RESUMO
Helium is a powerful tracer of primitive material in Earth's mantle. Extremely high (3)He/(4)He ratios in some ocean-island basalts suggest the presence of relatively undegassed and undifferentiated material preserved in Earth's mantle. However, terrestrial lavas with high (3)He/(4)He ratios have never been observed to host the primitive lead-isotopic compositions that are required for an early (roughly 4.5 Gyr ago) formation age. Here we show that Cenozoic-era Baffin Island and West Greenland lavas, previously found to host the highest terrestrial-mantle (3)He/(4)He ratios, exhibit primitive lead-isotope ratios that are consistent with an ancient mantle source age of 4.55-4.45 Gyr. The Baffin Island and West Greenland lavas also exhibit (143)Nd/(144)Nd ratios similar to values recently proposed for an early-formed (roughly 4.5 Gyr ago) terrestrial mantle reservoir. The combined helium-, lead- and Nd-isotopic compositions in Baffin Island and West Greenland lavas therefore suggest that their source is the most ancient accessible reservoir in the Earth's mantle, and it may be parental to all mantle reservoirs that give rise to modern volcanism.
RESUMO
The Joint Environment and Human Health (E&HH) Programme has explored how both man-made and natural changes to the environment can influence human health. Scientists have tackled the complicated mix of environmental, social and economic factors that influence health, particularly focusing on naturally occurring toxins, man-made pollutants, nanoparticles and pathogens to see:* how they spread within the environment* how their properties change as they interact with other substances or organisms* how we become exposed to them, and* their impact on human health.The Programme has not only succeeded in bringing together scientists from a broad range of environmental, social and biomedical backgrounds, but also fostered new relationships with end users and policy makers. This new community is helping to provide the multidisciplinary capacity able to respond in an interdisciplinary way to resolve problems that are intrinsically interfacial in character. Many of these questions relate to complex issues such as the environmental biology and geochemistry of soils and how these influence the transport, accessibility and bioavailability of chemical pollutants and infectivity of pathogens. The dispersion of harmful particles in the atmosphere is another area of major concern where the E&HH Programme has broken new ground by showing how the chemical and physical properties of such particles influence their environmental behaviour and may govern their toxicity and resultant pathological reactions induced following inhalation. Working groups and networks have identified potential health problems concerning the transport and emergence of human pathogens associated with food, soil, air and water. The consequence(s) of global and regional climate change for the environmental behaviours of pollutants and pathogens have been considered by a number of the projects supported by the E&HH programme.The selection of articles in this supplement reflect the broad scope of the E&HH programme. By effectively identifying and interconnecting these interdisciplinary elements, the E&HH programme has fostered the emergence of new ways of solving problems in areas of research that have, until recently, had little connection with one another. This has not only helped build new research groupings, but has also led to exciting new scientific developments as described in this issue of Environmental Health.
