Problems with the dating of sediment core using excess Pb in a freshwater system impacted by large scale watershed 210 sediments. Pb dating of freshwater and coastal sediments have been extensively conducted over the past 40 years for historical pollution reconstruction studies, sediment focusing, sediment accumulation and mixing rate determination.
In areas where there is large scale disturbance of sediments and the watershed, the vertical profiles of excess Pb Pbxs could provide erroneous or less reliable information on sediment accumulation rates. We analyzed one sediment core from Hendrix Lake in southwestern Arkansas for excess Pb and Cs. Using the peak Hg activity as a time marker, the obtained sediment accumulation rates agree dating with the Cs-based rates.
Four independent evidences two-marker events based on Cs and two marker events based on Hg mining activity result in about the same sedimentation rates and thus, we endorse earlier suggestion that Pb profile always needs to be validated with at least one another independent method.