Pollutants from burning structures linger in waterways after wildfires

The remains of a house and car after the Carr Fire passed through the western edge of Reading, California, in 2018. Credit: Cecilio Ricardo/USDA Forest Service

With the increasing frequency of wildfires, as well as pollutants in water from burning watersheds, researchers say in a review paper that highlights the need for more research in the area.

“The effects of fires have not only been studied on forests and grasslands, but also on homes, vehicles and other man-made materials,” said Stephen Leduc of the U.S. Environmental Protection Agency’s Center for Public Health and Environmental Assessment. “There have been only a few studies of pollutants mobilized from these types of fires.”

Leduc is one of the authors of the new research paper, which was published today in Water Resources Research.

The paper looks at water trends after wildfires as documented across 184 scientific papers since 1980. Among the trends they identified are: current flow often for a few years after a wildfire, as do sediments and water temperature. Nutrients are often increased, along with toxic metals and some organic chemicals, sometimes reaching concentrations 10 to 100 times higher than pre-fire levels.

Some post-fire chemicals in water, such as arsenic, can exceed regulatory limits, even in treated drinking water. Among the reports cited in the review were elevated levels of the carcinogen benzene in tap water after homes and vehicles were burned in Paradise Township, California. The researchers also found higher concentrations of metals in the ash from these fires, which may affect runoff.

The review found that little research has been done on the types of pollutants that come from urban wildfires. This leaves water managers and planners at a disadvantage when recovering from a fire.

“We point to this as a major gap in the scientific understanding of the effects of fires,” Leduc said.

said Dennis Halema, a hydrologist at the Desert Research Institute in Las Vegas, who was not involved in the study. “There is a lot of interest, but at the end of the day, successful water quality monitoring efforts come from projects that have been approved in a timely manner.”

The study also looked at the effects of Forest fires on the surrounding ecosystem.

“Fires are increasing in places like the western United States due in part to Climate changeand there is the potential for fire-scorched areas to become long-term stresses on water quality if previous plants were slow to recover or failed altogether,” Leduc said.[But] Burned areas can be targeted recovery efforts, such as anti-erosion or agriculture. One restoration effort, referenced in the paper, was by Pueblo Santa Clara after the Las Conchas fire in 2011.

The authors write that they hope their review will help water quality managers and communities plan and recover from the effects of wildfires on their waters.


The link between forest fires and drinking water pollution


more information:
MJ Paul et al, Wildfire leads to changes in water intake: a review with considerations for water quality management, Water Resources Research (2022). doi: 10.1029/2021WR030699

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