Record of the accumulation of sediment and trace metals in a Connecticut, U. S. A. , salt marsh. [Dating deposition of trace metals from polluted air masses

Abstract

The nonlinear rate of accretion of a Connecticut salt marsh during the past century was estimated from the /sup 210/Pb distribution with depth by assuming a constant flux of /sup 210/Pb to the surface. This rate was found to be in general agreement with the smoothed record of relative mean sea level rise measured independently by the New York City tide gage since 1893. The rate of deposition of Mn, Fe, Cu, Zn, Pb and total inorganic matter on the surface of the salt marsh may be calculated from the age and sediment properties measured at small depth increments. Changes in the inorganic matter content are attributed to variations in land use on the watershed since it was cleared for agriculture. Fe, Mn, and inorganic matter are principally derived from stream transport of eroding soil, while the observed increases in the fluxes of Cu, Zn, and Pb are largely explained as increased supply via the atmosphere during the period of industrialization since the Civil War. Salt marshes thus may supply a refined record of the deposition of trace metals from polluted air masses over long periods of time.