Changing atmospheric fallout of magnetic particles recorded in recent ombrotrophic peat sections.

Magnetic measurements of ombrotrophic peat allow a reconstruction of changes in the past fallout of magnetic particles through the atmosphere. In recent peat profiles from three sites in Britain and Northern Ireland, a marked increase in saturated isothermal remanent magnetization of the peat is recorded in levels which can be shown to postdate the onset of the Industrial Revolution. Furthermore the spatial variation in contemporary isothermal remanent magnetization values is consistent with a recent industrial and urban origin for the bulk of the magnetic minerals present. Pre-Industrial Revolution values are between two and three orders of magnitude lower, suggesting that the natural cosmic and terrestrial sources previously cited for such material have been dominated in recent times by the products of human activity. Magnetic measurements provide a simple, rapid, and nondestructive method of monitoring and differentiating various types of particulate atmospheric fallout for both recent and preindustrial times.