THE GEOCHEMICAL COMPOSITION AND REACTIVITY OF DUSTS DEPOSITED BY THE SEPTEMBER 11, 2001 WORLD TRADE CENTER COLLAPSE

As part of an environmental study of the World Trade Center (WTC) area after the attacks of September 11, 2001 (http://greenwood.cr.usgs.gov/pub/open-file-reports/ofr-01-0429/ ), we characterized the inorganic geochemistry of dusts deposited in lower Manhattan by the collapse of WTC buildings. Sweep samples were collected within the first two weeks after September 11, 2001, from 2 indoor and 15 outdoor localities. Most results of this work were released via the internet to WTC emergency response personnel on September 18 and 27, 2001. Major-element compositions (Si, S, Mg, Al, Fe, C) of the dusts represent the contributions of glass fibers, concrete, gypsum wallboard, metals, paper, and other materials within the office buildings. Trace-element compositions (Zn, Ba, Pb, Cu, Cr, Mo, Sb, Ti) reflect contributions from paints, lighting, electrical wires, pipes, computer equipment, electronics, and other diverse materials. Leach tests of the dusts with water (1 part dust added to 20 parts by mass deionized water; mixture shaken for 5 minutes; leachate filtered and analyzed) show the dusts are quite chemically reactive. Alkaline leachate solutions were produced due to rapid partial dissolution of calcium hydroxide (from concrete) and gypsum particles. Indoor dusts generated higher pH levels (11.8-12.4) than outdoor dusts (8.2-10.4), indicating that outdoor dust samples had reacted with rainfall or other waters prior to collection. Although caustic, indoor dusts are not as caustic as drain cleaner or cement. Leach tests with simulated lung fluids (SLF) (1 part dust added to 20 parts SLF at 37°C; mixed for 24 hours; leachate filtered and analyzed) produced smaller pH shifts due to the buffering capacity of SLF components. Some metals in the dusts (Al, Cr, Sb, Mo, Ba, Cu, Zn, Co, Ni) are quite soluble in water; many of these are even more soluble in SLF due to complexing with chloride, citrate, and glycine. Results indicate that: 1) disposal of WTC dusts and debris should use appropriate measures to prevent leaching of metals into ground waters; and 2) cleanup of dusts and debris should be done with appropriate respiratory protection and dust control to prevent possible inhalation of alkaline material containing potentially bioavailable heavy metals and metalloids.