Presence of uranium and plutonium in marine sediments from gulf of tehuantepec, mexico

Uranium and plutonium were determined in the Tehua II-21 sediment core collected from the Gulf of Tehuantepec, Mexico. The analyses were performed using radiochemical separation and alpha spectroscopy. Activity concentrations of alpha emitters in the sediment samples were from 2.56 to 43.1 Bq/kg for ²³⁸U, from 3.15 to 43.1 Bq/kg for ²³⁴U and from 0.69 to 2.95 Bq/Kg for ^239+240Pu. Uranium activity concentration in marine sediment studied is generally high compared with those found in sediments from other marine coastal areas in the world. The presence of relatively high concentrations of anthropogenic plutonium in the sediments from the Gulf of Tehuantepec suggests that anthropogenic radionuclides have been incorporated and dispersed into the global marine environment.     

Arsenic determination in soils and hair from schools in past mining activity areas in Ron Phibun district,Nakhon Si Thammarat province,Thailand and relationship between soil and hair arsenic

Arsenic (As) in soils and hair collected from schools in Ron Phibun district, Nakhon Si Thammarat province, Thailand, where former tin mining operation were located, was determined by hydride generation atomic absorption spectrophotometry. The relationship between As content in soils and hair with distance from secured landfill was also investigated. Soil and hair samples were collected from 6 schools in summer (February) and rainy season (July). For soils, silt+clay (<45 µm) fraction and sand (45 µm–2 mm) fraction were analyzed. The average concentrations of arsenic in soils during summer (21.70 ± 16.79 mg/kg) and rainy season (22.45 ± 14.17 mg/kg) were at the same concentration level. The average arsenic content in hair samples was 2.24 ± 0.05 mg/kg in rainy season which was higher than 1.05 ± 0.04 mg/kg in summer. It was found that arsenic contents in hair and soils are correlated with the distance from the secured landfill. Most importantly, a positive relationship between arsenic content in hair and soil was obtained for rainy season, which indicated that arsenic in soil corresponded to arsenic in hair. The cancer risk from soils ranged from 4.48 × 10^?7 to 2.06 × 10^?6 indicating low carcinogenic risk to school children.     

Application of nuclear analytical techniques for assessment of coastal impact

Marine sediments contain a record of past events and proved to be an interesting indicator matrix for this study. Instrumental neutron activation analysis and energy dispersive X-ray fluorescence techniques offer adequate sensitivity for analysis of trace elements. Grain size analysis of sediment samples before and after tsunami showed a shift in textural characteristics of the sediment which is not observed during regular monsoon and seasonal changes. Some general characteristics of sediments revealed sand content ranges between 39 and 65% and silt from 33 to 53%. Clay content was found low averaging 5.4% and varied from 2 to 13% (by weight). The concentration of Cu, Ni, Fe, Pb, Zn, Mn, Rb, Sr, Ti, K, and Ca varies from 12 to 53, 19?C46, 21,952?C36,785, 21?C39, 39?C67, 335?C856, 47?C61, 223?C400, 4,991?C8,054, 11,000?C15,791, and 5,878?C11,214?mg?kg^?1, respectively. The positive correlation was observed for Cu, Ni, Ti, K, and Rb with respect to Fe. The negative correlation was observed for Ca, Sr, Zn, and Pb with respect to Fe, indicating the different source for these metals in the marine sediment. Decrease of the particle-reactive element in the tsunami impacted sediment indicates removal of clay component in the sediment, which is supported by the presence of low Th/U ratio.     

Reassessment and comparison of natural radioactivity levels in relation to granulometric contents of recently excavated major river sediments

