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The assessment of contaminant stressors on biota of the Rio Grande/Rio Bravo resulted from an effort of the USGS Biomonitoring for Environmental Status and Trends (BEST) program, to implement pilot projects to evaluate environmental contaminants and their effects on ecosystems. This study resulted in a database of approximately 3,000 concentration values that were georeferenced for use with GIS programs such as Arc View.
The data and common domain software as well as other layers of information were incorporated into a CD-ROM that wildlife managers and biologists could use to query and obtain information on contaminants in biota of the Rio Grande/Rio Bravo. The database contains information on contaminants reported in the peer-reviewed and gray literature from 1965-1997.
Most of the contaminants in water, sediments, and biota were organochlorine pesticides (OCs), polychlorinated biphenyls and trace elements. DDE (a metabolite of dichloro-diphenyl-trichlorethane - DDT) was the OC most commonly detected in water, sediments, and biota. Mercury (Hg) was one of the heavy metals most frequently reported; however, selenium (Se), arsenic (As), lead (Pb), copper (Cu), and zinc (Zn), were also very common. The highest concentrations of OCs and metals were reported predominantly in Lower Rio Grande Valley locations (68%) from Falcon Dam to the mouth of the river. Twenty six (20%) of the locations with maximum concentrations of contaminants in biota corresponded to portions of Llano Grande Lake and the Arroyo Colorado. New contaminant data from studies in the Rio Grande (i.e., results from the second phase of the binational study) have been incorporated.
The CD-ROM is available upon request. It is anticipated that this product will have a broad distribution and will be of interest to resource managers and scientists interested in contaminant issues of the U.S.-Mexico border. The Rio Grande GIS contaminant database contains a series of files that are readily accessible through Arc View or Arc Explorer. Included in the CD is a common domain version of Arc Explorer that can be downloaded for use and search of the GIS database.
Currently, we are updating the database to incorporate additional contaminant information up to 2004. This material will be available on the web early in 2005.
The CD-ROM is available upon request. Contact Miguel_Mora@usgs.gov
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