Atmospheric contaminant deposition to the Great Lakes determined from the integrated Atmospheric Deposition Network

While atmospheric transport brings contamination to the Great Lakes, the relative importance of this mechanism is not known. Thus, the United States and Canada signed an agreement calling for the monitoring of atmospheric deposition of toxic organics to the Great Lakes. This led to the creation of the Integrated Atmospheric Deposition Network (IADN) which is designed to collect data representative of the atmosphere over the lakes and to establish a database that could be used in research on atmospheric processes. Three workshops have been held to calculate atmospheric deposition based on data from the literature and IADN. The most recent update is based on a more robust database than were earlier calculations, a direct result of IADN. Improvements have occurred in analytical methodologies and data reduction techniques. The greater quantity of data has allowed incorporation of more terms in the loading equation; however, the uncertainties involved are still large. Errors are attributed to inaccuracies in physio-chemical parameters, inaccuracies in deposition velocities of particulates, and, to a lesser extent, insufficient sampling and inadequate analytical sensitivity.