Phytoremediation of Contaminated Soil and Leachate by Vetiver Grass: A Case Study from Khanh Son Landfill, Da Nang City, Viet Nam

This study investigates the distribution, bioaccumulation, and correlations of six heavy metals (Cu, As, Fe, Cd, Zn, and Pb) in leachate, soil, and vetiver grass at Khanh Son landfill. The concentration of iron (Fe) was the highest across all matrices, with 12.85 ± 1.06 mg L<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>in leachate, 61.93 ± 3.28 mg kg<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> in soil, and 86.68 ± 3.90 mg kg<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> in vetiver. Zinc (Zn) and copper (Cu) were notably abundant in plant tissues, with concentrations of 59.07 ± 2.72 mg kg<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and 69 ± 4.26 mg kg<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>, respectively. Arsenic (As) and cadmium (Cd) showed lower accumulation, with the lowest levels in leachate and soil. Lead (Pb) was highest in soil at 48.29 ± 3.31 mg kg<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>, but its uptake by vetiver was minimal at 1.3 ± 0.13 mg kg<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>. The Pollution Index (PI) showed lead (Pb) had the highest contamination level (PI = 2.41), while zinc (Zn) and iron (Fe) exhibited very low contamination (PI = 0.35 and 0.00, respectively). The bioaccumulation factor (BF) analysis indicated that cadmium (Cd) had the highest BF (3.049), suggesting effective accumulation by vetiver, while lead (Pb) had a very low BF of 0.027. Pearson correlation analysis showed a significant negative correlation between Fe and As (r = -0.820) in soil, and a positive correlation between Cd and Zn (r = 0.776). Principal Component Analysis (PCA) explained 98.89% of the total variance, with PC1 accounting for 62.91% and PC2 for 35.97%. The PCA biplot clearly separated leachate, soil, and vetiver samples, further highlighting the potential role of vetiver in phytoremediation. These findings underscore the complex behavior and potential of vetiver grass in managing heavy metal contamination in landfill ecosystems.