by Angela Herring

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.

Originally published in news@Northeastern on June 30, 2014