ResearchMWatch Uncovering hazardous waste landfill threats
An analysis of nitrous oxide (N2O) isotopomers—isotope-containing molecules—in the western North Pacific Ocean has led Japanese scientists to conclude that the ocean is a significant source of N2O, second only to N2O terrestrial production sources. N2O’s known sources are mainly microbial production in soils and water, and human activities, such as fossil fuel combustion. There is still significant uncertainty concerning the estimated magnitude of N2O sources and sinks. Isotopic signatures of N2O are a useful tool for inferring the molecule’s production mechanism and its global budget, say Sakae Toyoda and co-workers at the Tokyo Institute of Technology, the National Institute for Environmental Studies, and the National Institute of Advanced Industrial Science and Technology, all in Japan. For the first time, the researchers measured the intramolecular 15N distribution and nitrogen/oxygen isotope ratios in the western North Pacific Ocean, revealing that the site preference (14N15N16O versus 15N14N16O) for the intramolecular 15N distribution varies widely with ocean depth. This, they say, indicates that there is oceanic subsurface and deepsource mixing of chemical species relevant to the occurrence of N2O isotopomers. Because N2O isotopomers “contain” biogeochemical information about the molecule’s production, consumption, and transportation, they also provide clues about the nature of the N2O production mechanism in the ocean. Further isotopomer investigations, the researchers say, should help refine assessments of the sources and sinks of this important greenhouse gas, which is one of the six gases addressed in the Kyoto Protocol. (Geophys. Res. Lett. 2002, 29 (3), 10.1029/ 2001GL014311)
Children born to mothers living near hazardous waste landfills are 40% more likely to develop chromosomal abnormalities, such as those associated with Down’s syndrome, according to a recent European study. Previously, the study team reported that there is a 33% higher risk of nonchromosomal abnormalities, such as cleft palate.
The environmental group Friends of the Earth used the study to reiterate its calls for immediate government action to reduce landfilling of hazardous wastes by increasing landfill tax rates and setting statutory targets. (Lancet 2002, 359, 320–322)
Ocean circulation slowdown warms waters, slows CO2-to-air inputs PHOTODISC
Oceanic contributions to the atmospheric N2O budget
The team from the London School of Hygiene and Tropical Medicine studied 245 cases of chromosomal anomalies and 2412 healthy individuals (the control group) who lived near 23 landfill sites in Denmark, France, Italy, England, and Belgium. After adjusting for maternal age and socioeconomic status, they found that the risk associated with chromosomal anomalies was 40% higher in those born within 3 km of a site compared with those born 3–7 km away. The study looked at births between 1986 and 1994. Team leader Martine Vrijheid admits that it remains unclear whether these increased risks result from living near a hazardous waste landfill site or from other factors. Most importantly, she says, it is not known how much, if any, exposure mothers had to chemicals from the landfills. Dirk Hazell, chief executive of the United Kingdom’s Environmental Services Association, questions the relevancy of the study, adding that there are superior pools of more recent data from other studies (Environ. Sci. Technol. 2001, 35, 438A–439A). And he stresses that the research, which included eight sites in the United Kingdom, do not demonstrate causality.
Two U.S. scientists report that they have detected a decades-long slowdown in Pacific Ocean currents. The change, they say, affects surface water temperatures and the release of CO2 from seawater, while also having a significant effect on marine ecosystems. Researchers Michael McPhaden of the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle, Wash., and Dongxiao Zhang of the University of Washington, also in Seattle, examined water circulation records for the past 50 years. The data indicate that since the mid-1970s, sea surface temperatures in the tropical Pacific have risen about 0.8 °C, and seawater circulation has decreased about 25% from 47 ⫻ 106 to 35 ⫻ 106 m3/s. The researchers suggest that the circulation changes may be associated with the naturally occurring Pacific Decadal Oscillation and also may be influenced by greenhouse gas buildup. Although available data do not clearly indicate the effect of the latter, what is perhaps of greater interest is understanding the extent to which the circulation changes affect Pacific fisheries. McPhaden and Zhang say it is difficult to assess whether the supply of nutrients to the surface layer of the ocean has decreased from the 1970s to the 1990s, because of a lack of data. The circulation-associated slowdown in CO2 release from ocean water is significant, as the equatorial Pacific is the largest oceanic source of CO2 to the atmosphere. (Nature 2002, 415, 603–608)
APRIL 1, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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