Soil radon time series: Surveys in seismic and volcanic areas

Soil radon surveys have been performed in a long term monitoring basis with SSNTD (LR 115 type II), in order to observe possible fluctuations due to high magnitude seismic events and volcanic eruptions. Five-year radon time series are available in stations located in an intense seismic zone located along the Pacific coast of Mexico. The series analyses have been performed as a function of the local seismicity and geological characteristics. A discussion is intended to explain the lack of biunivocal relation between single radon peaks and earthquakes for the long term monitoring data using SSNTDs. Examples of short term radon anomalies obtained with continuous probes are also discussed as a function of local earthquakes and meteorological perturbations. Additionally, complementary results from recent changes in the activity pattern of an active volcano indicate that degassing process induced anomalous soil radon emanation correlated with the volcanic activity changes.     

Spatial and temporal variations of radon concentration in soil air

The spatial and temporal variability of the soil gas radon concentration in typical soils is studied. The results obtained will be further used to predict indoor radon levels. To this end, 50 measuring points along geologic sections with known physicogeological parameters of soils were chosen. The soil gas radon concentration was measured with SSNTDs (Type III-b) at a depth of 70 cm from June to October, 2000. The radon exposure time was 72–96 h. The average radon concentration in the soil pore air for an urban area was 11 kBqm⁻³ (1.7–24 kBqm⁻³). Small-scale spatial variations in the concentration were found to lie within a narrower range. The effect of meteorological conditions on the soil gas radon concentration was investigated by performing 8 series of measurements at 5 closely spaced points in September–October, 2000. A significant correlation was found between the soil radon concentration and atmospheric pressure (K=−0.86), ambient temperature (K=0.75), and soil temperature (K=0.75).     

Determination of radon distribution patterns in the upper soil as a tool for the localization of subsurface NAPL contamination

A radon survey was carried out at an abandoned military airfield, heavily contaminated with non-aqueous phase-liquids (NAPLs). Geo-statistical analysis of the data was used to confirm the validity of the chosen soil gas sampling pattern. The survey revealed a non-uniform distribution of the soil gas radon concentration in the upper soil in spite of a virtually homogenous geological situation. The radon distribution pattern showed minimum zones with radon concentrations decreased by up to 90% with regard to the local background level. The determined radon minimum anomalies could be explicitly associated with the NAPL subsurface contamination. The observed effect is due to the strong partitioning of radon into NAPLs from soil gas or groundwater. Corresponding partitioning coefficients were determined in the laboratory for some NAPL. As result of the study, it was shown that naturally occurring soil gas radon has the potential to be used as an indicator for the localization of subsurface NAPL contamination. As possible options for survey equipment, the AlphaGUARD radon monitor and passive solid-state nuclear track detectors were successfully evaluated.     

A method for estimating the convective radon transport velocity in soils

A method for estimating the convective radon transport velocity in soils is developed. The approach under review is based on measurements of the radon concentration in soil air. Mathematical models for describing the convective radon transport velocity are discussed. Data on the convective radon transport velocity in commonly encountered soil types are presented. The results obtained from a 2-month experiment aimed at investigating the effect of the atmospheric condition on the convective radon transport velocity are reported. The soil gas radon concentration at 30–70 cm depth was measured by means of passive track detectors (Type III-b SSNTDs) with 72–96 h exposure time.     

基体干扰对ICP-AES分析土壤样品中主、次量元素的影响研究

为了研究分析方法中的干扰因素对于分析结果的影响程度,针对地球化学中常用的分析手段ICP-AES法,选择土壤标准物质采用与被测样品相同消解方法,作为工作校准曲线来抵消基体影响因素。比较了在土壤基体和无土壤基体条件下测得的土壤样品中各主、次量元素结果的相对偏差,分析了其中联系和规律。发现无土壤基体干扰的结果RE值均在0左右浮动,正负偏移比例基本一致,若排除谱线干扰因素的话,基体匹配方法能有效消除土壤中基体干扰影响。而土壤基体干扰对Al,Ca,Fe,Mg,P,Ti和Ba元素分析结果有较大负偏差影响,最大偏离差Mg 279.5 nm谱线达-14.49%,影响程度排序为Ti,Mg＞P,Fe＞Ca,Ba＞Al,对其他元素Na,Cr,Cu,V,Li,Mn,Ni和Sr则无明显影响。与原本设想的结果相反,基体干扰对我们视作基体的高含量元素测试结果影响十分大,反而对次量元素影响表现并不显著。在综合基体干扰中,Ca和Mg两元素自身组分含量影响权重明显,表现为自身组分含量与分析结果相对偏差值有明显线性相关性。其他元素自身组分与基体影响结果无线性趋势,自身含量的影响权重很小。谱线的选择,干扰因素的排除对结果的确定十分重要。干扰影响的因素和规律一直是ICP光谱学者致力研究探索的课题。这些研究结果对ICP-AES分析土壤样品时谱线的选择及结果准确度的判定有很好的指导意义。     

