Performance characteristics of sequential separation and quantification of lead-210 and polonium-210 by ion exchange chromatography and nuclear spectrometric measurements

A selective separation and quantitative determination procedure for 210Pb and 210Po in various environmental matrices from different sources such as IAEA-326 soil, phosphate rocks (PR), and phosphogypsum (PG) was developed. The tested samples were digested sequentially using concentrated mineral acids (HF, HNO3) by a programmable high-pressure microwave digestion system. The sample solution was loaded onto a preconditioned ion exchange column (Sr-resin) for chromatographic separation. Polonium-210 was eluted by 6 M HNO3 then spontaneously deposited onto polished silver discs to be measured using low-background alpha spectrometry. Lead-210 was sequentially eluted using 6 M HCl solution, precipitated as lead oxalate, dissolved in HNO3 solution, and mixed with scintillation cocktail to be measured by liquid scintillation counting (LSC). Performance of the developed procedure was tested using a reference soil (IAEA-326), with recommended isotope values, that was used as a quality control to assess separation and quantification efficiency (recovery %). The minimum detectable activities of 210Pb and 210Po were found to be 24 and 0.28 Bq kg(-1) for the measurements using LSC and alpha spectrometry, respectively. The recoveries (%) of 210Pb and 210Po were found to be 80 and 60%, respectively. To test the validity of the proposed LSC method, a comparative study was performed by measuring 210Pb activity concentration in test samples by nondestructive gamma-ray spectrometry.     

Preparation and Characterization of Biodegradable Blend Membranes of PBS/CA

Asymmetric membranes of cellulose acetate/poly (butylene succinate) were prepared using immersion precipitation technique. The blended membranes were characterized by contact angle, scanning electron microscopy, thermogravimetric analysis, degradation test in compost and dynamic test of raisin wastewater treatment. Results demonstrated that hydrophilicity of cellulose acetate was enhanced by addition of poly (butylene succinate) up to 50 %. Furthermore, polymeric composition affects cross sectional structure of the membranes by controlling formation of macrovoids. Addition of poly (butylene succinate) improved the membranes thermal stability and obviously their degradation in compost. The prepared membranes were able to reject the wastewater pollutants properly.     

Performance evaluation of a bipolar electrolysis/electrocoagulation (EL/EC) reactor to enhance the sludge dewaterability

The present study aimed to evaluate the performance of a bipolar electrolysis/electrocoagulation reactor designed to enhance the sludge dewaterability. The reactor was 15 L in volume, with two series of plates used in it; Ti/RuO₂ plates for the electrolysis of the sludge, and also aluminum and iron plates for electrocoagulation process. The dewaterability of the sludge was determined in terms of its capillary suction time (CST) and specific resistance to filtration (SRF), while the degree of sludge disintegration was determined based on the value of degree of sludge disintegration (DD_SCOD). The maximum reduction in CST and SRF was observed at a detention time of 20 min and a voltage of 30 V. However, increasing of both detention time and voltage significantly increased the values of CST and SRF even to an extent that they both exceeded those of the untreated sludge. The optimal degree of sludge disintegration achieved by the present study was 2.5%, which was also achieved at a detention time of 20 min and a voltage of 30 V. As reported previously, increased DD_SCOD values led to increasing CST and SRF values, due primarily to the disruption of the sludge flocs. According to the results from the present study, it can be concluded that simultaneous application of electrocoagulation and electrolysis is effective in enhancing the sludge dewaterability, because electrocoagulation helps to achieve a higher degree of sludge disintegration while maintaining the desired sludge dewaterability.     

Characterization of the TE-NORM waste associated with oil and natural gas production in Abu Rudeis, Egypt

The present study was conducted to characterize the Technically Enhanced Naturally Occurring Radioactive Materials (TE-NORM) waste generated from oil and gas production. The waste was characterized by means of dry screening solid fractionation, X-ray analysis (XRF and XRD) and gamma-ray spectrometry. Sediment of the TE-NORM waste was fractionated into ten fractions with particle sizes varying from less than 100 microm to more than 3 mm. The results showed that the TE-NORM waste contains mainly radionuclides of the 238U, 235U and 232Th series. The mean activity concentrations of 226Ra (of U-series), 228Ra (of Th-series) and 40K in the waste samples before fractionation (i.e. 3 mm) were found to amount to 68.9, 24 and 1.3 Bq/g (dry weight), respectively. After dry fractionation, the activity concentrations were widely distributed and enriched in certain fractions. This represented a 1.48 and 1.82-fold enrichment of 226Ra and 228Ra, respectively, in fraction F8 (2.0-2.5 mm) over those in bulk TE-NORM waste samples. The activity ratios of 238U/226Ra, 210Pb/226Ra, 223Ra/226Ra and 228Ra/224Ra were calculated and evaluated. Activity of the most hazardous radionuclide 226Ra was found to be higher than the exemption levels established by IAEA [International Atomic Energy Agency, 1994. International Basic Safety Standards for the Protection against Ionizing Radiation and for the Safety of Radiation Sources. GOV/2715/94, Vienna]. The radium equivalent activity (Ra-eq), radon (222Rn) emanation coefficient (EC) and absorbed dose rate (Dgammar) were estimated and these are further discussed.     

Quantification of human adenovirus in irrigation water-soil-crop continuum: are consumers of wastewater-irrigated vegetables at risk?

