Technology M Solutions position patterns, MacLeod notes, the Great Lakes have been a source of atmospheric toxaphene since 1982. To evaluate how contaminants travel fessor at the University of Canada is especially concerned across North America, researchers California−Berkeley’s School of Public about the movement of persistent from two leading institutions have Health. “If the pollutant interacts pollutants into its northernmost redeveloped a continental-scale comwith the vegetation, which a lot of the gions, where the traditional diet of inputer model that incorporates toxic semivolatile [chemicals] do, you can’t digenous peoples exposes them to release data collected by the U.S. and just track the air,” he says, explaining high concentrations of toxins that acCanadian governments and uses geothat water and soil can become very cumulate in body fat, MacLeod says. graphical information systems (GIS) important reservoirs for chemicals. The model can import chemical software to display results as maps. “BETR fills an important niche for release data collected by the U.S. Although it is still in develToxics Release Inventory and opment, the multimedia the Canadian National model has proven capable Pollution Release Inventory. of predicting historical conIt is also capable of accounttamination patterns. ing for diffuse sources of The Berkeley−Trent chemical releases such as (BETR) modelwhose automobiles, phthalate esname reflects its origins at ters from plastics, and solthe U.S. Department of vents from paints. The Energy’s Lawrence Berkeley model is notable for verticalNational Laboratory (LBNL) ly segmenting the atmosand Trent University in phere to include upper and Canadacan draw links belower air currents, as well tween environmental contas for depicting freshwater aminant measurements and separately from coastal long-range transport prewater, MacLeod says. It also dictions. Modeling reincludes equations for desearchers at the Society of scribing flows of contamiEnvironmental Toxicology nants through vegetation, and Chemistry meeting in soil, and sediments. Madrid, Spain, last year, The model calculates the The BETR modeldescribeshow toxaphene,a pesticide thatw ashiswhere BETR was first introfate of contaminants based toricallyused in the southeastern United States,hasspread across duced, identified this capaon their chemical properties North America.The darkerthe area on the map,the higherthe bility as a crucial research and environmental conditoxaphene concentration. need. tions and uses 168 mass BETR is the first model that is demultimedia models,” he concludes. balance equations to measure contatailed enough to depict the fate of MacLeod has used the BETR minant flows inside and between the persistent organic pollutants, which model to simulate the continent-wide ecoregions. It is sufficiently complex can travel on a continental scale for flow of toxaphene, a chlorinated herto allow for bidirectional flow between thousands of miles, and to track the bicide and pesticide historically apecoregions. movement of these chemicals beplied in the southeastern United MacLeod is currently collaborating tween different regions, explains the States. “The model agrees well with with Deborah Bennett of the Harvard model’s principal developer, Matt previous measurements,” he says. It School of Public Health to add MacLeod, a graduate student at correctly predicts that applying the human exposure calculations to Trent’s Canadian Environmental chemical in the Mississippi Delta reBETR’s chemical fate model. “We Modelling Centre. gion will result in atmospheric transshould ultimately be able to use the There are other continental modport and deposition into the Great model to deduce the contribution of els, but they are focused on air transLakes region, where environmental chemical releases in each BETR report patterns of chemicals such as monitoring shows that the chemical gion to the total amount of chemical mercury, says Tom McKone, who continues to accumulate in Great that people are exposed to from enviholds joint appointments as a senior Lakes fish despite sharply curtailed ronmental exposure pathways,” he scientist at LBNL and an adjunct prousage. Because of those historical desays. KELLYN S. BETTS MATT MACLEOD, TRENT UNIVERSITY
Modeling continent-wide contamination
© 2001 American Chemical Society
DECEMBER 1, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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