River sediment depositions on the bottom of rivers most frequently consist of sand and gravel particles, which make them particularly valuable for the building construction. Knowledge of radioactivity present in building material enables one to assess any possible radiological hazard to mankind by the use of such materials. The natural radionuclide (²³⁸U, ²³²Th and ⁴⁰K) contents have been analyzed for the recently excavated sediment samples of Cauvery, Vellar, Ponnaiyar and Palaru rivers with an aim of evaluating the radiation hazard nature. To know the radiological characteristics of the sediment, the different radiological parameters are calculated. Natural radioactivity level is higher in Palaru river and it is lower in Vellar river sediments. In all the rivers, concentration of ²³⁸U is decreased, and concentrations of ²³²Th and ⁴⁰K are increased towards the river mouth. Granulometric analysis shows that the sand is the main constituent in all the river sediment samples. Content of sand is gradually decreased, and contents of silt and clay are gradually increased towards the river mouth. Cluster analysis was carried out to find the similarity level between the radioactivity and granulometric measurements. The radioactivity level of all the four river sediments mainly depends upon the contents of silt and clay. Averages of the all calculated radiation hazard indices are lower than recommended level in Cauvery, Vellar and Ponnaiyar river sediments. Therefore, the sediment of the above rivers does not pose any significant radiological threat to the population when it is used as a building construction material.     

Statistical evaluation of recovery of 3,4-dichloroaniline in soil as function of particle size and analyte concentration

A great mean value of recovery for extraction of 3,4-dichloroaniline from a soil is calculated from individual recovery values evaluated for four different fractions of the soil. Then the uncertainty associated to this great mean recovery is calculated and used to know whether to apply or not the correction in routine analysis performed for the same kind of soil and the same analyte. The most representative fractions that, as a function of particle size, can be identified in a soil are: sand (2.000-0.063 mm), coarse silt (0.063-0.020 mm), fine silt (0.020-0.002 mm) and clay (≤0.002 mm). These fractions are here considered as sub matrices of the matrix soil.To evaluate the mean recovery and its uncertainty, as a function of the sub matrix and the analyte concentration, the four blank soil fractions were spiked with the analyte at three concentration levels (10.0, 50.0 and 100.0 mg/kg) and three replicates were performed for each experiment. The 36 samples were extracted by accelerated solvent system and the amounts of 3,4-dichloroaniline were determined by RP-HPLC analysis. From the 36 individual recovery values, the great mean and its uncertainty are calculated.Experiments performed on samples of soil of similar composition, spiked with known concentrations of the same analyte showed the goodness of the mean recovery value.     

Study of uranium isotopic composition in groundwater and deviation from secular equilibrium condition

Uranium concentration in groundwater reflect both redox conditions and uranium content in host rock. In the present study an attempt has been made to study the uranium concentration and activity ratios of uranium isotopes to present the geochemical conditions of the groundwater in Malwa region of Punjab state, India and the reason for high uranium levels and variation of activity ratios from secular equilibrium conditions. Uranium concentration in groundwater samples was found to be in the range of 13.9 ± 1.2 to 172.8 ± 12.3 μg/l with an average value of 72.9 μg/l which is higher than the national and international guideline values. On the basis of uranium concentration, the groundwater of the study region may be classified as oxidized aquifer on normal uranium content strata (20 %) or oxidized aquifer on enhanced uranium content strata (80 %). The ²³⁸U, ²³⁵U and ²³⁴U isotopic concentration in groundwater samples was found to be in the range of 89.2–1534.5, 4.4–68.5, and 76.4–1386.2 mBq/l, respectively. Activity ratios of ²³⁴U/²³⁸U varies from 0.94 to 1.85 with a mean value of 1.11 which is close to unity that shows secular equilibrium condition. High value of ²³⁴U isotope than ²³⁸U may be due to alpha recoil phenomenon. The plot of AR of ²³⁴U/²³⁸U against the total uranium content in log scale reveals that the groundwaters of the study region either belongs to stable accumulation or normal oxidized aquifer.     

Molecular turnover time of soil organic matter in particle‐size fractions of an arable soil

