Evaluation of copper and lead immobilization in contaminated soil by single, sequential and kinetic leaching tests

The effectiveness of natural clay, calcium phosphate, poultry manure and rice husks as cheap and ecologically non-invasive amendments for immobilizing Cu and Pb in contaminated soil was assessed. A moderately contaminated soil was sampled from a cultivated field in the vicinity of an active waste dump, characterized and amended with the immobilizing agents at 5 to 20% w/w. Single (calcium nitrate), sequential (optimized European Communities Bureau of Reference, BCR method) and kinetic (ethylenediaminetetraacetic acid, EDTA) leaching tests were performed before and after soil amendments. Single extractions showed that metal immobilization efficiencies, E were generally high (20 ≤ E ≤ 81%), increased as the agent dose and varied in the order: phosphate > natural clay > poultry manure > rice husks. BCR extractions showed that the agents attenuated Cu and Pb mobilities and induced changes in their fractionation patterns as most of the hitherto mobile fractions became associated with the less bioavailable forms. Two metal forms: readily labile and less labile, with apparent leaching rates k1 (10-2 min-1) and k2 (10-3 min-1), respectively were identified by fitting EDTA leaching data into a two-first-order model. The immobilizing agents suppressed both k1 and k2 for Cu and only k2 for Pb. These agents may reduce risks resulting from Cu and Pb contamination in soil since metal mobility is related to its bioavailability.Key words: Bioavailability, chemical extraction, contaminated soil, immobilizing agent

Phytoremediation of heavy metal-contaminated sites: Eco-environmental concerns, field studies, sustainability issues and future prospects

Environmental contamination due to heavy metals (HMs) is of serious ecotoxicological concern worldwide because of their increasing use at industries. Due to non-biodegradable and persistent nature, HMs cause serious soil/water pollution and severe health hazards in living beings upon exposure. HMs can be genotoxic, carcinogenic, mutagenic, and teratogenic in nature even at low concentration. They may also act as endocrine disruptors and induce developmental as well as neurological disorders and thus, their removal from our natural environment is crucial for the rehabilitation of contaminated sites. To cope with HM pollution, phytoremediation has emerged as a low-cost and eco-sustainable solution to conventional physico-chemical cleanup methods that require high capital investment and labor alter soil properties and disturb soil microflora. Phytoremediation is a green technology wherein plants and associated microbes are used to remediate HM-contaminated sites to safeguard the environment and protect public health. Hence, in view of the above, the present paper aims to examine the feasibility of phytoremediation as a sustainable remediation technology for the management of metals-contaminated sites. Therefore, this paper provides an in-depth review on both the conventional and novel phytoremediation approaches, evaluate their efficacy to remove toxic metals from our natural environment, explore current scientific progresses, field experiences and sustainability issues and revise world over trends in phytoremediation research for its wider recognition and public acceptance as a sustainable remediation technology for the management of contaminated sites in 21st century

Mixed contaminant interactions in soil: Implications for bioavailability, risk assessment and remediation

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