燃煤烟气脱硝技术的应用与进展

介绍了近年来国内外应用和正在研究开发的一些主要的燃煤烟气脱硝技术,并对这些技术的优缺点作了比较和评述。     

瓦斯气体在煤层中的扩散机理及模式

根据气体在多孔介质中的扩散模式 ,结合煤结构的实际特点 ,分析了瓦斯气体在煤孔隙中的扩散机理 ,得出瓦斯在煤体中几种扩散模式 :菲克型扩散、诺森扩散、过渡型扩散、表面扩散和晶体扩散。从微观上看 ,影响瓦斯气体在煤层中扩散的主要因素是瓦斯气体的平均自由程和煤不同尺寸微孔隙的分布情况。根据不同孔隙分布的煤层 ,探讨了各种扩散模式的适用条件     

水中微量甲基膦酸类化合物的树脂富集与GC／MS分析

本文使用三种阴离子交换树脂（即大孔弱碱型Ｄ－３０１－Ｒ,强碱型Ｄ－２９６,２０１Ｘ７）柱对水中微量甲基膦酸类化合物的富集方法进行了研究。含磷毒剂降解产物的水样用气相色谱／质谱法进行定性定量分析。结果表明,Ｄ－３０１－Ｒ阴离子交换树脂柱对甲基膦酸的富集回收率高于６０％。     

石墨探针直接收集、石墨探针炉原子吸收法测定APM中痕量银

本文采用一定气孔性的石墨探针直接收集大气颗粒物（APM）,然后用石墨探针炉原子吸收法直接测定收集在探针上的APM中痕量银。实验表明:峰面积吸光度与银的浓度在0—120ng·ml~(-1)范围内呈线性关系,银的特征量为6.75pg,检测限（3σ）为11.74pg,RSD（n=11）为3.92％,分析标准物质NBS1648（城市颗粒物）,其回收率和RSD（n=5）分别为90.2—105.0％和6.0％,证明此法准确、灵敏、快速、简便。     

Separation of dissolved iron from the aqueous system with excess ligand

A new technique for the separation and pre-concentration of dissolved Fe(III) from the ligand-rich aqueous system is proposed. A solid phase extraction (SPE) system with an immobilized macrocyclic material, commonly known as molecular recognition technology (MRT) gel and available commercially, was used. Synthetic Fe(III) solution in aqueous matrices spiked with a 100-fold concentration of EDTA was used. Dissolved iron that was ‘captured’ by the MRT gel was eluted using hydrochloric acid and subsequently determined by graphite furnace atomic absorption spectrometry. The effect of different variables, such as pH, reagent concentration, flow rate and interfering ions, on the recovery of analyte was investigated. Quantitative maximum separation (∼100%) of the dissolved Fe(III) from synthetic aqueous solutions at a natural pH range was observed at a flow rate of 0.2 mL min^-1. The extraction efficiency of the MRT gel is largely unaltered by the coexisting ions commonly found in natural water. When compared with different SPE materials, the separation performance of MRT gel is also much higher.     

Novel polymer monolith microextraction using a poly-(methyl methacrylate-co-ethylene dimethacrylate) monolith and its application to the determination of polychlorinated biphenyls in water samples

A novel and simple method based on polymer monolith microextraction (PMME) coupled to gas chromatography with electron-capture detection (GC-ECD) was developed for the determination of six polychlorinated biphenyls (PCBs) residues in water samples. The proposed method used poly-(methyl methacrylate-co-ethylene dimethacrylate) (MMA-co-EDMA) monolith as extraction media. Several factors affecting experiments such as sample flow rate, sample volume, the type of eluent, eluent volume, eluent flow rate, effect of salt addition and carry over effect were investigated and optimized systematically. The limits of detection (LODs) for six PCBs were 0.028-0.043 ng mL⁻¹ in water samples. The intra-day and inter-day precisions (R.S.D.) were less than 9.2% and 9.6%, respectively. The proposed method was successfully applied to the determination of six PCBs in tap water, lake water and industrial waste water and the trueness has been evaluated by recovery experiments. The obtained relative recoveries were in the range of 63.3-105.6%.     

