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Simpson, Neal1, Dibyendu Sarkar1 
(1) University of Texas at San Antonio, San Antonio, TX

ABSTRACT: Heavy Metals in Sediments of a Sludge Disposal Lake

Mitchell Lake in the San Antonio metropolitan area is a natural lake of 600 acres that was used as a sludge disposal lagoon between 1901 and 1987. The lake is closed to general public because of its current state of pollution, resulting in, among other negative environmental conditions, extremely odorous algal blooms and poor water quality. San Antonio Water Systems, the current owner of Mitchell Lake has developed a Master Plan to transform the 1300 acres lake area into a national wildlife refuge. Improvement of water quality has been identified as the number one priority in the plan. Mitchell Lake water has elevated levels of heavy metals resulting from long-term desorption and re-dissolution of metals from the sludge-impacted lake sediments. In order for the most appropriate remediation technique to be identified and applied, a baseline study of metal geochemistry in the sediments is currently under progress. Sediments have been sampled in triplicates from twelve strategic locations within the lake. The sediments are being analyzed for both total and bioavailable concentrations of heavy metals typical to sewage sludge, such as Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. Surface water and porewater samples are also being analyzed. Metal concentrations in water and sediments will be mapped using a GIS system to characterize the potential spatial variability in heavy metal distribution. Future studies geared towards water quality improvement of Mitchell Lake will be designed based on the data generated in this study.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.