There was once a serious leak of deadly chemicals in the Soviet Union, Mikhail Gorbachev got the people to cut down many trees, they were put in pits, set on fire, and then covered in soil. After five days they had stopped smouldering, and the biochar was put on the spillage, which was soaked up by the fine powder. Apple trees were planted on the top of the spillage and the fruit tested for pollution every year, none got to the trees. Biochar is the way to go in cleaning up the soil from pollutants.