共查询到16条相似文献,搜索用时 187 毫秒
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通过共沉淀法制备纳米Fe_2O_3-SnO_2光催化剂,采用XRD、SEM等测试手段对其进行形貌、物象、粒径一系列的表征,研究结果显示制得的催化剂仍保持纯SnO_2四方金红石型结构.研究了Fe_2O_3-SnO_2光催化剂投加量、Fe_2O_3与SnO_2物质的量比、煅烧温度、煅烧时间、氨氮初始浓度、p H值、H2O2浓度以及光照反应时间等因素对海水养殖废水中氨氮降解效率的影响.在紫外光照射下进行正交实验,确定最优化反应条件:催化剂投加量为0.4 g/dm3,煅烧时间为3 h,物质的量比为1∶2,氨氮初始含量为50 mg/dm3,光照反应时间为2 h.这5个因素对Fe_2O_3-SnO_2光催化氧化速率影响的大小程度依次为:Fe_2O_3与SnO_2物质的量比煅烧时间Fe_2O_3-SnO_2光催化剂投加量氨氮初始浓度光照时间.氨氮去除率可以达到85.1%,相同条件可见光下也可达到82.3%. 相似文献
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The invasions of the alien species such as Spartina alterniflora along the northern Jiangsu coastlines have posed a threat to biodiversity and the ecosystem function.Yet,limited attention has been given to their potential influence on greenhouse gas(GHG) emissions,including the diurnal variations of GHG fluxes that are fundamental in estimating the carbon and nitrogen budget.In this study,we examined the diurnal variation in fluxes of carbon dioxide(CO_2),methane(CH_4),and nitrous oxide(N2O) from a S.alterniflora intertidal flat in June,October,and December of 2013 and April of 2014 representing the summer,autumn,winter,and spring seasons,respectively.We found that the average CH_4 fluxes on the diurnal scale were positive during the growing season while negative otherwise.The tidal flat of S.alterniflora acted as a source of CH_4 in summer(June) and a combination of source and sink in other seasons.We observed higher diurnal variations in the CO_2 and N_2O fluxes during the growing season(1 536.5 mg CO_2 m~(–2) h~(–1) and 25.6 μg N_2O m~(–2) h~(–1)) compared with those measured in the non-growing season(379.1 mg CO_2 m~(–2) h~(–1) and 16.5 μg N_2O m~(–2) h~(–1)).The mean fluxes of CH_4 were higher at night than that in the daytime during all the seasons but October.The diurnal variation in the fluxes of CO_2 in June and N_2O in December fluctuated more than that in October and April.However,two peak curves in October and April were observed for the diurnal changes in CO_2 and N_2O fluxes(prominent peaks were found in the morning of October and in the afternoon of April,respectively).The highest diurnal variation in the N_2O fluxes took place at 15:00(86.4 μg N_2O m~(–2) h~(–1)) in June with an unimodal distribution.Water logging in October increased the emission of CO_2(especially at nighttime),yet decreased N_2O and CH_4 emissions to a different degree on the daily scale because of the restrained diffusion rates of the gases.The seasonal and diurnal variations of CH_4 and CO_2 fluxes did not correlate to the air and soil temperatures,whereas the seasonal and diurnal variation of the fluxes of N_2O in June exhibited a significant correlation with air temperature.When N_2O and CH_4 fluxes were converted to CO_2-e equivalents,the emissions of N_2O had a remarkable potential to impact the global warming.The mean daily flux(MF) and total daily flux(TDF) were higher in the growing season,nevertheless,the MF and TDF of CO_2 were higher in October and those of CH_4 and N_2O were higher in June.In spite of the difference in the optimal sampling times throughout the observation period,our results obtained have implications for sampling and scaling strategies in estimating the GHG fluxes in coastal saline wetlands. 相似文献
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基于自旋-轨道-晶格Hamilton量,应用团簇自洽场方法,研究了双层钙钛矿结构材料K3Cu2F7基态的晶格、磁及轨道结构,发现近孤立的双层的对称破缺和Jahn-Teller晶格畸变使得Cu2+离子在每层内交替占据 z2-x2〉/ z2-y2〉轨道,进而导致双层的层间表现为强的反铁磁耦合,层内为弱的铁磁耦合.强反铁磁耦合导致层间 相似文献
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采用化学沉淀法成功制备了Cu2+/SnO2复合纳米光催化剂,采用XRD、SEM等测试手段对复合纳米光催化剂的粒径、形态等进行表征。在紫外光条件下,分别改变催化剂掺杂比、催化剂煅烧温度、催化剂投加量、柴油初始含量和光照时间等单因素,探究不同条件对Cu2+/SnO2复合纳米光催化剂降解海洋柴油污染物的影响。结果表明,自制复合纳米光催化剂可以有效降解海水中的柴油污染物,在紫外光作用下,于400℃下煅烧Cu/Sn掺杂比为0. 03的Cu2+/SnO2复合纳米光催化剂、投加量为0. 2 g/dm3、柴油初始含量为0. 15 g/dm3、H2O2溶液含量为0. 2 g/dm3、溶液的p H为7、光照时间3 h时效果最好,海水中柴油的去除率最高,达到86. 98%。Cu2+/SnO2复合纳米光催化剂用聚丙烯纳米球负载后可以实际应用于海洋中,便于回收。 相似文献
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于2014年的5月(春季)和9月(秋季)在台湾海峡及其邻近南海和东海海域,采用水气平衡法进行了2个航次的海表和大气pCO_2连续走航观测,同时获取了海表温度、海表盐度、风速及气压等数据,并采用海-气CO_2分压差减法估算了海-气CO_2通量.结果显示,春、秋2个航次平均海表pCO_2分别为387±16μatm和408±18μatm.温度是影响台湾海峡及其邻近海域海表pCO_2的主控因子,水团混合和其他因素等也对海表pCO_2有一定影响.2014年春、秋季节,对研究区域的海-气CO_2释放通量的估算结果分别为0.11±1.60 mmol/(m2·d)和2.51±1.10 mmol/(m2·d).台湾海峡海表pCO_2既存在显著的季节变化,又存在较大的空间差异. 相似文献
