己二酸和己二酸钠强化石灰石WFGD的对比研究

在湍球塔设备上进行了己二酸和己二酸钠强化石灰石WFGD的对比研究,考察了2种添加剂对脱硫过程的强化和缓冲作用,分析计算了2种添加剂对石灰石的利用率。实验结果表明,2种添加剂可以在较低浆液pH下维持较高脱硫率,并且2种添加剂均促进了CaCO₃的溶解,在相同条件下己二酸钠有更好的脱硫效果,而己二酸有更好的缓冲作用,且己二酸促进CaCO₃溶解的效果更显著。     

Characteristics and provenance of dustfall during an unusual floating dust event

This study aims to investigate the characteristics, provenance, and particle-related pollution of an intense dustfall event that occurred in Beijing on 16–17 April 2006. Satellite images reveal that the aeolian dust originated in northeastern Alxa League of Inner Mongolia and passed southeastward across northern Ningxia, middle Inner Mongolia, northern Shaanxi, Shanxi, and Hebei provinces. The dust then moved out of continental China in the vicinity of Beijing and Tianjin. The floating dust led to severe air pollution in Huhhot, Datong, and Beijing. We measured dustfall by collecting dust samples, investigated particle morphology, and calculated the mass medium diameter (MMD) of the dustfall using a scanning electron microscope (SEM). Major elements and mineral content of the dust particles were determined by electron probe and powder X-ray diffractometer, respectively. The relative abundance of dustfall during this event was 12.5–15.0 g m^?2, making up about 10% of the total annual dustfall in Beijing. Dustfall amounted to 205 thousand tons in Beijing, the largest amount observed in recent years. The dust particles were mostly angular, subangular and subrounded in morphology, and the MMD was nearly 12 μm. Particles <10 μm accounted for 54.7% by number, but fine sand particles (larger than 50 μm) made up 53.7% by volume. Particles with diameters larger than 20 μm made up of the predominant volume of the samples (90.35%). Hence, this dustfall event was characterized by a high content of fine sand and coarse silt particles. The principal elements in the dust particles were C, O, Si, Al, Fe, and Ca, whereas the major minerals were quartz, Na-feldspar, calcite, and clay minerals.     

掺杂La3+纳米ZnO的制备及其光催化性能

采用共沉淀法制备了不同La3＋含量的La3＋-ZnO催化剂,采用x射线衍射仪、透射电子显微镜等对催化剂的结构、相组成、形貌和粒径进行了表征,比较了不同La3＋含量的La3＋-ZnO催化剂对罗丹明B降解率的影响。实验结果表明,掺杂La3＋导致ZnO粒径减小,比表面积增大,延长了光生电子-空穴对的寿命,提高了ZnO的光量子产率,La3＋-ZnO催化剂的光催化活性比ZnO显著增强。La3＋质量分数为0．8％时,罗丹明B降解率最高,为92．5％。经La3＋质量分数0．8％的La3＋-ZnO催化剂降解后罗丹明B已被完全降解为无机小分子。     

Impact assessment of cadmium contamination on rice (Oryza sativa L.) seedlings at molecular and population levels using multiple biomarkers

Assessment of environmental contamination on ecology (plant) at molecular and population levels is important in risk quantification and remediation study. Random amplified polymorphic DNA (RAPD) assay and related other fingerprinting techniques have been employed to detect the genotoxin-induced DNA damage and mutations. This research compared the effects occurring at molecular and population levels in rice seedlings exposed to cadmium (Cd) concentrations of 15-60 mg l(-1) for 8 days with quartz sand culture. Inhibition of root growth and increase of total soluble protein content in root tips of rice seedlings were observed with the increase of Cd concentration. For the RAPD analyses, 12 RAPD primers of 50-70% GC content were found to produce unique polymorphic band patterns and subsequently were used to produce a total of 180 bands of 179-3056 bp in molecular size in the control root tips of rice seedlings. Results produced by these RAPD primers indicate that changes in RAPD profiles of root tips after Cd treatment include modifications in band intensity and gain or loss of bands by comparison with control. The effect of changes was dose-dependent. Genomic template stability compares favourably with the traditional indices such as root growth and soluble protein content. The DNA polymorphisms detected by RAPD analysis can be applied as a suitable biomarker assay for the detection of genotoxic effects of Cd contamination on plants.     

Enhanced photoelectrocatalytic performance of Zn-doped WO(3) photocatalysts for nitrite ions degradation under visible light

WO(3) and Zn-doped WO(3) thin films were prepared on indium-tin oxide glass by a dip-coating. The composite films were characterized by UV-Vis absorption spectra, X-ray diffraction and scanning electron microscope. The effect of preparation conditions (concentration of Zn, annealing temperature, number of layers) on the photocurrent was studied. It was found that the photocurrent under visible light displayed the highest value for 2% Zn-WO(3) films annealed at 400 degrees C. The photocatalytic activity of the Zn-doped WO(3) was evaluated in terms of decay rate of nitrite ions under visible light. The influence of applied potential, initial pH and nitrite concentration on the reaction rate was studied. The experiments demonstrated that NO(2)(-) could be efficiently degraded on the doped photoanode that showed a higher activity than the undoped WO(3) especially under high anodic potential (>0.7 V). The rate of degradation was enhanced in aqueous NaCl solutions. Furthermore, it was demonstrated that the photodegradation mechanism of NO(2)(-) proceeded mainly indirectly via OH radicals. The possible reason of enhancement of reaction rate was also discussed.     

