Designing Biochars for in Situ Remediation of Metal Contaminated Mine Spoils.

Biochar in conjunction with other soil amendments can be used for in situ remediation of metal-contaminated mine spoils for improved site phytostabilization. For successful phytostabilization to occur, biochar must improve mine spoil health with respect to plant rooting plus uptake of water and nutrients. An inappropriate biochar may negatively impact plant growth conditions resulting in poor plant establishment and growth. Matching the appropriate biochar for each mine site requires reconnaissance of spoil chemical and physical conditions and then identifying which properties need rectified to promote plant growth. A rectification hierarchy needs to be established with the primary limiting factor being addressed first, then successive limitations addressed simultaneously or thereafter. We posit that spoils at each site will have a unique chemical, physical, and biological signature that will affect plant growth. Quantifying these and other conditions beforehand allows for the production of designer biochar with specific characteristics tailored for specific plant growth deficiencies within each spoil. Additionally, we recommend the use of proximally located, undisturbed soils to establish spoil remediation targets. In our work, we have developed a decision-tree flow-chart that identifies salient chemical, physical and microbial characteristics needed for plant growth. Combined with our knowledge of site conditions, we can then design a biochar best suited for site-specific remediation. We also propose a framework for monitoring changes in soil conditions and health and plot their progress to gauge their improvement.