Accumulation Rates and Chronologies from Depth Profiles of 210Pb in
Sediments of Northern Beibu Gulf, South China Sea
Abstract
Being a complex environment subject to coastal and marine processes,
little is understood concerning the evolution of northern Beibu Gulf and
the human impacts on its ecosystem. Since various environmental
information can be stored in the deposited sediments, it is considered
to be useful tracers for natural and anthropogenic processes. The aim of
this study is to determine a detailed reconstruction of the
sedimentation rates in the past decades by applying the 210Pb dating
method. To achieve this, 3 sediment cores located in different regions
along the coast of northern Beibu Gulf were collected. 226Ra and 210Pb
were measured using gamma spectrometry and age determination was
analyzed by the CRS model. Physical parameters (water content, grain
size and bulk density) and TOC were determined for each core. The
results showed that the average sediment mass accumulation rates (dry
mass) calculated from 210Pb profiles was 0.043-0.008 g cm-2 yr-1in core
of Sanniang Bay and 0.028?0.003 g cm-2 yr-1 in core of Lianzhou Bay.
Sediment mass accumulation rates decreased with increasing water depth.
The sedimentation rate was 0.54 cm/y in Sanniang Bay and 0.38 cm/y in
Lianzhou Bay. Water content and grain size did not change much with age
variation, while TOC showed a general decline during past decades,
probably due to the terrigenous input. This study provides a
chronological framework for comparing the depositional histories and
inventories of various pollutants that have been measured in the same
sediment cores. This information will be useful for resolving scientific
environmental quality and coastal management in northern Beibu Gulf.