Interseasonal distribution and partitioning of heavy metals in subtidal sediment of Qua Iboe Estuary and associated Creeks, Niger Delta (Nigeria)

An analysis of the distribution and chemical forms of selected metals: cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni) and lead (Pb) in subtidal sediments of Qua Iboe Estuary and adjourning creeks, collected between June 2000 and January 2001, were studied using a sequential chemical extraction method. The concentration of metals in each extracted fraction was determined using inductively coupled plasma spectrometer (ICP-AES). Pb, Cd and Cu appear to be the most abundant metal in the sediments of the systems, and are predominantly associated with the residual, organic and oxidisable phases. Results indicate that there are also insignificant components that are bound to both the exchangeable and carbonates fractions. Ni is largely associated with bioavailable phases with insignificant bound to organic matter and residual fractions. In general, an insignificant component of Cd and Pb are bound to organic matter phase. Moreover, speciation results indicate that metal contamination in the ecosystems investigated primarily comes from human-mediated sources. Thus, based on index of geoaccumulation calculated, sediments of these ecosystems have been classified as uncontaminated by Cr, Cu and Ni, strongly contaminated by Pb and extremely contaminated by Cd

Review

Previous surgical procedures devised for intractable pain are the excision of painful area of the skin, peripheral neurotomy, intraspinal or intracranial posterior rhizotomies, anterolateral spinal cordotomy, spinothalamic tractotomy at medulla and mesencephalon for the pain of organic origin, and the prefrontal lobotomy for psychogenic pain. Unfortunately, these procedures are followed either by disturbance of physiologic sensory function or by changes of affect and personality. Partial gasserian gangliolysis successfully alleviated the trigeminal neuralgia without significant sensory disturbance of the face. Recent advances in stereotaxic technique has enabled us to attack the thalamus and other deep subcortical centers. This new method, together with recent neuroanatomico-physiological progress in regard to pain tract through intralaminar nuclear complex, resulted in discovery of thalamotomy destroying the nucleus centrum medianum with or without adjacent intralaminar nuclei, which eliminates the organic pain without any detectable sensory deficit. Anterior cingulectomy or cingulumotomy has developed to alleviate the psychogenic pain without psychological changes. These are the ideal pain-relieving procedures. A new method of percutaneous cervical cordotomy can be safely used for the debilitated patients with terminal malignant diseases

Source Evaluation and Trace Metal Contamination in Benthic Sediments from Equatorial Ecosystems Using Multivariate Statistical Techniques

race metals (Cd, Cr, Cu, Ni and Pb) concentrations in benthic sediments were analyzed through multi-step fractionation scheme to assess the levels and sources of contamination in estuarine, riverine and freshwater ecosystems in Niger Delta (Nigeria). The degree of contamination was assessed using the individual contamination factors (ICF) and global contamination factor (GCF). Multivariate statistical approaches including principal component analysis (PCA), cluster analysis and correlation test were employed to evaluate the interrelationships and associated sources of contamination. The spatial distribution of metal concentrations followed the pattern Pb>Cu>Cr>Cd>Ni. Ecological risk index by ICF showed significant potential mobility and bioavailability for Cu, Cu and Ni. The ICF contamination trend in the benthic sediments at all studied sites was Cu>Cr>Ni>Cd>Pb. The principal component and agglomerative clustering analyses indicate that trace metals contamination in the ecosystems was influenced by multiple pollution sources

The two principal components calculated by PCA reflecting the relationship of investigated trace metals and sedimentary variables.

<p>The two principal components calculated by PCA reflecting the relationship of investigated trace metals and sedimentary variables.</p

Spatial distribution of trace metals in benthic sediments of mangrove ecosystems of Niger Delta during wet and dry seasons.

<p>Spatial distribution of trace metals in benthic sediments of mangrove ecosystems of Niger Delta during wet and dry seasons.</p

Trace metals concentrations (mg/kg) in sediment samples obtained for wet and dry seasons.

<p>Trace metals concentrations (mg/kg) in sediment samples obtained for wet and dry seasons.</p

Hierarchical clustering analysis (Ward's Method) showing the relevant association among the parameters.

<p>Distance metrics are based on the Euclidean distance single linkage method (proximity matrix).</p

Map of study area showing the ecosystems in Niger Delta region of Nigeria (Inset: Map of Nigeria).

<p>Map of study area showing the ecosystems in Niger Delta region of Nigeria (Inset: Map of Nigeria).</p

Correlation matrix for trace metals, TOC, clay, sand and silt in benthic sediments.

<p>Correlation matrix for trace metals, TOC, clay, sand and silt in benthic sediments.</p

Relationships between trace metals in nonresidual/residual geochemical fractions and their corresponding individual contamination factors (ICFs) during the wet and dry seasons.

<p>The regression lines and equations in black color indicate metals in nonresidual fractions and ICFs; the regression lines and equations in red color represent metals in residual fractions and ICFs.</p