USE OF GEOCHEMICAL PROXIES TO IDENTIFY WATERSHED INPUTS TO LAKE MAUMELLE, CENTRAL ARKANSAS

Geochemical characterization of Lake Maumelle, one of the primary drinking water sources for central Arkansas, provides insight into natural and anthropogenic perturbations in the watershed that have impacted its water quality. We used traditional geochemical parameters combined with total organic carbon, aqueous soil-derived metals, and lignin and tannin compositions to track the response of creeks and adjacent coves to land use within Lake Maumelle. Data from six creeks and five corresponding coves were collected throughout the summer to evaluate possible changes in the water quality related to land management. Several geochemical parameters were elevated in creeks without concomitant increases in adjacent coves, suggesting deposition, recycling, or dilution of constituents transported from the watershed. Preliminary results indicate that primary production controls dissolved oxygen levels and organic carbon compositions within coves, whereas a greater proportion of organic matter in creeks was plant derived. Creeks from parts of the watershed that have been affected by clear-cutting show a two fold increase in silica and plant-derived compounds, compared to relatively protected areas in the northeast and southern portions of the watershed. Cove geochemistry, including silica and iron, is remarkably consistent, despite having contrasting compositions across the different streams sources. From this, it is apparent that some dissolved species are well mixed between coves and the main body of the lake. As such, increased contributions of phenolic plant compounds that are efficiently redistributed throughout the lake may be problematic, given their potential for forming carcinogenic disinfection by-products.