# Preparation and Modification of Biochar Materials and their Application in Soil Remediation
## 4 Application of Biochar in Soil Remediation
### Removal of Persistent Organic Pollutants (POPs)  
The persistent organochlorine pesticides in farmland soils in are still seriously polluted, and the polycyclic aromatic hydrocarbon pollution caused by sewage irrigation cannot be ignored. Biochar has a strong adsorption capacity for organic pollutants, and the process can be understood as the accumulation and collection of organic pollutants on biochar. Table 6 shows the research on the removal of POPs from soil by using biochar in the past two years.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Raw Material** & **Tested Soil** & **Pollutants** & **Remediation Effect** & **Reference** \\ \hline Fir wood chips & rice soil & 2,4-dichlorophenol, phenanthrene & Reduced the degradation and mineralization of both pollutants. Increased the accumulation of their metabolites in soil. & [118] \\ Mixed wood shavings & loamy & Pyrene, polychlorinated biphenyl and dichroaldehydeiphenyl/globicrobialyhene & At the biochar dose of 10\%, bioavailability and accessibility by 37\% and 41\%, respectively, compared to unamended soil. & [119] \\ Rice husk & agricultural soil & (DD) & Oxylhord degraded faster in biochar amended soil than in unamended soil. & [120] \\ Rice hull & loamy clay, sandy & oxyfluor & Bixhord decreased the oxyfluor uptake by soybean plants by 18-63\%, and the adsorption capacity of oxyfluor by soybean decreased. & [121] \\ Orbhard pruning biomass & vineyard & PAHs & Change resulted more intense for light PAHs. The soil properties (TOC, pH, GGC, bulk density) were modified after two consecutive applications & [121] \\ Corn straw and bamboo & soil contaminated & PAHs & The locustation of PAHs in rice tow was reduced, especially high molecular weight PAHs. The total and bioavailable concentration of PAHs in the soil treated with exons straw biochar were both lower than that of the control group. & [100] \\ Corn straw and bamboo & with PAHs & PAHs & \\ \hline \end{tabular}
\end{table}
Table 6: Study on the application of biochar to remove persistent organic pollutants (POPs) in soil.  
[PERSON] et al. [122] studied the removal effect of PAHs in soil by microwave, CO\({}_{2}\), and H\({}_{2}\)O activation of willow biochar. The results showed that the biochar samples with the best effect after activation reduced the concentration of PAHs dissolved in the coal plant soil (near cooking plant battery) and bitumen plant soil from 153 to 22 ng/L and 174 to 24 ng/L, respectively, and the PAHs concentration decreased by 86%. The concentration of PAHs dissolved in the asphalt soil (from an industrial waste deposit) decreased from 52 to 16 ng/L, and bioacceptable PAHs reduced to almost zero. [PERSON] et al. [123] applied biochar from corn straw and pig manure to black soil containing thiazolprid, and explored the adsorption and degradation process of thiazolprid. The results showed that the biochar changed the microbial community of soil by changing the physicochemical properties of the soil, thus promoting the biodegradation of thiazolprid.  
In general, biochar can enhance the adsorption capacity of soil for organic pollutants, reduce their activities of desorption and flow in the soil, and bioavailability in soil pore water, provide essential nutrients to improve soil microbial activity, and improve soil physical and chemical properties, etc. [124].