Study on enzymatic activities and behaviors of heavy metal in sediment–plant at muddy tidal flat in Yangtze Estuary

Rhizosphere sediments and plant samples were collected at five sites in a muddy tidal flat of Yangtze Estuary. The enzymatic activities and heavy metal concentrations in the sediment–plant system of the muddy tidal flat were analyzed. The results indicated that in muddy tidal plants, Cr and Zn were accumulated in roots and more Mn was transported upwards and accumulated in the plant tissues above the ground. The urease activities, content of Active Mn, Active Zn and Active Cu, and the concentration of Zn in the whole plant–sediment system were influenced by OM and EC in the rhizosphere sediment. Enzymatic activities were sensitive to the heavy metals in sediment–plant system of the muddy tidal flat. Urease activities were inhibited by Active Mn and Active Zn. Catalase activities were greatly activated by Active Cr and Active Mn. Acid phosphatase activities could be activated by Active Cr. Alk-pho had positive correlations with Cr in the plant body (R = 0.795, p < 0.01). The activities of urease could be used as an index for the evaluation of Active Mn and Active Zn in the rhizosphere sediment. The activities of alkaline phosphatase could be an effective indicator for the phyto-availability of Cr in sediment–plant system of Yangtze Estuary.