The choice of analytical method and sample pretreatment has significant consequences for the shape of particle‐size distribution (PSD) frequency curves, and therefore for the evaluation of soil ...textural parameters. Here, the comparison of several granulometric methods based on different physical principles is presented: wet sieving (WS), based on gravity and the mechanical force of water, was combined with pipette (PP) sedimentation/settling velocity, Micromeritics SediGraph (MS) sedimentation/x‐ray attenuation and Coulter Counter (CC) electroresistance particle counting. The Malvern Mastersizer (MM), an instrument based on laser diffraction, was used without WS. Twelve typical temperate‐region soil types were chosen for this study on the basis of their mineral composition, organic matter content, conductivity and magnetic susceptibility. The modalities of PSD frequency curves obtained by different methods were compared. The results showed considerably larger clay‐fraction contents determined with the sedimentation techniques, PP and MS, than that obtained by CC or MM. Statistical correlation and regression models were used to compare the fractions of clay, silt and sand obtained with different methods. Linear correlations were found in almost all cases, except those comparing clay fractions obtained by CC with those obtained by MM, PP and MS methods. These correlations were non‐linear. The observed difference was attributed to the presence of aggregates and/or magnetic properties of soil particles. However, more data are needed to verify this hypothesis. The implications of sample pre‐treatment with dispersant and hydrogen peroxide (H₂O₂) were evaluated by the MS and CC techniques and observed by the scanning electron microscope. H₂O₂ was found to be an efficient disaggregating agent. The use of dispersant resulted in the increased amount of the clay fraction measured by the MS method.
Relatively recently, in the last 20 years, it was discovered that methane hydrate (MH) deposits are globally distributed in the permafrost and oceans. Before 1965 when first deposits were discovered ...in nature, it was believed that MH can occur only in laboratory conditions or in vast parts of the Universe. Presently it is presumed that this solid crystalline compounds in which CH4 molecules occupies the water ice lattices (nominal chemical formula of MH is C4H62O23) can serve as an energy source favorably to the all of the world remaining conventional hydrocarbon sources. The worldwide estimates of MH deposits range from 2x1014 m3 to 3.053x1018 cubic meters. This uncertainty partly results from our limitations in geological understanding of the MH deposits, which is due to the relatively bad quality of data obtained by presently available seismic and electromagnetic techniques. Moreover, MH deposits can become vulnerable to climate changes, which were already occurring in geological past whit tremendous consequences for the global life on Earth. Thus, further development of advanced techniques is needed to enhance our abilities to better characterize, quantify and monitor the MH deposits. In the work presented 14 MeV neutrons and associated alpha particle imaging (API) where used to quantify the amount of MH in the sample. Samples were prepared from sea sediment, quartz sand and MH simulant. MH simulant with chemical formula C4H46O23 was made from sucrose (25 % by mass) and water. MH quantity was measured by measuring the carbon content in the sample 1-8.
723 sediment samples collected along the eastern Adriatic coast have been analyzed using Energy Dispersive X-Ray Fluorescence. Factor Analysis and GIS have been used for the evaluation of the ...resulting data base containing information on K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Br, Rb, Sr, Y, and Pb concentration levels in order to find spatial relationships in distribution of measured elements. This study can be used to identify background values and to evaluate sediment quality standards.
► Sediment samples from the Adriatic Sea were analyzed for 16 chemical elements. ► Anomalies in distribution of elemental concentrations have been determined. ► FA was used to find factors related to concentration distributions. ► Chromium is naturally elevated in the eastern Adriatic Sea up to 410μgg−1.
The 14-MeV neutron-induced nuclear reactions which might contribute to better understanding of the so-called "cosmological lithium problem" have been discussed. The big bang nucleosynthesis theory ...predicted 7 Li overestimated value could be lowered by 2 n-induced reactions on Li isotopes and/or 7 Be destruction via resonance in the d + 7 Be → 9 B process. Proposals for 6 Li + 2 n and 7 Li + 2 n reactions' cross section evaluations and measurements are discussed in some details. In addition, we discuss also a preliminary measurements of n-n coincidences from the 10 B(n,2n) 9 B reaction with two neutron detectors placed outside the cone of 14-MeV tagged neutron beam. From the time-of-flight measurements and known geometry, we tried to deduce the neutron energies and calculate the 9 B missing mass spectrum. Improvements for better measurements are suggested.
The distribution of major and trace elements in the coastal sea sediments along the Eastern Adriatic coast was evaluated. The concentrations of K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Br, Rb, Sr, ...Y, and Pb in 376 samples were measured on the grain fraction <2
mm by the use of energy dispersive X-ray fluorescence. Contour maps for concentrations of toxic elements Zn, Cu, As and Pb were produced in order to show metals accumulation areas.
