Comparative studies on the concentration of rare earth elements and heavy metals in the atmospheric particulate matter in Beijing, China, and in Delft, The Netherlands

Atmospheric particulate matter (APM) was collected at three sampling sites in Beijing, China, from February to June 1998. The concentrations of rare earth elements (REE) and cobalt (Co), zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) in the APM were determined by inductively coupled plasma mass spectrometry (ICP-MS). The results obtained in Beijing, China, were compared to that obtained in Delft, the Netherlands, in 1997. The influence of coal combustion was considered. The results demonstrated that the content of APM, the concentrations of REE and Co, Zn, Cd, Pb in the APM in Beijing, China, were higher than that in Delft, the Netherlands. From the ratios of La to Ce, and La to Sm, which may be used as tracers for the origin of the REE, it is concluded that the origins of REE in China differ from those in the Netherlands.     

Location and migration of cations in Cu(2+)-adsorbed montmorillonite

Locations of Cu2+ ion in Cu(2+)-adsorbed montmorillonite have been studied by electron paramagnetic resonance (EPR), supplemented by X-ray diffraction (XRD) and differential thermal analysis (DTA). In the EPR spectra of Cu(2+)-adsorbed montmorillonite, three signals, corresponding to Cu2+ ion, have been simultaneously recorded. Some Cu2+ ions seemed to replace the original interlayer metal cations and some entered into the hexagonal cavities. A small fraction of Cu2+ ions penetrated into the octahedral vacancies. There were two ways for the adsorption of Cu2+ ion by montmorillonite--exchangeable and specific. On heating, the hydrated Cu2+ ion in the interlayer loses the coordinating water and then enters into the hexagonal cavities. When the heating temperature further increased, dehydroxylation occurs, which facilitates Cu2+ ion in the hexagonal cavities to penetrate into the octahedral vacancies.     

Atmospheric xenon radioactive isotope monitoring

The Comprehensive Nuclear Test Ban Treaty (CTBT) organisation is implementing a world-wide monitoring network in order to check that the State Signatories comply with the treaty. One of the monitoring facilities consists of an atmospheric noble gas monitoring equipment. According to the requirements annexed in the treaty, the French Atomic Energy Commission (CEA) developed a device, called SPALAX, which automatically extracts xenon from ambient air and makes in situ measurements of the activities of four xenon radioisotopes (131mXe, 133mXe, 133Xe, 135Xe). The originality of this device is noticeable essentially in the gas sample processing method: thanks to the coupling of a gas permeator and of a noble gas specific adsorbent, it can selectively extract and concentrate xenon to more than 3 x 10 E6. This process is carried out continuously without cryogenic cooling, without any regeneration time. The detection of the xenon radioactive isotopes is done automatically by high spectral resolution gamma spectrometry, a robust technology well-suited for on-field instrumentation. In the year 2000, a prototype was involved in an international evaluation exercise directed by the CTBT organisation (CTBTO). This exercise demonstrated that the SPALAX equipment perfectly met the requirements of the CTBTO for such systems. On the basis of the continuous 24-h resolution record of the atmospheric xenon radioactive isotopes concentrations, the SPALAX system also demonstrated that ambient levels of 133Xe can fluctuate quickly from less than the detection limit to over 40 x 10(-3) Bq m(-3). In order to build an industrial version of this equipment, the CEA entered into a partnership with a French engineering company (S.F.I., Marseille, France), which is now able to produce an industrial version of SPALAX, i.e. more compact and more efficient than the prototypes. The 133Xe minimum detectable concentration is 0.15 x 10(-3) Bq m(-3) air per 24 h sampling cycle.     

Constitutional tolerance to heavy metals of a fiber crop, ramie (Boehmeria nivea), and its potential usage

It is observed that ramie (Boehmeria nivea), an economic fiber crop, can establish and colonize metal-contaminated sites in China. Metal tolerance and accumulation by ramie originating from 13 metal-contaminated and 4 “clean” sites in China were compared under field and hydroponic conditions. All selected populations and germplasms displayed good growth performance under diverse metal-contaminated habitats; while growth responses, metal accumulation and tolerance were similar among the 8 populations and 2 germplasms when exposed to solutions containing elevated As, Cd, Pb, or Zn in the laboratory. These revealed that ramie possesses a certain degree of constitutional metal tolerance. To our knowledge, this is the first report of constitutional metal tolerance possessed by a fiber crop. Ramie can be considered as a good candidate for both fiber production and phytoremediation of sites contaminated by multi-metals, as it accumulates relative low metal concentrations, but possesses both high biomass and high economic value.     

Monitoring method for airborne glymes and its application in fuel exhaust emission measurement.

A monitoring method based on solvent extraction of adsorbed target glymes followed by gas chromatograph-mass spectrometry GC-MS analysis was developed for seven glymes, namely ethylene glycol dimethyl ether, propylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The best recoveries of target glymes were achieved when using a combination of sample collection medium of graphitised carbon black (GCB) with a solvent mixture of methylene chloride and methanol (95/5, v/v). Method detection limits ranged from 1.5 microg/m3 for diethylene glycol diethyl ether to 13.2 microg/m3 for ethylene glycol diethyl ether based on a sample volume of 3.4 1. Using this method, diethylene glycol dimethyl ether and diethylene glycol diethyl ether were detected and measured successfully in diluted vehicle exhausts in diesel fuel engine tests.     

