Interactive effects of cadmium and pyrene on contaminant removal from co-contaminated sediment planted with mangrove Kandelia obovata (S., L.) Yong seedlings

- Cd-Pyr co-contamination had prohibitive effects on the growth of K. obovata.
- Pyr increased more Cd remove to plant tissues, increased Cd toxicity to K. obovata.
- Cd toxicity inhibited the degradation of Pyr in co-contaminated sediments.
- Cd toxicity inhibited the growth of microorganisms in sediments treated with Pyr.

The interactive effects of cadmium (Cd) and pyrene (Pyr) on contaminant removal from co-contaminated sediment planted with Kandelia obovata were investigated by a pot experiment. We found that dry weight of plant was significantly decreased under high level of Cd-Pyr combined stress. High Pyr caused the increase of Cd toxicity to K. obovata under high Cd stress because more Cd translocated to the plant tissues. Cd toxicity inhibited Pyr degradation in co-contaminated sediments and higher Pyr degradation was found in the rhizosphere than that in the non-rhizosphere sediment under high Cd treatment. The total number of microorganisms in sediments tended to decrease with increasing Cd under Cd-Pyr combined stress and more amount existed in the rhizosphere sediment. In conclusion, Cd and Pyr removal by K. obovata can influence interactions between these two pollutants in co-contaminated sediment. This suggests that this mangrove can effectively remedy sites co-contaminated with these two types of contamination.