Environmental significance of heavy metal deposition records in the last 100 years in the southern Bohai Strait

A sediment core was collected in the southern Bohai Strait. The particle size, radioactive dating of ²¹⁰Pb and ¹³⁷Cs, and contents of the heavy metals were measured on the sediment samples. In addition, the geoaccumulation index and potential ecological risk index were used to evaluate the contamination history of heavy metals in the study area in the past 100 years. Results indicate that the average sedimentation rate was 0.505 cm/a, the contents of heavy metals and the grain size show a similar trend in vertical direction and a certain grain size effect. The geoaccumulation index indicates that the heavy metals pollution degree was low in the study area, while the potential ecological risk index indicates that the pollution of heavy metals was in the middle potential ecological risk in the study area in a significant decreasing trend since 2013. The heavy metal depotition record could be divided into three stages. From 1897 to 1977 was the stage of slow economic development, during which the heavy metal contamination was low. From 1977 to 2001 was the stage of rapid economic development due to China’s reform and opening-up, during which environmental problems was prominent. From 2001 to 2021 was the stage of economic development and environmental protection, during which the contamination of heavy metals was controlled by the combined effects of sedimentary environment and human activities.