T110 Sigma Gamma Epsilon Undergraduate Research (Posters)

Monday, 1 November 2010
8:00 AM - 6:00 PM
Hall D

CHARACTERIZATION OF GEOCHEMICAL CYCLES IN LION CREEK WATERSHED, OAKLAND, CA

Paper number: T110-23
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

Water quality and sediment core analyses document the influence of acid mine drainage on the Lion Creek watershed. The Lion Creek watershed in Oakland, CA comprises three creeks: Lion, Leona, and Horseshoe, with the Leona tributary draining a former sulfur mine, which produces acid mine drainage. Horseshoe and Leona Creeks discharge into Lion Creek, which empties into Lake Aliso on the Mills College campus. Historically (pre-1990), lake levels in Lake Aliso were maintained. Currently, the lake alternates between full and empty. In summer, Aliso is full to provide a source of irrigation water to Mills; in winter Aliso is drained for flood protection. As Mills develops a water use plan for Aliso and Lion Creek, understanding whether the Lake acts as a source and/or a sink for contaminants is essential. Since July 2009, Lion, Leona, and Horseshoe Creeks, the Lake Aliso inlet and outlet, and the Lion Creek outlet from Mills were sampled monthly. Water quality was captured in the natural tributaries (Lion and Horseshoe), acid mine drainage waters (Leona), and the combined conditions at the lake inlet and beyond. Sediment cores were collected from Lake Aliso to provide a history of lake conditions.

Lion and Horseshoe Creeks exhibit geochemistry representative of natural chemical evolution. The former sulfur mine influences Leona Creek, which has elevated conductivity and sulfate, and low pH. Decreased conductivity and sulfate at the lake inlet are consistent with dilution of Leona Creek. In winter (lake empty), water quality indices are consistent between the lake inlet and outlet. In summer months, there is a marked difference between the water quality at the lake inlet and outlet, suggesting a change in the geochemical cycling in the lake. Alternating oxic and anoxic laminations in the sediment cores also suggest regular changes in geochemical cycling. Further, summer dissolved oxygen and temperature decrease with depth in the lake, which likely leads to anoxic conditions in the sediments when the lake is full. Ongoing research includes analysis of metals in water and sediment and an investigation of microbial diversity, which will expand our knowledge of biogeochemical cycling in the Lion Creek watershed. This research will guide management and remediation efforts and may limit pollution at Mills and in San Francisco Bay.