Environmental ▼News Clear-cutting increases mercury in runoff esearchers have found signifiing,” says Porvari. Although the reenhanced methylation following cant increases in total and searchers only have data for three clear-cutting and soil treatment, methyl mercury in runoff from years following clear-cutting, their particularly in the spring when a forested watershed following data suggest that levels of mercury snow melts and forms small pools clear-cutting of the trees and subsein runoff remain high for several of water in the catchment area. quent soil treatment. The findings, years. Total mercury levels in runoff Other researchers have previously which are reported in this issue of reached a maximum (27.9 ng/L) the shown that mercury methylation is ES&T (pp 2389–2393), suggest that, first and second years after clearenhanced in catchments containing even several years after they have cutting, but levels remained quite wetlands, and the amount of methyceased, forestry practices conhigh even in the third year. lation that occurs depends on the tribute a substantial type of wetlands amount of toxic mer(Environ. Sci. Technol. cury to runoff, which 1996, 30, 2719–2729). eventually makes its In all samples anaway into lakes and fish. lyzed by Porvari and colBoreal forest soils efleagues, total mercury ficiently accumulate was correlated with total mercury from the atmosorganic carbon, indicatphere, which is primarily ing that the mercury was of anthropogenic origin, bound to organic matter. but there have been few Clear-cutting has been reports about the factors shown to increase the controlling the mobility leaching of nutrients of mercury in soils. and organic matter into Petri Porvari, a docrunoff, but this is the toral student at the first time researchers Researchers have shown that clear-cutting followed by soil treatUniversity of Helsinki in have shown the connecment increases the levels of total and methyl mercury in runoff from Finland, along with tion between clear-cutforest catchments. Matti Verta and Merja ting and increased Haapanen of the Finnish Methyl mercury, on the other mercury in runoff. Researchers in Environment Institute and John hand, showed a more delayed reQuebec, Canada, have reported inMunthe at IVL Swedish Environsponse and didn’t reach its peak creased levels of methyl mercury in mental Research Institute, analyzed (3.6 ng/L) until the second year. fish in lakes with partially clear-cut runoff samples from a small spruce “That is the most interesting part of watersheds, although they did not catchment in southern Finland for the study,” says Porvari. “It seems investigate forestry practices as the total mercury, methyl mercury, and that the effect of increased methysource. total organic carbon. Samples were lation comes later, probably due to Mercury runoff from forested taken from an area where trees had the conditions in the soil,” he says. catchments can be more significant been clear-cut. One year after clearClear-cutting decreases the than atmospheric deposition to cutting, the soil was treated to proamount of evapotranspiration from lakes. “It depends entirely on the mote the growth of newly planted the forest and therefore increases the watershed area-to-lake area ratio,” trees by a process called mounding, amount of water in the watershed. says Steve Lindberg of Oak Ridge in which the soil is turned over with “The soil becomes saturated, and soil National Laboratory, whose work a large plow into raised mounds so that was formally aerobic becomes has focused primarily on atmosthat it is drier and warmer. anaerobic,” says David Grigal, an pheric mercury. “If you have an inConcentrations of total and emeritus professor at the University creasingly larger ratio, then runoff methyl mercury in the runoff were of Minnesota’s Department of Soil, becomes relatively more important significantly higher after clear-cutWater, and Climate. Those are just compared to atmospheric depositing, as well as after the soil treatthe conditions needed for the bactetion. If you have a watershed and ment process. “Interestingly, the ria that methylate mercury to thrive. a lake with the same surface area, effects appear to be quite long lastPorvari and colleagues observed then the atmosphere, even under PETRI PORVARI
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catchment runoff and 0.12 g/yr would enter it from atmospheric deposition. Whether the mercury in the runoff is newly deposited mercury, which has been shown to be more bioavailable than older mercury, or mercury that has been locked up in the soil for many years, is difficult to determine. “You have atmospheric deposition accumulating in these pools, and you’ve also got old mercury that’s been sitting in the pools. I think it’d be pretty tough to separate the two out without using isotopes,” says Lindberg. —BRITT E. ERICKSON
Concerns over common perfluorinated surfactant
RACHEL PETKEWICH
Perfluorooctanoic acid (PFOA), a perfluorinated surfactant produced in the United States by DuPont and used in the manufacture of Teflon, Goretex, and stain-resistant carpets, may pose a developmental risk to children at concentrations already found in the blood of women and children, according to a U.S. EPA preliminary risk assessment released on April 14. “The data before us raise concerns,” according to Steve Johnson, EPA’s Office of Pollution Prevention and Toxics assistant administrator, who announced that the agency is accelerating its investigation of
A perfluorinated surfactant used to make Teflon could pose a risk to children.
PFOA because of the analysis. The agency is also taking the unusual step of publicly negotiating enforceable consent agreements with the manufacturers and users to require research and reduce PFOA emissions. But the agency is not considering emergency action at this time because there is too much “scientific uncertainty” about the sources and pathways of PFOA exposure in the general population and too much uncertainty about the animal testing data, he said. PFOA, sometimes referred to as C-8, has widespread applications in chemical manufacturing, aircraft production processes, and some electronic products. Following the unexpected discoveries concerning the environmental fate and toxicity of perfluorooctane sulfonates (PFOS) (Environ. Sci. Technol. 2001, 35, 154A–160A), EPA began investigating PFOA. PFOA is a persistent pollutant and small concentrations are found in human blood, according to the risk assessment. Unlike PFOS, PFOA does not appear to biomagnify in animals. However, an ongoing, five-year study of nine retired 3M workers suggests a mean serum
News Briefs Public buses in Iceland fill up on hydrogen The world’s first public hydrogen fueling station opened for business in Reykjavik, Iceland, on April 24. The new station, which was produced collaboratively by Icelandic New Energy, Ltd., Daimler-Chrysler, and Shell, is a milestone toward Iceland’s goal to create the world’s first hydrogen economy. The station services three hydrogen fuel cell-powered buses running regular routes throughout the city. The buses fill up on compressed hydrogen gas produced by on-site electrolysis of tap water. The electricity required for this reaction is obtained from renewable, geothermal energy, which is widespread throughout the country.
Cleaning up snowmobiles By designing a well-performing snowmobile with lower emissions, less noise, and improved fuel economy, University of Idaho students won the annual Society of Automotive Engineers’ (SAE) Clean Snowmobile Challenge for the second year in a row. Held at Michigan Technological University in March, the contest drew students from 12 universities across the country to reengineer existing snowmobiles, which are notorious polluters. “The engineering challenge lies in the fact that teams are also judged on how well [the snowmobiles] perform and how much fun they are to ride,” according to the SAE. Idaho’s four-stroke engine-powered design placed first in the emissions, noise, and fuel economy categories. Other schools won the handling, braking, and acceleration categories. For more information about the contest, visit www.sae.org/students/snow.htm.
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these accelerated input rates [due to clear-cutting and soil treatment], would still dominate,” he says. Methyl mercury is a different story. “Methyl mercury is generally on the order of 1% [of the total mercury] in atmospheric deposition,” says Lindberg. As a result, the watershed area-to-lake area ratio can be much smaller and the contribution of methyl mercury from runoff will still dominate. According to Porvari, for a hypothetical forest lake with an area of 1 km2 and a catchment area of 10 km2, approximately 0.2 g/yr of methyl mercury would enter the lake from the
