Inside the Laboratory: Using Comprehensive Two-Dimensional Gas Chromatography to Characterize and Quantify DDT Contamination on the Deep-Sea Floor

"Inside the Laboratory" is a joint series with LCGC and Spectroscopy, profiling analytical scientists and their research groups at universities all over the world. This series spotlights the current chromatographic and spectroscopic research their groups are conducting, and the importance of their research in analytical chemistry and specific industries. In the second part of this edition of “Inside the Laboratory,” Christopher Reddy of Wood Hole Oceanographic Institution discusses why comprehensive two-dimensional gas chromatography is the optimal technique for investigating complex mixtures of organic chemicals in the environment. Along with his colleague Bob Nelson, they have studied most significant oil spills over the past several decades, natural and manmade halogenated chemicals in marine mammals, and chemical waste dumped on the deep-sea floor laden with dichlorodiphenyltrichloroethane (DDT) and related chemicals.

DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane) is a widely recognized organochlorine insecticide that was extensively used for agriculture and vector-borne disease control, such as malaria, until its ban by the Stockholm Convention due to environmental concerns (1,2). Despite this, the World Health Organization (WHO) approved its limited use for vector control in some tropical countries in 2006. DDT's persistence has led to significant health and environmental issues. Some of these environmental and health issues include the accumulation of DDT in ecosystems and biomagnification in living organisms (1). Despite the impact of DDT on ecosystems being unclear, scientists are concerned about this pollutant being on the deep-sea floor and are dedicated to cleaning up DDT from the ocean.

Chris Reddy, a Senior Scientist at the Woods Hole Oceanographic Institution, his colleague Bob Nelson, and their team have been investigating an offshore California dumpsite, which revealed significant contamination from industrial-scale ocean dumping of organic waste, particularly DDT and its byproducts (3,4). Using autonomous and remotely operated underwater vehicles, they surveyed and sampled the site, finding discarded waste containers that structured the suboxic benthic environment (3). The sediment analysis they conducted showed highly variable p,p-DDT concentrations, peaking at 257 μg/g—approximately 40 times higher than levels at a nearby DDT Superfund site (3).

Reddy is interested in constraining the extent and types of contaminants on the seafloor from waste dumping. In the first part of our conversation with Reddy, he spoke about the history of DDT dumping and the nested approach using autonomous and remotely operated underwater vehicles to analyze the DDT dump site.

In the second part of our three-part conversation with Reddy, he answers the following questions:

• What challenges did you encounter in characterizing and quantifying the contamination on the deep seafloor?
• The study reports peak concentrations of p,p-DDT ∼40 times greater than at the nearby DDT Superfund site. What does this finding reveal about the extent and severity of contamination?
• What are the potential ecological consequences of such widespread contamination on deep-sea benthic communities?
• Can you talk about how your team has used comprehensive two-dimensional gas chromatography in your laboratory?

This interview is the second part of our three-part conversation with Reddy.

You can watch Part 1 of our interview with Reddy here.

You can watch Part 3 of our interview with Reddy here.

References

1. Mansouri, A., Cregut, M., Abbes, C. et al. The Environmental Issues of DDT Pollution and Bioremediation: A Multidisciplinary Review. Appl. Biochem. Biotechnol. 2017, 181, 309–339. DOI: 10.1007/s12010-016-2214-5
2. Eskenazi, B.; Chevrier, J.; Rosas, L. G.; et al. The Pine River Statement: Human Health Consequences of DDT Use. Environ. Health Perspect. 2009, 117 (9), 1359–1367. DOI: 10.1289/ehp.11748
3. Kivenson, V.; Lemkau, K. L.; Pizarro, O. P.; et al. Ocean Dumping of Containerized DDT Waste was a Sloppy Process. Environ. Sci. Technol. 2019, 53, 2971–2980.
4. Christopher Reddy Personal Website. Available at: https://christopherreddy.com/about (accessed 2025-01-07).