Atmospheric Deposition of Toxic Pollutants to the Great Lakes As Measured by the Integrated Atmospheric Deposition Network

Abstract

To determine atmospheric deposition of anthropogenic contaminants to the Great Lakes, the United States and Canada established the Integrated Atmospheric Deposition Network (IADN), designed to collect regional data representative of the air over the lakes. In this paper, we present an update of atmospheric loadings to the Great Lakes for seven organochlorine pesticides, four polychlorinated biphenyl (PCB) congeners and total-PCBs, four polycyclic aromatic hydrocarbons (PAHs), and four trace metals. Calculations are based on gas, particle, and precipitation samples obtained in 1993 and 1994 at the five master IADN sampling stations. Air−water exchange is the dominant process for most organochlorines and lower molecular weight PAHs. Within the uncertainty in the data given here, current atmospheric loadings are indistinguishable from air−water equilibrium having been achieved over the lakes. In other words, the deposition of most organochlorine compounds into the Great Lakes is about balanced by the evaporation of these compounds from the lakes. Uncertainties in gas-transfer loadings are due to our inexact knowledge of physiochemical parameters, averaging of data over long time scales, and insufficient data for nonatmospheric sources.

The impact of urban areas on the deposition of air toxics to adjacent surface waters: A mass budget of PCBs in Lake Michigan in 1994

“…The 1991 and 1994 (w/o urban influence) budgets were updated to be temporally consistent with data from the AEOLOS results for 1994-95, and included new atmospheric deposition estimates (e. g., Hornbuckle et al, 1995;Hoff et al, 1996;Hillery et al, 1998).…”

“…The riverine inputs in 1991 are derived from Marti and Armstrong (1990) as modified in direct proportion to the water column loss rate of Pearson et al (1996); in 1994, the loss rate of Offenberg and Baker (2000) is applied. The precipitation inputs in 1991 are derived from Eisenreich and Strachan (1992) whereas in 1994, the updated regional signal and the urban-influenced loading (Hoff et al, 1996;Hillery et al, 1998) are applied. The dry particle deposition inputs in 1991 derive from Strachan and Eisenreich (1998), Eisenreich and Strachan (1992) and then updated according to the AEOLOS results for 1994 .…”

“…The Integrated Atmospheric Deposition Network (IADN) operating in the Great Lakes (Hoff et al, 1996;Hillery et al, 1998) and the Chesapeake Bay Atmospheric Deposition Study (CBADS) were designed to capture the regional atmospheric signal, and thus sites were located in background areas away from local sources. However, many urban/industrial centers are located on or near the Great Lakes and other coastal waters.…”

“…However, many urban/industrial centers are located on or near the Great Lakes and other coastal waters. Emissions of pollutants into the urban atmosphere are likely reflected in elevated local and regional pollutant concentrations and localized intense atmospheric deposition that is not observed in the regional signal (Hoff et al, 1996;Hillery et al, 1998). The southern basin of Lake Michigan is subject to contamination by air pollutants such as PCBs and PAHs, Hg and trace metals (Baker, 1997) because of its proximity to industrialized and urbanized Chicago, IL and Gary, IN.…”

Persistent Organic Pollutants

“…Air-water exchange represents one of the most important pathways for loading of POPs to many large water bodies including the Great Lakes (Eisenreich and Strachan 1992, Hillery, et al 1998, Hoff et al 1996 and Chesapeake Bay (Bamford et al 1999, Gustafson and Dickhut 1997, Nelson et al 1998 which are huge fisheries providing food for many people. The primary model used to describe the transfer of POPs between the air and water is the Whitman two-film model popularized by Liss and Merlivat (1986).…”