Results are in for Healing City Soils project

October 4, 2016
RRU Communications
Soil testing for Healing City Soils
“The message is, on average, there’s no risk to people’s health.” School of Environment and Sustainability Prof. Matt Dodd

A Royal Roads study of backyard and community gardens in Victoria and Esquimalt has found overall no risk to human health from the city’s soil.

But researchers with the Healing City Soils project say individual properties with higher concentrations of heavy metals will have to be tested further.

Bachelor of Science in Environmental Science students dug into 68 residential and community gardens in Fernwood, Esquimalt, Vic West, James Bay and Fairfield to determine the level of heavy metals in the earth as part of the joint initiative.

The partnership brought Royal Roads together with the Greater Victoria Compost Education Centre and DIY Fungi, with funding from the City of Victoria and the Victoria Foundation, to raise awareness about potential soil contamination in backyard gardens.

Students from the Ground Zero Environmental Services team, Shawna Cheyne, James Heron and Michael Rae, took 137 soil samples from volunteer sites around Victoria and Esquimalt, testing for eight different metals known to cause human health effects.

After collecting the samples, the students dried and sieved the soil, removing debris such as rocks, before using a screening device, an X-ray fluorescents portable analyser, to look for heavy metals. From there, Cheyne said 30 samples with high metal concentration readings were sent to an accredited laboratory for comparison.

Cheyne said the group found in some soil samples levels of arsenic, chromium, zinc, copper and lead were above the Canadian Council of Ministers of Environment (CCME) soil quality guidelines for residential land use. Zinc and lead were the two metals students found most often above the CCME guideline levels and many of the sites exceeded levels only slightly. She said historical circumstances, such as the existence of an old garage on a now residential site, or a house that underwent renovations, could possibly explain spikes in the data.

After establishing the presence of certain metals in the soil, the team analysed bioavailability — the degree to which various metals are available for absorption and use in the body if ingested — the major factor in predicting harmful effects on human and animal health.

“On average, we found there was low potential health risk based on the metal concentrations found,” Cheyne said. “The project was looking at a general overview. What future research will have to do is look at the sites that had the higher metal concentrations and analyse them further.”

School of Environment and Sustainability Prof. Matt Dodd, who directed the students, said overall Victoria’s soils are healthy and safe for backyard and community gardeners. But some homes would have to undergo further tests.

“The message is, on average, there’s no risk to people’s health,” he said. “There are areas that have elevated concentrations but we have to do some more work to figure out if there are any associated health risks.”

Dodd added a common way lead enters the soil of people’s homes is through leaded paint.

Soil ecologist and Greater Victoria Compost Education Centre executive director Marika Smith said the students’ work was significant given that Victoria City Council is considering allowing residents to sell backyard fruit and veggies at roadside stands to improve local food security.

“Everyone wants to grow food in the city, but they forget about the life-giving stuff that is the soil,” Smith said. “A lot of people don’t know what’s on their property, and if you’re going to distribute produce to the public, you definitely want to know what shape your soil is in.”

The Compost Education Centre and DIY Fungi will be working with the students to create memos for each volunteer household on which specific metals, if any, were detected in their soil. Smith says they hope to expand the project to Oak Bay and Saanich next year.

DIY Fungi project coordinator Danielle Stevenson said gardeners with higher levels of metals in their soil would be given information on how to grow food safely, or how to remediate their soil naturally.

The Compost Education Centre will continue working with the students to create an online map to depict soil health across the city. The map, along with a public forum and workshops, will be launched later this fall, with fact sheets to answer residents’ questions.

“We want people to feel empowered and have the knowledge and skills to grow healthy food where they live,” Stevenson said.

For Cheyne, and the rest of the Ground Zero team, the study was a hands-on example of the kind of field and lab work scientists do — with some extra pressures thrown in.

“We had to communicate with homeowners and sponsors, and work with other people. It was challenging but also fun,” Cheyne said. “It was a good overall project to prepare you for being a scientist when you’re out in the real world.”