Natural radionuclides Po-210 and Pb-210 in the Delaware and Chesapeake Estuaries: modeling scavenging rates and residence times

作者：Marsan D^*; Rigaud S; Church T

来源：Journal of Environmental Radioactivity, 2014, 138: 447-455.

DOI：10.1016/j.jenvrad.2014.08.014

• (210)po
• (210)pb
• Estuaries
• Redox
• Chesapeake Bay
• Delaware Bay

During the spring and summer months of 2012, Po-210 and Pb-210 activity were measured in the dissolved and particulate phases from the Delaware and upper Chesapeake estuaries. The upper Delaware estuary, near the freshwater end member, was characterized by high-suspended matter concentrations that scavenged dissolved Po-210 and Pb-210. Box models were applied using mass balance calculations to assess the nuclides residence times in each estuary. Only 60% of the dissolved Po-210 and 55% of the dissolved Pb-210 from the Delaware estuary were exported to coastal waters. A large fraction of soluble Po-210 and Pb-210 within the estuary was either reversibly adsorbed onto suspended particles, trapped in sediment accumulation zones (such as intertidal marshes), bioaccumulated into phytoplanlcton and discharged to the coastal ocean. The upper Chesapeake estuary was largely characterized by sub-oxic bottom waters that contained higher concentrations of dissolved Po-210 and Pb-210, hypothesized to be subjected to redox cycling of manganese. The Delaware and Chesapeake estuary mean residence times for Po-210 differed significantly at 86 +/- 7 and 126 +/- 10 days respectively, while they were similar for Pb-210 (67 +/- 6-55 +/- 5 days). The difference in residence times corresponds to the greater extent of biogeochemical scavenging and regeneration processes within the upper Chesapeake.

• 出版日期2014-12