Trends in the sample preparation and analysis of nanomaterials as environmental contaminants

Much research on the use of nanomaterials in different applications is being conducted in areas such as water treatment, catalysis, oil processing, medicine, food, sensors, energy storage, building materials, constructions, and others. Nanoparticles are ultra-small particles with exceptional properties, but some nanoparticles and nanomaterials may exhibit harmful properties when leaked into the environment. Due to the lack of analytical methods for the detection and analysis of nanoparticles in complex matrices, not much is known about the potential risks associated with nanomaterials. Therefore, more knowledge is needed of the sampling and analysis of nanomaterials (NMs) as environmental contaminants. This review is undertaken to identify and assess key characteristics in potential sampling and analysis methods for identifying and quantifying the occurrence of NMs in numerous types of environmental media. To select suitable sampling and analysis methods, information on NM sources and transformation in environmental media is essential and thus is also discussed. This provides more information about the negative impacts of NMs on the environment. Challenges and future perspectives on the determination of NMs are also discussed.     

Levels, risk assessment and sources of PM10 fraction heavy metals in four types dust from a coal-based city

The concentrations of V, Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Hg and Pb in PM₁₀ fraction of four types of dust in a coal-based city, Fushun were detected by inductively coupled plasma-atomic emission spectroscopy. Results showed that most of the average concentrations for 11 metals in dust were higher than Chinese soil background values, especially for Cu, Zn, Hg, Cd and Pb with higher pollution index values. The re-suspended dust from residential and school building surfaces showed middle and high level of pollution by geoaccumulation index assessment which should raise attention as their potential health risk to local residenter and students. Six hotspots were found from spatial distribution analysis, locating at the northeast corner, central area close to mines, southwest area adjacent to an expressway, northeast area close to power plants, the city center and the industrial district reflecting the influence of agricultural activities, mining activities, vehicle emission, coal combustion and industrial activities. Correlation and principal component analysis showed accordant results indicating that vehicle emission, industrial activities, coal combustion and crustal materials were the main sources for heavy metals in PM₁₀ fraction of fugitive dust in Fushun.     

A review of ARGs in WWTPs: Sources,stressors and elimination

Antibiotic resistance genes (ARGs) in aquatic environments, which seriously endanger human health and ecological safety, have become a worldwide concern due to their easy diffusion and proliferation. Wastewater treatment plants (WWTPs), which receive resistant bacteria and ARGs from a wide variety of sources (i.e., livestock farms, hospitals, antibiotic manufactures, and households), are regarded as important emission sources of aquatic ARGs. This review presents a quantitative profile of the majority sources of ARGs in the influent of WWTPs and discusses the potential factors that affect the concentration distribution of ARGs. Specifically, a noteworthy existence of ARGs, which ranged from 1E + 05 to 1E + 11 copies/mL, was detected in livestock breeding wastewater, and household wastewater (caused by the unlimited utilization of antibiotics) was determined to be the predominant contributor of ARGs in WWTPs. We summarized the selective pressure on ARGs and determined the positive correlation of the concentration of ARGs and the existence of many containments, including antibiotics, heavy metals (Zn and Cu were frequently reported), quaternary ammonium compounds, etc. In the last section, physical, chemical, and biological treatments for the removal of ARGs and their effluent in WWTPs are discussed and prospective future studies are summarized.     

Experimental study of vapor-cell magneto-optical traps for efficient trapping of radioactive atoms

We have studied magneto-optical traps (MOTs) for efficient on-line trapping of radioactive atoms. After discussing a model of the trapping process in a vapor cell and its efficiency, we present the results of detailed experimental studies on Rb MOTs. Three spherical cells of different sizes were used. These cells can be easily replaced, while keeping the rest of the apparatus unchanged: atomic sources, vacuum conditions, magnetic field gradients, sizes and power of the laser beams, detection system. By direct comparison, we find that the trapping efficiency only weakly depends on the MOT cell size. It is also found that the trapping efficiency of the MOT with the smallest cell, whose diameter is equal to the diameter of the trapping beams, is about 40% smaller than the efficiency of larger cells. Furthermore, we also demonstrate the importance of two factors: a long coated tube at the entrance of the MOT cell, used instead of a diaphragm; and the passivation with an alkali vapor of the coating on the cell walls, in order to minimize the losses of trappable atoms. These results guided us in the construction of an efficient large-diameter cell, which has been successfully employed for on-line trapping of Fr isotopes at INFN’s national laboratories in Legnaro, Italy.     

