Mobility and environmental fate of heavy metals in fine fraction of dumped legacy waste: Implications on reclamation and ecological risk.

ABSTRACT

The study evaluates mobility and chemical speciation of heavy metals (HMs) in fine fraction (<4 mm) collected from municipal solid waste dumpsite located in Mumbai, India to assess its reclamation feasabilty. A total of fifteen samples were collected from five zones (named chronologically, zone A to zone E, with the increasing waste age) at 1-m depth interval to understand temporal variation in mobility and potential pollution risk of heavy metals. The results depicted that Zn had the highest concentration in the fine fraction, followed by Cu > Cr > Pb > Ni > Cd. Furthermore, HMs concentration showed increasing trend with the waste age. According to hiererachial cluster analysis, two cluster were observed in the analyzed samples which could be differentiated with age of the waste. Further, the chemical speciation differed for all assessed HMs and had a significant change with age. HMs were dominant in non-bioavailable forms, except for Cd that had significant distribution in all forms. In addition, Cd (23%) and Zn (17%) showed high mobility amongst all analyzed HM, while Cr (0.4%) had the least. According to pollution assessment and chemical speciation results, Cd was identified as the most polluting and mobile HM. The study shows that the mobile form of HMs is low and needs to be considered while deciding the remediation routes and environment hazards.