The composition and molecular residence time of soil organic matter (SOM) in four particle‐size fractions (POM >200 µm, POM 63–200 µm, silt and clay) were determined using Curie‐point pyrolysis/gas chromatography coupled on‐line to mass spectrometry. The fractions were isolated from soils, either continuously with a C₃ wheat (soil ¹³C value = ?26.4‰), or transferred to a C₄ maize (soil ¹³C value = ?20.2‰) cropping system 23 years ago. Pyrograms contained up to 45 different pyrolysis peaks; 37 (ca. 85%) were identifiable compounds. Lignins and carbohydrates dominated the POM fractions, proteins were abundant, but lignin was (nearly) absent in the silt and clay fractions. The mean turnover time (MRT) for the pyrolysis products in particulate organic matter (POM) was generally <15 years (fast C pool) and 20–300 years (medium or slow C pools) in silt and clay fractions. Methylcyclopentenone (carbohydrate) in the clay fraction and benzene (mixed source) in the silt fraction exhibited the longest MRTs, 297 and 159 years, respectively. Plant‐derived organic matter was not stored in soils, but was transformed to microbial remains, mainly in the form of carbohydrates and proteins and held in soil by organo‐mineral interactions. Selective preservation of plant‐derived OM (i.e. lignin) based on chemical recalcitrance was not observed in these arable soils. Association/presence of C with silt or clays in soils clearly increased MRT values, but in an as yet unresolved manner (i.e. ‘truly’ stabilized, or potentially still ‘labile’ but just not accessible C). Copyright © 2009 John Wiley & Sons, Ltd.     

Adsorption — Desorption equilibria of some radionuclides in sediment — Sea water system

Chemical and physical properties of Suez Canal bottom sediments (SCBS) and sea water at port Tawfeek area, the south entrance of Suez canal, have been studied. The SCBS was separated into its size fractions (natural sediment, sand, silt and clay). These different sediment fractions were allwed to be in equilibrium with⁸⁹Sr,⁶⁰Co and¹³⁴Cs solutions. Desorption studies were carried out on these contaminated sediments.     

Experimental investigation of radiocesium sorption on ceramic clay using a batch method

In this study, radiocesium sorption on ceramic clay was investigated as a function of particle size and initial ¹³⁷Cs concentration using a batch method. Ceramic clay samples taken from the Sö?üt(?nisar) clay deposit were composed of kaolinite, dickite and quartz. The equilibrium time and the liquid–solid ratio were determined as 60 min and 250 mL g^?1, respectively. The distribution coefficients (K _d) for variable liquid–solid ratio and the percentage adsorption (P _Ad) were calculated. The values of K _d and P _Ad ranged from 483 to 3165 mL g^?1 and 34–93%, respectively. The K _d and P _Ad values increased with increasing particle size, but decreased with increasing initial concentration. The sorption data were interpreted in terms of a Langmuir isotherm. The results indicated that the Sö?üt(?nhisar) ceramic clay has good sorption capacity for cesium.     

Distribution of heavy metal concentrations in surface sediments in Dubai Creeks, United Arab Emirates

Dubai is developing rapidly and many developmental activities are concentrated around its Creek. The present study reports the lateral distribution of heavy metals and compares it with local historical record of heavy metal concentrations. For this purpose surface sediment samples were collected and analyzed for metal contents, total organic carbon content (TOC), mineralogy and grain size. The percentages of the different grain size fraction of the collected sediments were as follow 65% for sand size, 15% for silt size fraction, and the rest accounted for clay size fraction. The microscopic analyses indicate that the sediment composed mainly from carbonate and quartz with traces of rock fragments. Such mineral composition is not believed to be a potential source of heavy metal. The study found that the average recorded heavy metal concentrations in the collected sediment samples were 87, 96, 127, 38.5, and 279 ppm for Cr, Cu, Ni, Pb, and Zn, respectively. Those values were slightly higher than metal concentrations recoded in 2001 with 1.22 (Cr), 2.5 (Cu), 2.87 (Ni), 0.69 (Pb), and 2.1 (Zn) folds. However, in 2001 and 2003 the measured metal contents, along the creek, were lower than those of the average earth crust. Along the Creek most metals recorded the highest concentrations in the upper reach of the Creek. The distribution of the measured heavy metals was not affected significantly with the TOC values. The present study also documented obvious related point sources of pollution.     

