Salt Spring’s recent pattern of summer drought and above-average precipitation in the fall and winter may have brought about a peculiarly smelly situation on the island’s north end.
The “Fernwood Reek” can be described as a strong sulphuric swamp gas that’s been noticeable on a short section of North End Road — even inside moving vehicles — over the past few months. To the east, the area is close to some of the famous saline springs that give the island its name. There is a documented peat soil deposit to the west.
Harold Harkema’s family has lived since around 1959 on a large farm where some of the springs are located, on land now owned by Rob and Sally Dailly. A strange phenomenon of moving fields has long been witnessed on part of the property.
“We’ve always called it the floating swamp,” said Harold’s wife Sandy Harkema. “Basically it’s like a bog, and it’s very interesting.”
Harkema added that many visitors have been asking about the smell this year. It’s not something the family has ever experienced before to such a degree.
“It is bad now and we don’t know why,” she said. “We would like to know too.”
According to water-research.net, sulphur-reducing bacteria, which use sulphur as an energy source, are the primary producers of large quantities of hydrogen sulphide — the gas most commonly associated with the rotten egg smell. The bacteria live in oxygen-deficient environments and chemically change natural sulphates in water to hydrogen sulphide (H2S). They flourish in hot water, which is why hot springs often carry a reek.
“Hydrogen sulphide gas also occurs naturally in some groundwater. It is formed from decomposing underground deposits of organic matter such as decaying plant material,” the website explains.
H2S can enter surface water through springs, from where it escapes into the atmosphere. It is often present in wells drilled in shale or sandstone — of which much of Salt Spring’s north end is composed — and near coal or peat deposits and oil fields.
While the smell might therefore originate in the island’s springs, it could actually be the peat bog that is the source. An article by Lily Strelich in Eos: Earth and Space Science News explains how drought changes that way peat bogs cycle mercury and sulphur.
“Drought conditions can effectively transform peat bogs from sulphate sinks to sources by oxidizing the peat deposits and mobilizing the sulphate that they had previously sequestered,” she writes.
The article further explains that peat is normally saturated and without oxygen, but drought conditions can dry and oxidize it, releasing sulphate when the peat is rewetted.