210Polonium and 210lead radionucidles in the Delaware and Chesapeake estuarine and coastal regions
Date
2013
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
One of the primary objectives of this thesis is to present an integrated study
of the 210Pb and 210Po radioactive tracers, and assess their use as tracers for
particle and trace element export from different estuarine and coastal
environments. In order to achieve this main objective, the thesis was split into
three sections, each enhancing the understanding of the natural radionuclides
210Pb and 210Po in the estuarine and costal system.
Chapter 1 is dedicated to testing the sampling and analytical methods of
210Po and 210Pb extraction from estuarine and coastal waters, specifically
comparing the two most widely used scavenging methods, Fe(OH)3 and CoRAPDC.
The chapter describes experiments conducted on about 100 samples collected
from the Delaware estuary, Chesapeake estuary, Delaware intertidal marsh and an
offshore continental slope site. Data in the chapter clarifies the accuracy and
reliability of each method and includes suggestions to enhance them. Other details
include results of calculations, error propagation, spike calibration, plating
efficiency and the MnO2 scavenging method.
Chapter 2 presents a synthesis of the estuarine and coastal
biogeochemistry of 210Po and 210Pb in the Delaware and Chesapeake estuaries. A
single box model is presented using steady state equations to determine residence
times of the radionuclides. This chapter presents five highlights: 1) How 210Pb and
210Po dissolved and particulate data can revel key biogeochemical processes and
rates in estuaries; 2) Are regional differences in estuaries dominated by a single or
compilation of biogeochemical process; 3) Do subRoxic bottom waters affect the
distribution of 210Po and 210Pb; 4) Can disequilibria between parent (210Pb) and
grandRdaughter (210Po) be used to identify and quantify principle processes; 5)
Will a simple mass balance model result in reliable net scavenging residence times
for the Delaware and Chesapeake estuaries.
Chapter 3 will advance the simple single boxRmodel from chapter 2 to a
more complex twoRlayer model. The model will include evaluations of the fate of
not only 210Po and 210Pb in the Delaware and Chesapeake estuaries but also the trace elements Fe, Cu, Cd, Ni, Zn, Pb, Cr, Co and Mn. Residences times, presented as
halfRlives along with rates and partition coefficients will be identified for the water
column including at the sediment water interface.
The thesis will revisit the major conclusions obtained from the work
presented along with suggestions for future work. Appendix sections include
supporting hydrographic data and a compilation of salt marsh trace metal results
conducted in Graz, Austria. Trace metal work included a suite of 26 elements
measured in a core, two species of mussels, Spartina)alterniflora marsh plant and
the sea surface microlayer (SML) from an intertidal Delaware salt marsh.
Description
Keywords
210 Polomium, 210 Lead, Estuarine and Coastal, Radionuclide Tracers