Correlations between radon in soil gas and the activity of seismogenic faults in the Tangshan area,North China

The spatial variation of soil gas radon values were correlated with the seismogenic faults and earthquakes in the Tangshan area (north China). Radon concentrations were measured at 756 sites in an area about 2500 km² from April to May 2010. The background and anomaly threshold values calculated were 4730.4 Bq/m³ and 8294.1 Bq/m³, respectively. Radon concentrations highlight a decreasing gradient from NE to SW in the area. Higher values mostly distributed in the NE sector of the Tangshan fault and the Luanxian fault where the Tangshan (Ms 7.8), and Luanxian (MS 7.1) earthquakes occurred in 1976 and 17 earthquakes with MS = 3.0 occurred in this area since 2005. Radon values illustrated a close relation with the shallow fault trace and earthquake activity in the area. The active fault zones and the associated fractures formed by the larger earthquakes, act as paths for radon migration.     

Temperature dependence of the calibration factor of radon and radium determination in water samples by SSNTD

The sensitivity of a ²²⁶Ra determination method of water samples by SSNTD was measured as a function of storage temperature during exposure. The method is based on an etched track type radon monitor, which is closed into a gas permeable foil and is immersed in the water sample. The sample is sealed in a glass vessel and stored for an exposure time of 10–30 days. The sensitivity increased more than a factor of two when the storage temperature was raised from 2 °C to 30 °C. Temperature dependence of the partition coefficient of radon between water and air provides explanation for this dependence. For practical radio-analytical application the temperature dependence of the calibration factor is given by fitting the sensitivity data obtained by measuring ²²⁶Ra standard solutions (in the activity concentration range of 0.1–48.5 kBq m⁻³) at different storage temperatures.     

Microfluidic chip-inductively coupled plasma mass spectrometry for trace elements and their species analysis in cells

Abstract

Accurate identification and quantification of trace elements and their species in cells is an important prerequisite for the exploration of their physiological function and related mechanisms of process involving trace elements/species in human body. Inductively coupled plasma mass spectrometry (ICP-MS) is a powerful analytical instrument for trace elements detection, while it still suffers from insufficient limits of detection, interference from complex cell matrix, and incompatible sample consumption in cells analysis. Microfluidic chips which possess advantages of low sample/reagent consumption, rapid analysis speed and high spatial resolution provide perfect miniaturized and integrated platforms for cell analysis. In this article, microfluidic chip-ICP-MS techniques for trace elements and their species analysis in cells were reviewed. Both chip-based pretreatment techniques (e.g., magnetic solid phase microextraction (MSPME), monolithic capillary microextraction (MCME), liquid phase microextraction (LPME)) including chip-based array microextraction techniques for trace elements and their species analysis and droplet chip for single cell analysis were introduced. The newly developed methods of microfluidic chips in combination with ICP-MS for trace elements and their species analysis in small numbers of cells and even single cell were critically discussed, including chip-based MSPME/MCME/LPME-(electrothermal vaporization-ICP-)MS, on-line chip-based array MSPME/MCME-ICP-MS, on-line chip-based array MSPME-high performance liquid chromatography-ICP-MS and online droplet chip-time-resolved ICP-MS. These methodologies were demonstrated with high sensitivity, high throughput, good matrix resistance and low sample/reagent consumption, contributing to the quantification of trace elements/species in cells and even single cells. Relevant 20 references are included herein, and the development trend of microfluidic chip-ICP-MS techniques for cells analysis is prospected.     

