| SS9.01 Ecosystem Science Practiced in an Urbanized Estuary: South San Francisco Bay |
| Gee, A, K, University of California at Santa Cruz, Santa Cruz, USA, ali@es.ucsc.edu |
| Bruland, K, W, University of California at Santa Cruz, Santa Cruz, USA, bruland@cats.ucsc.edu |
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| A NOVEL APPROACH TO TRACKING EQUILIBRIUM AND KINETIC PARTITIONING OF CADMIUM AND LEAD BETWEEN DISSOLVED AND PARTICULATE FORMS IN SOUTH SAN FRANCISCO BAY, CA |
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| Partition coefficients (KD) for six metals in South Bay vary over three orders of magnitude, with Cd and Pb behaving as end-member metals with respect to sorption. Additions of the low occurrence stable isotopes 106Cd and 204Pb are used as tracers to determine the exchange kinetics of these metals in laboratory studies of natural water and suspended sediments from South Bay. Equilibrium and kinetic sorption parameters are quantified according to a general model for metal partitioning assuming pseudo-first-order kinetics. As a result of the dissolved metal isotope additions, partition coefficients for both metals drop and then increase back to near ambient KD values after two weeks. Curve-fitting concentration versus time profiles from dissolved and exchangeable particulate data sets allows determination of kinetic rate constants. The kinetic results predict that sorption equilibria in South Bay should be reached on the order of a month for Cd and a week for Pb. Metal sorption exchange rates calculated using these kinetic results indicate that sorption exchange between dissolved and suspended particulate phases can cause dynamic internal cycling of these metals in South Bay. |
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