Recovered but Polluted? Post-Biomining Monitoring of Microplastic Contamination in the Topsoil of the Recovered Land

Legacy waste poses a significant threat to both human and environmental health. Biomining has emerged as a potential treatment of legacy waste accumulated over the years, clearing the land occupied for urban forests, green spaces, and other recreational purposes. Among the various waste fractions of legacy waste, plastics are of particular concern. Multiple studies have confirmed the presence of microplastics in leachates from dumpsites and landfills; however, limited research is available on microplastic contamination in recovered land/topsoil after biomining. As the World Health Organization recognizes microplastics as emerging pollutants of concern, assessing their occurrence in topsoil must be studied in post-biomining to ensure environmentally safe use of the recovered land. This study investigates post-biomining microplastic contamination in the topsoil of the recovered land once occupied by legacy waste at Gandhinagar dumpsite, with preliminary analysis of di-n-butyl phthalate (DBP), a common plasticizer. Results revealed an average contamination of 113.64 ± 9.91 × 10³ microplastics/kg in the topsoil of the recovered land. Fragment-shaped microplastics were dominant (≈ 75%), while fibers contributed 25–47%. The majority were small-sized particles (0.2–1.0 mm). ATR-FTIR analysis indicated that the microplastics were mainly composed of polyethylene, acrylonitrile butadiene styrene, and polypropylene. Furthermore, DBP was detected at 1.32 ± 0.2 mg/kg in the topsoil, indicating chemical leaching from degrading plastic waste as well as microplastics. These findings underline the critical importance of post-biomining monitoring of microplastic contamination and raise concerns regarding the presence of plastic additives in the recovered lands.