Work place air particulate monitoring of automobile workshops for public health and safety

Twenty-eight pairs of coarse and fine air particulate samples were collected in front of an automotive workshop located at Tasmasipabad on Chaklala Road in Rawalpindi using a Gent sampler and polycarbonate filters. These samples were collected during the period; 7th to 27th of April 2009. The gravimetric data (PM_2.5 and PM₁₀) were obtained for these samples and were found to exceed the Pakistani standards. Black carbon (BC) was also determined using reflectance measurements and it was found that BC contributed significantly more to the fine mass than to the coarse fraction; i.e. ~10 to ~3 %, respectively. This is not surprising as soot is emitted by combustion processes and is usually found in the fine particulate mass. Using instrumental neutron activation analysis technique all 28 pairs of filters were analyzed for >30 elements. Major elements, in the coarse mass fraction, include Al, K, Fe, Sr, Na, and Zn implying soil as the major source while BC was found to be a higher contributor of PM_2.5. An episode of high PM_2.5 was observed on the 18th of April 2009. Back trajectory analysis showed that the air mass originated from the Middle East where a dust storm was in progress over Iraq.     

Headspace Solid‐Phase Microextraction (HS‐SPME) for the Determination of Benzene,Toluene, Ethylbenzene,and Xylenes (BTEX) in Foundry Molding Sand

Abstract

The use of headspace solid‐phase microextraction (HS‐SPME) to determine benzene, toluene, ethylbenzene, and xylenes (BTEX) in foundry molding sand, specifically a “green sand” (clay‐bonded sand) was investigated. The BTEX extraction was conducted using a 75 µM Carboxen‐polydimethylsiloxane (CAR‐PDMS) fiber, which was suspended above 10 g of sample. The SPME fiber was desorbed in a gas chromatograph injector port (280°C for 1 min) and the analytes were characterized by mass spectrometry. The effects of extraction time and temperature, water content, and clay and bituminous coal percentage on HS‐SPME of BTEX were investigated. Because green sands contain bentonite clay and carbonaceous material such as crushed bituminous coal, a matrix effect was observed. The detection limits for BTEX were determined to be ≤0.18 ng g^?1 of green sand.     

Pressurized fluid extraction of polycyclic aromatic hydrocarbons using silanized extraction vessels

We have investigated the extraction efficiency of a pressurized fluid extraction system using an Ottawa sand matrix, soils and a certified reference material (HS-6) spiked with the 16 polycyclic aromatic hydrocarbon (PAHs) associated with method EPA 8100. Acceptable recoveries were achieved for all PAHs using a nominal sand concentration of 2.0 μg.g^-1. However, similar experiments that were conducted at a concentration of 0.20 μg.g^-1 afforded poor recoveries and poor reproducibility for the six-ring PAHs indeno(1,2,3-cd)pyrene, dibenz(a)anthracene, and benzo(ghi)perylene. These were not adequately addressed by the use of indeno(1,2,3-cd)pyrene-d12 and benzo(g,h,i)perylene-d12 surrogates. Silanization of vessels using dichlorodimethylsilane adequately passivates the system but is only required for the high surface area retention frits. Replicate analyses at concentrations of 200 and 20 ng.g^-1 demonstrated that detection limits in the low ppb range (ng.g^-1) are achieved for Ottawa sand, dry soil and soil with moisture contents up to a mass fraction of 30 %. Such performance is consistent with the analytical requirements of the Canadian Sediment Quality Guidelines. Improved analyte recoveries were also observed for the certified reference material HS-6 which were further improved by increasing extraction temperatures from 100 to 150 °C.

Advanced binderless board-like green nanocomposites from undebarked cotton stalks and mechanism of self-bonding

Self-bonding of air-dried undebarked cotton stalks during hot pressing in a closely fitting mold was studied. Advanced board-like green nanocomposites from ground undebarked cotton stalks were introduced for the first time in the present work. The dry forming process was adopted. Moderate molding pressure and temperature were selected and applied in a tight die, thus saving water and energy and avoiding the use of any binders to achieve an environment-friendly green product. Green nanocomposites having densities in the range of 1.27–1.29 g/cm³ and 1.03–1.06 g/cm³ were prepared. Particle size and cell wall morphological structure were found to play a major role in self-bonding. Properties of composites prepared from the fine fraction of cotton stalks were superior to those prepared from the cotton stalk coarse fraction at the same conditions. This is attributed—among other things—to the dominance of pith (parenchymal cells) in the fine fraction. Such cells possess a high lumen-to-cell wall ratio, which renders them more deformable under pressure, leading to more intercellular or interparticle bonding. Advanced binderless green nanocomposites having bending strength as high as 637 kg/cm² and water absorption as low as 12.1 % were obtained from the ground undebarked cotton stalks. The results show clearly that the advanced green nanocomposite obtained by the dry forming process, without the addition of any binders, is superior to hardboard obtained from cotton stalks by the conventional wet web formation process. The mechanism of self-bonding is discussed.     

