Xiaolong Shao

Influence of early diagenesis on the vertical distribution of metal forms in sediments of Bohai Bay, China

The influence of early diagenesis on the vertical distribution of metal forms in the sediments of Bohai Bay was discussed in this paper. The results showed that the concentrations were: Al > Fe ≈ Ca > Mn > Cr > Zn > Cu > Pb > Cd. In vertical distribution, the forms of Cr and Pb were stable from the top to the bottom. However, the exchangeable forms and acid-extracted forms of Cd, Cu and Zn presented an obvious declining trend. The metals would be transformed to more stable forms during the early-diagenesis process. Further analysis found that early diagenesis can change the sedimentary environment, affecting pH, oxidation-reduction potential (ORP), total dissolved solid (TDS) and the structure of organic matter (OM), all main factors influencing metal forms in the sediments of Bohai Bay.

Temporal variation of sedimentation rates and potential factors influencing those rates over the last 100 years in Bohai Bay, China

Fourteen sediment cores were collected from Bohai Bay, China, which is close to the fast-developing megacities such as Beijing and Tianjin, and dated using excess Pb-210 and Cs-137. Using the constant rate of supply model (CRS), the temporal variation of sedimentation rates over the last 100years in Bohai Bay was determined, and its main factors influencing sedimentation rates were discussed. The sedimentation rates before 1980 were relatively stable, ranging from 0.26±0.04g/(cm2·y) in 1920 to 0.39±0.08g/(cm2·y) in 1980. A gradual increase in sedimentation rate was found from 0.39±0.08g/(cm2·y) in 1980 to 0.84±0.13g/(cm2·y) in 2010. Riverine input was the main factors influencing sedimentation rates in Bohai Bay before 1980. After 1980, the accelerated increase in sedimentation rate may be attributed to the large-scale reclamation along the coastline. It is worth noting that eutrophication caused by an increase in sewage discharge and overuse of chemical fertilizer, also may influence recent acceleration in sedimentation rate.