Biomass and chemical amendments for enhanced phytoremediation of mixed contaminated soils

Pot experiments were conducted to investigate the impact of biomass amendments (biochar, compost and nutrient solution) and chemical amendments (Ethylenediaminetetraacetic acid (EDTA) and Igepal CA-720) on the phytoremediation of soil co-contaminated with organic and metal contaminants by Helianthus annuus (sunflower) and Avena sativa (oat plant). Mixed contaminated soil was prepared by mixing clean soil with naphthalene, phenanthrene, lead (Pb), cadmium (Cd), and chromium (Cr). To study the biomass amendments, soil was amended with biochar, compost, or a nutrient solution. To study chemical amendments, plants raised in contaminated soils were amended with a solution of EDTA, Igepal CA-720 or both. The combination of biomass and chemical amendments were studied by treating composted soil with either EDTA or Igepal CA-720. The results showed that the biochar and compost amendments improved the growth characteristics and biomass of the plants. Growth improvement was best observed for sunflower plants in composted soil. Average maximum plant height of sunflower in contaminated soil was increased by 115% with the addition of compost. Cd and Pb removal was best in the presence of biochar and compost amendments, but Cr removal was unaffected by the use of amendments. The best removal rate was observed for Pb by oat plant in compost amended soil, with average final Pb concentration decreased by 57.8% with the addition of compost to soil. Nutrient solution amendment did not improve the removal of the metal contamination from the soil. The overall growth and biomass were less for plants grown in soil that was treated with chemical amendments. A combination of compost and chemical amendments also did not provide positive results on the plant growth or contaminant dissipation. Polycyclic aromatic hydrocarbon (PAH) degradation improved in the presence of all of the amendments studied. The results suggest that biochar and compost amendments can improve the plant growth characteristics and enhance phytoremediation of mixed contaminated soils.