Fish consumption reduces transfer of BDE47 from dam to murine offspring

Fish and seafood are important contributions to a healthy diet, but also contain persistent organic pollutants (POPs) like polybrominated diphenylethers (PBDEs) and polychlorinated biphenyls (PCBs). Discrepancies have been found between intake and accumulated levels of POPs, where fish consumers have had similar levels of POPs to the general population. Similarly fish oil consumption has been found to reduce accumulation of POPs. This study examined the accumulation of BDE47 or PCB153 in mice fed diets with different nutritional composition, using female mice with pre-weanling pups exposed through gestation and lactation. A fish-based diet was compared to a standard casein-based rodent diet. All diets had low background levels of environmental contaminants and were spiked with BDE47 or PCB153 to levels representing a realistic (∼0.004 μmol kgbw⁻¹ d) or a high dietary exposure (∼1.3 μmol kgbw⁻¹ d). Accumulation of BDE47 or PCB153 in offspring tissues after 18 d lactation reflected the maternal exposure levels. However, the pups of dams fed a fish-based diet had consistently lower BDE47 accumulation in liver, fat and stomach than pups from casein-fed dams. Similarly the pups of dams fed a high dose of PCB153 in a fish diet also accumulated less PCB153 than pups of the dams fed a casein diet, although not significant. In conclusion, the fish based diets seemed to reduce transfer of BDE47 and PCB153 from dams to pups. The study highlights that in-depth knowledge about nutritional impact on toxicokinetics is of great interest to vulnerable consumers.     

Quantification of carbamazepine and atrazine and screening of suspect organic contaminants in surface and drinking waters

A new approach for the identification of suspect trace organic contaminants in drinking and surface waters is presented. Samples were initially analyzed using a target determination method for two contamination tracers, carbamazepine (CBZ) and atrazine (ATZ). This method used offline solid-phase extraction and online solid-phase extraction techniques coupled to liquid chromatography-triple quadrupole mass spectrometry to accelerate the sample preparation process and improve method performance. CBZ and ATZ were found respectively in 31% and 56% of the samples, and concentrations were usually <20 ng L⁻¹. These samples were re-analyzed with a similar method on a quadrupole time-of-flight mass spectrometer to identify suspect contaminants by means of exact mass measurements and isotope patterns. A database of 264 common organic contaminants was built and used in conjunction with a Molecular Feature algorithm to identify the presence of these substances in drinking and surface water collected from different sources at various locations across Canada. Several organic contaminants were identified in the samples, but only the presence of caffeine, desethylatrazine, simazine and venlafaxine could be verified by comparison to pure standards. The presence of desethylatrazine was also confirmed by MS/MS experiments. These results suggest that target analysis for tracers of organic contamination may be a helpful tool to prioritize samples which should be further screened for suspect contaminants. This study also shows that the combination of separation techniques (offline and online SPE, LC) contribute to advance the applicability of high-resolution mass spectrometry for the identification of trace organic contaminants by accelerating the preparation step, reducing complexity and increasing analyte concentrations for optimal detection.     

Naphthenic acid biodegradation by the unicellular alga Dunaliella tertiolecta

Naphthenic acids (NAs) are a major contributor to toxicity in tailings waste generated from bitumen production in the Athabasca Oil Sands region. While investigations have shown that bacteria can biodegrade NAs and reduce tailings toxicity, the potential of algae to biodegrade NAs and the biochemical mechanisms involved remain poorly understood. Here, we discovered that the marine alga Dunaliella tertiolecta is able to tolerate five model NAs (cyclohexanecarboxylic acid, cyclohexaneacetic acid, cyclohexanepropionic acid, cyclohexanebutyric acid and 1,2,3,4-tetrahydro-2-naphthoic acid) at 300 mg L⁻¹, a level which exceeds that of any single or combination of NAs typically found in tailings ponds. Moreover, we show that D. tertiolecta can metabolize four of the model NAs. Analysis of NA-amended cultures of D. tertiolecta via low resolution gas chromatography-mass spectrometry allowed us to quantify decreasing NA levels, identify metabolites, and formulate putative mechanisms of biodegradation. Degradation of cyclohexanebutyric acid and cyclohexanepropionic acid proceeded via β-oxidation and resulted in the transient accumulation of cyclohexaneacetic acid and cyclohexanecarboxylic acid, respectively. Cyclohexanecarboxylic acid was metabolized via 1-cyclohexenecarboxylic acid suggesting that further degradation may occur by step-wise β-oxidation. When D. tertiolecta was inoculated in the presence of oil sands tailings water from the Athabasca region, biodegradation of single-ring NAs was observed relative to controls. This result corroborates the trend we observed with the single-ring model NAs.     

Stable carbon isotope analysis (δ13C values) of polybrominated diphenyl ethers and their UV-transformation products

Polybrominated diphenyl ethers (PBDEs) are frequently detected in food and environmental samples. We used compound specific isotope analysis to determine the δ¹³C values of individual PBDEs in two technical mixtures. Within the same technical product (DE-71 or DE-79), BDE congeners were the more depleted in ¹³C the higher brominated they were. In contrast, the products of light-induced hydrodebromination of BDE 47 and technical DE-79 were more enriched in ¹³C because of more stable bonds between ¹³C and bromine. As a result, the δ¹³C values of the irradiated solution progressed diametrically compared to those of the technical synthesis. The ratio of the δ¹³C values of BDE 47 to BDE 99 and of BDE 99 to BDE 153 are thus suggested as indicators to distinguish native technical products from transformation products. Ratios <1 are typical for native congeners (e.g. in DE-71) while the reversed ratio (>1) is typical of transformation products.