Marsan D, Rigaud S, Church T
School of Marine Science and Policy, University of Delaware, Newark, DE 19716-3501, USA.
J Environ Radioact. 2014 Dec;138:447-55. doi: 10.1016/j.jenvrad.2014.08.014. Epub 2014 Sep 16.
During the spring and summer months of 2012, (210)Po and (210)Pb 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 (210)Po and (210)Pb. Box models were applied using mass balance calculations to assess the nuclides residence times in each estuary. Only 60% of the dissolved (210)Po and 55% of the dissolved (210)Pb from the Delaware estuary were exported to coastal waters. A large fraction of soluble (210)Po and (210)Pb within the estuary was either reversibly adsorbed onto suspended particles, trapped in sediment accumulation zones (such as intertidal marshes), bioaccumulated into phytoplankton and discharged to the coastal ocean. The upper Chesapeake estuary was largely characterized by sub-oxic bottom waters that contained higher concentrations of dissolved (210)Po and (210)Pb, hypothesized to be subjected to redox cycling of manganese. The Delaware and Chesapeake estuary mean residence times for (210)Po differed significantly at 86 ± 7 and 126 ± 10 days respectively, while they were similar for (210)Pb (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.
2012年春夏季节，对特拉华河和切萨皮克湾上游河口的溶解相和颗粒相中钋-210（(^{210})Po）和铅-210（(^{210})Pb）的活度进行了测量。靠近淡水端元的特拉华河上游河口，其特征是悬浮物质浓度高，能清除溶解态的(^{210})Po和(^{210})Pb。利用质量平衡计算应用箱式模型来评估各河口核素的停留时间。特拉华河河口溶解态(^{210})Po中只有60%、溶解态(^{210})Pb中只有55%输出到沿海水域。河口内很大一部分可溶性(^{210})Po和(^{210})Pb要么可逆地吸附在悬浮颗粒上，被困在沉积物堆积区（如潮间带沼泽），生物累积到浮游植物中，然后排放到近岸海洋。切萨皮克湾上游河口的主要特征是底部水处于缺氧状态，其中溶解态(^{210})Po和(^{210})Pb浓度较高，据推测这与锰的氧化还原循环有关。(^{210})Po在特拉华河和切萨皮克湾河口的平均停留时间分别为86±7天和126±10天，二者差异显著，而(^{210})Pb的平均停留时间相似（67±6 - 55±5天）。停留时间的差异对应于切萨皮克湾上游生物地球化学清除和再生过程的更大程度。
