Leaking Landfills

Increasingly frequent extreme weather events flush contaminants — including landfill leachate — into coastal waterways.

When the garbage truck whisks household waste away from your curb, your trash ends up in a municipal landfill. The EPA regulates the location of landfill sites to protect both humans and the environment from contamination. 

Additionally, sanitation engineers place the waste in a clay and plastic-lined pit and compact it with layers of dirt to contain any potential leaks. However, no system is perfect.

Landfill liners still sometimes leak, releasing “leachate.” As rainwater falls and percolates through compacted waste and comes into contact with the buried garbage, the water leaches, or draws out different nutrients from the trash. If the landfill liner doesn’t contain the leachate, liquid waste can make its way into surrounding rivers and groundwater, with potentially serious environmental impacts.

El Moore’s new study is especially timely as more frequent severe weather flushes contaminants into waterways. Moore, a Mountains to Sea Fellow with North Carolina Sea Grant and the NC Water Resources Research Institute, is using fluorescence to identify how much landfill leachate is present in tributary streams in the Neuse and Tar-Pamlico watersheds.

Nitrogen in Nutrient-Sensitive Waters 

One of the main chemicals leachate contains is nitrogen, which on its own is not harmful. “Everything needs nitrogen to live,” says Moore. “If it was just a tiny bit getting in, it might not be a water quality concern.” 

However, nitrogen becomes problematic when too much is present. 

Drinking water with a high concentration of nitrogen disrupts the transportation of oxygen through the bloodstream. According to the US Geological Survey, infants under 4 months are at the highest risk because they lack the enzyme needed to reverse the decrease in oxygen, resulting in what is commonly known as “blue baby syndrome.” While most adults are not at a high risk for adverse effects, pregnancy and health conditions that increase the body’s demand for oxygen increase those risks.

Excess nitrogen can also lead to excessive growth of algae and aquatic plants. These “blooms” deplete the supply of oxygen for inhabitants and prevent sunlight and heat from reaching deeper waters. In some cases, the blooms can even be dangerous (as “harmful algal blooms” or HABs) for people and pets who come in contact with the water. 

The Neuse and Tar-Pamlico Rivers both are “nutrient sensitive waterways,” according to the North Carolina Department of Environmental Quality. Given these rivers’ high amounts of dissolved nutrients, including nitrogen, leachate entering the system could worsen existing nutrient issues.

Fluorescence as a Fingerprint 

In addition to leachate, there are many sources of excess nutrients in both watersheds, Moore says, including the surrounding wetlands, street runoff, and agricultural runoff, to name a few. So, how do the researchers know that it is leachate specifically affecting the water? 

Ultraviolet fluorescence.

When ultraviolet light hits chemicals, they absorb some of the energy from the light waves and begin to glow. According to Moore, different chemicals absorb different amounts of energy, and, therefore, give off different amounts of light.

“Our model uses this fluorescence as a sort of fingerprint,” says Moore. Because Moore already knows the concentration of chemicals in each type of contaminant, the model matches the amount of light given off to the source and identifies which contaminants are present in the water sample.

Moore is sampling a handful of smaller rivers and culverts (tunnels or pipes that allow water to flow underneath roads), all of which are tributaries in the Neuse or Tar-Pamlico watershed. 

Preliminary results from the study show that 20% of the water samples Moore took have a make-up of at least 5% leachate. Samples from Jerry’s Creek, near the Edgecombe County landfill, showed the most consistent and concerning results.

“Across all sites, almost every sample appeared to have at least 1% leachate in it, according to our model,” says Moore. “However, it is hard to make a definitive statement about what it means for water quality when the concentration of leachate measures in the 1-5% range.”

Moore says the next steps are to finish sampling and to continue to investigate the impact of leachate on larger waterways.

“The main goal for everyone who works in and around these watersheds is to keep the water safe,” says Moore. “We care about the phytoplankton that live there. We care about the people who recreate around there. The core of the research is to determine if this landfill leachate is a problem.”

More

Managing Coastal Nitrogen Pollution

The Guide to Coastal Living: Algal Blooms

Ecosystem Solutions: Reducing Nutrient Load

Safeguarding Water

Lily Soetebier is a contributing editor for Coastwatch and an award-winning science communicator at North Carolina Sea Grant. She is pursuing an M.S. in technical communication from North Carolina State University.