RECENT URBAN ENVIRONMENTAL IMPACTS AS RECORDED IN LAMINATED SEDIMENT FROM SUMMIT LAKE, AKRON, OHIO

Summit Lake, a kettle lake located in Akron, Ohio, was once part of the Ohio-Erie Canal and has long been used by industry for cooling water and the public for recreation. At present, much of the lake shore is being redeveloped to enhance public urban recreational opportunities. In November 2019, we collected sediment cores from the lake to assess how sediment quality has changed since it was studied 16.5 years ago. Down-core profiles of sediment color, density, organic content, magnetic properties and heavy metals were measured. Correlation of the magnetic susceptibility profiles of the Nov. 2019 and May 2003 cores indicate that 14 cm of sediment accumulated in the last 16.5 years. This sedimentation rate yields an estimate of 52,000 m³ of total lake sedimentation in the last 16.5 years. The black mud contained faint rhythmic laminations which became obvious rhythmic color triplets of brown, white and red colored mud once the split cores began to oxidize. The brown mud contains more organic matter than either the white or red mud layers suggesting a seasonal cycle whereby the brown mud accumulates when the lake is more productive. Sediment Cu, Cr, and Zn concentrations have remained nearly constant since 2003 (14 cm core depth) and may reflect the background metal influx to the lake from the urbanized watershed. However, Pb concentration continues to decline since 2003 (14 cm core depth). If recent trends continue then Pb is projected to attain the consensus-based probable effect concentration (128 mg/kg) by about the year 2035.