Abstract
An estimate of the labile fractions of different trace metals (Mn and Pb) in soil from two dumpsites with complexing agents (EDTA and Citrate) was carried out. The dump sites used for this study receives both commercial and domestic wastes. Physiochemical parameters and the total metal concentrations of the soil was determined, extraction with EDTA and Citrate were used to study the potential metal extraction capacity at different time intervals and the extraction rates of metal released as a function of time (between 0 to 24 hr). The relatively low levels of silt, clay, organic matter and CEC indicates high permeability, hence leachability of heavy metals in the soil and suggest that it might be amenable to remediation by soil washing. The removal efficiency showed that complete solubilization of metals did not occur, as not all the complexing agents added to the soil, was bound to the target metal. This might be due to the presence of other ions such as Ca and Fe which form relatively high stable complexes. EDTA yielded much more than citrate for both metals under consideration. Lead was extracted more than Manganese, which suggest Lead has been more labile in solution than Manganese and EDTA as a stronger complexing agent than citrate. The level of extraction was constant for the period of 60 min to 720 min after which it increased considerably
Highlights
Industrial development and urbanization have led to serious increase in the amount of solid wastes frequently discharged into the natural environment
Chelating agents are most effective extractants, which can be introduced in the soil washing to enhance heavy metal extraction from contaminated soils
The extractions were carried out in triplicates. 0.05 mol dm3EDTA and 0.1 mol dm-3Citrate solutions was used for the extractions, as it has been found optimal for assessing the maximum extractability of metals (Jerome et al, 2007 and Fangueiro et al, 2002)
Summary
Industrial development and urbanization have led to serious increase in the amount of solid wastes frequently discharged into the natural environment. Unlike organic compounds that can be biodegraded with time or can be incinerated, metals are robust and remain a potential threat to the environment and human health for a long time (Hong et al, 2002) The concentrations of these heavy metals have been found to increase along time. Soil washing remediation technology is used to remove undesirable contaminants in soil and sediments by dissolving or suspending them in a washing solution (Freeman and Harris, 1995; Moutsatsou et al, 2006; Weihua et al, 2010), and by concentrating contaminants in small volume of soil through particle size separation (Detzner et al, 1998; McCready et al, 2003) This is based on findings that contaminants tend to bind either physically or chemically to clay, silt or organic soil particles. This study is aimed at estimating the labile fractions of Mn and Pb from dump sites by comparing EDTA and Citrate extractions
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