Study of 10Be in the sediments from the Krossfjorden and Kongsfjorden Fjord System,Svalbard

The distribution of ¹⁰Be, as well as the major elements concentrations and the grain size in surface and core sediment samples, collected from Krossfjorden and Kongsfjorden, Svalbard have been studied for understanding the origin of ¹⁰Be and an estimation of its accumulation rate. The ¹⁰Be concentration in sediments varies between 0.90 × 10⁸ and 2.53 × 10⁸ atoms g^?1. Our results show that atmospherically produced ¹⁰Be dominates over terrigenous (in situ) sources of ¹⁰Be in the studied samples. The calculated ¹⁰Be accumulation rate varies from 3.1 × 10⁶ atoms cm^?2 year^?1 to 8.6 × 10⁶ atoms cm^?2 year^?1 which is higher than the accumulation rate observed in the deep sea sediment cores of the Arctic Ocean and the Norwegian Sea. The higher accumulation rate of ¹⁰Be is attributed to the higher influx of glacier melt water into the fjord system.     

WATER TRANSPORT BY A SPREADING SURFACTANT IN FINE DISPERSE MATERIALS

A surface active substance (surfactant) spreads on the water film lying on the surface of fine disperse materials (clay, oxides), with lower velocity than on the surface of bulk water and on coarse materials (sand).

The spreading surfactant carries the underlying water although the surface is not continuous and water is present as a thin film.

The ratio of the transported water to the spread surfactant decreases with increasing specific surface, being > 10⁴ on sand surface and < 10 on fine disperse materials (clay, oxides).

The amount of transported water increases with increasing specific surface and increasing water film thickness. The driving force for water transport is the surface pressure; the presence of another surfactant is therefore prejudicial for the spreading and transport of underlying water.

The water transport by the spreading surfactant is accompanied by the streaming potential, which is inversely related to the specific surface.     

Continuous Production of Isomalto-oligosaccharides by Thermo-inactivated Cells of <Emphasis Type="Italic">Aspergillus niger</Emphasis> J2 with Coarse Perlite as an Immobilizing Material

The coarse perlite 40–80 mesh was selected as an immobilizing material and put into a packed bed reactor (PBR) to continuously convert maltose to isomalto-oligosaccharides (IMOs). The PBR was prepared by mixing the thermo-inactivated cells (TIC) from Aspergillus niger J2 strain with the coarse perlite, then the mixture was put into an overpressure-resistant column. Compared with diatomite 40–80 mesh and thin perlite 80–120 mesh in PBR, coarse perlite was chosen as the best filtration aid, when the ratio of coarse perlite versus TIC was 1:1. The thermal and pH stability of the free and immobilized TIC and the optimum conditions for the transglycosylation reactions were determined. The results show that approximately 75 and 82% and 87 and 91% of α-glucosidase activity were reserved for free and immobilized TIC at temperatures from 30 to 60 °C and pH from 3.00 to 7.00 for 12 h, respectively. With 30% malt syrup under the conditions of 50 °C and pH 4.00, a mini-scale packed bed reactor (Mi-PBR) and medium-scale packed bed reactor (Me-PBR) could continuously produce IMO over 25 and 34 days with the yield of effective IMO (eIMO) ≥?35% and total IMO (tIMO) ≥?50%, respectively. The strategy of mixing the coarse perlite with TIC in PBR is a novel approach to continuously produce IMO and has great application potential in industry.     

N-Alkanes in an Equatorial Sedimentary Environment: Their Distribution as a Function of Particle Size

Abstract

In order to investigate the biogeochemistry of organic matter deposited in an equatorial deltaic environment, the Mahakam delta, Borneo, analysis of geochemical markers has been realised both on various sediments and on sediments separated as a function of particle size.

