Biomonitoring of Heavy Metals in the Ambient Air Around International Bridges of El Paso TX/Juarez, Mex., Using Tumbleweed and Chelating Agents Jason G. Parsons, Tenoch Benitez, Jose R. Peralta- Videa, Alejandro Martinez, Rafael Corral, Roberto Hurtado, and Jorge Gardea-Torresdey The Department of Chemistry at the University of Texas at El Paso, El Paso TX, 79968

Introduction The international ports of entry in the El Paso, TX/Ciudad Juarez, Mexico border region are a significant source of air pollutants due to a high vehicular traffic

Current Heavy Metals Sampling Techniques (among others) Filter Sampling: Filters, high, and low volume samplers required Precipitation Sampling: Requires a wet collector

Direct measurement of toxic substances in the environment by the use of living organisms. Inexpensive and environmentally friendly approach to determine inorganic contaminants at trace levels Biomonitoring

Chelating Agents Chemical compounds which create complexes with heavy metals, therefore increasing their bioavailability for living organisms to consume (e.g. plants).

Methodology

Tumbleweed seeds were collected around El Paso, TX from a site that does not have any previous report on metal contamination. Seeds sown in black plastic bags

Three month old plants were misted with the chelating agents and placed at the bridges over a four week period. Experiment Setting

Sample processing The aerial portion of the plants were then collect, dried and weighed.

The weighed samples were microwave digested using the EPA method 3051.

Element determination The samples were analyzed for elemental content using a Perkin Elmer Elan DRCII ICP-MS

Results

Metal Uptake in Tumbleweed plants without chelating agents

Metal content in shoots of plants treated with 0.1 M EDTA and 0.1 M Citrate EDTACitrate

Metal content in shoots of plants treated with 0.5 M EDTA and 0.5 M Citrate EDTACitrate

Metal content in shoots of plants treated with 1.0 M EDTA and 1.0 M Citrate EDTACitrate

Conclusions The concentrations of metals deposited in plant shoots appeared to be related to the relative amounts of traffic at each of the sampling sites (higher at Zaragoza and lower at Santa Teresa). There were no effects of the concentration of chelating agents upon the accumulation of metals on tumbleweed shoots. The data showed that Tumbleweed plants have the capability to be used for the biomonitoring of heavy metals from polluted air.

Acknowledgements SCERP project A SCORE Dudley Family for Dr. Gardea Endowed Chair The Dudley family for the Endowed Research Professorship in Chemistry The STAR Grant