Arsenic - Not Always the Smoking Gun for Chemical Munitions
Article by Guest Author: Michael Tomlinson
While arsenic can be the smoking gun for discarded military chemical munitions and agents, it is not always the smoking gun. The waters off the State of Hawai'i, especially off the island of O'ahu, have served as disposal sites for dredge spoil as well as discarded military munitions (DMM), both conventional and chemical. In 1944 in the area designated HI-05, off the south shore of O'ahu, 16,000 World War II M47A2, 100-pound (45 kg) mustard bombs were discarded in waters deeper than 1,970 feet (600 m). As part of the Hawai'i Undersea Military Munitions Assessment (HUMMA) Program, the University of Hawai'i at Mnoa (UHM) Department of Oceanography undertook an ambitious sampling program that included collecting sediment samples with UHM's manned submersibles for analysis of select chemical agents (CA) and their degradates (e.g., sulfur mustard or HD, Lewisite, and their degradates), energetics (e.g., RDX, TNT and its degradates), as well as arsenic, copper, lead, and mercury. The analysis of any sediment that tested positive for CA was performed by the U.S. Army Edgewood Chemical Biological Center (ECBC). UHM Oceanographers used multivariate statistics, specifically, nonmetric multidimensional scaling (NMDS), to look for patterns in the data.
The results of NMDS analysis (plot) indicate that arsenic (As) and lead (Pb) are associated with samples collected from control sites and DMM that tested negative for CA and not with the samples that tested positive for chemical agents such as HD and its degradates 1,4-dithiane (1,4-Dt); mercury (Hg) also clustered with the samples containing CA. Lewisite and its degradates were not detected in the sediments and yet arsenic was detected in sediments at concentrations ranging from <1.3 to 40 parts per million (ppm) with the highest concentrations occurring at the control sites and DMM sites where chemical agents were not detected but dredge spoil occurred.
