- By Sarah Oktay

Researchers from the Environmental, Coastal, and Ocean Sciences Department Sarah Oktay, Dan Brabander, Curtis Olsen, and graduate student Joseph Smith, have been working in collaboration with John Kada of the Department of Energy's Environmental Measurements Laboratory and Tom Bullen of the U.S. Geological Survey to investigate whether ash and debris from the World Trade Center (WTC) collapse can be identified in New York Harbor sediments. Their initial findings, which were funded by a small grant for exploratory research through the National Science Foundation's Chemical Oceanography Program, were published on January 21 in the international scientific newspaper EOS.

To begin, researchers collected 30–40-centimeter-deep sediment (river mud) cores in the Hudson River near the WTC site. These cores were sliced into one-centimeter-thick intervals, which were examined for chemical, radioisotopical, geological, and textural components. The results from the sediment sections were compared to ash and debris collected near "Ground Zero" a week after the attack. The researchers found a "geochemical fingerprint" incriminating WTC substances as a definitive source for a fraction of the sediment found at the 1–3-centimeter-depths, which is known as the "event horizon." The evidence included visual (fiberglass rods and fibers), chemical (elevated zinc and copper concentrations), and geological (significant gypsum and drywall-type elemental abundances and calcium and strontium ratios) signatures indicative of WTC building material. In other words, both during and after the explosions, material generated by the catastrophe rained down on the Hudson, was washed into the Hudson, or redispersed into the air or water during site remediation activities and eventually found its way to these sediments.

In addition, the short-lived radioisotope 131I was unexpectedly found in the surface sediments of both cores. The 131I was most likely introduced into the Hudson River through treated sewage wastewater containing organic by-products from medical treatments administered in area hospitals and is unrelated to the collapse of the World Trade Center buildings. The 131I found does not represent a health threat and its discovery helps validate the work of other ECOS researchers who have discovered caffeine, pharmaceuticals, human pathogens, and other sewage-derived contaminants in similar urban estuaries, such as Boston Harbor.

Currently, ECOS scientists are collecting cores in a wider area throughout New York Harbor and taking deeper cores in the same harbor slips in order to learn more about the preservation over time and extent of the WTC "geochemical fingerprint." This fingerprint may provide new information for assessing the potential environmental and human health impact of the World Trade Center catastrophe, and for corroborating sediment and contaminant transport models developed for the lower Hudson River estuary.

Image: ECOS's Joseph Smith, graduate student, and Sarah Oktay, research associate, hold sediment cores gathered from the Hudson River on July 24, 2002 to analyze for traces of the World Trade Center. (Photo by Alexia Berry)