Biochar is effective in reducing heavy metals in soil and plants, but its long-term effectiveness is not well understood. Research shows that biochar can immobilize heavy metals for 2-3 years, but this effect may decrease over time. Factors like acid rain, soil conditions, and biotic factors can weaken biochar's effectiveness. More field experiments are needed to study biochar's long-term effects and develop more stable forms of biochar for remediation.