Soil water balance in the Lake Chad Basin using stable water isotopes and chloride of soil profiles

ABSTRACT

The Lake Chad Basin (LCB) is an endorheic transboundary catchment highly vulnerable to drought. For effective groundwater management, recharge areas need identification and replenishment quantification. At present, little research exploring unsaturated zone water flow processes and groundwater recharge are available. In this study, 12 vertical soil profiles were analysed for stable water isotopes and chloride concentration to estimate evaporation and groundwater renewal. Most δ¹⁸O and δ²H isotope profiles reveal typical arid environment patterns, with maximum enrichment at depths between 2.5 and 20?cm and depletion towards the surface (atmospheric influence) and depth (mixing and diffusion). Average annual dry season evaporation rates in Salamat and Waza Logone range from 5 to 30?mm, in Bahr el Ghazal and Northern Lake Chad from 14 to 23?mm. According to the chloride mass balance (CMB), the average annual recharge rate is estimated between 3 and 163?mm in Salamat and Waza Logone and less than 1 mm in Bahr el Ghazal and Northern Lake Chad. Based on the CMB results, potential recharge sites were identified, while estimated soil evaporation corresponds to plant water use at the initial growing stage, which is an important component in irrigation water management.     

Application of SSNTD for maintenance of radiation and nuclear safety of the Sarcophagus

Object “Shelter” (known world-wide as the Sarcophagus) is a source of very high radiological and nuclear hazard. Transfer of the Sarcophagus into an ecologically safe site is a task not only for Ukraine but also for the world community. A composite approach to maintenance of radiation and nuclear safety of the Sarcophagus applying spectrometric methods using solid state nuclear track detectors (SSNTD) is suggested in this paper. The aspects are: (1) monitoring of transuranium element inhalation intake to a human body of nuclear workers; (2) neutron flux evaluation in some premises of the Sarcophagus; (3) fuel hot particle detection in air of working zones; (4) radon and thoron simultaneous measurements.     

Novel synthesis of nanocomposite for the extraction of Sildenafil Citrate (Viagra) from water and urine samples: Process screening and optimization

A sensitive analytical method is investigated to concentrate and determine trace level of Sildenafil Citrate (SLC) present in water and urine samples. The method is based on a sample treatment using dispersive solid-phase micro-extraction (DSPME) with laboratory-made Mn@ CuS/ZnS nanocomposite loaded on activated carbon (Mn@ CuS/ZnS-NCs-AC) as a sorbent for the target analyte. The efficiency was enhanced by ultrasound-assisted (UA) with dispersive nanocomposite solid-phase micro-extraction (UA-DNSPME). Four significant variables affecting SLC recovery like; pH, eluent volume, sonication time and adsorbent mass were selected by the Plackett-Burman design (PBD) experiments. These selected factors were optimized by the central composite design (CCD) to maximize extraction of SLC. The results exhibited that the optimum conditions for maximizing extraction of SLC were 6.0 pH, 300 μL eluent (acetonitrile) volume, 10 mg of adsorbent and 6 min sonication time. Under optimized conditions, virtuous linearity of SLC was ranged from 30 to 4000 ng mL⁻¹ with R² of 0.99. The limit of detection (LOD) was 2.50 ng mL⁻¹ and the recoveries at two spiked levels were ranged from 97.37 to 103.21% with the relative standard deviation (RSD) less than 4.50% (n = 15). The enhancement factor (EF) was 81.91. The results show that the combination UAE with DNSPME is a suitable method for the determination of SLC in water and urine samples.     

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高压覆膜制样X射线荧光光谱法测定土壤和水系沉积物中的氯研究

氯是化探样品分析中的重要元素,而X射线荧光光谱法是测定卤族元素的重要技术手段.已有研究表明,X射线荧光光谱法在测定氯时,同一样片中氯的测定值随重复测定次数的增加而逐渐增大或减小.采用高压覆膜制样技术制片,测定土壤和水系沉积物中的氯,氯(24～40000μg·g-1)校准曲线的相关系数明显改善,RM S(均方根)由未贴膜...     

