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CEE Professor Loretta Fernandez Develops Approach to Water Pollution Testing

July 25, 2014

Assistant Professor Loretta Fernandez, who holds a joint appointment in the Department of Civil and Environmental Engineering and Marine and Environmental Sciences, was featured in News@Northeastern for her research on water pollution testing. Prof. Fernandez has created a simple water quality sampler which will determine the contamination levels of persistent organic pollutants in our waterways. The samplers collect organic pollutants in the same way as fish, passively, by existing and staying in a marine environment. These samplers have already enabled researchers to test the effectiveness of remediation strategies in known contaminated sites.

Source: News @ Northeastern

Some of the toxins found in our air and water­ways were put there inten­tion­ally: DDT, for instance, was intro­duced to pro­tect against malaria and other insect-​​borne dis­eases. Others find their way into the envi­ron­ment unintentionally.

“The chem­i­cals are made for one pur­pose, but they have been inad­ver­tently spilled into the envi­ron­ment,” said North­eastern Uni­ver­sity assis­tant pro­fessor Loretta Fer­nandez, who holds joint appoint­ments in the Depart­ment of Civil and Envi­ron­mental Engi­neering and the Depart­ment of Marine and Envi­ron­mental Sci­ences.

Regard­less of how they got there, these so-​​called “per­sis­tent organic pol­lu­tants” are next to impos­sible to remove from the habi­tats in which they end up. No bac­teria or other organ­isms have evolved to break them down, Fer­nandez expla­nined, and they can be detected decades after they’re first intro­duced. This is a problem because the toxins get into the tis­sues of organ­isms that live nearby, and they often end up in humans either directly or indi­rectly, like when we find con­t­a­m­i­nated had­dock on our dinner plates.

To date, there hasn’t been a very good way to deter­mine the levels of per­sis­tent organic pol­lu­tants in the envi­ron­ment, Fer­nandez said. A single water sample—which only offers a snap­shot of a single place at a fleeting moment in time—would have to go through a series of pumps and fil­ters before any mean­ingful data could be har­nessed; taking a 2,000– to 4,000-liter sample from an entire body of water could take days to com­plete. Fur­ther­more, researchers couldn’t be sure that the final value cap­tured by this process would be truly rep­re­sen­ta­tive of the level of con­t­a­m­i­nant that ends up in live tissues.

“What you want is a mea­sure of the dis­solved con­tent,” Fer­nandez said, “since that cor­re­lates directly with what ends up in tissue concentrations.”

For her part, Fer­nandez has spent the better part of a decade devel­oping a very com­pre­hen­sive, yet simple, alter­na­tive approach. “I just got plastic sheeting from the hard­ware store for this,” said Fer­nandez, holding up a device that looks more like a child’s art project than a state-​​of-​​the-​​art research tool.

Fer­nandez’ sam­plers act like fake fish, hanging out in a marine environment—either secured in the water column or buried in the sed­i­ment below—and col­lecting the per­sis­tent organic pol­lu­tants the same way the fishes’ fatty tis­sues do so: passively.

In one project, a col­lab­o­ra­tion with researchers at the U.S. Envi­ron­mental Pro­tec­tion Agency, Fer­nandez’ sam­plers are working to cap­ture accu­rate dis­solved con­cen­tra­tions of DDT near the Palos Verdes Shelf off the coast of Los Angeles County. “The Mon­trose Chem­ical Com­pany, from the mid 1940s until the 1980s, were dis­charging their waste through the waste­water out­fall,” she said. “This com­pany was the largest DDT fac­tory in the world.” More than three decades after the locale was named the planet’s deepest super­fund site and the com­pany ceased its old dumping prac­tices, the chem­ical is still present in the water at very high levels.

Attempts to reme­diate the area have focused on over­laying the bottom sed­i­ment where most of the DDT has set­tled with a new layer of clean sand. But with Fer­nandez’ sam­plers, the team was able to show that the pilot caps weren’t doing the job as intended. “What we found was that there was no dif­fer­ence between the two,” she said. “We saw the exact same con­cen­tra­tions in the water [at capped sites] as we saw above nearby sed­i­ments where there was no cap put down. The reason is that the cap has essen­tially been recapped by just a small amount of con­t­a­m­i­nated sed­i­ment form else­where on the shelf.”

The con­clu­sion, she said, is that reme­di­a­tion isn’t as simple as sprin­kling some clean sand on top of the con­t­a­m­i­nated sed­i­ment. Instead, she and her col­leagues are inves­ti­gating methods of adding an absorbent mate­rial to the cap­ping sand. “It’s not get­ting rid of the DDT; it’s not degrading the DDT; it’s just holding onto it more strongly,” Fer­nandez said.