NERL Research Abstract EPA's National Exposure Research Laboratory GPRA Goal 1 - Clean Air Significant Research Findings Impact of Urban Areas on the Deposition of Air Toxics to Adjacent Great Waters Scientific Problem and Policy Issues Research Approach The Clean Air Act Amendments of 1990 mandated that EPA report on the contribution of atmospheric deposition to pollution loadings in the Great Waters (the Great Lakes, the Chesapeake Bay, Lake Champlain and coastal waters) and that EPA identify the sources of those pollutants. For example, atmospheric mercury depositing in the Great Lakes was thought to emanate from anthropogenic sources concentrated in the industrialized urban areas along the southern shores of Lake Michigan, Lake Erie, and Lake Ontario. To gain a better scientific understanding of atmospheric deposition to the Great Waters, NERL entered into two collaborative cooperative agree- ments: one agreement was to investigate the source areas, transport, transformation, and deposition of atmospheric mercury in the Great Lakes region; the second agreement considered deposition of polychlorinated biphenyls (PCBs) to Lake Michigan and the Chesapeake Bay. In the Great Lakes basin, a regional atmospheric mercury monitoring net- work was established in 1995 consisting of ten sites located in seven states and provinces. Measurements of gas- and particle-phase mercury were made simultaneously at all the sites, along with measurements of particulate mass and trace elements. Samples were collected for a 24-hour period beginning at about 8:00 a.m. on an every-sixth day schedule for a duration of two years. Precipitation samples collected at selected sites were analyzed for mercury and trace element concentrations. For studying PCB deposition to Lake Michigan, two shore-based and three over-water, ship-based locations were utilized in three two-week intensive field campaigns. Atmospheric gas- and particle-phase PCB samples were collected in consecutive 12-hour periods at all sites. Precipitation samples were also collected on an event basis, and water-column samples for particulate and dissolved-phase PCB were collected from the ship. ------- Results and Implications Research Collaboration and Publications Urban areas adjacent to the Great Waters were found to have significant impacts on the deposition of both mercury and PCBs. In the Great Lakes, anthropogenic mercury sources located within the Great Lakes region were found to have had a significant impact on gas- and particle-phase mercury levels. Atmospheric deposition patterns for the Great Lakes region will likely reflect the observed spatial differences observed in concentration measure- ments, resulting in greater annual deposition in the eastern and southern parts of the region. Thus, conclusions from previous studies of atmospheric mercury done in the northern and western parts of the Great Lakes region should not be extrapolated to the entire region. Similarly, it was found that PCB emissions from the Chicago area increased atmospheric concentrations off shore, leading to significantly increased particulate and air-water PCB exchange fluxes in Lake Michigan compared to the regional signal. The general message is that urban-industrial areas are major sources of hazard- ous air pollutants, which may be persistent and bioaccumulative. Proximate, down-wind water bodies experience enhanced atmospheric concentrations leading to increased atmospheric depositional fluxes. The Impact of Urban Areas on the Deposition of Air Toxics to Adjacent Great Waters studies were designed and conducted by research teams from the Universities of Michigan, Minnesota, Maryland, Delaware, the Illinois Institute of Technology, and Carnegie Mellon University. Scientists from EPA's National Exposure Research Laboratory collaborated in the studies by providing sampling equipment, assisting with field sampling operations, and performing analyses of ambient air samples for concentrations of trace elements. Additional EPA support was provided by the Great Lakes Na- tional Program Office, which was instrumental in securing the use of the EPA research vessel Lake Guardian for conducting the over-water measurement campaigns. Some of the recent peer-reviewed publications generated from these studies are listed below: Caffery, P.F., J.M. Ondov, M.J. Zufall, and C.I. Davidson. Determination of size de- pendent dry particle deposition velocities with multiple intrinsic elemental tracers. Environ. Sci. Technol. 