Evaluation of the Phytoremediation Potential and Heavy Metal Accumulation in Sunflower (Helianthus annuus) and Sicklepod (Senna obtusifolia) Grown on Dumpsite Soil in Dutsin-Ma, Katsina State

Abstract

Open municipal solid waste dumpsites present major soil pollution risks in semi-arid environments. This study evaluated the physicochemical properties of soil from the Kadangaru municipal solid waste dumpsite in Dutsin-Ma, Katsina State, Nigeria, and assessed the tissue accumulation and phytoremediation indices of Helianthus annuus (sunflower) and Senna obtusifolia (sicklepod) over a 10-week pot experiment. Dumpsite soil exhibited a moderately alkaline pH (7.94 ± 0.22), elevated electrical conductivity (892.6 ± 45.8 µS/cm), high organic matter (8.76 ± 0.92%), and increased cation exchange capacity (18.45 ± 1.86 cmol/kg) relative to pristine control soil. Initial soil heavy metal concentrations followed the sequence Zn (142.86 ± 8.92 mg/kg) > Pb (86.42 ± 4.21 mg/kg) > Cu (68.24 ± 5.18 mg/kg) > Cr (42.18 ± 3.64 mg/kg) > Ni (24.56 ± 2.14 mg/kg) > Cd (4.86 ± 0.52 mg/kg). H. annuus achieved higher total metal uptake (292.64 ± 18.42 mg/kg) than S. obtusifolia (273.92 ± 16.86 mg/kg). Tissue distribution in H. annuus followed a root > shoot > leaf pattern, yielding Bioconcentration Factors (BCF: 0.33–0.40) and Translocation Factors (TF: 0.59–0.76) below 1.0, establishing its role as a broad-spectrum phytostabilizer. Conversely, S. obtusifolia demonstrated preferential leaf accumulation for Pb (TF = 1.48 ± 0.18) and Cd (TF = 1.47 ± 0.19), classifying it as a selective phytoextractor for these metals. These findings demonstrate distinct physiological strategies for managing multi-metal soil contamination in Northern Nigeria.