Modelling of ²¹⁰Pb behaviour in the catchment and sediment of Lake Tali Karng, Victoria, and estimation of recent sedimentation rates.

Abstract

The technique of ²¹⁰Pb dating of sediments over time scales of up to 120 years is described and illustrated by a study of Lake Tali Karng. Results from the study of a sediment core from the deepest part of the lake shows that the flux of unsupported ²¹⁰Pb to the sediment is about 145 mBq cm^-2 year^-1. Over the last 100 years, about 75 cm of sediment has accumulated at an average rate of 150-200 mg cm^-2 year^-1. Calculations using two models to convert ²¹⁰Pb activity-depth profiles to age-depth profiles indicate that the sedimentation rate has increased slightly over the last 100 years. It is estimated that about 14% of the ²¹⁰Pb falling in the catchment reaches the lake sediment, but depending on the assumptions made the possible range is 7-60%.