Metal Accumulation in Soils, Invertebrates, and Whiptail Lizards in the Northern Chihuahuan Desert

Allyson Benson-Pedraza, University of Texas at El Paso


Smelting activities by the American Smelting and Refining Company (ASARCO) lead to the substantial release of metal pollution into the El Paso, Texas, and border cities region. To-date few studies have examined metal accumulation within vertebrate taxa in these areas. As reptiles are currently experiencing population declines globally for a variety of reasons including pollution, lizards were chosen to be evaluated for trace element (As, Cu, Cr, Cd, Pb, and Zn) concentrations. These metals were measured within soils, invertebrate prey items, and the livers of three species of whiptail lizards (Aspidoscelis) from the un-remediated University of Texas at El Paso (UTEP) campus, and a control site, the Indio Mountains Research Station (IMRS), in Hudspeth County, TX. Invertebrate and lizard samples were collected from each study site over the course of two field seasons in 2020 and 2021. Soils were analyzed for metal concentrations using a portable x-ray fluorescence (p-XRF) machine and underwent pH testing to address metal bioavailability. Inductively coupled plasma triple quadrupole mass spectrometry (ICP-QQQ-MS)was used to analyze metals within pooled invertebrate groups and individual lizard livers. Soils demonstrated persistently high metal concentrations at UTEP, whereas IMRS exhibited significantly lower As, Cu, Pb, and Zn concentrations. Soil pH across all study sites were found to be alkaline (pH < 7) indicating a reduced potential for metal bioavailability. Metal concentrations observed in each trophic level were highest in soils as compared to invertebrates and whiptail lizard livers, apart from cadmium which was highest in lizard livers. Invertebratesamples collected for this study included the primary diet items of whiptail lizards which include the orders Orthoptera, Coleoptera, Araneae, Isoptera, and the family Cicadidae. Metal concentrations within invertebrates varied by metal, taxonomic group, and study site. Among the whiptail lizards only A. neomexicana was encountered at the UTEP site, while A. marmorata and A. tesselata were found at IMRS. Lizard liver concentrations of As, Cd, Cu, and Pb at UTEP were significantly higher than at IMRS. Generally, at the UTEP site whiptail lizards exhibited lower concentrations of metals than invertebrates, with the exception of lead and cadmium. Overall, this study demonstrated how whiptail lizards inhabiting a historically polluted urban Chihuahuan Desert environment are accumulating higher quantities of toxic metals as compared to their remote counterparts. Further research is necessary to understand the full extent of the physiological, biological, and ecological impacts that this metal pollution event has caused whiptail lizards to endure in the El Paso, TX region.

Subject Area


Recommended Citation

Benson-Pedraza, Allyson, "Metal Accumulation in Soils, Invertebrates, and Whiptail Lizards in the Northern Chihuahuan Desert" (2022). ETD Collection for University of Texas, El Paso. AAI29322530.