Using ²¹⁰Pb measurements to estimate sedimentation rates on river floodplains

Area of Science:

• Environmental Science
• Geomorphology
• Radiochemistry

Background:

• River floodplains are crucial sediment sinks, necessitating accurate sedimentation rate measurements.
• Fallout radionuclides like cesium-137 (¹³⁷Cs) and lead-210 (²¹⁰Pb) show potential for dating recent floodplain sediments.
• Lead-210 (²¹⁰Pb) offers advantages over ¹³⁷Cs, but its application to floodplains requires model refinement.

Purpose of the Study:

• To investigate contemporary overbank sedimentation rates on UK river floodplains.
• To compare the effectiveness of excess ²¹⁰Pb and ¹³⁷Cs in estimating sedimentation rates.
• To evaluate different models for interpreting excess ²¹⁰Pb data in floodplain environments.

Main Methods:

• Collected sediment cores from seven diverse UK river floodplain sites.
• Measured excess ²¹⁰Pb and ¹³⁷Cs activity in sediment samples.
• Applied and compared various models (e.g., CICCS, Composite CRS) to estimate sedimentation rates using ²¹⁰Pb data.
• Utilized ¹³⁷Cs measurements for independent validation of ²¹⁰Pb-derived rates.

Main Results:

• Sedimentation rates were estimated using both ¹³⁷Cs and excess ²¹⁰Pb.
• A reasonable consistency was observed between ¹³⁷Cs and ²¹⁰Pb estimates, but model-dependent differences were noted.
• The CICCS and Composite CRS models, when using excess ²¹⁰Pb, generally provided the most reliable sedimentation rate estimates, validated by ¹³⁷Cs.

Conclusions:

• Excess ²¹⁰Pb is a viable tool for dating floodplain sediments, but model selection is critical.
• ¹³⁷Cs serves as a valuable independent marker for validating sedimentation rate models.
• The CICCS and Composite CRS models are recommended for estimating medium-term sedimentation rates on river floodplains using excess ²¹⁰Pb.