Thomas J. Murphy

Precipitation Inputs of PCBs to Lake Michigan

Abstract Event precipitation samples were collected in Chicago, Illinois and on Beaver Island, Michigan and analyzed for polychlorinated biphenyls (PCBs). The weighted mean concentration of PCBs in 31 samples of rain was 119 ng/L (119 parts in 10 12 ). This would indicate a deposition of 5000 kg/yr of PCBs to Lake Michigan from wet precipitation. The concentrations of PCBs in rainfall were found to be as high on Beaver Island as in Chicago. This is interpreted as indicating that the sources of PCBs to the atmosphere are diffuse and/or that residence times in the atmosphere are long. Precipitation is now the major source of these materials to the lake and future problems in the lake with PCBs will be determined mainly by the magnitude of the atmospheric inputs of PCBs to the lake.

Inputs of Phosphorus from Precipitation to Lake Michigan

Precipitation samples were collected at six locations around Lake Michigan and analyzed for the concentrations of the different forms of phosphorus present. The concentrations were found to be higher in the southern part of the lake. Precipitation-weighted concentrations of total phosphorus and dissolved reactive phosphates were found to be 0.023 mg/1 and 0.011 mg/1, both higher than the concentrations found in the open lake of 0.009 and 0.002 mg/1. Inputs of total phosphorus to the lake were calculated to be 1.0 × 106& kg/yr or about 18% of the present phosphorus budget of the lake. More than 40% of the phosphorus in precipitation is in the form of dissolved reactive phosphates and it is estimated that about 0.6 × 106& kg/yr of the phosphorus coming into the lake in precipitation becomes available to organisms in the lake.

Atmospheric Deposition of PCBs into Green Bay

Concentrations of polychlorinated biphenyls (PCBs) were measured in air and precipitation samples collected at three locations along the eastern shore of Green Bay. Total PCBs in air ranged from 0.3 ng/m3 near the city of Green Bay at the southern end of the bay to less than 0.1 ng/m3 at the northern end of the bay. It was determined that the Teflon™ surface of the precipitation collector adsorbed large amounts of PCBs from the air, and perhaps also from precipitation. Because contaminants on this surface probably interact with precipitation, the PCBs could not be quantified in the samples. Over 90% of the airborne PCBs were in the vapor phase as estimated by high-volume sampling. Wind-sector sampling near the city of Green Bay indicated that both the urban area and volatilization from surface waters of the bay are sources of airborne PCBs.

Net Atmospheric Inputs of PCBs to the Ice Cover on Lake Huron

This report describes the first measurements of the net atmospheric deposition of PCBs to the ice cover of a body of water. The net deposition of PCBs includes the wet, dry, and vapor deposition, less any evaporation. The measurements were made on ice cores collected from the frozen surface of Lake Huron late in the ice seasons of 1978 and 1979. Intrusions of lake water into the accumulated deposition layer of ice and snow were not encountered in these studies. Such intrusions, however, have complicated other attempts to use this method. Possible reasons for not encountering them in this study are discussed. For Saginaw Bay, a net deposition rate of 2.0 gm/km2/mo of PCBs to the ice was found for the winters of 1977–1978 and 1978–1979. Upon ice break-up and thaw in the spring, all of the PCBs accumulated on the ice are likely to enter the bay. For inner Saginaw Bay, this would have been 8 kg in March 1978 and 6.5 kg in March 1979.

Contamination of Teflon surfaces by PCBs in the atmosphere

Abstract Collection of a valid precipitation sample involves careful attention to all aspects of the sampling and analysis process. Difficulties in obtaining low field blanks were experienced for a collector used in a project to determine precipitation inputs to Green Bay of Lake Michigan. The cause of high field blanks was found to be PCBs scavenged from the atmosphere and adsorbed on the Teflon™ surface of the sampler. These PCBs were extracted from the collector surface by the methanol used as a rinse solvent. The amounts of PCBs on the surface were found to be a factor of 20–50 higher than the amounts in a typical precipitation sample. After rinsing the Teflon surface several times with methanol, additional PCBs could be obtained by rinsing the surface with hexane or dichloromethane.

Concentrations of Phosphorus in Precipitation in the Lake Michigan Basin

Six locations around Lake Michigan were sampled. While precipitation inputs of phosphorus are not a concentrated input and thus will not cause severe local effects, they are distributed over the surface of the Lake in the euphotic zone, where the effect on the Lake is greatest. 12 references.

BOOK REVIEW: Lake Effect: Two Sisters and a Town's Toxic Legacy . Nancy Nichols. 2008. Island Press, Washington, DC. 192 pp.

edge that, in turn, makes the book much more rich and valuable than could otherwise be the case. This comes out in any one of the 25 twoto three-page Profiles scattered throughout the text. They range from FSC and the Amazon ~Profile 4.3! to the Silicon Valley Toxics Coalition ~Profile 10.3! to Conservation International’s Center for Environmental Leadership in Business ~Profile 12.1!. For each, core individuals were interviewed and their many efforts highlighted. The profiles alone are worth the read.