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31.
Jasper Lewis Russell De Young Richard Ferrare D. Allen Chu 《Atmospheric environment (Oxford, England : 1994)》2010,44(35):4510-4520
Aerosol distributions from two aircraft lidar campaigns conducted in the California Central Valley are compared in order to identify seasonal variations. Aircraft lidar flights were conducted in June 2003 and February 2007. While the ground PM2.5 (particulate matter with diameter ≤ 2.5 μm) concentration was highest in the winter, the aerosol optical depth (AOD) measured from the MODIS and lidar instruments was highest in the summer. A multiyear seasonal comparison shows that PM2.5 in the winter can exceed summer PM2.5 by 68%, while summer AOD from MODIS exceeds winter AOD by 29%. Warmer temperatures and wildfires in the summer produce elevated aerosol layers that are detected by satellite measurements, but not necessarily by surface particulate matter monitors. Temperature inversions, especially during the winter, contribute to higher PM2.5 measurements at the surface. Measurements of the mixing layer height from lidar instruments provide valuable information needed to understand the correlation between satellite measurements of AOD and in situ measurements of PM2.5. Lidar measurements also reflect the ammonium nitrate chemistry observed in the San Joaquin Valley, which may explain the discrepancy between the MODIS AOD and PM2.5 measurements. 相似文献
32.
Chuan-Yao Lin C.-C. Chang C.Y. Chan C.H. Kuo W.-C. Chen D. Allen Chu Shaw C. Liu 《Atmospheric environment (Oxford, England : 1994)》2010,44(2):182-193
To quantify the possible sources of the high ambient ozone concentration in the low troposphere over Taiwan, ozone sounding data from a two-year intensive field measurement program conducted in April and early May of 2004 and 2005 in northern Taiwan has been examined. We found that the vertical ozone distributions and occurrence of enhanced ozone in the lower troposphere (below 6 km) mainly resulted from (1)Type NE: the long-range transport of ozone controlled by the prevailing northeasterly winds below 2 km, (2)Type LO: the local photochemical ozone production process, and (3)Type SW: the strong southwest/westerly winds aloft (2–6 km). In the boundary layer (BL), where Asian continental outflow prevails, the average profile for type NE is characterized by a peak ozone concentration of nearly 65 ppb at about 1500 m altitude. For type LO, high ozone concentration with an average ozone concentration greater than 80 ppb was also found in the BL in the case of stagnant atmospheric and sunny weather conditions dominated. For type SW, significant ozone enhancement with average ozone concentration of 70–85 ppb was found at around 4 km altitude. It is about 10 ppb greater than that of the types NE and LO at the same troposphere layer owing to the contribution of the biomass burning over Indochina. Due to Taiwan's unique geographic location, the complex interaction of these ozone features in the BL and aloft, especially features associated with northeasterly and south/southwesterly winds, have resulted in complex characteristics of ozone distributions in the lower troposphere over northern Taiwan. 相似文献
33.
KOH活化花生壳生物质炭对亚甲基蓝吸附性能研究 总被引:2,自引:0,他引:2
以花生壳生物质炭(P-BC)为原料,KOH为活化剂,采用化学活化法制得活化生物质炭(K-BC),通过考察对亚甲基蓝的吸附性能,研究了花生壳生物质炭的最佳活化条件,并利用N2吸附-脱附实验、SEM等对最佳活化条件下的生物质炭进行表征。结果表明,K-BC活化的最佳条件为碱炭比为1.5∶1,活化温度为800℃,活化时间为90 min,此时K-BC的比表面积达到597.93 m2/g,总孔容达到0.76 cm3/g。并考察了亚甲基蓝初始浓度、pH等对K-BC吸附亚甲基蓝的影响,随着初始浓度的增加,吸附平衡时间显著延长,亚甲基蓝去除率显著降低;当pH=6时,K-BC对亚甲基蓝的吸附量最大;K-BC对亚甲基蓝的吸附动力学曲线符合伪二阶动力学模型,吸附平衡时K-BC对亚甲基蓝的吸附能力为80~149.95 mg/g。 相似文献
34.
Hsin Chu Guang Huei Hao Ting Ke Tseng 《Journal of the Air & Waste Management Association (1995)》2013,63(4):574-581
ABSTRACT The catalytic incineration of dimethyl sulfide and dimethyl disulfide [(CH3)2S and (CH3)2S2] over an MnO/Fe2O3 catalyst was carried out in a bench-scale catalytic incinerator. Three kinetic models (i.e., the power-rate law, the Mars and Van Krevelen model, and the Langmuir-Hinshelwood model) were used to analyze the results. A differential reactor design was used for best fit of kinetic models in this study. The results show that the Langmuir-Hinshelwood model may be feasible to describe the catalytic incineration of (CH3)2S and (CH3)2S2. This suggests that the chemical adsorption of O2 molecules is important in this incineration. 相似文献
35.
