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681.
Many of the products of the reaction of naphthalene (Naph) with the OH radical in a reaction chamber were identified. Previously unidentified products included 1,2-naphthoquinone (NQ), oxygenated indenes and benzopyrones. Possible pathways for the formation of 1,2-NQ and 1,4-NQ are proposed. In the chamber reactions, more 1,2-NQ than 1,4-NQ partitioned to the particle phase. From this result we infer that, in the atmosphere, the percentage of 1,2-NQ in the particle phase should be greater than that for the 1,4-NQ. Because both of these compounds are considered to be toxic, and since they appear in both the gas and particle phases in the reaction chamber, and by implication in the atmosphere, it is considered important that both the gas and particle phases of these two compounds should be measured to assess their impact on human health. 相似文献
682.
The use of flat gas-permeable membranes was investigated as components of a new process to capture and recover ammonia (NH3) in poultry houses. This process includes the passage of gaseous NH3 through a microporous hydrophobic membrane, capture with a circulating dilute acid on the other side of the membrane, and production of a concentrated ammonium (NH4) salt. Bench- and pilot-scale prototype systems using flat expanded polytetrafluoroethylene (ePTFE) membranes and a sulfuric acid solution consistently reduced headspace NH3 concentrations from 70% to 97% and recovered 88% to 100% of the NH3 volatilized from poultry litter. The potential benefits of this technology include cleaner air inside poultry houses, reduced ventilation costs, and a concentrated liquid ammonium salt that can be used as a plant nutrient solution. 相似文献
683.
As more attention is being paid to the characteristics of atmospheric amines, there is also an increasing demand for reliable detection technologies. Herein, a method was developed for simultaneous detection of atmospheric amines in both gaseous and particulate phases using gas chromatography-mass spectrometry (GC-MS). The amine samples were collected with and without phosphoric acid filters, followed by derivatization with benzenesulfonyl chloride under alkaline condition prior to GC-MS analysis. Furthermore, the method was optimized and validated for determining 14 standard amines. The detection limits ranged from 0.0408-0.421 µg/mL (for gaseous samples) and 0.163-1.69 µg/mL (for particulate samples), respectively. The obtained recoveries ranged from 68.8%-180% and the relative standard deviation was less than 30%, indicating high precision and good reliability of the method. Seven amines were simultaneously detected in gaseous and particulate samples in an industrial park using the developed method successfully. Methylamine, dimethylamine and diethylamine together accounted for 76.7% and 75.6% of particulate and gaseous samples, respectively. By comparing the measured and predicted values of gas-particle partition fractions, it was found that absorption process of aqueous phase played a more important role in the gas-partition of amines than physical adsorption. Moreover, the reaction between unprotonated amines and acid (aq.) in water phase likely promoted water absorption. Higher measured partition fraction of dibutylamine was likely due to the reaction with gaseous HCl. The developed method would help provide a deeper understanding of gas-particle partitioning as well as atmospheric evolution of amines. 相似文献
684.
A method for measuring gas entrapment in granular iron (Fe0) was developed and used to estimate the impact of gas production on porosity loss during the treatment of a high NO3- groundwater (up to approximately 10 mM). Over the 400-d study period the trapped gas in laboratory columns was small, with a maximum measured at 1.3% pore volume. Low levels of dissolved H2(g) were measured (up to 0.07+/-0.02 M). Free moving gas bubbles were not observed. Thus, porosity loss, which was determined by tracer tests to be 25-30%, is not accounted for by residual gas trapped in the iron. The removal of aqueous species (i.e., NO3-, Ca, and carbonate alkalinity) indicates that mineral precipitation contributed more significantly to porosity loss than did the trapped gases. Using the stoichiometric reactions between Fe0 and NO3-, an average corrosion rate of 1.7 mmol kg-1 d-1 was derived for the test granular iron. This rate is 10 times greater than Fe0 oxidation by H2O alone, based on H2 gas production. NO3- ion rather than H2O was the major oxidant in the groundwater in the absence of molecular O2. The N-mass balance [e.g., N2g and NH4+ and NO3-] suggests that abiotic reduction of NO3- dominated at the start of Fe0 treatment, whereas N2 production became more important once the microbial activity began. These laboratory results closely predict N2 gas production in a separated large column experiment that was operated for approximately 2 yr in the field, where a maximum of approximately 600 ml d-1 gas volumes was detected, of which 99.5% (v/v) was N2. We conclude that NO3- suppressed the production of H2(g) by competing with water for Fe0 oxidation, especially at the beginning of water treatment when Fe0 is highly reactive. Depends on the groundwater composition, gas venting may be necessary in maintaining PRB performance in the field. 相似文献
685.
686.
建立了二氯甲烷提取、高效毛细管柱分离、气相色谱-氮磷检测器测定水中呋喃丹的方法.优化了试验条件,以HP-5和HP-1301双柱定性,方法在0.00 mg/L~1.00 mg/L之间线性良好,检出限为2.0×10-5 mg/L,RSD≤6.5%,加标回收率为93.6%~110%. 相似文献
687.
688.
吹扫捕集-色质联机测定水中挥发性硫醚 总被引:2,自引:1,他引:2
采用吹扫捕集-色质联机测定水中挥发性硫醚,采用外标法,使用SIM模式对甲硫醚、乙硫醚和二甲二硫醚三种成分进行定量,方法的检出限分别为0.02、0.05和0.08μg/L,三种物质浓度在0.40~40μg/L范围内,测定结果有良好的线性,一次回归曲线的相关系数分别为0.9998、0.9999和0.9999。利用该方法对内河等实际样品进行分析,结果平行性良好,加标回收率在75.2%~88.4%之间。 相似文献
689.
气相色谱与原子吸收联用的几种连接方法的比较及其评价 总被引:1,自引:0,他引:1
对气相色谱与原子吸收联用的几种连接方法进行了比较,对几种连接方法的性能做了评价,并就操作条件选择、影响分离和测定的一些因素等进行了讨论。 相似文献
690.