Analysis of 226Ra, 232Th and 40K in soil samples for the assessment of the average effective dose

The activity concentrations of the natural radionuclides namely ²³⁸Ra, ²³²Th and ⁴⁰K are measured for soil samples collected from different locations of Faridkot and Mansa districts of Punjab. HPGe detector, based on high-resolution gamma spectrometry system is used for the measurement of activity concentration. The range of activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the soil from the studied areas varies from 21.42 Bq kg⁻¹ to 40.23 Bq kg⁻¹, 61.01 Bq kg⁻¹ to 142.34 Bq kg⁻¹ and 227.11 Bq kg⁻¹ to 357.13 Bq kg⁻¹ with overall mean values of 27.17 Bq kg⁻¹, 95.22 Bq kg⁻¹ and 312.76 Bq kg⁻¹, respectively. Radium equivalent activities are calculated for the analyzed samples to assess the radiation hazards arising due to the use of these soil samples in the construction of dwellings. The absorbed dose rate calculated from activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K ranges between 9.87 and 18.55, 38.01 and 88.68 and 9.40 and 14.79 nGy h⁻¹, respectively. The total absorbed dose in the study area ranges from 61.10 nGy h⁻¹ to 112.86 nGy h⁻¹ with an average value of 84.80 nGy h⁻¹. The calculated values of external hazard index (H _ex) for the soil samples of the study area range from 0.36 to 0.68. Since these values are lower than unity, according to the Radiation Protection 112 (European Commission, 1999) report, soil from these regions is safe and can be used as construction material without posing any significant radiological threat to population. The corresponding average annual effective dose for indoor and outdoor measured in the study area are 0.42 mSv and 0.10 mSv respectively.      

A mass spectrometric line for tritium analysis of water and noble gas measurements from different water amounts in the range of microlitres and millilitres

This paper describes the procedure followed for noble gas measurements for litres, millilitres and microlitres of water samples in our laboratory, including sample preparation, mass spectrometric measurement procedure, and the complete calibrations. The preparation line extracts dissolved gases from water samples of volumes of 0.2 μ l to 3 l and it separates them as noble and other chemically active gases. Our compact system handles the following measurements: (i) determination of tritium concentration of environmental water samples by the ³He ingrowth method; (ii) noble gas measurements from surface water and groundwater; and (iii) noble gas measurements from fluid inclusions of solid geological archives (e.g. speleothems). As a result, the tritium measurements have a detection limit of 0.012 TU, and the expectation value (between 1 and 20 TU) is within 0.2 % of the real concentrations with a standard deviation of 2.4 %. The reproducibility of noble gas measurements for water samples of 20–40 ml allows us to determine solubility temperatures by an uncertainty better than 0.5 °C. Moreover, noble gas measurements for tiny water amounts (in the microlitre range) show that the results of the performed calibration measurements for most noble gas isotopes occur with a deviation of less than 2 %. Theoretically, these precisions for noble gas concentrations obtained from measurements of waters samples of a few microlitres allow us to determine noble gas temperatures by an uncertainty of less than 1 °C. Here, we present the first noble gas measurements of tiny amounts of artificial water samples prepared under laboratory conditions.     

Ultrasonically synthesis of Mn- and Cu- @ ZnS-NPs-AC based ultrasound assisted extraction procedure and validation of a spectrophotometric method for a rapid preconcentration of Allura Red AC (E129) in food and water samples

This study is devoted on Allura Red as food colorant preconcentration and determination in beverage, fruit juice and drink water samples is based on usage of Mn- and Cu- @ ZnS-NPs-AC as new sorbent for ultrasound-assisted-dispersive solid-phase microextraction (UA-DSPME) combined with ultraviolet–visible spectrophotometric based method (UV–Vis). Contribution of volume of eluent, pH, sorbent mass and sonication time on response following conduction of 28 experiments were optimized and investigated while their significantly justified according to p-value. Values of “Prob > F” less than 0.0500 is proportional with their significant influence on recovery of analyte. Under the optimum conditions 0.14 mL of THF; pH of 2.5; 8 mg of sorbent and 3 min sonication time guide and help achievement of limit of quantification (LOQ) and limit of detection (LOD) of 6.08 and 20.26 ng mL⁻¹, respectively. The accuracy of method was validated according to calculation of recovery following spiking 400 and 600 ng mL⁻¹ to blank solution and recovery as more reliable indication of accuracy 93.41 and 102.17% recoveries with RSD < 3.5%, which demonstrate the successful applicability of present method for real sample analysis. The maximum sorbent capacity was 50.0 mg g⁻¹ based on Langmuir isotherm as best model with high correlation coefficient. Combination of UA-DSPME and UV–Vis lead to higher sensitivity and lower cost for accurate and repeatable monitoring of Allura Red level in beverage, fruit juice and drink water samples with acceptable recovery and reasonable RSD%.     

