Great Lakes Monitoring

The Integrated Atmospheric Deposition Network (IADN)

The Integrated Atmospheric Deposition Network (IADN) has been in operation since 1990 under the guidance of an implementation plan signed in that year. The first implementation plan committed the United States and Canada to work cooperatively towards the initiation of the IADN. It also guided the five original, cooperating IADN agencies in meeting their joint obligation. Since 1999 the program is comprised of the following three agencies:

In 1997, the IADN Steering Committee reviewed the progress of the IADN program in a technical summary. The Second Implementation Plan for IADN (IP2), signed in 1998, outlines goals and plans for IADN for the period 1998-2004.

IADN is specifically called for, by name, in Annex 15 of the Great Lakes Water Quality Agreement (GLWQA). In Canada, these activities are delivered federally through the Great Lakes program, and activities delivered at the provincial level are described in the Canada-Ontario Agreement (COA). The mandate for IADN also resides in Section 112(m) of the U.S. Clean Air Act Amendments of 1990 (CAA). The U.S./Canada Binational Great Lakes Toxics Strategy (BGLTS), signed in 1997, calls for monitoring of the atmospheric deposition of toxic chemicals to the Great Lakes basin. Many of the "challenges" in the BGLTS are directly related to IADN capabilities and goals.

The goals of IADN are to:

Determine, with a specified degree of confidence the atmospheric loadings and trends (both spatial and temporal) of priority toxic chemicals to the Great Lakes and its basin on, at least, a biennial basis;
Acquire quality-assured air and precipitation concentration measurements, with attention to continuity and consistency of those measurements, so that trend data are not biased by changes in network operations or personnel; and
Help determine the sources of the continuing input of those chemicals.

Station Placement and Number

IADN has been designed with one Master Station on each of the five Great Lakes, supplemented by a number of Satellite Stations to provide more spatial detail for deposition. The Master Stations offer the complete range of measurements made in the Network, measuring wet and dry deposition of Semivolatile Organic Compounds (SVOCs) and trace metals. Satellite Stations may contain only a portion of the measurements made at the Master Stations. IADN also estimates gas exchange of the SVOCs with the lake surfaces by using the air concentration measurements of the SVOCs at these sites in combination with water concentration measurements of the same chemicals made by other programs.

The Network is "a leading international effort in the assessment of the role of the atmospheric impacts of persistent, toxic substances on aquatic systems" (Peer Review, 1997). The second phase of IADN is scheduled to run until 2004. No major changes to the Network are anticipated, although potential modifications will be discussed and plans implemented.

The Integrated Atmospheric Deposition Network (IADN)

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