Heavy metal deposition and its impact on ecological environment in Sanduao Bay of Fujian Province during the past century under the influence of human activities

Heavy metals are difficult to be biodegraded, meanwhile easy to form toxic environmental factors. The evolution of heavy metals pollution in sediments is a common global ecological environmental problem since industrialization. To reveal the relationship between human activities and heavy metals deposition in Sanduao Bay of Fujian Province, 6 sediment cores were collected in the Bay for grain size testing, ²¹⁰Pb dating and assay of Cu, Pb, Zn, Cr, As, Cd and Hg contents. The results show that over the past century, heavy metal contents in sediments of Sanduao Bay exhibit a significant increase trend. The top is 1.01-2.8 times higher than the bottom, and the evolution process can be divided into three stages, relatively stable period during 1900-1950s, slowly increasing during 1950-2000s, and sharply increasing since the 2000s. Those changes are closely related to population and economic development. The content of heavy metals in landward zone is generally higher than that in seaward zone, and the evolution trend of sediments in landward zone has been different from the sediments in seaward zone since 2000s. The heavy metals content of sediments in landward zone has decreased, while the heavy metals content of sediments in seaward zone has increased sharply in Sanduao Bay. This spatial difference is closely related to the change of grain size and regional industry distribution. Heavy metals have a great impact on the marine ecological environment of Sanduao Bay. As the increasing intensity of fish farming in the Bay, enough attention should be paid to the rapid increase of heavy metal contents in the Bay in recent years, so as to improve the management and remediation to avoid marine ecological damage.