REMEDIATION TECHNIQUE FOR CADMIUM CONTAMINATED GROUNDWATER: A SYSTEMATIC REVIEW

Heavy metal pollution in soil has seriously affected the living environment of human beings Among all heavy metal pollution, cadmium (Cd) is one of the most difficult to migrate pollutants in soil. Therefore, this systematic review includes the remediation techniques of Cd-contaminated groundwater that using. Different remediation techniques, including pump and treat, permeable reactive barrier, adsorption, biosorption, electrochemical, precipitation, ion exchange and bioremediation are reviewed. The advantages and disadvantages of some remediation technologies for cadmium from groundwater are outlined in order to assist the selection of a suitable technology for a groundwater remediation project. Bioremediation is a common remediation strategy used with low Cd concentrations due to the ability of the bacterial cells to bioremediate Cd

Predicting copper speciation in estuarine waters – Is dissolved organic carbon a good proxy for the presence of organic ligands?

A new generation of speciation-based aquatic environmental quality standards (EQS) for metals have been developed using models to predict the free metal ion concentration, the most ecologically relevant form, to set site-specific values. Some countries such as the U.K. have moved toward this approach by setting a new estuarine and marine water EQS for copper, based on an empirical relationship between copper toxicity to mussels (<i>Mytilus</i> sp.) and ambient dissolved organic carbon (DOC) concentrations. This assumes an inverse relationship between DOC and free copper ion concentration owing to complexation by predominantly organic ligands. At low DOC concentrations, the new EQS is more stringent, but above 162 μM DOC it is higher than the previous value. However, the relationship between DOC and copper speciation is poorly defined in estuarine waters. This research discusses the influence of DOC from different sources on copper speciation in estuaries and concludes that DOC is not necessarily an accurate predictor of copper speciation. Nevertheless, the determination of ligand strength and concentrations by Competitive Ligand Exchange Adsorptive Cathodic Stripping Voltammetry enabled the prediction of the free metal ion concentration within an order of magnitude for estuarine waters by using a readily available metal speciation model (Visual MINTEQ)

Temporal variability in dynamic and colloidal metal fractions determined by high resolution in situ measurements in a UK estuary

In recent environmental legislation, such as the Water Framework Directive in the European Union (WFD, 2000/60/EC), the importance of metal speciation and biological availability is acknowledged, although analytical challenges remain. In this study, the Voltammetric In situ Profiler (VIP) was used for high temporal resolution in situ metal speciation measurements in estuarine waters. This instrument simultaneously determines Cd, Cu and Pb species within a size range (ca<4. nm) that is highly relevant for uptake by organisms. The colloidal metal fraction can be quantified through a combination of VIP measurements and analyses of total dissolved metal concentrations.VIP systems were deployed over tidal cycles in a seasonal study of metal speciation in the Fal Estuary, southwest England. Total dissolved concentrations were 4.97-315. nM Cu, 0.13-8.53. nM Cd and 0.35-5.75. nM Pb. High proportions of Pb (77 ± 17) and Cu (60 ± 25) were present as colloids, which constituted a less important fraction for Cd (37 ± 30). The study elucidated variations in the potentially toxic metal fraction related to river flow, complexation by organic ligands and exchanges between dissolved and colloidal phases and the sediment. Based on published toxicity data, the bioavailable Cu concentrations (1.7-190. nM) in this estuary are likely to severely compromise the ecosystem structure and functioning with respect to species diversity and recruitment of juveniles. The study illustrates the importance of in situ speciation studies at high resolution in pursuit of a better understanding of metal (bio)geochemistry in dynamic coastal systems. © 2011 Elsevier Ltd

Cadmium resistant bacteria mediated cadmium removal: a systematic review on resistance, mechanism and bioremediation approaches

Cadmium-resistant bacteria that are used to remove cadmium (Cd) are becoming increasingly of the most important and hygienic method. Resistant mechanisms are involved in different ways, and some of them which can be used in cadmium removal techniques based on their molecular mechanisms and minimum inhibitory concentration (MIC). This review summarises recent improvements in understanding the mechanisms by which bacteria are either intrinsically resistant or acquire resistance to cadmium to be used as a way for cadmium removal

Trapped ion chain as a neural network

We demonstrate the possibility of realizing a neural network in a chain of trapped ions with induced long range interactions. Such models permit to store information distributed over the whole system. The storage capacity of such network, which depends on the phonon spectrum of the system, can be controlled by changing the external trapping potential and/or by applying longitudinal local magnetic fields. The system properties suggest the possibility of implementing robust distributed realizations of quantum logic.Comment: 4 pages, 3 figure

Error-Resistant Distributed Quantum Computation in Trapped Ion Chain

We consider experimentally feasible chains of trapped ions with pseudo-spin 1/2, and find models that can potentially be used to implement error-resistant quantum computation. Similar in spirit to classical neural networks, the error-resistance of the system is achieved by encoding the qubits distributed over the whole system. We therefore call our system a ''quantum neural network'', and present a ''quantum neural network model of quantum computation''. Qubits are encoded in a few quasi-degenerated low energy levels of the whole system, separated by a large gap from the excited states, and large energy barriers between themselves. We investigate protocols for implementing a universal set of quantum logic gates in the system, by adiabatic passage of a few low-lying energy levels of the whole system. Naturally appearing and potentially dangerous distributed noise in the system leaves the fidelity of the computation virtually unchanged, if it is not too strong. The computation is also naturally resilient to local perturbations of the spins.Comment: 10 pages, 7 figures, RevTeX4; v2: another noise model analysed, published versio