Effects of biochars derived from different pyrolysis temperatures on growth of Vallisneria spiralis and dissipation of polycyclic aromatic hydrocarbons in sediments

sWheat straw biochars produced at 400 and 700 °C (BC400 and BC700) were used to investigate their effects on the growth of Vallisneria spiralis and the dissipation of phenanthrene and pyrene in sediments. Biochar amendment inhibited the growth of V. spiralis to some extent at the end of 54-day experiment, and the inhibition was stronger by BC700 than by BC400. In unplanted sediments, PAH dissipation was significantly retarded by BC400 but slightly increased by BC700 although bioavailable fraction of the contaminants extracted by butanol was more significantly reduced by the addition of BC700. It is possible that the contaminants sorbed to BC700 are still bioavailable to bacteria. Planting V. spiralis significantly enhanced the dissipation of phenanthrene and pyrene in biochar-unamended sediments, but showed only small effect on the dissipation in biochar-amended sediments. Moreover, redox potential was much higher in planted sediments than in unplanted sediments no matter whether the biochars were amended or not, suggesting that oxygen is not the limiting factor for the degradation in biochar-amended sediments.