Various human activities have the potential to release trace metals to the environment, including manufacturing and power generation. An ALCOA operated chlor-alkali manufacturing plant on the shoreline of Lavaca Bay, Texas discharged large quantities of mercury into the bay from 1966 to 1970. For this study, sediment cores were taken from two different locations in the bay in order to investigate the diagenetic behavior of anthropogenic mercury and the fluxes of mercury from sediments to the water column. In a second study a number of sediment cores were retrieved from central Texas lakes in the proximity of a coal-fired power plant in search of local, anthropogenic effects on metals.

In the first study, very high and variable mercury concentrations were found at depth in the sediment column, in some cases as high as 15 micro-g/g. In addition, surface sediments were found to have high mercury concentrations, with an average of 0.5 micro-g/g. The dissolved mercury concentrations in sediment pore water were also very high and variable, ranging from 8.5 ng/L to 3.56 micro-g/L. Since mercury was found to be mobile in these sediments, I estimated its transfer across the sediment water interface through molecular diffusion as well as the transfer from anoxic sediments, deeper in the sediment column to oxic sediments at the surface. The calculated sediment water transfer was found to be large enough to affect filter feeding organisms. Remobilization of Hg in the sediment column was too small to account for the high Hg concentration in surface sediments. Other activities, such as dredging, are believed to strongly influence the distribution of Hg in the sediment column.

In the second study, elevated metal concentrations were found in recently deposited sediments in some of the lakes. For example, in a sediment core from Lake Carlos there was a ten fold increase in mercury concentration between approximately 100 years old (10 ng/g) and surface (100 ng/g) sediment. Similar trends were found for other trace elements (Cd, Se, Ni ). Since all the lakes studied here should be receiving the same background atmospheric deposition, the recent increases are believed to be related to the emissions from the local coal fired power plant.