Timing the increase in atmospheric sulphur deposition in the Adirondack Mountains

Abstract

The timing and magnitude of increases in the flux of atmospherically-derived anthropogenic substances to remote areas can be estimated from their distributions in lake sediments. For transition metals^1–4 or trace organics^5–7, this is done simply by comparing their distributions with that of geochronological tracers. This approach is not directly applicable to species which exhibit significant post-depositional mobility. Diagenetic mobilization must be assessed from the distribution of the species in the sediment pore waters. However, by using this and related information, loading histories can be calculated. We have done this for sulphate, the major anionic component of modern precipitation^8–11, for a watershed located in the Adirondack Mountains of New York State. Our results suggest that previous estimates for the onset of increased sulphur deposition in eastern North America^12,13 are too old by a factor of about two, and that significant increases did not occur until about 1930.