Black Mayonaise

What Exactly Is the Black Mayonnaise at the Bottom of the Gowanus Canal?

Photo by Susan De Vries  by Craig Hubert

There are numerous mysteries about the Gowanus Canal. But the most baffling, not to mention terrifying, is the thick dark sludge that makes it way through the oily waters, that which has been called black mayonnaise.

Aside from its gross name — which is a pretty good descriptor, to be honest — there has rarely been an acceptable explanation of what black mayonnaise is, exactly, and how it is formed. So we reached out to Christos Tsiamis, the EPA’s Senior Project Manager for the Gowanus Superfund cleanup, and asked him to explain.

gowanus canal black mayonnaiseA core sample from the former First Street Basin near the BRT Power Station. Photo via EPA’s Gowanus Canal Facebook Group

Black mayonnaise is the “result of chemical waste that was discharged from the industries that operated along the canal as well as by New York City sewage and street runoff,” wrote Tsiamis in an email.

“The combination of the chemicals and sewage gave the sediment the soft texture of mayonnaise, while the combination of liquid tar from the manufactured-gas plants, petroleum products (such as motor and lubricating oils), decomposed organic matter and sewage gave to this sediment its black color.”

gowanus canal brooklyn superfund sitesPhoto by Hannah Frishberg

A 10-foot-high layer of black mayonnaise lays over the original native sediment at the bottom of the canal. But is it dangerous?

The answer is a resounding yes.

“It contains a multitude of chemicals (in the dozens) many of which are toxic and dangerous to human health upon repeated exposure or from consumption of fish that is caught at the canal (or at close proximity to it) over time,” wrote Tsiamis. This was determined by a risk assessment study conducted by the EPA in 2010.

Will the cleanup cleanse the canal of black mayonnaise forever? Two months of dredging, starting in December, is expected to permanently clean the bottom of the canal, according to Tsiamis. Meanwhile, the Gowanus’ two new underground holding tanks are expected to keep a good part of sewage and street run-off from overflowing into the canal during storms. “After the storm passes, the liquid held by these tanks will be pumped for treatment to the city’s treatment facilities,” he said.

Tsiamis says these measures will free the canal of black mayonnaise forever. But the EPA will be checking every five years anyway, just in case the substance inexplicably returns.

Until next time,

Garbage Girl

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POPS, PCBs and Plastic Pellets

In 2005, Dr. Hideshige Takada founded International Pellet Watch (IPW) to track and study plastic pellets.  Pellets are the raw material that gets remelted and molded into plastic products.  Citizens across the globe collected plastic pellets from the beaches they visited and sent them to his laboratory at Tokyo University of Agriculture and Technology.  The content of the pellets are analyzed to determine its global POP distribution. The results are sent to the participants via email and released on the web.

So far, pellet samples from approximately 200 locations in about 40 countries have been analyzed.  Five samples are analyzed from each location to see piece-to-piece variability.  About 1000 pellet samples have been analyzed so far.  POPs were detected in every one of those 1000 pellet samples from around the world, even from remote islands, providing evidence that plastic pellets transport POPs for long distances.

POPs are hazardous human-made chemicals that are resistant to degradation in the environment. Polychlorinated biphenyls (PCBs), different sorts of organochlorine pesticides (e.g. DDTs and HCHs) and brominated flame-retardants are all POPs.

Analyzing plastic pellets enables IPW to observe spatial patterns of POP concentrations. For example, PCB concentrations were two to three orders of magnitude higher in highly-industrialized areas.  Even though, usage of PCBs was banned in the 1970s, they accumulated in the bottom sediments in coastal zones and rivers.  (General Electric caused The Hudson River to become a Super Fund Site by dumping PCBs into the water for decades).  Due to their persistent and hydrophobic nature, PCBs are easily remobilized by wind, waves, and currents, sediments stirred up by organisms, dredging and underwater construction.  PCBs continue to contaminate coastal waters by becoming absorbed into plastic pellets.

I googled plastic pellets and . . . . yikes!

https://www.google.com/search?q=plastic+pellets&oq=plastic+pellets&gs_l=psy-ab.3..35i39k1l2j0l4j0i67k1j0l3.165391.167158.0.168302.11.11.0.0.0.0.166.1252.3j8.11.0….0…1.1.64.psy-ab..0.11.1249…0i22i30k1j0i22i10i30k1.0.qqd1N-bxI3U

Until next time,

Garbage Girl