Sediments were selected from two levels (-150m and -500m) of a continuous core sampled in the Mahakam delta in 1981 (Misedor Programme) and represent various lithotypes of the deltaic environment and different diagenetic conditions. After separation into sand size (> 50 μm), silt size (50–5 4mUm) and clay size (< 5 μm) fractions, free lipids have been extracted and hydrocarbons isolated by micro-column chromatography, and analysed by capillary gas liquid chromatography. Concentrations and carbon number distributions of n-alkanes are discussed in terms of the relationship between the sedimentary environment and the importance of terrigenous inputs. The distribution patterns of n-alkanes of different sediment size fractions are characterized by the predominance of high molecular weight compounds in the range C23–C37, which are also encountered for the actual deltaic plain flora: mangrove and nipah-nipah. Carbon Preference Index (CPI) values are higher in the coarse and intermediate fractions reflecting their enrichment in continentally-derived vegetation debris.     

Analysis of Six Phenolic Endocrine Disrupting Chemicals in Surface Water and Sediment

An efficient and reliable method based on gas chromatography–mass spectrometry (GC–MS) was developed for the extraction and analysis of six phenolic endocrine disrupting chemicals (EDCs), such as 4-nonylphenol (4-NP), nonylphenol-mono-ethoxylate (NP1EO), nonylphenol-di-ethoxylate (NP2EO), 4-tert-octylphenol (4-t-OP), bisphenol A (BPA) and 4-cumylphenol (4-CP) in surface water and sediment. The method was developed by using microwave-assisted extraction (MAE), solid phase extraction (SPE) and derivatization procedure. The MAE procedures were performed by optimizing three key process factors, consisted of extraction solvent, extraction temperature and holding time, affecting the extraction efficiency from sediment samples. For SPE, various parameters that may affect the recovery efficiency of water samples, such as SPE phase cartridge, elution solvent, as well as pH of water samples, were investigated. A series of derivatization conditions, such as derivatization reagent, reaction temperature and reaction time, were improved. The method achieved good repeatability and reproducibility with relative standard deviations <13% for all target EDCs in the both samples. Satisfactory recoveries for spiked water and sediment samples ranged from 85 to 101% and 74 to 105%, respectively. The limits of quantification varied from 0.20 (4-t-OP) to 11.50 ng L^?1 (NP2EO) and from 0.31 (4-t-OP) to 9.50 ng g^?1 dry weight (dw) (NP2EO) for water samples and sediment samples, respectively. The established method was successfully applied to the analysis of target EDCs in surface water and sediment samples collected from Caohai site of Dianchi Lake, China. The results showed that NP1EO, NP2EO and BPA were the three dominant phenolic EDCs in the site, reaching 114, 97 and 149 ng L^?1 in surface water, while 444, 186 and 178 ng g^?1 dw in surface sediment, respectively.     

Studies on natural and anthropogenic radionuclides in sediment and biota of Mumbai Harbour Bay

Mumbai Harbour Bay (MHB) is a recipient of low level treated effluents from BARC, Trombay and its also a recipient of domestic and industrial wastes from the city of Mumbai and adjoining areas. Sediment samples were collected from various locations of MHB to determine the concentrations of naturally occurring radionuclides like ²²⁶Ra, ²²⁸Ra and ⁴⁰K which varied between 4.0 and 26.0, 5.5 and 19.9, 249.6 and 557.6 Bq kg _(dry) ^?1 respectively and are comparable to the worldwide average concentration. The mean value ratio of ²²⁸Ra/²²⁶Ra in sediment was found to be 1.4, indicating a relatively higher mobility of ²³⁸U compared to ²³²Th. The concentration of anthropogenic radionuclide ¹³⁷Cs in sediment and biota ranged between 3.6 and 54.5 Bq kg _(dry) ^?1 , <0.08 and 0.5 Bq kg _(wet) ^?1 respectively. The ingestion dose to ‘General Public’ due to ¹³⁷Cs intake is 0.02 μSv years^?1 which is negligible compared to the internationally accepted limit of 1,000 μSv years^?1 to ‘members of public’.