Beneficial effect of growing <i>Melastoma malabathricum</i> with the addition of bamboo biochar and EDTA in removing soil heavy metal(loid)s contamination

A study was conducted to investigate the synergistic effect of growing <i>Melastoma malabathricum</i> with the addition of bamboo biochar (BB) and ethylenediaminetetraacetic acid (EDTA) in reducing soil heavy metal(loid)s. Soils from the Chini watershed, a Man and Biosphere Reserve by UNESCO, which faces mining activities, were collected, analyzed, and used for a greenhouse experiment. The experiment was set up with five treatments by growing <i>M. malabathricum</i> with BB and/or EDTA, a control, and blank (organic soil). <i>M. malabathricum</i> demonstrated robust growth throughout the experiment, displaying no common phytotoxic symptoms when growing with the contaminated soil. Applying BB and EDTA gradually increased 50% of plant height and biomass and improved the uptake of heavy metal(loid)s: Fe:42%, As:62%, Pb:83%, Cr: 88%, and Al: 5%. This treatment also achieved the highest phytoextraction efficiency, with reductions of heavy metal(loid)s in the soil (up to 33%) compared to the control. Growing <i>M. malabathricum</i> with BB and EDTA additions was a promising method in reducing soil heavy metal(loid)s, making it beneficial for restoration efforts at ex-mining sites, particularly at the Chini watershed in the future. Research on removing heavy metal(loid)s in the contaminated soil has been an interesting topic for decades. Many researchers reported the functional significance of several plants for phytoremediation and the potential of other soil conditioners, such as biochar and EDTA, in removing HMs. However, the synergistic effect of growing <i>M. malabathricum,</i> a well-known metal hyperaccumulator, with the addition of bamboo biochar (BB) and/with EDTA in removing heavy metal(loid)s (HMs) are unknown and has never been reported. This study discovered a significant reduction of HMs such as Al, Fe, As, Pb, and Cr in the contaminated soil when growing <i>M. malabthricum</i> with the addition of bamboo biochar and EDTA. Given that <i>M. malabathricum</i> is a low-cost, widely available plant, this approach offers a new and practical approach for remediating contaminated soils, especially in the Chini Watershed, a UNESCO Man and Biosphere Reserve.