First results from laser spectroscopy on bunched radioactive beams from the JYFL ion-beam cooler

A new RFQ ion-beam cooler and buncher, installed after the mass-separating magnet of the ion guide isotope separator, IGISOL, JYFL, has dramatically increased the scope of on-line laser spectroscopy at this facility. The device, operated in a bunching mode, has permitted new measurements on short-lived radionuclei in the Ti, Zr and Hf chains at a sensitivity two orders of magnitude greater than that previously achieved. The device has also opened new prospects for laser-based nuclear spectroscopy at the facility, particularly collinear resonance ionisation spectroscopy. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: pc@mags.ph.man.ac.uk     

Photofission for the production of radioactive beams: Experimental data from an on-line measurement

A PARRNe 1 experiment (Production d'Atomes Radioactifs Riches en Neutrons) aimed at the production of neutron-rich radioactive noble gases produced by photofission has been performed at CERN. The LEP Pre-Injector (LPI) has been used to deliver a 50 MeV electron beam. The results obtained show clearly that the use of an electron beam to produce neutron-rich fission fragments for futur RNB facilities is an option that should not be neglected. Received: 20 July 2001 / Accepted: 5 June 2002 / Published online: 19 November 2002 RID="a" ID="a"e-mail: ibrahim@ipno.in2p3.fr Communicated by D. Guerreau     

Localisation of moving sources in a multipath propagation environment

A new algorithm is presented for tracking correlated narrow-band sources in the presence of colored Gaussian noise. A fast cumulant-based preprocessing method is used to remove unknown noise and a Kalman filtering is used to track the source parameters. The use of a Kalman filtering avoids the data association problem and improves the tracking performance for crossing tracks. It is applied to the outputs of Newton’s algorithm to track moving sources. In this paper, the algorithm is developed for the special case in which the updated cumulant matrix is obtained by substituting a new matrix of the current data. The rank tracking problem is not considered in this study.We demonstrate the performance of the proposed algorithm by computer simulations of the tracking of moving targets emitting correlated signals, we also tested the proposed algorithm on the real data recorded during an underwater acoustic experiments.     

First energy and angle differential measurements of e+e−-pairs emitted by internal pair conversion of excited heavy nuclei

We present the first energy and angle resolved measurements of e⁺e⁻-pairs emitted from heavy nuclei (Z≥ 40) at rest by internal pair conversion (IPC) of transitions with energies of less than 2 MeV as well as recent theoretical results using the DWBA method, which takes full account of relativistic effects, magnetic substates and finite size of the nucleus. The 1.76 MeV E0 transition in ⁹⁰Zr (⁹⁰Sr source) and the 1.77 MeV M1 transition in ²⁰⁷Pb (²⁰⁷Bi source) have been investigated experimentally using the essentially improved setup at the double-ORANGE β-spectrometer of GSI. The measurements prove the capability of the setup to cleanly identify the IPC pairs in the presence of five orders of magnitude higher β⁻ and γ background from the same source and to yield essentially background-free sum spectra despite the large background. Using the ability of the ORANGE setup to directly determine the opening angle of the e⁺e⁻–pairs (Θ_e+e−), the angular correlation of the emitted pairs was measured within the range covered experimentally (40°≤Θ_e+e−≤ 180°). In the ⁹⁰Zr case the correlation could be deduced for a wide range of energy differences E _Δ of the pairs (−530 keV ≤E _Δ≤ 530 keV). The ⁹⁰Zr results are in good agreement with recent theory. The angular correlation deduced for the M1 transition in ²⁰⁷Pb is in strong disagreement with theoretical predictions derived within the Born approximation and shows almost isotropic character. This is again in agreement with the new theoretical results. Received: 22 April 1997 / Revised version: 16 December 1997     

非线性渗流方程分界面的正则性

本文用Harnack不等式研究了具有非线性源和对流项的一般渗流方程正解分界面的Hoelder连续性。