Particulate and dissolved Pb-210 activities in the shelf and slope regions of the Gulf of Mexico waters
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Concentration profiles of dissolved and particulate 210Pb were measured on horizontal transects of the continental shelf and slope regions of the Gulf of Mexico. Vertical profiles in the slope station in the presence and absence of warm-core ring enable us to evaluate the differences in the scavenging intensity of 210Pb. A comparison of the rate of production of 210Pb in the overlying water column to that of its mean annual flux calculated from the sediment inventory allows us to get a better insight in to the lateral transport and deposition of 210Pb to the slope sediments over a < 100 year time scale. Our results indicate that there is no general increase of dissolved or particulate 210Pb concentration with depth. The scavenging residence time of 210Pb for the entire 1500-m water column varied between 0.06 and 4.7 years. There was a strong correlation between the inventory of total (dissolved + particulate) 210Pb and depth of the water column. The ratio of measured sediment inventory (F) of 210Pb to its production (P) in the overlying water column varied between 0.69 and 1.63, suggesting that, at time, lateral inputs from boundary scavenging in a few sites are dominant, while in other places, vertical scavenging is the primary mechanism of transport for 210Pb. 2002 Elsevier Science Ltd. All rights reserved.
