Environmental▼News chemicals used as surfactants and stain protectors, in an effort to obtain monitoring data that could lead to sources. “We’ve found telomer alcohols in the atmosphere, and we’ve shown that the alcohols persist long enough to make it to the Arctic,” says Mabury, referring to research published in September (Environ. Sci. Technol. 2003, 37, 312A). “We’ve hypothesized that PFCAs are among the breakdown products, and we’ve found them—although we haven’t yet proved the link,” he says. The Canadian scientists found low (nanogram-per-gram) levels of PFCAs with molecules containing
9–15 carbon atoms in samples of many different Arctic animals that were collected by subsistence hunters and trappers. Total PFCA concentrations were about 3–20fold lower than total PFOS concentrations for all animals except mink. Mammals feeding at higher trophic levels had greater concentrations of PFCAs than did those at lower positions. “The information about carboxylic acids provides a new avenue to explore the sources of these compounds to the Arctic,” says toxicologist Kannan Kurunthachalam at the University of New York, Albany. —REBECCA RENNER
With levels of atmospheric mercury in 1998 and found no significant instill rising, it would surprise no one crease compared to yellowfins of if concentrations of the neurotoxin similar weight hooked in 1971, even in big, long-lived carnivorous fish, though the team’s model predicted like tuna, are also on the increase. a 9–26% increase in inorganic merBut for one Pacific tuna population, cury in the surface mixed layer over levels of organic methylmercury the 27-year interval. If mercury in (MeHg ) are the same as they were the ocean’s upper levels were the 30 years ago, according to a study by Princeton geochemist François Morel and his colleagues that was published in the December 15 issue of ES&T (Environ. Sci. Technol. 2003, 37, 5551–5558). Morel’s group believes that the steady levels point to a source of MeHg production in the deep ocean, where mercury concentrations respond very slowly to changes from atmospheric mercury Mercury levels in Pacific tuna are lower than expected. deposition. Other scientists with expertise in mercury accumulation desubstrate for MeHg production, scribe the work as provocative but there should have been a concomiremain skeptical of the Morel tant increase in the compound in group’s explanation. They note that tuna. Mercury cycling is extraordiorganic mercury concentrations narily complex, says Morel, but “the change with time in seabirds. tuna cut through the noise and preFishing has also altered oceanic sents a surprisingly clear picture.” food webs in ways that could signifWhat’s known about mercury’s icantly affect MeHg accumulation route from air to water to fish in highly fished species like tuna, comes largely from work on freshaccording to fisheries biologist water systems. In lakes, it is James Wiener at the University of thought that anaerobic sulfateWisconsin in La Crosse. reducing bacteria in the sediments Morel’s team measured mercury synthesize MeHg. Other factors in yellowfin tuna caught off Hawaii play a role, but the methylation
rate is related to the total concentration of mercury in the water column. Mercury concentrations in freshwater fish have indeed changed as deposition rates have varied. Biologists assumed that the same mechanism holds true for the ocean, with anaerobic bacteria probably involved at depths of about one kilometer. At this depth, which represents the base of the surface layer, oxygen is at a minimum. However, if the same mechanism held, tuna caught recently should have more MeHg than those caught years ago, says Morel. Instead, Morel’s team thinks that the deep ocean must be the MeHg source. Hydrothermal vents, which host sulfate-reducing bacteria and are likely to have high concentrations of mercury, are attractive candidates, they believe. “They have an interesting idea about the source of methylmercury in the oceans, but it must be tempered with caveats concerning other possible explanations,” such as whether these tuna give a representative picture, uncertainties in modeling, and effects of fishing on ocean food webs, says biogeochemist Cynthia Gilmour at the Academy of Natural Sciences’ Estuarine Research Center in southern Maryland. —REBECCA RENNER
Where is the mercury?
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risks to children (Eniviron. Sci. Technol. 2003, 37, 201A). Although there are no PFCA sources in the Arctic and the carboxylates are too nonvolatile to undergo long-range transport, Mabury, Jonathan Martin (also of the University of Toronto), and colleagues looked for long-chain PFCAs because they hypothesized that such compounds are the likely breakdown products of more volatile precursors (telomer alcohols). EPA has been conducting public meetings since April to negotiate binding consent agreements with manufacturers of telomer alcohols, which are precursors for
