A study completed in the spring of 2018 in Illinois and published January 23, 2019, in the journal Groundwater, is the first time that microplastics have been detected in groundwater aquifers.
The study was conducted in collaboration with scientists at the Illinois State Geological Survey, Illinois State Water Survey, Loyola University Chicago, and ISTC on two aquifer systems in Illinois. Not only were microplastics identified, but researchers found a variety of medicines and household contaminants.
“Plastic in the environment breaks down into microscopic particles that can end up in the guts and gills of marine life, exposing the animals to chemicals in the plastic,” said John Scott, a researcher at the Illinois Sustainable Technology Center and study co-author.
“As the plastics break down, they act like sponges that soak up contaminants and microbes and can ultimately work their way into our food supply.”
Groundwater in karst aquifers
About 25 percent of the Earth’s water reservoirs are karst aquifers. Karst is formed when bedrock undergoes a breakdown as acidic water gets into cracks on the surface.
As the bedrock – typically limestone – continues to degrade, the cracks will get bigger. Eventually, these fractures will become wider, and before long, a drainage system of some sort may start to form underneath. As groundwater flows down through the cracks and crevices in the limestone, everything from sewage to runoff from roads and agricultural fields is carried down to the aquifer below,
A total of 17 groundwater samples from wells and springs – 11 from a highly fractured limestone aquifer near the St. Louis metropolitan area and six from an aquifer containing much smaller fractures in rural northwestern Illinois were collected.
Microplastic contamination – What does it mean?
All but one sample contained microplastics – with the highest concentration being found in a sample from a spring in the St. Louis area, the study reports. That sample had a maximum concentration of 15.2 particles per liter. But as Scott says, trying to explain what this concentration means is a challenge with no published risk assessments or regulations.
Samuel V. Panno, an Illinois State Geological Survey researcher and lead author of the study points out that the concentrations the team recorded were comparable to those of surface water concentrations found in the rivers and streams in the Chicago area.
“The research on this topic is at a very early stage, so I am not convinced we have a frame of reference to state expectations or bounds on what is considered low or high levels,” said Tim Hoellein, a biology professor at Loyola University Chicago and study co-author. “Our questions are still basic – how much is there and where is it coming from?”
Karst water supplies may be unsafe
Karst formations are cavernous and therefore have high rates of permeability, resulting in a reduced opportunity for contaminants to be filtered. Groundwater in karst areas is just as easily polluted as surface streams. This presents a problem – but also leads to an opportunity for further studies.
“Imagine how many thousands of polyester fibers find their way into a septic system from just doing a load of laundry,” Scott said. “Then consider the potential for those fluids to leak into the groundwater supply, especially in these types of aquifers where surface water interacts so readily with groundwater.”