The possibility of using a fast neutron beam with the associated alpha particle (AAP) technique in conjunction with a specially designed probe for carbon-to-oxygen (C/O) nuclear well logging was ...investigated. Measurements were performed to show the influence of borehole fluid, iron casing, and the cement around the casing in the C/O analysis. Tests were conducted by using fast neutron activation analysis (FNAA), as the conventional approach for C/O measurements in well logging and by using AAP. Analyzed samples were made from quartz sand and graphite powder mixed in different C/O ratios characteristic for the oil-containing formations. Diesel fuel was used as a simulant of the borehole fluid. Monte Carlo (MC) simulations were conducted and the results were compared with the experimental data. In both tests, the linear relation between the measured and real C/O ratios was obtained, but when the FNAA was used, the linear relation was significantly influenced mainly by the presence of the borehole fluid. Contrary to FNAA, the AAP technique resulted in a significant reduction of the background signal coming from the borehole fluid.
The possibility of the detection of “dirty bomb” presence inside sea containers is evaluated. The method proposed for explosive and fissile material detection makes use of two sensors (X-rays and ...neutrons). A commercial imaging device based on the X-ray radiography performs a fast scan of the container, identifies a “suspect” region and provides its coordinates to the neutron based device for the final “confirmatory” inspection. In this two sensor system a 14MeV neutron beam defined by the detection of associated alpha particles is used for interrogation of only volume elements marked by X-ray sensor. The object’s nature is determined from passive and neutron induced, gamma energy spectra measurements. Experimental results (time-of-flight and gamma energy spectra) obtained for the irradiation 30kg of TNT, depleted uranium and other materials hidden inside the container are presented.
•A neutron probe for oil logging was developed with an outside diameter of 43 mm.•NP was equipped with a four-segmented alpha particle detector operable at high temperatures.•The possibility of ...measuring the C/O ratio as a function of the angle around the NP axis was shown.•Measurements were done on geological samples taken from Croatian oilfields.•Measurements on the high-temperatures show degradation of the signal coming from the gamma-ray detector.
A recently developed concept of a neutron probe (NP) -for C/O oil logging, based on associated alpha particle technique, has been developed and demonstrated by using a specially constructed NP. The NP contains a high-temperature alpha particle detector as well as a gamma detector with high energy resolution, suitable for a high-temperature environment. The probe was tested on samples collected from Croatian oil fields and on samples prepared with known C/O ratios. This NP in comparison to conventional neutron activation probes significantly reduces the background signal coming from the borehole and measures the C/O ratio depending on the azimuth angle around the borehole longitudinal axis. The time (position) resolution was found to be 2 ns enabling inspection of the C/O ratio in rock formations’ layers down to 10 cm thickness. The NP was successfully tested for different environmental temperatures up to 175 °C. The pulse amplitude degradation coming from the gamma detector was noticed to be a function of the temperature.
A neutron-based sensor has been developed able to measure the water cut and the chlorine content in crude oil. The sensor is based upon the use of a pulsed fast neutron source. Two different cases ...were studied. Case ‘‘A’’: chlorine detection with no water present and case ‘‘B’’: water cut measurements with no chlorine present. The minimum detection limits for case A and case B were found to be (62 ± 6) mg/L and (2 ± 2) vol%, respectively.
•A neutron sensor for on-line determination of water-cut and chlorine impurities in crude oil was developed.•Measurements were done on geological samples taken from Croatian oilfields and on standard samples prepared in the laboratory.•Since both chlorine and oxygen have similar gamma-ray lines at 6.1 MeV, these two were separated by choosing a different pulsing frequency for the neutron beam.•A similar setup (neutron probe) could be easily made for monitoring individual wells.
A next generation system, as an upgrade of a robotic mobile system for anti-personnel landmine clearance, was considered. In contrast to the first generation system where the fast neutron activation ...method and the associated alpha particle imaging (API) was supposed to be used for finding the residual explosives and/or landmines, in the next generation system fast neutrons (FN) was considered to be used only for the confirmation of the explosive in the suspected object previously found by the ground penetrating radar (GPR), metal detector (MD) and infrared imaging (IR). Such system is expected to have the acceptable price and the optimal demining vehicle speed of 10 cm/s. In contrast to the previous system only one neutron generator (NG) is needed. In order to study the possibility of FN to confirm the presence of TNT explosive in the real environment the tests were made with the soil of different moisture contents. Comparative study was done by using the 7.62 cm × 7.62 cm BGO, 7.62 cm × 7.62 cm LaBr 3 : Ce and 7.62 cm × 7.62 cm NaI(Tl) gamma-ray detectors. Although nitrogen was easily detected in larger amount of TNT explosive, its signal was weak in detection of Anti-Personal (AP) mine like DLM2.4. The presences of soil additionally diminish the possibility of nitrogen detection even in the Anti-Tank mines (AT).
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