Effect of Pinus radiata derived biochars on soil sorption and desorption of phenanthrene.

Biochars are anthropogenic carbonaceous sorbent and their influences on the sorption of environmental contaminants need to be characterized. Here we evaluated the effect of Pinus radiata derived biochars on soil sorption and desorption of phenanthrene. Two biochars separately produced at 350 degrees C and 700 degrees C and three soils were tested. Biochar amendment generally enhanced the soil sorption of phenanthrene. The biochar produced at 700 degrees C generally showed a greater ability at enhancing a soil's sorption ability than that prepared at 350 degrees C. The single-step desorption measurement showed an apparent hysteresis in biochar-amended soils. After 28 d equilibration, the sorptive capacity of biochar-amended soil (with an organic carbon content of 0.16%) significantly decreased. This study clearly suggested that biochar application enhanced soil sorption of hydrophobic organic compounds, but the magnitude of enhancement depended on the preparation of biochars, the indigenous soil organic carbon levels, and the contact time between soil and biochar.