Polycyclic Aromatic Hydrocarbons Concentration in Straw Biochar with different Particle Size

Biochar, a carbon-rich material formed by a biomass pyrolyzed at relatively low temperatures (≤700 °C), showed attractive sorption capacity on both organic pollutants and heavy metals and wildly used in various areas of environmental engineering. However, polycyclic aromatic hydrocarbons (PAHs) may also be assumed to be produced for the oxygen-limited pyrolysis condition in biochar production process. It is not well known about the affect of particle size in concentration and distributing characteristic of PAHs of biochar. In the current study, twenty-seven PAHs concentration in maize straw biochar produced with different powder particle size (9.31, 20.26, 60.77, 71.07, 101.9 μm) were quantified, and the ∑27PAHs, total LMW PAHs, total MMW PAHs and total HMW PAHs concentration were analyzed. As the particle size increase, the ∑27PAHs concentrations show a trend of firstly increase and then decrease, and the maximum appears at 60.77 μm (166.52 ng/g) and the minimum appears at 101.90 μm (14.63 ng/g). LMW total PAHs and total MMW PAHs concentrations firstly increase and then decrease, with the particle size increasing from 9.31 μm to 101.9 μm. Meanwhile, the total HMW PAH concentrations decrease gradually when biochar particle size increasing. Compared to US, UK background soil concentrations and Canada standards, it is appropriate to conclude that PAHs in straw biochar have minimal effects after application to soil especially at 101.9 μm.