super(210)Pb and super(137)Cs measurements in the Circum Bohai Sea coastal region: sedimentation rates and implications

The representative super(210)Pb and super(137)Cs age-depth profiles were selected from more than 100 sites in the Circum Bohai Sea (CBS) coastal region to examine the sedimentation rates and associated environmental changes. There are three unique super(210)Pb sub(exc) distribution patterns: 1) ideal-decaying type, representing relatively constant sediment supply and quieter environmental setting; 2) wiggling type, but with approximately equivalent amplitude, representing coarser sediments and associated stronger flow current environment; and 3) episodic-eventinfluencing type, each representing typhoon storm-influenced depositional environment. Our results also show that there is a lower sedimentation rate (ca. 0.1 cm/a) in the coastal lowlands, a higher sedimentation rate (ca. 0.5-3 cm/a) in the intertidal flat and an intermediate rate of ca. 0.58 cm/a in the subtidal zone near the Huanghua Harbor. The interbedded silt layer occurring in the core sediment reveals lower super(210)Pb activities, indicating a discontinuous sedimentation mostly due to typhoon events which dwarfs against super(210)Pb and super(137)Cs applicability. Overall, the super(210)Pb and super(137)Cs measurements of the present study provide physical insight into the evaluation of the coastal-marine ecological environment and associated management.