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Sediment Quality Index: Assessing Risks in the Aquatic Environment of the Great Lakes |
| By: K. Schaefer and M. Forbes (S&T Liaison) |
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Financial resources can be directed to sites where clean-up will provide maximum environmental benefit. When clean-up and restoration are complete, further benefits for the waterfront area will come.
The Problem
Cleaning up contaminated sediments is critical to improving water quality - a major concern to Canadians - but clean-up is costly and technologically challenging.
Contaminants accumulate in the sediments of lakes and rivers and are a continuing threat to other parts of the environment. Environmental program managers and decision makers need a means to identify the highest risk areas so they can focus clean-up efforts and use resources to produce maximum environmental benefits.
Seeking Solutions through S&T
Environment Canada developed a sediment quality index (SQI) to help assess risks of persistent, bioaccumulative, and toxic substances in the aquatic environment. Previously, the sheer quantity and complexity of sediment data made it difficult to communicate trends in sediment quality to managers, governments and the public. This tool allows scientists to interpret and communicate sediment quality data to stakeholders, and provides a tool for ranking sediments in relation to urgency for action to protect aquatic biota and wildlife.
The SQI is based on an algorithm similar to a water quality index, such as the Canadian Council of Ministers of the Environment Water Quality Index (2001). The SQI translates large and complex sediment data into a simple index based on three elements:
- scope – the percent of variables that did not meet guidelines;
- frequency – the percent of failed tests relative to the total number of tests in a group of sites;
- amplitude – the magnitude by which the failed variables exceeded guidelines.
Environment Canada and the U.S. Environmental Protection Agency integrated available data from the open waters of each of the Great Lakes. Data on lead, zinc, copper, cadmium and mercury have been integrated to date. Across the Great Lakes basin, the general trend in sediment quality for the five metals is generally indicative of trends for a wide range of persistent toxics.
When applied in the Great Lakes, the SQI ranged from "fair" in Lake Ontario to "excellent" in eastern Lake Erie. Areas of lakes Erie, Ontario and Michigan show the poorest sediment quality as a result of historical and contemporary urban and industrial activity.
Transforming Knowledge into Action
Who can use these results?
The SQI can be used to support management decisions and priorities for dealing with contaminated sediments, mapping the extent of historic contamination, and determining effectiveness of management actions in protecting the aquatic environment.
Use of the SQI has expanded to include contaminants in streambed and river sediments for whole-watershed assessments. Results can assist the federal government, the provinces and industry in managing contaminated sediments not only in pollution hot-spots such as Great Lakes Areas of Concern, but also in other ecosystems. Multi-stakeholder programs, such as Remedial Action Plans for the Great Lakes, can use the SQI to assess environmental impairments related to toxic chemicals.
Between 1993 and 2001, 10 sediment remediation projects were undertaken in the corridor of the Detroit River and western Lake Erie at a cost of $130 million USD.
A recent report by York University estimates the net cumulative economic benefit as a result of the Hamilton Harbour Randle Reef clean-up is $126 million over 25 years.
The economic benefit is estimated at $1 billion when all projects are implemented and Hamilton Harbour is "delisted" as a Great Lakes Area of Concern.
Benefits to Canadians
Sediment quality assessments based on the SQI help identify the most troubling sites where clean-up should be a priority to prevent extensive food web contamination. The key benefit for Canadians is that financial resources can be directed to sites where clean-up and restoration will provide maximum environmental and economic payoff for waterfront areas.
Communicating the results of sediment quality studies can be confusing due to the numerous chemicals typically included. The sediment quality index provides a practical method of summarizing complex quality data, making it easier to communicate to decision makers and the general public, who benefit from increased understanding of the risks to their water quality and the options and opportunities for sediment clean-up.
For more information:
Grapentine, L., Marvin, C., and Painter, S. 2002. Development and evaluation of a sediment quality index for the Great Lakes and associated Areas of Concern. Human and Ecological Risk Assess. 8(7):1549-1567.
Marvin, C.H., Charlton, M.N., Reiner, E.J., Kolic, T., MacPherson, K., Stern, G.A., Braekevelt, E., Estenik, J.F., Thiessen, L., and Painter, S. 2002. Surficial sediment contamination in Lakes Erie and Ontario: A comparative analysis. J. Great Lakes Res. 28(3):437-450.
Marvin, C., Grapentine, L., and Painter, S. 2004. Application of a sediment quality index to the lower Laurentian Great Lakes. Environ. Monit. Assess. 91:1-16.
Painter, S., Marvin, C., Rosa, F., Reynoldson, T.B., Charlton, M.N., Fox, M., Thiessen, P.A.L., and Estenik, J.F. 2001. Sediment contamination in Lake Erie: A 25-year retrospective analysis. J. Great Lakes Res. 27(4):434-448.
S&T Liaison | Tel 905 336 4513 | Fax 905 336 4420
© Her Majesty the Queen in Right of Canada, represented by the Minister of Environment, 2007.
Catalogue No. En164-15/4-2007E-PDF; ISBN 978-0-662-46659-8
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