An assessment of the effect of chemical scavenging within submarine hydrothermal plumes upon ocean geochemistry Article

Kadko, D. (1993). An assessment of the effect of chemical scavenging within submarine hydrothermal plumes upon ocean geochemistry . EARTH AND PLANETARY SCIENCE LETTERS, 120(3-4), 361-374. 10.1016/0012-821X(93)90250-D

cited authors

  • Kadko, D

authors

abstract

  • Profiles of 210Pb over the Endeavour and North Cleft Segments of the Juan de Fuca Ridge are used to model a time scale for the scavenging, by hydrothermal plumes, of reactive elements in seawater. The hydrothermal plumes above these ridge segments are sites of intense scavenging removal of 210Pb. At Endeavour, the total 210Pb activities within the plume are as low as 8 dpm/100 l and dissolved activities are as low as 3 dpm/100 l. At the North Cleft, which is characterized by higher particulate Fe concentrations, the total 210Pb activities are 4.5 dpm/100 l, the dissolved activities are 1-2 dpm/100 l and the 210Pb activities are deficient with respect to the activity of the 210Po daughter. These are perhaps the lowest 210Pb activities ever measured in the deep sea. The large gradient of 210Pb between the plume and surrounding deep water suggests that scavenging is focused into the plumes through horizontal transport. The implication, therefore, is that this process might impact the ocean on a scale larger than that local to the ridge crest. By coupling published measurements of particle flux from Endeavour with 210Pb activities on particles trapped at that site, the total volume of seawater stripped of 210Pb per year for that site was calculated to be 7.4 × 1012 l/y. Globally, the extrapolated volume flux of seawater stripped of reactive constituents is 5.7 × 1015 l/y, such that the entire ocean is processed in this manner in 2.4×105 y. The geochemical cycle of elements with ocean residence times much shorter than this (e.g., Pb and Th) will not be greatly affected by hydrothermal scavenging. On the other hand, this process holds significance for the geochemistry of other elements scavenged by hydrothermal plumes, such as P and V, whose ocean residence times are > 104 y. © 1993.

publication date

  • January 1, 1993

published in

Digital Object Identifier (DOI)

start page

  • 361

end page

  • 374

volume

  • 120

issue

  • 3-4