Sedimentation rate at Setiu lagoon using natural radiotracer 210Pb technique

Abstract

This study was conducted to determine the sedimentation rate of soil at Setiu Lagoon by using natural radiotracer 210Pb. The area covers a 10 km length lagoon involving 5 sampling stations of approximately 2 km apart. The sediment samples were collected using a corer box comprising of a meter long transparent PVC plastic pipe inserted manually into the sediment bed 2 m below the water surface. The sediment core extracted were then cut into several 5 cm interval, labeled and stored in a close beaker. A total of 24 samples were collected from the 5 sampling stations. The measurement of 210Pb activity was made using Hyper Purity Germanium (HPGe). The total activity of 210Pb was measured from gamma ray peak of energy 46.5 keV and supported 210Pb by the weighted average decay of 226Ra daughters at 295, 351 and 609 keV. Unsupported 210Pb was calculated as the difference between the total and the supported 210Pb activity. Two models were used in this study to calculate the sedimentation rate; the Constant Initial Concentration (CIC) and Advection-Diffusion Equation (ADE) model. The results show that, there are differences in sedimentation rate values of each model for each station. The sedimentation rates obtained using CIC model varies from 0.08 to 0.37 cm/yr whereas ADE model varies from 0.43 to 0.93 cm/yr.