GSA Connects 2022 meeting in Denver, Colorado

Paper No. 19-6
Presentation Time: 9:00 AM-1:00 PM

GEOCHEMICAL CHARACTERIZATION OF BASE METALS IN STREAM WATER AND SEDIMENTS IN THE CADDO LAKE WATERSHED, CASS, HARRISON AND MARION COUNTIES, TEXAS


ERTONS, Melanie, Department of Geology, Stephen F Austin State University, P.O. Box 13011, SFA Station, Nacogdoches, TX 75962, FAULKNER, Mindy, Earth Sciences and Geologic Resources, Stephen F Austin State University, P.O. Box 13011, SFA Station, Nacogdoches, TX 75962 and WATKINS, Joseph W., Department of Geology, Stephen F. Austin State University, P.O. Box 13011, Nacogdoches, TX 75962

The Caddo Lake watershed is located in northeastern Texas and encompasses much of Cass, Harrison, and Marion counties. The watershed is drained by major streams and tributaries flowing in an easterly direction over Eocene-aged rocks and sediments of the Wilcox and Claiborne groups, and empty into the western arm of Caddo Lake. Since 1995, Caddo Lake and some of its tributaries have been included on the State of Texas Clean Water Act 303(d) list by the Texas Commission on Environmental Quality (TCEQ) for impairment due to mercury content in edible tissue, depressed dissolved oxygen, base metal concentrations, and low pH values. The purpose of this multi-year study was to characterize base metal concentrations in stream water and sediments in the Caddo Lake watershed, and document the potential watershed transport and contribution to the impairment of Caddo Lake. Recent water (n = 58) and sediment (n = 116) sampling at 29 sites revealed copper, lead, and zinc concentrations within normal limits and below EPA actionable standards. Mercury concentrations were elevated at 21 of the 29 sampling sites, which could lead to methylation and bioavailability to organisms at all trophic levels.