Massive DDT dump discovered off the Los Angeles coast is bigger than anyone thought
The seabed near Southern California hides a very dirty secret: decades of chemicals dumped in thousands of barrels. And the toxic debris field is even larger than expected, containing at least 27,000 drums of DDT and industrial waste, scientists recently found.
High concentrations of DDT (dichlorodiphenyltrichloroethane, an insecticide widely used for pest control in the 1940s and 1950s) had already been detected in ocean sediments between the coast of Los Angeles and Catalina Island in 2011 and 2013. At At the time, scientists who excavated the seabed of the area identified 60 barrels (possibly containing DDT or other wastes) and found DDT contamination in the sediment, but the full extent of contamination of the area was unknown.
Now, a research expedition presents a clearer picture of the deepwater dump site. Their findings reveal an expanse of ocean floor strewn with at least 27,000 barrels of industrial waste – and possibly as many as 100,000, researchers at the Scripps Institution of Oceanography at the University of California. said in a press release.
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From March 10 to 24, a team of 31 experts aboard the Scripps Sally Ride research vehicle created high-resolution acoustic maps of the seabed of the San Pedro Basin, spanning 36,000 acres (146 square kilometers) 19 kilometers away. the southern California coast 8 miles from Catalina Island. Two autonomous underwater vehicles (AUVs) named REMUS 6000 and Bluefin swam at depths of up to 3,000 meters below sea level, using sonar to locate the barrels.
These containers were quite small – less than 3 feet (1 m) high – and those that were buried looked even smaller in sonar scans, Scripps oceanographer and data scientist Sophia Merrifield told a conference. virtual press release on April 27. So researchers had to develop algorithms that would automate the process of identifying and counting these tiny objects, Merrifield explained.
“We had to be able to pump hundreds of gigs [gigabytes] thanks to an algorithm that would detect these very small, very bright targets, ”she said.
Images of the 60 sunk barrels spotted in 2011 and 2013 have helped scientists calibrate their algorithms. The result categorized not only the location of an object, but also its size and brightness, “so that we could do a more in-depth analysis of patterns and classification of target types,” Merrifield said.
From the AUV scans and analysis of the data, scientists on the expedition discovered that more than 90% of the study area contained debris, said Eric Terrill, chief scientist of the expedition and director. from the Marine Physics Laboratory at Scripps, during the press conference. Researchers found 100,000 pieces of human-made debris and identified the subset which was likely barrels containing DDT and other types of industrial waste, Terrill said.
This accumulation of spills on the bottom did not happen overnight. While Los Angeles today is primarily associated with Hollywood and filmmaking, oil and gas were once thriving industries in the region, and much of the mining and processing waste ended up in the area. ocean, Terrill said at the press event.
“The dumping of industrial waste into the ocean actually started in the 1930s and continued until the early 1970s,” Terrill said.
Companies also dumped the waste of agricultural DDT manufacturing byproducts into the sea, and in 1985 the Los Angeles Water Quality Control Board issued a disturbing report describing “decades of systematic neglect” in official monitoring of disposal of toxic wastes, resulting in irreversible damage to the marine environment, “the The Los Angeles Times reported that year.
It is estimated that companies have dumped between 386 and 772 tons (350 and 700 metric tons) of waste at offshore sites in the San Pedro Basin for nearly four decades, Terrill said. But it was unclear what the extent of the spill was, where exactly it happened, and if the containers with the waste were leaking (and how much).
A nearby location in the Palos Verdes plateau is already recognized as highly contaminated with DDT and PCBs (polychlorinated biphenyls, another toxic industrial compound) and is designated as a Superfund site – a place so steeped in hazardous waste that it has been targeted by the Environmental Protection Agency (EPA) for the cleanup, Terrill said.
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Vital clues emerged in 2011 and 2013, when David Valentine, professor of earth sciences and biology at the Marine Institute at the University of California at Santa Barbara, captured remote camera images of 60 barrels of industrial waste on the seabed, describing the toxic mess in a study. published in 2019 in the journal Environmental science and technology.
Then, in October 2020, investigative reports by the LA Times unearthed damning details about the DDT spill. Shipping logs for the Montrose Chemical Corporation of California – the largest manufacturer of DDT in the United States, based in Los Angeles from 1947 to 1982 – noted that thousands of barrels containing DDT were transported each month and dumped in deep waters near Catalina. The crews later began dumping the barrels closer to the California coast.
They also took other measures to speed up the work. “When the barrels were too buoyant to sink on their own, according to one report, crews simply pierced them,” the LA Times reported.
Although the research team does not yet know how many of the newly described 27,000 barrels contain DDT, the survey provides a starting point for studying the environmental impact of containers. The team’s findings have already prompted California Senator Dianne Feinstein to ask the EPA “to prioritize urgent and meaningful action to address this serious threat to human and environmental health,” in a letter to the agency written on March 12.
Scientists plan to analyze data from the R / V Sally Ride expedition for a future peer-reviewed study, but the publication of these early results (first in March, then in more detail on April 26) draws l Pay attention to the scope of the landfill site. and the threats it may pose to ocean ecosystems and marine life, the scientists said.
“Present this now as a way to convey information to policy makers and for other efforts,” Merrifield said.
“We hope the data will inform the development of strategies to deal with the potential impacts of the spill,” added Terrill.
Originally posted on Live Science.