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This paper reports that stoichiometric, amorphous, and uniform Er2O3 films are deposited on Si(001) substrates by a radio frequency magnetron sputtering technique. Ellipsometry measurements show that the refractive index of the Er2O3 films is very close to that of a single layer antireflection coating for a solar cell with an air surrounding medium during its working wavelength. For the 90-nm-thick film, the reflectance has a minimum lower than 3% at the wavelength of 600 nm and the weighted average reflectances (400--1000 nm) is 11.6%. The obtained characteristics indicate that Er2O3 films could be a promising candidate for antireflection coatings in solar cells. 相似文献
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生物固氮作用是一个重要的海洋新氮来源,在海洋生物地球化学循环中扮演着不可替代的角色。基于稳定同位素(15N2)示踪吸收法,是目前直接测定海洋生物固氮速率最有效的手段。其中,高效、洁净地将15N2引入海水培养体系,并准确定量培养体系底物的同位素示踪水平,是同位素示踪吸收法准确获取固氮速率的关键。本研究针对15N2同位素示踪剂引入这一关键环节进行了探讨,确认改进气泡法是将15N2引入海水培养体系的首选操作。在对培养体系造成的较小扰动的情况下,可将培养体系氮气底物的15N原子丰度提升至10%以上,相对于另一种导入同位素示踪剂的手段——预溶解海水法,改进气泡法将培养瓶中氮气底物的15N原子丰度提升了近200%。此外,改进气泡法还具有最小化痕量金属沾污、操作简便等优点。将改进气泡法结合与稳定同位素比值质谱测定结合,是准确测定水体生物固氮速率的推荐方法。 相似文献
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The generalised gradient approximation based on density functional theory is used to study the structural and electronic properties of the endohedral fullerene dimer (N2@C60)2. Four N atoms sit at the cage centres in the form of two N_2 molecules. The density of states and Mulliken charge analysis explore that the energy levels from -6 to -10 eV are mainly influenced by the N2 molecules. 相似文献
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This paper evaluates the simultaneous measurement of dissolved gases (CO2 and O2/Ar ratios) by membrane inlet mass spectrometry (MIMS) along the 180° meridian in the Southern Ocean. The calibration of pCO2 measurements by MIMS is reported for the first time using two independent methods of temperature correction. Multiple calibrations and method comparison exercises conducted in the Southern Ocean between New Zealand and the Ross Sea showed that the MIMS method provides pCO2 measurements that are consistent with those obtained by standard techniques (i.e. headspace equilibrator equipped with a Li–Cor NDIR analyser). The overall MIMS accuracy compared to Li–Cor measurements was 0.8 μatm. The O2/Ar ratio measurements were calibrated with air-equilibrated seawater standards stored at constant temperature (0 ± 1 °C). The reproducibility of the O2/Ar standards was better than 0.07% during the 9 days of transect between New Zealand and the Ross Sea.The high frequency, real-time measurements of dissolved gases with MIMS revealed significant small-scale heterogeneity in the distribution of pCO2 and biologically-induced O2 supersaturation (ΔO2/Ar). North of 65°S several prominent thermal fronts influenced CO2 concentrations, with biological factors also contributing to local variability. In contrast, the spatial variation of pCO2 in the Ross Sea gyre was almost entirely attributed to the biological utilization of CO2, with only small temperature effects. This high productivity region showed a strong inverse relationship between pCO2 and biologically-induced O2 disequilibria (r2 = 0.93). The daily sea air CO2 flux ranged from − 0.2 mmol/m2 in the Northern Sub-Antarctic Front to − 6.4 mmol/m2 on the Ross Sea shelves where the maximum CO2 influx reached values up to − 13.9 mmol/m2. This suggests that the Southern Ocean water (south of 58°S) acts as a seasonal sink for atmospheric CO2 at the time of our field study. 相似文献
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The 3rd Chinese National Arctic Research Expedition(CHINARE–Arctic III) was carried out from July to September in 2008. The partial pressure of CO2(pCO2) in the atmosphere and in surface seawater were determined in the Bering Sea during July 11–27, 2008, and a large number of seawater samples were taken for total alkalinity(TA) and total dissolved inorganic carbon(DIC) analysis. The distributions of CO2 parameters in the Bering Sea and their controlling factors were discussed. The pCO2 values in surface seawater presented a drastic variation from 148 to 563 μatm(1 μatm = 1.013 25×10-1 Pa). The lowest pCO2 values were observed near the Bering Sea shelf break while the highest pCO2 existed at the western Bering Strait. The Bering Sea generally acts as a net sink for atmospheric CO2 in summer. The air-sea CO2 fluxes in the Bering Sea shelf, slope, and basin were estimated at-9.4,-16.3, and-5.1 mmol/(m2·d), respectively. The annual uptake of CO2 was about 34 Tg C in the Bering Sea. 相似文献