Fig. 4
Chemical properties of biochar treatments made of sewage sludge, sawdust, and zeolite, content of A nitrogen, B oxygen, C carbon, D hydrogen, E carbon and nitrogen ratio, F hydrogen and carbon ratio, G oxygen and carbon ratio, H concentration of phosphorous in form of phosphate in water leachate of biochar (mg·l−1), I concentration of phosphate in biochar (mg·kg−1), J concentration of 16 priority PAHs according to U.S. EPA (mg·kg−1). Mean ± standard deviation (error bars) calculated from independent values (n = 4), different letters express the statistical differences at significance level p ≤ 0.05