Despite having been banned for for decades, many toxic chemicals still show up in the Back River in Baltimore County. That is why the county and the U.S. Department of the Interior recently funded a team from University of Maryland Baltimore County and USGS  to determine where the pollutants are coming from.

The team at UMBC tackling this challenge is led by Upal Ghosh, a professor of chemical, biochemical, and environmental engineering. His work focuses on how contaminants like polychlorinated biphenyls (PCBs) released in the past impact species such as fish, bald eagles, and even humans today. As an engineer, Ghosh thinks about projects from understanding mechanisms to solutions: “once we understand the system in a quantitative way through accurate measurements and modeling, we can start thinking about intervention.”

PCB levels are elevated in Back River, meaning there are sources of PCBs somewhere along the river or its tributaries. There is a fish consumption advisory in place there, which means fish caught could contain harmful levels of PCBs.

Ghosh’s team will be using a technique called passive sampling to measure ultra-low levels of PCBs in water. In traditional sampling methods, researchers will sample bottles of water, but since the team is looking for contaminants that will be at very low concentrations, a bottle may not collect enough water to detect the contaminants. Instead, they will leave specially-prepared polymer membranes at various locations in Back River for a month to provide a much more real sense of time-integrated ambient PCB concentrations. As a rough estimate, 1 gram of the polymer can detect more PCBs than collecting 1000 liters of water in the traditional way.

The goal of the study will be to identify the contaminant inputs into the river and determine the main contributors of PCBs to the water column. In order to accomplish this, they’ll look at 5-6 tributaries and move upstream and downstream as necessary. They are also investigating PCBs that are coming from a wastewater treatment plant with old infrastructure, and from sediments. The team has ideas for how to retrofit the treatment plant if that turns out to be the source. Otherwise, the contaminants could be coming from a terrestrial source. “If that’s the case, we need to treat the upland area to prevent pollutants from reaching the tributary,” explains Ghosh. “Understanding the transport correctly is key to finding the right solution to the problem.

If the team discovers where the PCBs are located, they can recommend strategies for intervention. The two traditional ways to remediate PCBs in sediments are to dredge the affected sediments or cover them with clean sediment. UMBC is also at the forefront of developing novel in-situ technologies for remediating PCB-impacted sediments.

Ghosh thinks that more energy and resources should be spent researching toxic contaminants in the Bay watershed. “I think in the Chesapeake Bay we haven’t addressed the issue of toxic pollutants [as much as other issues]. There’s been a lot of focus on nutrients, invasive species, etc., but contaminants were ignored.” He is hopeful this will change because of an agreement signed in 2014 by the Chesapeake Bay Program that addressed toxins. With so many fish consumption advisories within the watershed, addressing toxins is as pressing as ever. “The community needs to think, address, and find new solutions for legacy pollutants, in addition to making sure we are addressing new challenges.”