# Insights into PCDD/Fs and PAHs in Biomass Boilers Envisaging Risks of Ash Use as Fertilizers
## 3 Experimental Part
### Results and Discussion
#### 3.2.1 Chemical Composition and PCDD/F in Biomass, Sludge and Soil
In the biomass blends, only OCDD was detected, below 260 ng/kg, except in the case of BFB3 that also contains 1,2,3,4,6,7,8-HpCDD above the detection limit. Interestingly, this biomass blend includes the biomass sample showing the extreme concentrations of heavy metals (Table 4). The PCDD/Fs concentrations found in biomasses are consistent with levels found in natural sinks, for example, 5.4-330 ng/kg in pine needles from rural to higher industrialized areas [234]. Combustion/incineration systems are among the possible emission sources of PCDD/Fs found in soils and vegetation; however, they emit a broad range of PCDD/Fs congeners (preferentially PCDFs) which does not match the environmental profiles enriched in OCDD. [PERSON] and [PERSON] [235] realized that PCDD/Fs sources/deposition mass balances were inconsistent because of excessive OCDD and hepta-PCDD deposition. The excessive OCDD inventory was explained in light of the historical worldwide use of huge quantities of wood preservatives/fungicides containing PCP. In fact, OCDD was a contaminant of PCP preservatives fabrication, thus, it contributed directly to environmental PCDD/Fs sinks, namely soils and vegetation, essentially nearby production plants and application of PCP in agriculture. In addition, deposited PCP volatilizes forming OCDD in the atmosphere water droplets under UV light, spreading contamination all over the world. Notwithstanding PCP pesticide discontinuation, the legacy to the environment contamination is enormous. Still, great concerns on the use of chemicals in soils prevail, since by 2006, about 161 other pesticides were suspected to contain \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Sludge Mix** & **Biomass BFB1** & **Biomass BFB3** & **Biomass BFB4** & **Biomass GF** \\  & **(1\({}^{\circ}\)/2\({}^{\circ}\)-70/30)** & **(\(n\) = 5)** & **(\(n\) = 5)** & **(\(n\) = 4)** & **(\(n\) = 4)** \\ \hline Ash\% & 74 & 2.4–8.3 & 1.5–6.5 & 4.2–10.6 & 4.3–6.7 \\ N\% & 1.29 & 0.22–0.35 & 0.32–0.71 & 0.26–0.43 & 0.22–0.32 \\ S\% & 0.31 & 0.01–0.08 & 0.02–0.07 & 0.03–0.16 & 0.02–0.03 \\ S\%, avg & - & 0.04 & 0.05 & 0.08 & 0.03 \\ Cl\% & 0.60 & 0.08–0.28 & 0.04–0.19 & 0.10–0.12 & 0.15–0.24 \\ Cl\%, avg & - & 0.22 & 0.13 & 0.11 & 0.19 \\ Cu mg/kg & 12 & 3–5 & 3–55 & 6–11 & 6–9 \\ Ni mg/kg & 17 & 2–9 & 1–16 & 17–36 & 2–32 \\ Cr mg/kg & 9 & 9–17 & 2–22 & 28–58 & 21–60 \\ Zn mg/kg & 25 & 7–11 & 10–139 & 17–37 & 11–24 \\ Pb mg/kg & 12 & 1–3 & 1–34 & 2–6 & 2–5 \\ Cd mg/kg & \textless{}3 & \textless{}0.2 & \textless{}0.2–0.3 & \textless{}0.3 & \textless{}0.3 \\ Hg mg/kg & 0.061 & 0.007–0.021 & 0.012–0.030 & 0.012–0.026 & 0.015–0.047 \\ Mn mg/kg & 512 & 172–434 & 70–232 & 145–321 & 361–802 \\ Fe\% & 0.18 & 0.04–0.14 & 0.03–0.33 & 0.08–0.32 & 0.10–0.31 \\ Al\% & 0.49 & 0.07–0.36 & 0.07–0.33 & 0.15–0.70 & 0.20–0.53 \\ Ca\% & 23.2 & 0.34–1.83 & 0.21–0.98 & 0.72–1.56 & 0.58–0.82 \\ Na\% & 0.61 & 0.05–0.21 & 0.03–0.14 & 0.04–0.08 & 0.07/-0.12 \\ K\% & 0.50 & 0.17–0.39 & 0.11–0.34 & 0.28–0.47 & 0.40–0.66 \\ Mg\% & 0.39 & 0.06–0.20 & 0.05–0.12 & 0.12–0.16 & 0.10–0.20 \\ P\% & 0.35 & 0.03–0.07 & 0.02–0.47 & 0.08–0.18 & 0.09–0.13 \\ Si\% & 1.6 & 0.16–1.56 & 0.17–1.07 & 0.59–2.44 & 0.53–1.54 \\ S/Cl ratio & 0.5 & 0.02–1.0 & 0.3–0.6 & 0.2–1.3 & 0.1–0.2 \\ S/Cl ratio, avg & - & 0.29 & 0.4 & 0.7 & 0.1 \\ \hline \hline \end{tabular} Notes: n—number of individual samples analyzed, avg—average.  
\end{table} 
Table 4: Chemical composition of biomass (min–max) and sludge, in dry base. PCDD/Fs [236]. [PERSON] et al. [237] evidenced that OCDD contamination of agricultural soils in Australia is mainly due to the former use of pesticides, in particular PCP, and that resuspension to air and periodic burning of agricultural wastes contribute to disperse OCDD over non-agricultural fields.