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221.
Hao Chen Renzhi Hu Pinhua Xie Xingbiao Xing Liuyi Ling Zhiyan Li Fengyang Wang Yihui Wang Jianguo Liu Wenqing Liu 《环境科学学报(英文版)》2018,30(3):190-200
An OH radical measurement instrument based on Fluorescence Assay by Gas Expansion(FAGE)has been developed in our laboratory.Ambient air is introduced into a low-pressure fluorescence cell through a pinhole aperture and irradiated by a dye laser at a high repetition rate of 8.5 k Hz.The OH radical is both excited and detected at 308 nm using A-X(0,0)band.To satisfy the high efficiency needs of fluorescence collection and detection,a 4-lens optical system and a self-designed gated photomultiplier(PMT)is used,and gating is actualized by switching the voltage applied on the PMT dynodes.A micro channel photomultiplier(MCP)is also prepared for fluorescence detection.Then the weak signal is accumulated by a photon counter in a specific timing.The OH radical excitation spectrum range in the wavelength of 307.82–308.2 nm is detected and the excited line for OH detection is determined to be Q_1(2)line.The calibration of the FAGE system is researched by using simultaneous photolysis of H_2O and O_2.The minimum detection limit of the instrument using gated PMT is determined to be 9.4×10~5molecules/cm~3,and the sensitivity is 9.5×10~(-7)cps/(OH·cm~(-3)),with a signal-to-noise ratio of 2 and an integration time of 60 sec,while OH detection limit and the detection sensitivity using MCP is calculated to be 1.6×10~5molecules/cm~3and 2.3×10~(-6)cps/(OH·cm~(-3)).The laboratory OH radical measurement is carried out and results show that the proposed system can be used for atmospheric OH radical measurement. 相似文献
222.
Silicones are well-known useful materials varying in structure, reactivity, and chemical and physical properties, but they all contain a covalent bond between the silicon atom and an organic group. Most common of these polymers are those based on polydimethylsiloxane (PDMS) having a siloxane (Si–O–Si) repeat unit and two methyl groups on each silicon atom. All these polymers are manmade, and the organosilicon linkage is not found in nature. It was therefore erroneously assumed that these polymers do not degrade naturally in the environment. It is the purpose of this review to refute this myth and to describe the degradation processes of PDMS in the environment and any potential ecological impact on the terrestrial, aquatic, and atmospheric compartments. Although it was found that minor degradation takes place by hydrolysis of PDMS to dimethylsilandiol followed by oxidation of the methyl group to aldehyde and ultimately to CO2 by Arthobacter and Fusarium oxysporium schlechtendahl, the major degradation processes are abiotic. High molecular weight PDMS are initially depolymerized by soil hydrolysis of the siloxane bonds to yield organosilanol terminated oligomers. These organosilanols and low molecular weight linear PDMS and cyclics are evaporated into the atmosphere and are oxidized there by hydroxyl radicals to benign silica, water, and CO2. 相似文献
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224.
利用碳酸盐矿化菌在底物诱导下的酶化作用,分解产生碳酸根离子,矿化固结环境(土壤水体)当中的游离重金属离子,减少其危险。文章以Zn2+溶液模拟重金属离子污染体系,研究过程中发现,生产的矿化产物主要是ZnO.5(OH)62(CO)3。分别用菌粉和菌液进行微生物矿化试验,对矿化产物进行底物分解率,SEM,XRD,矿化粒径的对比研究。从对比研究结果看,菌粉复活后,可以达到与菌液基本相同的矿化效果。而菌粉相对于菌液而言,其主要优势在于能长时间储存,产品体积小,运输起来更方便,因此,菌粉具有更广泛的应用性。 相似文献
225.
CuCl2 does not cause Trp+ reversion in E. coli WP2. However, when the bacteria are exposed to CuCl2 and UV‐irradiated, a greater than 3‐fold enhancement of mutagenesis (compared to UV alone) is seen at 30 μMCuCl2, and significant enhancement is seen even at 3 μM. The mechanism for this comutagenic effect was studied using a restriction fragment of the E. coli gpt gene. Whereas UV or CuCl2 alone caused few strand breaks, UV + CuCl2 induced breaks at every site. This reaction was blocked by KI, a free radical scavenger. While UV alone induced alkali‐labile sites, UV+ CuCl2 induced many more such sites and altered the sequence specificity. We suggest that at least some of the comutagenic effect might be due to hydroxyl radical formed via a Fenton reaction. 相似文献
226.
