Document Title:

Effects of Military Aircraft Chaff on Water Sources Available to Sonoroan Pronghorn

Carrie Marr Anthony L. Velasco

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While the federally endangered Sonoran pronghorn (Antilocapra americana sonoriensis) population has plummeted on the Barry M. Goldwater Range in southwestern Arizona, biologists have questioned some range activities that may increase risk potential to the pronghorn. Sonoran pronghorn on the Barry M. Goldwater Range in southwestern Arizona are exposed to military radio-frequency chaff that is used by aircraft during training exercises. Chaff are fibrous, glass strands coated with metallic aluminum that disrupt an enemy’s radar; strands also were coated (historically) with a strip of lead to increase flutter [performance]. Considering the amount of chaff released over the last 50+ years, and the metals used on the chaff fibers, the risk potential to Sonoran pronghorn was high enough to warrant investigation. Sonoran pronghorn population levels are so low that the any additional stress placed upon species could be detrimental to the existence of the species. As a result, we studied Sonoran pronghorn oral exposure to chaff on the Barry M. Goldwater Range, Cabeza Prieta National Wildlife Refuge, Organ Pipe National Monument, and Luke Air Force Range (herein these properties are referred to collectively as BMGR), and Kofa National Wildlife Refuge (KNWR) as a reference site. Our sampling results indicated that exposure to aluminum or other metals in chaff will not cause adverse effects to Sonoran pronghorn. Chaff was detected more frequently on the BMGR than on KNWR but the difference was not statistically significant (P=0.0578). Increased chaff detection on BMGR did not appear to influence mean aluminum concentrations in soil or sediment, as aluminum concentrations were within Arizona background concentrations. We used conservative parameters in the model to estimate “worst case” aluminum exposure for pronghorn. We are confident that chaff releases at current levels have little potential to adversely affect Sonoran pronghorn. However, we recommend expanded investigations of Sonoran pronghorn risk potential at the more heavily impacted military training sites. We detected chaff at these locations more frequently, but did not test for all chemical compounds present at these sites. Our concerns originate from frequent observations of burned and unburned explosives residues in the North Tac and HE Hill areas. A survey for explosives in soil, sediment, plant, and water at these sites is highly recommended. We also recommend monitoring Sonoran pronghorn serum concentrations for sodium, phosphorus, and zinc based on work by Fox et al. (2000) and the possibility for aluminum potentiating a phosphorus deficiency.

U.S. Fish and Wildlife Service



U.S. Fish and Wildlife Service - Arizona Ecological Services Field Office

Last updated: June 12, 2015