Real time alteration of a nuclear waste glass and remobilization of lanthanide into an interphase

The development of predictive models for the long term evolution of nuclear waste glass requires the complete knowledge of the glass dissolution at the laboratory scale. A new approach was developed to determine the initial reaction during the first steps of experience, a new concept was developed, based on the combination of dynamic leaching test and the characterization of the altered materials. With this experimental set-up it is possible to follow in real time the glass alteration process at a fine temporal scale. The results put in evidence a singular behaviour of the lanthanide, shown by a concentration peak of La, Nd and Ce after 2 h and a quick decrease of their concentration measured on line in the solution during the leaching test. This fact is directly linked to the development of an interphase (altered layer which differs from the initial solid by its texture, structure and chemical composition) at the interface of the glass surface and the leaching solution. This work is an attempt to integrate the formation of the alteration products (here the interphase) during leaching into the dissolution mechanisms of a nuclear waste glass. A model is proposed and discussed.     

Application of an enzyme-linked immunosorbent assay for the detection of clenbuterol residues in swine urine and feeds

The present study outlines applications of an enzyme-linked immunosorbent assay (ELISA) for the analysis of clenbuterol residues. Antisera were raised from rabbits immunized with diazotized clenbuterol-bovine serum albumin (BSA) conjugate. The assay was specific to clenbuterol with a half-maximum inhibition concentration (IC₅₀) of 1.8 ng/mL and 2.5 ng/mL in blank swine urine and phosphate buffer solution, respectively. The assay had high cross-reactivity (86%) with mabuterol, but low with other adrenergic agonists and antagonists. The average recovery of clenbuterol, as measured with the ELISA, ranged from 90% to 112% in swine urine samples and from 86% to 95% in feeds, respectively. This new assay was compared with commercial ELISA test kits. An excellent correlation (r ² = 0.98) between the two methods and satisfactory recoveries suggest that the new assay can be suitable for the determination of clenbuterol residues in real samples. The assay was used to analyze clenbuterol residues in 103 swine urine samples and 68 feed samples collected from northern China. Approximately 50% of the urine samples and 25% of the feed samples analyzed were found positive (concentration of clenbuterol ≥ 1 ppb). The results indicate that clenbuterol was misused in some of the areas surveyed.     

Production of the monoclonal antibody against tylosin for immunoassay of macrolide antibiotics in milk

The objective of the present study was to develop an immunoassay for multi-determination of the residues of four macrolide antibiotics in milk. Tylosin was derivatized with 6-aminohexanoic acid to synthesize a hapten that was used to produce the monoclonal antibody. The obtained monoclonal antibody simultaneously recognized tylosin, acetylisovaleryltylosin, tilmicosin and desmycosin with crossreactivities of 100%, 91%, 49% and 76%, respectively. Then an indirect competitive immunoassay was developed to determine the four analytes in milk simultaneously. The limits of detection for the four analytes were in the range of 5.5–11.7 ng/mL depending on the compound. The recoveries of the four analytes from fortified blank milk were in the range of 78%–96% with coefficients of variation lower than 11.4%. The developed immunoassay could be used as a practical tool for rapid screening the residues of the four anlytes in milk.     

诱导喷嘴改进滤筒脉冲清灰效果的实验研究

改善清灰效果是提高滤筒除尘效率的关键和难点问题。运用自制脉冲喷吹实验台,采用诱导喷嘴(超音速引流喷嘴和气流散射器)对325 mm×660 mm滤筒进行脉冲喷吹清灰实验研究,并与采用普通喷吹孔的实验结果进行比较分析,得出采用诱导喷嘴时侧壁正压力峰值平均值是普通喷吹孔的1.465倍;且采用诱导喷嘴时各测点的不均衡系数为0.768～1.336,普通喷口为0.270～2.251,而不均衡系数越接近于1,其清灰效果越好;同时,采用诱导喷嘴时各测点基本在同一时刻达到正峰值。实验充分表明采用诱导喷嘴确保了滤筒长度方向上内壁清灰压力的均匀性,且对滤筒清灰效果有明显的改善作用。     

内电解人工湿地冬季低温尾水强化脱氮机制

针对湿地冬季运行效率低、污染物去除能力差,本研究通过对比无植物湿地、普通湿地和内电解湿地冬季低水温下(3~12℃)对污水厂尾水的脱氮效能,深入分析其微生物群落结构组成,揭示内电解湿地的强化脱氮机制.结果表明,内电解湿地可以更好地利用尾水中碳源,脱氮效果优势明显,出水TN浓度维持在(9±0.29)mg·L~(-1),TN平均去除率达42.27%,比无植物湿地和普通湿地分别高出17.91%、17.33%.冬季低温条件下,内电解湿地微生物活性仍很高,荧光显色法测得微生物活性达到0.224 mg·g~(-1),分别是无植物湿地和普通湿地的2.6、3.4倍,反硝化强度分别是无植物湿地和普通湿地的2.8、3.3倍.高通量测序表明,内电解湿地基质微生物群落多样性优于无植物湿地和普通湿地.检测出的脱氮微生物主要有脱氯单胞菌、根瘤菌、生丝微菌、红杆菌,还有自养反硝化细菌产硫酸杆菌.内电解湿地在脱氮微生物总量上有明显优势,脱氮微生物占微生物总量的7.13%,分别是无植物湿地、普通物湿地的3.8、8.7倍,因而脱氮效率更高.