25 Topics in Environmental Geochemistry

Friday, 3 May 2013
8:00 AM - 12:00 PM
Room 1040/1050

DATING A SEDIMENT CORE USING SPHEROIDAL CARBONACEOUS PARTICLE CHRONOLOGY SUPPLEMENTED WITH TRACE METAL AND DIATOM COMMUNITY STRUCTURE ANALYSES

Paper number: 25-10
Program: Theme Sessions
Time: 11:00 AM – 11:20 AM

Authors

Abstract

Spheroidal carbonaceous particles (SCPs), a type of insoluble fly-ash, are produced from the incomplete combustion of fossil fuels and are deposited in lake sediments. They are not damaging to the environment, but they are associated with detrimental agents such as heavy metals, sulfur, and organic pollutants. SCPs are not influenced by chemical and biological decomposition; therefore, they provide a baseline reference for ecosystem disturbance from atmospheric pollution deposition. We hypothesize that using SCPs will track anthropogenic inputs of atmospheric pollution; and that they can be used as a proxy for human influence as well as a primary dating tool since different SCP concentrations in lake sediments archive the local historical occurrence of industrial fossil fuel combustion. This allows for the opportunity of cores from reservoirs in regions with a history of steel mills (e.g. Northeast Ohio’s Mahoning Valley) to be dated primarily by a SCP chronology instead of costly alternatives, such as 137Cs and 210Pb dating methods. Developing a method to date cores using a SCP chronology is significant to the historical environment reconstruction process since it fills in data gaps by describing historical variables and their effects in the environment.

To examine this hypothesis, a sediment core was taken from the depositional basin of Mosquito Creek Reservoir using a 5-cm diameter piston corer and was immediately sectioned at 1.12cm resolution on shore. Mosquito Creek Reservoir, which is located in Trumbull County and in part of the Mahoning Valley industrial region, was dammed in accordance with the Federal Flood Control Act in 1944 to alleviate floods on the Mahoning River. Even though Mosquito Creek Reservoir is relatively young, significant anthropogenic atmospheric inputs are able to be recorded. A chronology was constructed by comparing SCP concentrations to a local historical timeline of events involving industrial fossil fuel combustion, and it was supplemented with trace metal and diatom community structure analyses for validation. This study will lend a better understanding of using a SCP chronology to date cores while filling in data gaps for similar regions and reservoirs where steel mills were or are prevalent today.