The analysis of BTEX and other substituted benzenes in water samples using solid phase microextraction (SPME) and quantification by gas chromatography with flame ionization detection (GC-FID) was validated. The best analytical conditions were obtained using PDMS/DVB/CAR fibre using headspace extraction (HS-SPME) at 50 [degree]C for 20 min without stirring. The linear range for each compound by HS-SPME with GC/FID was defined. The detection limits for these compounds obtained with PDMS/DVB/CAR fibre and GC/FID were: benzene (15 ng L(-1)), toluene (160 ng L(-1)), monochlorobenzene (54 ng L(-1)), ethylbenzene (32 ng L(-1)), m-xylene (56 ng L(-1)), p-xylene (69 ng L(-1)), styrene (35 ng L(-1)), o-xylene (42 ng L(-1)), m-dichlorobenzene (180 ng L(-1)), p-dichlorobenzene (230 ng L(-1)), o-dichlorobenzene (250 ng L(-1)) and trichlorobenzene (260 ng L(-1)). This headspace SPME-GC-FID method was compared with a previously validated method of analysis using closed-loop-stripping analysis (CLSA). The headspace SPME-GC-FID method is suitable for monitoring the production and distribution of potable water and was used, in field trials, for the analysis of samples from main intakes of water (surface or underground) and from the water supply system of a large area (Lisbon and neighbouring municipalities). 相似文献
Hybridization between Aegilops geniculata, A. biuncialis and bread wheat Triticum aestivum has been evaluated during two seasons under simulated field conditions to estimate the field hybridization rate under Central Spain conditions. The mean frequencies of hybridization between A. biuncialis and A. geniculata with wheat were 0.34% and 0.31%, respectively. Data from 10 hybrid plants for each combination showed that hybrids can be partially fertile by backcrossing with wheat parent, with percent averages of 3.17 grains/spikelets for A. biuncialis × wheat hybrids and 2.87 grains/spikelets for A. geniculata × wheat hybrids. Self-pollination, although at very low rates, was also possible in hybrids. The potential risks associated with natural hybridization in the context of transgenic wheat cultivation are discussed. 相似文献
A dicentric X chromosome was found in a female fetus during cytogenetic studies performed on amniotic cells. Blood samples from the parents showed normal karyotypes and the pregnancy was terminated. The mechanism for the formation of this ‘de novo’ rearrangement is discussed. 相似文献
We report a series of 350 patients submitted to transabdominal chorionic villus sampling (CVS). A technique using two ultrasound-guided needles and a suction pump was used. In most cases, the procedure was performed between 9 and 13 weeks. Twenty-one pregnancies were selectively terminated; nine spontaneous abortions followed the procedure and one fetal loss after 28 weeks was recorded; 153 pregnancies are in progress and 169 delivered fetuses are alive and well. Transabdominal biopsy is a feasible and effective technique for CVS. 相似文献
Effective selective collection (SC) has been increasing in many countries of the European Union. As a consequence the composition of residual municipal solid waste (RMSW) is changing not only because of economic development, but also due to the collection system. The input of RMSW treatment plants is thus not homogeneous. This paper analyses two case studies involving a total of five SC scenarios and their impact on the generation of solid recovered fuel (SRF) with/without bio-drying, post-treatment and packaging take back programs (TBPs). These case studies are based on two types of SC: kerbside and drop-off. The latest regulation on SRF classification is taken into account: energy content, Cl and Hg concentrations are assessed and discussed. The role of the respirometric index (RI) is also analyzed. Results show that when SC is highly efficient RMSW can be classified directly as SRF, but only if the introduction of RI does not set stringent respirometric targets. The role of packaging TBPs is important as the residual waste remaining after the packaging has been processed, can be valorized increasing the lower heating value (LHV) of the residual RMSW and minimizing the streams that should be landfilled. The source separation of food waste has a significant impact on the suitability of bio-drying: when the SC of food waste is very efficient, its percentage in the RMSW may be too low for effective bio-drying. 相似文献
Environmental Science and Pollution Research - Dimethoate ([O,O-dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate]) is an organophosphate insecticide and acaricide widely used for... 相似文献
Environmental Science and Pollution Research - This work studies the effects of different bromide-based ionic liquids, with phosphonium and ammonium cations, towards several environmental... 相似文献
The removal of heavy metals from wastewater has become a global challenge, which demands the continuous study of efficient and low-cost treatment alternatives such as adsorption. In this research, the removal of zinc was evaluated using batch adsorption processes with nonconventional materials such as graphene oxide (GO), magnetite (MG), and their composites (GO:MG), formulated with three weight ratios (2:1, 1:1, and 1:2). Graphene was synthesized by the modified Marcano method, using pencil lead graphite as a precursor. MG and the composites were synthesized by chemical coprecipitation of ferrous sulfate and ferric chloride. The materials were characterized by Raman and Fourier transform infrared spectroscopies, scanning electron microscopy, X-ray diffraction, and the Brunauer–Emmett–Teller method to determine the functional groups, microstructural and morphological characteristics, and specific surface area. Batch adsorption tests were carried out to optimize the adsorbent dose and contact time with zinc solutions of 10 ppm. Zinc adsorption reached equilibrium at 2 h, with an optimal dose between 0.25 and 1.0 g/L. The maximum zinc removal efficiencies/adsorption capacities were 98.6%/165.6, 83.4%/47.6, 83.5%/21.9, 72.8%/19.9, and 82.2%/9.25 mg/g using GO, 2GO:1MG, 1GO:1MG, 1GO:2MG, and MG, respectively. Furthermore, the analysis of the isotherm and adsorption kinetics models determined that the adsorption processes using MG and the composites fit the Sips and pseudo-second-order models. 相似文献
River estuaries, continental shelf, and sediment contamination are closely linked from the point of view of sediment transport and diffusion that is governed by different factors such as sea waves and currents, river flows and floods, and sediment characteristics. Taking these factors into consideration, we have examined marine environmental and marine bottom sediments off the mouth of a stream to highlight the main ways of sediment and contaminant transport and diffusion on the continental shelf. For this purpose, we followed a multidisciplinary approach, studying circulation of water masses, hydrological characteristics of water column, distribution and main characteristics of sediment grain size, sediment mineralogical composition, and metal concentrations of bottom sediments. Our results allowed identifying the presence of preferential ways of sediment deposition and areas of sediment spread for the Entella Stream, as well as the origin of some metals.