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  • Author or Editor: M. Rahman x
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The study presents an analysis of spatial and structural diversity of Sal ( Shorea robusta ), the dominant species of sal forests in Bangladesh by using a neighbourhood analysis approach. The simple field method permits relatively unskilled persons to collect data. Most of the indices can be calculated in the field and the data analysis is comparatively easy. Therefore, the applicability of the method was tested by using different setting of reference trees compared with the full sampling for each plot in the Madhupur sal forests. The results indicate that a group of one reference tree and its four neighbours can be used efficiently to describe the spatial and structural diversity in homogeneous young forests at low costs and in short time. The indices can be easily interpreted allowing quantitative comparisons between different types of forest stands. Sal can be considered as the dominant and comparatively faster growing species than other associate species.

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A simple and sensitive method for the determination of some metalloids and heavy metals in water samples is presented. The method is based on the preconcentration of the attachment of chelating functionalities with metalloids and toxic metals irreversibly and targeted towards toxic metals adsorbed on modified activated carbon, activated carbon and red soil particles at pH 3.0–9.0±0.2, followed by quantitative determination using instrumental neutron activation analysis (INAA), on the absorbers. Attachment results from attraction that may be physical, chemical, electrical, or a combination of all three. The efficient removal of metalloids and toxic metals, especially arsenic, chromium and mercury is anticipated. The adsorption capacity of the chemically modified activated carbon materials was evaluated for the above mentioned metalloid and toxic metal ions in the presence of iron ions and simulated water samples. Red soil particles containing iron was utilized in the control of oxidation-reduction reaction with metalloids and toxic metals. The preconcentration of the elements of interest on red soil particles, activated carbon and modified activated carbon at different depths, pH and oxidation states was investigated. The results obtained showed good agreement with certified values giving relative errors of less than 10%.

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A new filtering column has been developed on the covalent attachment of chelating functionalities to simple, highly hydrophilic adsorbent material, which can then complex heavy metal ions irreversibly and targeted towards toxic metals removal. The capacity of the chemically modified sorbent (modified charcoal) materials used in this work was evaluated for the above mentioned heavy metal ions in the presence of iron ions and simulated water samples. The methods are based on preconcentrations of the elements of interest on activated carbon and zirconium loaded activated carbon using specific conditions of pH and oxidation states followed by a final determination by neutron activation analysis (NAA). It has been investigated that zirconium loaded activated carbon is able to adsorb As (V), Se (VI), Cr (VI) and Hg (II) at any pH while activated carbon is able to adsorb As (III), Se (IV), Cr (III) and Hg(I) at higher pH.

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Results are reported on lab-scale experiments on the removal of134Cs and60Co from liquid radioactive waste originating from Radioisotope Production Laboratory. Low cost and-simple nickel ferro-cyanide precipitation was applied for the separation of radionuclides from low-level radioactive liquid waste. Using the optimal nickel concentration of 0.75M and optimum cyanide concentration of 0.50M about 98% of the134Cs can be removed at an optimum pH of nearly 10. Furthermore, using the same method nearly 60% of60Co has been removed. The nickel ferrocyanide precipitation method could be used for removal of Cs from low level liquid waste.

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Air particulate matter (PM) was collected in two size fractions using stacked filter units (SFUs) provided by the International Atomic Energy Agency (IAEA) from the industrial area of Islamabad. Nucleopore polycarbonate filters were used for collecting from Oct 98 to Jun 99 the particulate matter in coarse and fine size fractions. The samples were characterized by the instrumental neutron activation analysis (INAA). About 33 elements were quantified using different irradiation and counting protocols.

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The multi-elemental content of sixteen glass beads and eight glass samples from archeological site Sg Mas in Bujang Valley (finding from 5 th to 14 th century) were assayed by neutron activation analysis (NAA). Ten beads differed in colour and eight of them were opaque. Contents of twentyfour elements, which might be present in the samples as a flux, stabilizer, colorants or opacifier were examined. The elements Al, Br, Cl, Co, Cr, Fe, Hf, K, Mn, Na, Sc,Th, Zn and Zr were detectable in all samples. On the other hand, concentration of the elements As, Ba, Ca, Cs, Rb, Sb, Ta, Ti, U, and V were below the detection limit in some samples. The concentration of elements found are discussed in terms of color and/or opacity of the glass bead and glass samples. Although the elemental composition does not fully explain the color and opacity of the studied materials, it can still be used as fingerprint of the glass used for the bead making.

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Determination of toxic elements Cd, Pb and other heavy metals has been carried out for Rawalpindi - Islamabad region using the moss monitoring technique. The carpet moss samples (Hypnum Cupressiforme) were collected over an area of 196 km2 around lignite/coal-fired brick kilns for regular periods of time during 1997–1999. The elements were extracted into solution with multiacid digestion and then analyzed by atomic absorption spectrometry. The metal contents in moss samples from sites adjacent to coal-fired brick kilns was higher as compared to samples collected from the sites away from that sources. The results obtained by the "BIOMONITORING" technique, for the first time in this area, are presented.

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Целяу даннои работы является введение пространства последователяностеиces[(p n), (q n)] и характериэация классов матриц (ces[(p n), (q n)],ℓ) и (ces[(p n), (q n)],c), где ℓ и с — пространства ограниченных и, соответственно, сходяшихся комплексных последователяностеи. При специаляном выборе последователяностеи {p n} и {q n} получаутся некоторые иэвестные следствия.

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Tuna fish flesh homogenate, IAEA-436, was received under the IAEA Analytical Quality Control Services (AQCS) intercomparison programme. Instrumental neutron activation analysis (INAA) was used to determine Al, As, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hg, K, Mg, Mn, Na, Rb, Se, Sb, Sm, and Zn in this proposed reference material (RM). IAEA-407 (Fish Homogenate) and NIST-SRM-1572 (Citrus Leaves) were used for quality assurance (QA) purposes. Due to the very low levels of most elements in IAEA-436, large discrepancies were observed between our results for IAEA-436 and data cited by the IAEA.

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