# Biochar Amended Soils and Water Systems: Investigation of Physical and Structural Properties
## 3 Results and Discussion
### Specific Surface Area (BET-SSA)  
Values of total specific surface area (BET-SSA), obtained per Equation (11) for the loamy sand, for the loam and for the clay soils and for the soils amended with BC was also considered (Table 6).  
The BET-SSA (m\({}^{2}\)/g) obtained for the loamy sand, for the loam and for the clay increased with the increasing clay percentage and decreasing size of particles, with values equal to 1.19, 4.6 and 32.89, respectively. The BET-SSA values of the non-amended soils were consistent with ranges of specific surface areas for soils belonging to different textural classes [51] and showed a satisfactory agreement with the BET-SSA values reported by [PERSON] and [PERSON] [56] for soils with different textures. The BET-SSA obtained for the sole BC was equal to 280.7 m\({}^{2}\)/g, agreed with that reported by [PERSON] et al. [57] for one of their considered BC, and was close to that (244.0 m\({}^{2}\)/g) measured by [PERSON] and [PERSON] [58]. The SSA obtained by the BET analysis can be considered reliable, because the technique seems capable of yielding sensible estimates of SSA when applied to nitrogen sorption by systems in which there are few micropores, i.e., \(<\)0.002 um [59]. These micropores are out of the range of pore diameters explored in the soil water retention, as matric potentials lower than \(-\)15 bar (wilting point) are not considered.  
The BET-SSA (m\({}^{2}\)/g) increased for the three BC amended soils up to 18.1, 22.5 and 51.4, becoming 15.2, 4.8 and 1.6 times higher than those measured in the original loamy sand, loam and clay soils, respectively. These results demonstrated that in terms of specific surface area, the highest effect of BC was detected on the loamy sand, and the minimum effect was on the clay, with the loam in between. Increases in the BET-SSA due to BC addition to a fine sand and to a sandy loam were also reported by [PERSON] and [PERSON] [47].  
These results were consistent with those obtained in terms of aggregate stability and of water retention, which indicated an improvement due to BC addition in the order sandy loam > loam> clay. However, an increase in the BET-SSA, although slighter than that in the loamy sand and in loam, was observed in the clay soil that was consistent with the increase in the PAW. Figure 2 shows the tendency of the PAW to increase at increasing BET-SSA. Although referred to different textured soils and to different measurement techniques, a dependency can be recognized between the measured PAW and the measured total BET-SAA, as previously found by [PERSON] et al. [31] for a desert sandy soil.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Parameter** & **Loamy Sand** & **Loamy Sand + BC** & **Loam** & **Loam + BC** & **Clay** & **Clay + BC** \\ \hline BET-SSA (m\({}^{2}\)/g) & 1.19 \(\pm\) 0.02 & 18.1 \(\pm\) 0.23 & 4.6 \(\pm\) 0.55 & 22.25 \(\pm\) 1.3 & 32.89 \(\pm\) 1.5 & 51.48 \(\pm\) 1.67 \\ \hline \hline \end{tabular}
\end{table}
Table 6: BET Specific surface Area (BET-SSA) of the three considered soils amended and not amended with biochar.