A B S T R A C TPhytoremediation is the most environmental friendly and economical technology for restoring agricultural land contaminated by heavy metals. However, it is a slow process, requiring hundreds to thousands of years to reduce pollutant level to meet soil environmental quality standards for highly contaminated soils. Such a long period makes the practice of phytoremediation nearly impossible without economic revenue from crop production. Miscanthus floridulus (M. floridulus) is characterized by its high dry matter yield and strong vitality. This case study planted M. floridulus on fallow land that was contaminated by 6,000 mg/kg of lead to investigate the feasibility of phytoremediation. The case study results show that lead accumulated primarily in the roots of the M. floridulus. After one year of growing, the average lead content in the roots and shoots was 806.7 and 50.3 mg/kg, respectively. M. floridulus was effective for the phytostabilization of lead-contaminated soil and was a lead-tolerant plant. The cropping produced 22.4 ton/ha/year dry matter weight (shoot part) and removed 1.13 kg/ha/year of lead from the soil. The M. floridulus grown on contaminated fields could be used as biofuels, and each hectare of M. floridulus dry matter could generate 365.1 GJ of thermal energy per year, which is equivalent to the heat energy from combustion of 13.4 tons of hard coal. Furthermore, replacing hard coal with M. floridulus would reduce CO 2 emissions by 33.1 ton/ha per year. The yields, Pb-absorption concentrations, and carbon mitigation of M. floridulus may change in subsequent years for different environmental conditions; thus, it needs further planting trials for regionalization.
Phytoremediation is the most environmentally friendly remediation technology for heavy metal contaminated soil. However, the phytoremediation approach requires a long time to yield results, and the plants used must be economically profitable to maintain the sustainability of the process. Because high levels of bioethanol can be produced from sweet potatoes, an experiment was conducted by planting sweet potatoes in a lead-contaminated site to observe their growth and lead-uptake capacity, thereby enabling the evaluation of the phytoremediation efficiency of sweet potatoes. The lead content in the soil was approximately 6000 mg kg(-1), and the phytoavailable Pb content was 1766 mg kg(-1). Three starch-rich sweet potato varieties, Tainung No. 10 (TNG-10), Tainung No. 31 (TNG-31), and Tainung No. 57 (TNG-57), were used in the experiment. The results indicated that TNG-10, TNG-31, and TNG-57 had fresh root tuber yields of 94.5, 133.0, and 47.5 ton ha(-1) year(-1), produced 9450, 13,297, and 4748 L ha(-1) year(-1) of bioethanol, and removed 2.68, 7.73, and 3.22 kg ha(-1) year(-1) of lead, respectively. TNG-31 yielded the highest bioethanol production and the highest lead removal in the lead-contaminated site. Therefore, implementing phytoremediation by planting TNG-31 would decrease lead content and generate income, thereby rendering the sustainable and applicable activation of contaminated soil possible.
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