was a really golden opportunity," said Bell. "We normally would only be punching little holes in these trees and taking out little cores."

The tiny core samples had allowed them to study lead signatures in the tree rings. With the storm, Bell saw an opportunity to work on a bigger scale.

“My post-[doctoral student], Maggie Danek and myself immediately realized when we saw people cutting up these large old trees down in Bannerman Park that we can't let these go to the dump or whatever without taking a slice of them," said Bell.

Tree rings can be used to measure historical levels of lead pollution. (CBC)

Now, the team has all the slices it will ever need.

By measuring lead levels on each ring, they can see how levels have fluctuated in the local atmosphere.

The rings even show when cars were introduced to the city.

"Some of those are about a 170-years old," said Bell, talking about the chunky samples of wood now lying about in his lab at Memorial University.

"So they have a 170-year record of lead pollution in St. John's. We’re interested in that in terms of children’s health, and public health in the city."

The LeadNL team hopes the technique can one day be used for environmental monitoring throughout the province.