Sediment accumulation rates in Karachi coastal area Pakistan using .sup.210Pb dating method

Sediment accumulation rates and age of sediments were determined using .sup.210Pb dating method by applying constant rate of supply model of six bottom sediment cores, collected from various locations (Rehri Creek, Ghizri Creek, Korangi Creek, Manora Picnic Point, Sandspit and Sunairi Point) of Karachi coastal area of Pakistan. The results showed that an increase in accumulation rate was observed in the recent years in all the sediment cores which may be attributed to human activities and changes in patterns of water circulation. The mean values of sediment accumulation rates varied between 0.43 and 1.45 kg m.sup.-2 y.sup.-1 and the highest accumulation rates were observed in recent sediments of Manora Picnic Point (3.40 kg m.sup.-2 y.sup.-1), Korangi creek (2.88 kg m.sup.-2 y.sup.-1) and Ghizri creek (2.13 kg m.sup.-2 y.sup.-1), which may owe to the anthropogenic inputs (direct discharge of massive amount of industrial and domestic wastewaters into the sea) and addition of sediment loads by river run off during monsoon season. It was also inferred from the study that the bottom most layers of different sediment cores were estimated to be accumulated between 1889 and 1911.