Quantification of Po-210 and Pb-210 as tracer of sediment resuspension rate in a shallow riverine system: Case study from southeast Michigan, USA

Abstract

Polonium-210 and Pb-210 were measured in surficial benthic sediments and particulate matter collected in sediment traps deployed at five different locations in the Clinton River, a dynamic system, in Lake St. Clair in Southeast Michigan to quantify the sediment resuspension rates and determine the particle residence time. The mean ²¹⁰Po_xs/²¹⁰Pb_xs activity ratio of suspended trap and surficial bottom sediments were 0.72 ± 0.12 (n = 16, range: 0.42-0.89) and 0.79 ± 0.15 (n = 15, range: 0.40-1.00) indicating that a major fraction of trapped material is from resuspended bottom sediments. Sediment resuspension rate calculated using a single box model approach yielded a resuspension rate of 0.1-1.0 g cm^-2 yr^-1 using ²¹⁰Po and 0.2-1.4 g cm^-2 yr^-1using ²¹⁰Pb. Particle residence time varied from 0.3 to 3.9 days using ²¹⁰Pb and 0.9-13.4 days for ²¹⁰Po. This present study indicates that sediment resuspension is considerably high in Clinton River and thus any decision on remedial action towards the restoration such as dredging, natural attenuation is challenging. This present study has direct relevance to the transport and resuspension of other sulfur group elements (Se, O, etc) and lithogenic elements (e.g., Th).

Keywords: (210)Pb; (210)Po; (210)Po/(210)Pb activity ratio; Sediment resuspension rate.