Great Lakes Sediment Surveillance Program
EPA’s Great Lakes Sediment Surveillance Program (GLSSP) was initiated in 2010 to monitor the spatial distribution and temporal trends of persistent, bioaccumulative, and/or toxic chemicals in bottom sediments of the Great Lakes. These contaminants enter the lakes through various pathways and can attach onto particles that sink down to the sediments at the bottom of the lake and enter the food web, posing risks to aquatic life. This program helps EPA meet obligations under Section 118(c)(1)(B) of the Clean Water Act to establish a Great Lakes system-wide surveillance network to monitor the water quality of the Great Lakes with a specific emphasis on the monitoring of toxic pollutants.
Background and Objectives
This program collects and analyzes sediment contaminants in all five Great Lakes. Sediment surface samples are collected via a box corer and analyzed to monitor spatial distribution of surface sediment contaminants within the Great Lakes. Sediment core samples (100 cm long) are collected at a subset of sites via a multi-corer and are dated using radiometric dating techniques to determine the age of sediment layers within the core samples, with more recent sediment at the top and older sediment at the bottom. Analyzing the concentration of contaminants at different depths in the core reveals a timeline of contaminant trends over many decades. The United States Geological Survey Upper Midwest Water Science Center Mercury Research Laboratory performs mercury analysis for GLSSP samples.
Monitoring Locations
The GLSSP monitors more than 250 contaminants in sediment at 157 sites within the Great Lakes. These sites are focused in deep, offshore areas within the lakes and in areas downstream of 21 tributary mouths. Sediment collected from these depositional areas is analysed to monitor amounts and types of sediment contaminants in the Great Lakes.
Data and Trends
GLSSP sediment core data show that concentrations of PCBs and OCPs in Great Lakes sediments have decreased since the 1970s, when they were phased out of production. In general, higher concentrations of legacy contaminants have been observed near more urbanized areas within the Great Lakes. GLSSP data are available via the Great Lakes Environmental Database on the EPA Central Data Exchange.