1998,32: 1615-1622. Dachs, J., S.J. Eisenreich, J.E. Baker, F.C. Ko, and J.D. Jeremiason. Coupling of phytoplankton uptake and air-water exchange of persistent organic pollut- ants. Environ. Sci. Technol. 1999,33: 3653-3660. Franz, T.P., S.J. Eisenreich, and T.M. Holsen. Dry deposition of particulate PCBs and PAHs to Lake Michigan. Environ. Sci. Technol. 1998,32: 3681-3688. Offenberg, J.H. and J.E. Baker. Aerosol size distributions of poly cyclic aromatic ------- hydrocarbons in urban and over-water atmospheres. Environ. Sci. Technol. 1999,33:3324-3331. Offenberg, J.H. and J.E. Baker. Influence of Baltimore's urban atmosphere on organic contaminants over the Chesapeake Bay. J. Air Waste Manag. Assoc. 1999,49: 959-965. Ondov, J.M. and A.S. Wexler. Where do particulate toxins reside? An improved paradigm for the structure and dynamics of the urban mid-Atlantic aerosol. Environ. Sci. Technol. 1998,32: 2547-2555. Paode, R.D., S.C. Sofuoglo, J. Sivadechathep, K.E. Noll, T.M. Holsen, and G.J. Keeler. Dry deposition fluxes and mass size distributions of Pb, Cu, and Zn measured over southern Lake Michigan during AEOLOS. Environ. Sci. Technol. 1998, 32: 1629-1635. Shahin, U., J. Lu, S.M. Yi, R.D. Paode, and T.M. Holsen,. Long-term dry deposition fluxes measured around Lake Michigan with an automated dry deposition sampler. Environ. Sci. Technol. 1999,33:2113-2117. Simcik, M.F., T. Franz, H. Zhang, and S.J. Eisenreich. Gas-particle partitioning of PCBs and PAHs in the Chicago urban and adjacent coastal atmosphere: States of equilibrium. 'Environ. Sci. Technol. 1998,32: 251-257. Simcik, M.F., S.J. Eisenreich, and P. Lioy. Source apportionment and source/sink relationships of PAHs in the coastal atmosphere of Chicago and Lake Michi- gan. Environ. Sci. Technol. 1999,33: 5071-5080. Simcik, M.F., I. Basu, C.W. Sweet, and R.A. Hites. Temperature dependence and temporal trends of PCB congeners in the Great Lakes atmosphere. Environ. Sci. Technol. 1999,33: 1991-1995. Sofuoglo, S.C., R.D. Paode, J. Sivadechathep, K.E. Noll, T.M. Holsen and G.J. Keeler. Dry deposition and mass size distributions of mass, Al, and Mg measured over southern Lake Michigan during AELOS. Aerosol Sci. Technol. 1998,29: 281-293. Suarez, A.E., P.F. Caffery, P. V. Borgoul, J.M. Ondov, and F. Divita Jr. Use of an Ir tracer to determine the size distribution of aerosol emitted from a fleet of diesel sanitation trucks. Environ. Sci. Technol. 1998,32: 1522-1529. Zhang, H., S.J. Eisenreich, T. Franz, and J. Offenberg, Evidence for the increased gaseous PCB fluxes to Lake Michigan from Chicago. Environ. Sci. Technol. 1999,33:2129-2137. Zufall, M.J., C.I. Davidson, P.F. Caffery, and J.M. Ondov. Airborne concentrations and dry deposition fluxes of particulate species to surrogate surfaces deployed in southern Lake Michigan. Environ. Sci. Technol. 1998,32: 1623-1628. ------- Future Research These studies of the impact of urban areas on the deposition of air toxics to adjacent Great Waters began in 1993 and concluded in 1999 with the publication of journal articles describing study results. Federal funding for this research was administered under EPA cooperative agreement # CR820909 and cooperative agreement # CR822054. No additional NERL studies of urban area impacts on the deposition of air toxics to adjacent water bodies are planned at this time. ------- |