Gaussian basis set of triple zeta valence quality for the atoms from K to Kr: Application in DFT and CCSD(T) calculations of molecular properties

A contracted basis set of triple zeta (TZ) valence quality for the atoms from K to Kr was constructed from fully-optimized Gaussian basis sets generated in this work. Gaussian polarization functions (d, f, and g symmetries), which were optimized at the second-order Mφller–Plesset level, were added to the TZ set. This extends earlier work on segmented contracted TZ basis set for atoms H-Ar. This set along with the BP86 non-hybrid and B3LYP hybrid functionals were used to calculate geometric parameters, dissociation energy, harmonic vibrational frequency, and electric dipole moment of a sample of molecules and, then, comparison with results obtained with other basis sets and with experimental data reported in the literature is done. CCSD(T) atomic excitation energies and bond lengths, dissociation energies, and harmonic vibrational frequencies of some diatomics were also evaluated. Using density functional theory and gauge-including atomic orbitals, ⁵⁷Fe and ⁷⁷Se nuclear magnetic resonance chemical shifts in Fe(C₅H₅)₂, H₂Se, (CH₃)SeH, CSe₂, SeCO, H₂CSe, and SeF₆ were calculated. Comparison with theoretical and experimental values previously published in the literature was done. It is verified that in general these results give good agreement with experimental and benchmark values.     

Quantum chemical construction of a reduced reaction Hamiltonian and T 1 -relaxation and pure T 2 -dephasing rates for the proton transfer in 3-chlorotropolone

Separating multidimensional problems into that of a relevant system which is coupled to a bath of harmonic oscillators is a common concept in condensed phase theory. Focusing on the specific problem of intramolecular proton transfer in an isolated tropolone derivative, we consider the reactive proton moving in the plane of the molecule as the system and the remaining substrate normal modes as the bath. An all-Cartesian system-plus-substrate Hamiltonian is constructed employing density functional theory. It is then used to determine the temperature-dependent effective reduced reaction Hamiltonian and the state-to-state dissipation rates induced via the system-substrate coupling up to the bi-quadratic order. The important substrate modes for the T₁-relaxation and the pure T₂-dephasing rates, which are either intra- or inter-well in nature, are identified numerically and analyzed physically with molecular details. Received 19 November 2001 and Received in final form 19 February 2002     

Dissociation energy for the P2S2 ring in a family of thionation reagents and the corresponding chemical reactivity of separated species: a density functional theory analysis

In this work, 11 members of a 1,3,2,4‐dithiadiphosphetane 2,4‐disulfides family are analyzed from a theoretical point of view. These reagents are involved in thionation processes, where the first step implies the breaking bond between sulfur and phosphorus atoms to destroy the P₂S₂ ring, which is characteristic of these compounds. Thus, we estimate this breaking bond by analyzing the Gibbs energy over several temperatures, concluding that 3 of the most representative reagents of this family (Belleau, Davy, and Lawesson) are dissociated to yield 2 symmetrical species, for temperatures less than 400 K. This estimation, in gas phase, is reasonably good with respect to experimental information where these 3 reagents react at temperatures below 383 K. These 3 reagents present the lowest dissociation energies for several temperatures due to enthalpic and entropic contributions. Reagents and their monomers were analyzed by using the density functional theory framework to show that among the studied reagents, 3 of them exhibit similar behavior between themselves and correspond to the most used reagents in experimental thionation processes. For the separated species, the density functional theory chemical reactivity predictors indicate that the phosphorus atom has the biggest response when the system accepts electrons and sulfur atoms have the biggest response when the system gives electrons. This result is totally in accord with experimental suggestions for this kind of processes.