Distribution characteristics of heavy metals in surface sediments and core sediments of the Shenzhen Bay in Guangdong Province,China

The contents of zinc, chromium, cadmium, nickel, lead and copper were measured on both surface sediments and core sediments in the Shenzhen Bay. The average contents of these metals showed that the contents of all the metals have exceeded the background values in the coastal zone of Guangdong Province. cadmium is a heavy pollution matter which indicates a strong pollution level according to the ecological risk coefficient method. The ecological risk index of the whole area is 299 which belongs to middle and strong level. The area with strong pollution level is the nearshore area closing to the inside of Shenzhen Bay, Shakou coast is in the middle level while the weak pollution level occurs in the Shenzhen Estuary according to the ecological risk index. The four sediment cores can be divided into two parts based on lead-210 dating, sediment size analysis and economic development period in surrounding areas with a boundary of 1950. It has been a period with continuous increase of heavy metals since 1950 with strong human intervention. The sediment size, deposition rate and human activities have positive relationship with the contents of heavy metals which directly impact the pollution level of heavy metals in sediments of the Shenzhen Bay.