“The chemicals are made for one purpose, but they have been inadvertently spilled into the environment causing water pollution,” 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. Fernandez explained,no bacteria or other organisms have evolved to break them down and they can be detected decades after they were 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. Some of the toxins found in our air and waterways were put there intentionally: DichloroDiphenylTrichloroethane (DDT), for instance, was introduced to protect against malaria and other insect-borne diseases. Others find their way into the environment unintentionally. To date, there hasn’t been a very good way to determine the levels of persistent organic pollutants causing water pollution in the environment.
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 the contaminant that ends up in live tissues. 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.