在实验室模拟条件下,研究了Shewanella oneidensis MR-1作用下Fe(III)还原和As(III)氧化动力学及其影响因素.结果表明,Fe(III)被还原为Fe(II)的同时伴随着As(III)氧化为As(V);S. oneidensis MR-1 在含低浓度As(III)培养基上生长良好,在高浓度培养基上生长被抑制;As(III)通过制约菌体的生长与活性来抑制Fe(III)异化还原.同样,适量浓度的Fe(III)含量对As(III)氧化转化有很强的促进作用,但是过高浓度的Fe(III)浓度使得溶液中产生过多的Fe(II),从而对As(III)氧化转化有一定程度的抑制作用.此外,弱碱环境更有利于As(III)氧化转化. 相似文献
227.
Phosphate residue is a kind of hazardous solid waste and if not properly disposed of, could cause serious environmental contaminations. The abundant iron salt available in phosphate residue can be used to prepare photo-Fenton catalytic reagent for wastewater treatment. In this study, the phosphate residue was effectively purified by a hydrothermal recrystallization method, reaching an iron phosphate purity of 94.2%. The particles of iron phosphate were further processed with ball milling with th... 相似文献
228.
氢氧化镁是一种正在研究的用于脱除烟气中低浓度CO2的化学吸收剂。为了掌握工业用氢氧化镁粉末的溶解速率,利用缓冲溶液,在不改变溶液体积的情况下对不同悬浊液浓度、溶液温度、溶液pH值和搅拌速率情况下的氢氧化镁粉末溶解速率进行了研究。提高悬浊液浓度、提高溶液温度、降低溶液pH值和提高搅拌速率均能增大氢氧化镁的溶解速率。悬浊液浓度从0.1 mol/L增加到1 mol/L时,溶解速率增大了2.2倍;温度从23℃增加到52℃时,溶解速率增大了4.3~9.5倍;pH值从9.8降低到6.6时,溶解速率增大了78~225倍;搅拌速率从350 r/min增加到700 r/min时,溶解速率增大了1~2倍。 相似文献
229.
Public concerns over the toxicity of nanoparticles (NPs) are growing due to the rapid development of nanotechnology. An important mechanism of nanotoxicity is oxidative stress resulting from reactive oxygen species (ROS). In this study, the chemical production of ROS by inorganic NPs oxidizing the mammalian phenolic compound, l-3,4-dihydroxyphenylalanine (l-dopa) was evaluated using a ROS sensitive dye, 2′,7′-diclorodihydrofluorescin (DCFH). CeO2, Fe2O3 and Fe0 NPs enhanced ROS production during the autoxidation of l-dopa by more than four-fold in reactions that were dependent on O2. This is the first report of chemical ROS production due to interaction of phenolic compounds with NPs. Mn2O3 oxidized DCFH in a reaction that did not require O2 or l-dopa, suggesting a direct redox reaction between the Mn2O3 and the dye. CeO2, Mn2O3 and to a lesser extent Fe0 formed clear electron paramagnetic resonance (EPR) signature for hydroxyl radicals when incubated in aerobic aqueous suspensions with spin traps. The results indicate that NPs can generate ROS via chemical reactions with medium components and biomolecules susceptible to oxidation, such as l-dopa. NPs were reactive whereas micron-sized particles were not. The combined assay with l-dopa and DCFH is a method proposed to screen for chemical ROS production by NPs. 相似文献
230.
Free radical generation potential of automobile exhaust gas was examined by measuring hydroxyl (OH) radical photo-formation rates in exhaust gas-scrubbing water. Effects of automobile exhausts on physiological status of Japanese red pine trees (Pinus densiflora Sieb. et Zucc.) were also investigated to elucidate the mechanism how the free radicals derived from exhaust gas damage higher plants. Gasoline and diesel exhaust gases were scrubbed into pure water. Potential photo-formation rates of OH radical in aqueous phase (normalized to sun light intensity of clear sky midday on May 1 at 34°N) for gasoline and diesel cars were ave. 51 and 107 μM h−1 m−3 of exhaust gas, respectively. Nitrite was a dominant source (ca. 70-90%) of photochemical formation of OH radical in both gasoline and diesel car exhausts. The scrubbed solution of diesel car exhaust gas was sprayed for six times per week to needles of pine tree seedlings in open top chambers. Control, exhaust + mannitol (added as OH radical scavenger), and nitrite + nitrate standard solution (equivalent levels existed in the exhaust gas) were also sprayed. Two months sprays indicated that the sprayed solutions of diesel exhaust and nitrite + nitrate caused a decrease of maximum photosynthetic rate and stomata conductance in pine needles while the control and exhaust + mannitol solution showed no effects on photosynthetic activities of pine needles. These results indicated that OH radicals generated mainly from photolysis of nitrite occurring in the scrubbing solution of exhaust gas are responsible for the decrease of photosynthetic activities of pine needles. 相似文献