In one week, as fall nears its end, rake-wielding street sweepers will begin their work scouring the city’s roads.

Parking will be restricted and cars will be towed while the city sweeps away autumn and prepares for another Minnesota winter with ice-ridden conditions and salted roads.

Though it’s a matter of days before sweepers clear out the yearly debris of leafy trees, the city and the University of Minnesota have been preparing for snow since last spring.

Each April, city crews start purchasing batches of road salt in preparation for the coming winter. This year, however, the transaction had a slightly higher price.

“Typically, you buy it early in the season,” said Mike Kennedy, director of Minneapolis’ transportation maintenance and repair department.

The University has ordered 1,200 tons of road salt — or sodium chloride — to sprinkle over the next few months, said the University’s Landcare manager, Lester Potts, who calls himself the “chief snow shoveler.”

The city, meanwhile, has purchased 19,000 tons of the ice melter for the upcoming season, Kennedy said.

Through a purchasing venture coordinated by the Minnesota Department of Transportation, Potts said the city and the University buy road salt in bulk from large salt companies like Cargill Salt, North American Salt Company and Morton Salt.

MnDOT, “big salt” and other parties strike a deal through the “80-120 process,” Potts said.

Because of Minnesota’s wildly variable winter weather, the University — and other entities — are guaranteed to receive up to 120 percent of the volume of their purchase in cases of severe snow, and they must accept a minimum of 80 percent.

“We’ll basically react to the weather like we did last winter,” Potts said. “Last winter was tough. … It’d come in and snow, then you’d get those frigid temperatures afterwards. And de-icing chemicals — it was too cold for them to work.”

The price of road salt fluctuates, like that of any other commodity, and depends on factors like transportation cost, he said.

In that regard, Minneapolis’ proximity to the Mississippi River is an advantage, Potts said.

While some states have reported a significant jump in road salt prices, the cost has changed little in local markets, he said, where its delivery is less expensive because of barge shipping.

With its cost remaining relatively steady, Kennedy said he does not expect any big surprises for Minnesota road salt buyers this year.

“We saw between a 5 and 10 percent jump in price — not anything out the ordinary,” he said.

While Kennedy said he is unfazed by changes in road salt prices, he also said there is room to better understand the environmental effects of de-icers.

Ecology, evolution and behavior associate professor Emilie Snell-Rood recently conducted a study on the effect of sodium chloride on monarch butterflies, which particularly focused on the compound’s positive impacts.

“Sodium is a micro-nutrient in the diet of most animals,” she said. “[So] sodium availability has driven the evolution of a lot of really weird foraging behaviors.”

Snell-Rood said a dietary bump in road salt could change the physiology of monarchs and other creatures along asphalt’s fringe.

“Our results suggest that some amount of road salt might actually be increasing brain or muscle investment in things growing up on the side of the road,” she said, adding that the butterflies began suffering at a sodium chloride concentration of 6,000 parts per million.

She said even after snow melts, de-icers are still acting on the environment in unexpected ways.

“Things we do in the winter have effects throughout the entire summer,” Snell-Rood said.