Regression method of the hydrophobicity ruler approach for determining octanol/water partition coefficients of very hydrophobic compounds

A regression method was developed for the hydrophobicity ruler approach, which is an indirect method for determining the octanol/water partition coefficients of very hydrophobic compounds. Two constants introduced into the mathematical model were obtained by regression of the absorption data sampled before the partition equilibrium. A water miscible organic solvent was used to increase the solubility of the very hydrophobic compounds in the aqueous solution so that the hydrophobicity scale was reduced and the equilibration was accelerated. Polydimethylsiloxane/methanol aqueous solution and a series of 21 polychlorinated biphenyls (PCBs) were used to demonstrate the regression method. The PCB compounds with known experimental logK(o/w) values served as reference compounds, while the PCB compounds without known logK(o/w) values were determined. The distribution coefficients (logK(p/s)), uptake and elimination rate constants were obtained from the two regression constants for each compound (reference or unknown). The correlation of the logK(p/s) values of the reference PCB compounds with their logK(o/w) values was linear (logK(o/w)=2.69logK(p/s)+0.76, R(2)=0.97). The logK(o/w) values were compared with literature values and suggested that some values from the literature far off the calibration line could be inaccurate. The critical experimental factors, the merits of the regression method were discussed.     

Modeling transport and fate of nitrogen from urea applied to a near-trench paddy field

A simple but comprehensive model is developed to quantify N losses from urea applied to a near-trench paddy field, considering all the N-transformations such as urea hydrolysis, volatilization, nitrification, denitrification, and all the important transportations like runoff, lateral seepage, vertical leaching and crop uptake. Seasonal average data of field observations for three crop seasons were used for model calibration and validation, which showed that ammonia volatilization accounted for 26.5-29.4% of the applied N and N uptake by crop occupied 38.2-44.8%, while N losses via surface runoff, vertical leaching and lateral seepage varied from 5.6-7.7%, 4.0-4.9% to 5.0-5.3% of the applied N, respectively. These observed results were well predicted by our model, indicating that the model performed effectively at quantifying N losses via individual processes in a wide range of urea application rates and benefit for developing water and fertilizer management strategies for near-trench paddy fields.     

Optimization of digestion parameters for analysing the total sulphur of mine tailings by inductively coupled plasma optical emission spectrometry

The oxidation of sulphidic mine tailings and consequent acid generation poses challenges for the environment. Accurate and precise analysis of sulphur content is necessary for impact assessment and management of mine tailings. Here, the authors aim at developing a rapid and easy digestion procedure, which may analyse and measure the total amount of sulphur in mine tailings by using inductively coupled plasma. For evaluating effects of several variables, the researchers used a univariate (analysis of variance (ANOVA)) strategy and considered factors such as composition of the acid mixture, heating time, and refluxing device to optimize the performance. To do the experiment, the researchers have used two certified reference materials (KZK-1 and RTS-2) and samples of tailings from Musselwhite mine. ANOVA result shows that heating time is the most influencing factor on acid digestion of the reference materials whereas in case of a digestion of tailings sample, hydrochloric acid proved to be the most significant parameter. Satisfactory results between the measured and referenced values are found for all experiments. It is found that the aqua regia (1 ml HNO₃ + 3 ml HCl) digestion of 0.1 g of samples after only 40 min of heating at 95°C produced fast, safe, and accurate analytical results with a recovery of 97% for the selected reference materials.     

Bubble size distribution in a laboratory-scale electroflotation study

The performance of electroflotation (EF) is strongly influenced by the size of O₂ and H₂ bubbles. Therefore, in this study, the bubble sizes are measured in a lab-scale EF cell using a high-speed camera. The mean bubble size is found to vary in the range of 32.7–68.6 μm under different operating conditions. This study shows that the electrode material, current density, water pH, ionic strength, and frother (Tennafroth 250) concentration are important factors in controlling the bubble size. Furthermore, four mathematical distributions (normal, log-normal, Weibull, and gamma distributions) are fitted to the experimental data, among which the log-normal distribution is found to be the best fit based on the lower Anderson-Darling (AD) value.     

Comparative distribution of the scalp hair trace metal contents in the benign tumour patients and normal donors

The scalp hair samples of benign tumour patients (n = 77) and normal donors (n = 86) were analysed for selected trace metal contents using atomic absorption spectrophotometry. In the scalp hair of benign tumour patients, highest average levels were found for Ca (1,401 microg/g), followed by Na (476.9 microg/g), Mg (441.6 microg/g), Zn (438.3 microg/g), K (119.2 microg/g) and Fe (96.38 microg/g) while in comparison, the maximum mean levels in the scalp hair of normal donors were shown by Ca (556.5 microg/g), followed by Zn (154.2 microg/g), Mg (153.4 microg/g), Na (97.45 microg/g) and Fe (81.68 microg/g). Almost all metal levels revealed higher dispersion and asymmetry in the scalp hair of benign tumour patients compared with the normal donors. The average concentrations of Ca, Cd, Co, K, Mg, Mn, Na, Ni, Pb, Sb, Sr and Zn were significantly higher in the hair of benign tumour patients compared with the normal donors. Significant gender-based differences were also observed in the scalp hair metal contents of benign tumour patients. Strong positive correlations were found between Cd-Cr (0.547) and Cd-Co (0.507) in the hair of benign tumour patients whereas Ca-Mg, Mg-Sr, Co-Cd, Cr-Cd, Li-Cr, Li-Co, Li-Cd, Na-Cd, Na-Co and Na-Li exhibited strong relationships (r > 0.50) in the hair of normal donors. Cluster analysis (CA) and principal component analysis (PCA) were used for the source identification and apportionment of scalp hair trace metals in the two donor groups. The scalp hair of benign tumour patients and normal donors revealed six and five main clusters of trace metals, respectively. PCA extracted seven principal components of trace metals in the scalp hair of benign tumour patients while six principal components were observed in the case of normal donors. The study evidenced significantly different patterns of metal distribution in the hair of benign tumour patients in comparison with normal donors.