Environmental Science and Pollution Research - Because of health concerns regarding the presence of enteric viruses in wastewater effluents, this study was designed to investigate the occurrence of...     

A Comparison of Modified and Unmodified Cellulose Nanofiber Reinforced Polylactic Acid (PLA) Prepared by Twin Screw Extrusion

The goal of this work was to evaluate the effect of chemical modification of cellulose nanofibers (CNF) on the properties of polylactic acid (PLA) nanocomposites. Acetylated nanofibers (ACNF), with degree of substitution 1.07, were isolated from acetylated kenaf fibers by mechanical treatments. Acetylated nanofibers showed more hydrophobic properties compared to non-acetylated ones. The results showed that both crystallinity and thermal stability of acetylated nanofibers were lower than non-acetylated ones. The nanocomposites were prepared by premixing two PLA master batches, one with a high concentration of ACNF and the second with CNF. These were diluted to final concentrations (5?wt%) during the extrusion. The morphology studies of PLA and its nanocomposites showed nanofiber aggregates in both materials. The results showed that the tensile and dynamic mechanical properties were enhanced for both acetylated and non-acetylated nanocomposites compared to the neat PLA matrix while no significant improvement was observed for the acetylated nanocomposites compared to non-acetylated ones. However, the storage modulus increased slightly for acetylated nanocomposites compared to non-acetylated ones.     

Soil characteristics influence the radionuclide uptake of different plant species

The key point of food plant agriculture is how to regulate the harmonious relationship between the soil and the plant environment. This study deals with radionuclide uptake by two food plant and two fruit tree species in relation to the geochemical characteristics of the soil. Uranium and thorium content was determined in coastal black sand and inland cultivated soils. Four commonly cultivated species Eruca sativa, Lycopersicon esculentum, Psidium guajava and Mangifera indica were investigated. Physical and chemical properties of the soil were analysed in relation to uranium and thorium uptake by plants. The results revealed the ability of plants to accumulate uranium and thorium in their edible portions. The absorbed radionuclides were positively correlated with their concentrations in the soil and the geochemical characteristics of the soil. The transfer of radioactive elements from soil to plant is a complex process that can be regulated by controlling the geochemical characteristics of the soil, including pH, clay, silt and organic matter content that reduce the bioavailability of soil radionuclides to plants, and in turn reduce the risks of biota and human exposure to radionuclide contamination.     

Biochemical and histopathological changes of Biomphalaria alexandrina snails exposed to bisphenol A

The effects of sub-lethal concentrations of bisphenol A on some biochemical parameters in Biomphalaria alexandrina snail's hemolymph and tissues as well as on histological changes of the hermaphrodite gland were evaluated. Adult snails were exposed to sub-lethal concentrations for four weeks and samples of snails were investigated after two and four weeks. Total protein and albumin levels in hemolymph, as well as lipid peroxidation and glutathione contents of snails’ tissues, were measured. After two weeks of exposure, total protein content and albumin levels decreased in all groups. Elevation of lipid peroxidation levels was correlated with decreasing glutathione content in the treated snails. Histological examination of the hermaphrodite gland revealed deformations in eggs and affected sperm production.     

Concentration of four heavy metals (cadmium, lead, mercury, and arsenic) in organs of two cyprinid fish (Cyprinus carpio and Capoeta sp.) from the Kor River (Iran)

Concentration of heavy metals in aquatic animals mainly occurs due to industrial contamination. In this study, the concentrations of four heavy metals (cadmium, lead, mercury, and arsenic) in organs of two cyprinid fish and in water collected from three sections of the Kor River, Iran were determined using the inductively coupled plasma method. Pathological and hormonal changes due to metal contamination were also measured. The concentrations of heavy metals in tissue of fish from the middle sampling zone were significantly higher (p?<?0.05) than those from the other two sampling zones, whereas no significant differences (p?>?0.05) were detected between the two sexes and species. High levels of metals were found in the ovaries and testes; estradiol in females and progesterone and testosterone in males from the middle study site were significantly (p?<?0.05) lower than values from the other two sites. Pathological changes in blood cells, liver, and kidneys of fishes were significantly higher in highly polluted areas (middle sampling zone). These results show that industrial activities have polluted the river and that the maximum concentrations of Cd, Pb, and Hg were higher than the permissible levels for human consumption.     

Modified dehydrogenase enzyme assay for evaluation of the influence of Hg,Cd, and Zn on the bacterial community structure of a wastewater treatment plant

In this study, a traditional assay was modified to evaluate the effect of Hg, Cd, and Zn on the bacterial community of a sequencing batch reactor and activated sludge plants and heavy metal-resistant bacterial species were determined. After the isolation of metal-resistant bacteria, their 16S rRNA gene fragments were sequenced. The BLAST program was used to compare the resulting 16S rRNA sequences with those in GenBank database to identify the isolated bacterial species. Hg was found to be the most toxic metal for both bacterial communities investigated. Sequence batch reactor bacteria were comparatively more resistant to Hg, Cd, and Zn than those from activated sludge. The resistant strains were close to the members of genus Pseudomonas, Kocuria, Stenotrophomonas, Enterococcus, and Staphylococcus. The modified dehydrogenase enzyme assay seems to be simple, robust, and competent for evaluation of the impact of metals on bacterial activity. Sequencing batch reactor systems should be preferred over activated sludge when wastewaters containing hazardous metals are to be treated.