Heavy metal concentrations and enzymatic activities in the functional zone sediments of Haizhou Bay, Lianyungang, Jiangsu, China

Surface sediments were collected at 31 sites covering five functional zones of Haizhou Bay, Lianyungang, Jiangsu, China. Heavy metal concentrations and enzymatic activity of phosphatase and urease were determined on a dry-weight basis of sediments. Metal concentrations in sediments were comparable to the Chinese National Standard of Marine Sediment Quality and were as follows: Cu, 8.60–55.8 mg kg−1; Zn, 107–384 mg kg−1; Pb, 33.6–200 mg kg−1; Cd, 0.24–2.57 mg kg−1; Cr, 30.3–92.1 mg kg−1; As, 12.9–110 mg kg−1; Ni, 15.8–49.6 mg kg−1; Mn, 379–1272 mg kg−1; and Fe, 13,790–38,240 mg kg−1. A geoaccumulation index (Igeo) was calculated to help researchers understand the status of pollutants in the sediments. Igeo showed that Cd and As contamination existed in the study area. The mobility of the metals and the relationship between heavy metal concentrations of chemical fractions and enzymatic activities were also investigated. Results showed that Cd and Mn had higher mobility than other metals, and enzymatic activities may play an important role in controlling the bioavailability and transformation trend of heavy metals from one fraction to another in sediments.