A recent study led by the U.S. Geological Survey (USGS) in cooperation with the National Park Service found dozens of contaminants within the protected areas of Congaree National Park.
Researchers found 49 pharmaceuticals and 47 other contaminants, including pesticides and chemicals associated with wastewater, from 72 water and sediment samples collected from 16 river and lake sites around the park, according to USGS.
Officials say the levels of contaminants do not pose a health risk to park visitors who might drink or come in contact with them. However, they say additional research would be necessary to determine any adverse health impacts to aquatic organisms.
While a large variety of contaminants were found, USGS says many of them were detected in locations that could be explained by agriculture or wastewater treatment plants on rivers upstream and outside of the park.
However, some of the contaminants were found in lakes far away from the rivers flowing into the park, leading UGS to believe the source of these was likely people within the park.
Pharmaceuticals were found in water samples from across the park, with higher occurrences and concentrations near the Congaree and Wateree Rivers and in Horseshoe Lake, all of which are located downstream of municipal wastewater discharges from Columbia and Charlotte.
But Park Spokesman Scott Teodorski said some of those contaminants weren't completely unexpected.
"National parks are not islands and it's not uncommon. In fact it's very common for things to wash into the park via waterways," he said.
Metformin, a drug used to treat diabetes and one often found when wastewater discharges into rivers or streams, was the most frequently detected pharmaceutical. USGS says it was found in 61% of the samples, and was the only pharmaceutical observed in either water or sediments across all 16 sites.
Clint Shealy is the Assistant City Manager for Columbia Water and said they meet the standard requirements, but their treatment system isn't designed to remove such small doses.
"Most modern treatment systems aren't designed to remove those very very low levels that the study mentioned and found in the sediments and in the water column of the park. We can make water as pure as pure H2O, but is it economically and technically viable to do that? Could our ratepayers afford to pay for perfectly pure and clean water when the science doesn't dictate that those low trace amounts of compounds need to be removed?"
Some of the contaminants found, like antibiotics and antibacterials, have been shown in other studies to negatively affect microbes, which form the base of aquatic food webs, according to USGS. Other pharmaceuticals detected in the park have been shown to alter fish behavior and health, according to USGS hydrologist Paul Bradley.
The insect repellant DEET was one of the most commonly found contaminants in the park, being detected in 71 percent of all water samples, USGS says. It was found at least once in every surface water body within the park, including those deep in the park unaffected by wastewater discharges, says Bradley.
"Those are things definitely associated with human use, so those indicate to us that those are getting there from humans using and being in those areas," Teodorksi said.
In order to protect aquatic life and minimize human exposure to contaminants, all municipal wastewater is treated to add oxygen, disinfect water, and in some cases remove nutrients before it is released back into rivers and streams, according to USGS. However, USGS says wastewater treatment plants are not required to remove pesticides, pharmaceuticals, and other contaminants found at low levels in wastewater discharge.
According to USGS, the park’s marsh-like floodplains, which are characterized by low oxygen conditions, are not conducive to biodegradation. “Most of the detected contaminants are not going to disappear very quickly,” Bradley said.
To read the entire study, titled “Widespread Occurrence and Potential for Biodegradation of Bioactive Contaminants in Congaree National Park, USA,” click here.
To read a related article, “Sources of Commonly Used Chemicals in National Parks—USGS and National Park Service Working Together,” click here.