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331.
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The generation of reactive species in an aqueous goethite suspension, under room light and aeration conditions, was investigated using the electron paramagnetic resonance (EPR) technique employing spin trap agents. The trap reagents, including 5,5-dimethylpyrroline N-oxide (DMPO) and 2,2,6,6-tetramethylpiperidine (TEMP), were used for the detection of OH radicals (OH) and singlet oxygen (1O2), respectively. On the addition of DMPO to the goethite suspended solution, a DMPO-OH adduct was formed, which was not decreased, even in the presence of the OH scavenger, mannitol. This result implied a false positive interpretation from the DMPO-OH EPR signal. In the presence of TEMP reagent, a TEMP-O signal was detected, which was completely inhibited in the presence of the singlet oxygen scavenger, sodium azide. With both DMPO-OH and TEMP-O radicals in the presence and absence of radical scavengers, singlet oxygen was observed to be the key species formed in the room-light sensitized goethite suspension. In the goethite/H2O2 system; however, both OH and singlet oxygen were generated, with significant portions of DMPO-OH resulting from both OH and singlet oxygen. In fact, the DMPO-OH resulting from OH should be carefully calculated by correcting for the amount of DMPO-OH due to singlet oxygen. This study reports, for the first time, that the goethite suspensions may also act as a natural sensitizer, such as fulvic acids, to form singlet oxygen. 相似文献
333.
自振柱试验是测量土样动剪切模量和阻尼比的常用方法,但由于噪声等环境因素的影响,土样扭剪自由振动的衰减波曲线有时会因高频干扰出现不平滑现象,难以得到合理的测试结果。软件数字滤波是解决这类问题的有效方法。本文通过多种软件数字滤波方法优缺点的对比,认为平均滤波法和惯性滤波法能有效解决试验数据中的高频干扰问题,并分别选择适当的滤波参数,得到了平滑的自振衰减波曲线;最后,采用平均滤波法处理了两组自振柱试验数据。结果表明,软件滤波法确能有效消除不合理数据,得到符合一般规律的土体动剪切模量和阻尼比试验结果,从而验证了其在土体自振柱试验中的应用价值。 相似文献
334.
在不同pH值、Fe2浓度和过硫酸氢钾复合盐(PMS)浓度下,探究降解萘普生(NPX)的最佳条件,并通过分批投加Fe2+和改变投加顺序的方式,提高降解NPX的效率.结果表明,NPX在pH =3的条件下,降解效果最好;Fe2+浓度改变时,PMS/Fe2+/NPX=1/0.75/1条件下,NPX去除率最高;分批投加Fe2+和先投加Fe2+均可大幅提高NPX去除率.缓慢少量的产生硫酸根自由基(SO4--)更利于处理有机物,Fe2+的浓度则在产生自由基方面起着重要作用. 相似文献
335.
Ping Zhang Li M. Wang Tai F. Lin Xiao D. Wei Xiao Y. Liu 《Journal of environmental science and health. Part. B》2013,48(9):561-566
ABSTRACTA rapid and quantitative method for the determination of N6-Benzylademine (N6-BA) was established through the application of surface-enhanced Raman spectroscopy (SERS). The Raman peak intensities of N6-BA at 1002 cm?1 positively correlated to N6-BA concentrations in sprout extracts. The R2 reached 0.99, and RSDs calculated below 10% at the concentration range of 0.1 ~5μg mL?1. The average recoveries were 80.0% ~ 98.2% for blank samples intentionally contaminated at differing levels of 0.04, 0.4, and 1 μg g?1. The whole procedure, including sample preparation and SERS detection, did not exceed 30 min for a set of 6 samples. This study indicates that SERS is a promising technique for rapid tracing analysis and on-site testing of N6-BA. 相似文献
336.
K.M.S. Sundaram 《Journal of environmental science and health. Part. B》2013,48(3):541-579
Abstract Two formulation concentrates of the insecticide, RH‐5992 [N'‐t‐butyl‐N'‐(3,5‐dimethylbenzoyl)‐N‐(4‐ethylbenzoyI) hydrazine], an aqueous flowable (2F) and an emulsion‐suspension (ES), were diluted with water to provide spray mixes containing dosage rates ranging from 35 to 150 g of the active ingredient (AI)/ha. The mixes were sprayed in a laboratory chamber, onto balsam fir branch tips collected from field trees and greenhouse‐grown seedlings. Droplet spectra and spray mass recovery were determined on artificial samplers. Simulated rainfall of two different intensities was applied at different rain‐free periods, and rain droplet sizes were determined. Foliar washoff of RH‐5992 was assessed after application of different amounts of rain, and the increase in soil residues was evaluated. A direct relationship was indicated between the amount of rainfall and RH‐5992 washoff. The larger the rain droplet size, the greater the amount washed off. Longer rain‐free periods made the deposits more resistant to rain. Regardless of the amount of rainfall, rain droplet size and rain‐free period, foliar deposits of the 2F formulation were washed off to a greater extent than the ES formulation. The increase in soil residues due to foliar washoff was greater for the 2F than for the ES formulation. The deposits of the emulsion‐suspension were consistently more resistant to rain‐washing than those of the aqueous flowable formulation. 相似文献
337.
以好氧颗粒污泥接种小试柱形SBR,采用自配无机氨氮废水为进水,在中温(28~30℃)条件下通过逐步提升进水NH4^+-N浓度(100~650mg/L)和缩短水力停留时间(8~4h)快速培养硝化颗粒污泥。实验结果证实,以好氧颗粒污泥接种可以促使硝化颗粒污泥快速形成,36d时粒径〉0.21mm的颗粒污泥占总数的93%,颗粒污泥NH4-N比去除速率为50.53mgNH4^+-N/(gSS·h)。硝化颗粒污泥具有良好的短程硝化性能,亚硝酸盐产生速率和累积率分别保持在3.3kgNO2-N/(m^3·d)和85%以上。反应初期高FA和反应末期高FNA的共同抑制是该研究中实现和维持稳定短程硝化的关键因素。 相似文献
338.
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340.
M. Rajagopal 《International Journal of Green Energy》2016,13(11):1109-1119
A phase change material (PCM)-based flat plate modular heat exchanger for free cooling application, suitable for the diurnal temperature variation that prevails during the summer months of Bangalore city, India is designed and experimentally investigated. The flow and other parameters selected in the present study are meant to suit the accelerated charging of the PCM in the modular heat exchanger during the early morning hours, and to provide cool energy to the room during the daytime, by circulating the ambient air through the heat exchanger at a lower velocity. It is observed from the charging experiments that the decrease in the inlet air temperature has more influence in reducing the solidification time than the increase in the inlet air velocity. The heat exchanger designed in the present investigation is capable of maintaining the room temperature around 30°C for a longer duration of 8 hr when the heat load is 0.5 kW. It is suggested to design the modular heat exchanger with a surface area proportionate to the present heat exchanger size when the room heat load increases beyond 0.5 kW, in order to maintain a minimum comfortable temperature of 30°C in the room. 相似文献