Gun enthusiasts of the early 20th century riddled the La Crosse River marsh with lead. And decades after the last trap shoot, traces of the toxic metal remain.
University of Wisconsin-La Crosse researchers have found high lead levels in the sediment where La Crosse Gun Club members frequently shot skeet.
Their research was first reported last summer in the Tribune.
New samples taken this summer will help determine if lead is spreading from the marsh bed and threatening surrounding wildlife.
Lead can be absorbed by nearby vegetation and travel up the food chain, causing neurological and developmental problems in fish.
“At really high levels, it can be lethal,” said Gretchen Gerrish, a UW-L assistant professor of biology.
But there’s no indication the lead is threatening residents and no evidence of it reaching the city’s drinking water.
A $60,000 grant from the Environmental Protection Agency and $5,000 from the university is allowing the scientists to continue their research to better understand the scope of the contamination.
If enough lead is found in the sediment, water or fish, the marsh could be declared impaired, said John Sullivan, Mississippi River water quality specialist for the Wisconsin Department of Natural Resources.
The designation needs approval by the DNR and EPA. Officials would have to remove or control lead contamination in the marsh if it’s added to Wisconsin’s list of impaired water bodies.
All of that is yet to be determined, Sullivan said.
“We don’t know if the levels in the marsh are creating a water problem,” he said. “We’re not saying any remediation has to be done at this point and time.”
The next step is more testing.
On Tuesday, Ryan Perroy hoisted a surveying pole as he maneuvered his way through the marsh.
The UW-L assistant professor of geography and earth science has studied the marsh’s lead levels with Colin Belby, an assistant professor in UW-L’s geography and earth science department, since last year.
Perroy donned waders to help chart an improved map of the marsh.
“It will also help us understand our how the lead is moving through the sediments,” he said.
Whether it’s a meter down in the muck or on the surface of the marsh bed, the lead is there, UW-L researchers say. Hundreds of sediment samples taken last year show varying degrees of lead contamination throughout the marsh.
Belby declined to provide the exact numbers, but initial tests last year revealed levels of up to 1,200 parts per million — the maximum amount allowed in bare soil, and three times the legal limit for soil in areas with playing children.
Still, it’s unclear whether lead is contaminating the surrounding habitat, Belby said. The researchers are collecting and analyzing wildlife samples as part of the study.
Samples include duckweed and submerged plant life, aquatic insects such as mayflies and dragon flies, and fish.
Results won’t be available for at least a month, possibly two. The scientists plan to continue testing marsh water through the winter.