This study investigated the performance of lab-scale sequencing batch reactors (SBRs) that were inoculated with nitrifying activated sludge and bioaugmented with a Sphingomonas strain KC8 (a 17β-estradiol-degrading bacterium). The bioaugmented SBRs were supplied with synthetic wastewater (average initial total organic carbon (TOC) = 175 mg L−1 and average initial ammonia-N = 25 mg L−1) and daily dose of 17β-estradiol (1 mg L−1) and operated under three solid retention times (SRTs) of 5, 10, and 20 d. After three times periods of the operating SRTs, the overall removal of TOC (>87%) and ammonia (>91%) was similar in all the SBRs. Higher 17β-estradiol removals (>99%) were observed for the SBRs. Neither estrogens nor estrogenic activity was detected in the treated water, except some samples from the SBR operating under 5 d of SRT. The ratios of known estrogen degraders (Sphingomonas strain KC8 and ammonia-oxidizing bacteria) and amoA gene to the total bacterial population decreased as SRT increased, suggesting the presence of unknown estrogen-degraders in SBRs operating at SRT = 10 and 20 d. Real-time-terminal-restriction fragment length polymorphism analysis showed that the evenness of microbial community structures was not affected by the SRT; while, the diversity indices suggest that longer SRTs might lead to more diverse microbial community structure. Overall, the results suggested that bioaugmented bioreactors operating at long SRTs (10 and 20 d) were effective in removing 17β-estradiol to the non-estrogenic treatment endpoint. 相似文献
36.
研究构建了2个容积为1.1 L的好氧活性污泥反应器(即1号和2号反应器)1,号反应器每天直接通加低剂量臭氧(投加量为0.01 g O3/g TSS),不加臭氧的2号反应器作为对照平行运行,均采用每天换一次人工污水的充/排式操作。运行71 d的结果表明2,个反应器对人工污水COD的处理效果基本相同。反应器运行40 d后1,号反应器的污泥浓度比2号反应器的污泥浓度低1 400~1 700 mg/L并可稳定在8 200 mg/L,污泥减量化效果明显。低剂量臭氧的直接通加明显降低了胞内ATP浓度,并影响了微生物的抗氧化活性,2号反应器的平均超氧化物歧化酶和过氧化氢酶酶活比1号反应器分别高了24.3%和9.5%。PCR-DGGE对两反应器微生物种群的分析结果表明:Uncultured gammaproteobacteria bacteri-um、Nannocystis exedens和Uncultured actinobacterium为1号反应器的主要种群;而2号反应器的主要种群为Uncultured bacte-rium和Uncultured gammaproteobacteria bacterium。 相似文献
37.
复合型CoO/TiO2光催化剂降解亚甲基蓝动力学研究 总被引:1,自引:0,他引:1
以钛酸四丁酯为前驱体,采用溶胶凝胶法,制备了CoO掺杂的TiO2光催化剂。利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外可见漫反射(UV-vis DRS)对催化剂进行了分析、表征。以中压汞灯为光源,研究了亚甲基蓝(MB)在CoO/TiO2微粒水悬浮液中的降解动力学。结果表明:所制备的催化剂活性组分主要是锐钛矿型的二氧化钛和CoO固溶体,粒径为25~30 nm,分布均匀。亚甲基蓝的光催化降解动力学满足一级动力学,在一定的浓度范围内,反应速率常数随初始浓度增大而减少,适当的掺钴量可以有效地提高TiO2光催化活性,其最佳掺杂量重量百分比为0.25%。 相似文献
38.
The degradation of linuron, one of phenylurea herbicides, was investigated for its reaction kinetics by different treatment processes including ultraviolet irradiation (UV), ozonation (O3), and UV/O3. The decay rate of linuron by UV/O3 process was found to be around 3.5 times and 2.5 times faster than sole-UV and ozone-alone, respectively. Experimental results also indicate overall rate constants increased exponentially with pH above 9.0 while the increase of rate constants with pH below 9 is insignificant in O3 system. All dominant parameters involved in the three processes were determined in the assistant of proposed linear models in this study. The approach was found useful in predicting the process performances through the quantification of quantum yield (rate constant for the formation of free radical HOO− from ozone decomposition at high pH), rate constant of linuron with ozone (kO3,LNR), rate constant of linuron with hydroxyl radical (kOH,LNR), and α (the ratio of the production rate of OH and the decay rate of ozone in UV/O3 system). 相似文献
39.
137Cs+/90Sr2+-containing radioactive wastewater is one of the most important problems that the world has been facing with. A by-product, activated porous calcium silicate, is generated at high levels by the pre-desiliconizing and soda-lime-sintering processes for producing Al2O3 from high-alumina fly ash. In order to examine if this by-product could be used as an absorbent for removal of 137Cs+/90Sr2+ from radioactive wastewater, various parameters, such as pH, adsorbent dose, contact time, and initial concentration, were discussed. Results indicated that the equilibrium reached in about 2 hr. Activated porous calcium silicate was highly pH sensitive and able to remove Cs+/Sr2+ in a near-neutral environment. The adsorption equilibrium was best described by Freundlich isotherm equations, and the adsorption of Cs+/Sr2+ was a physical process. The adsorption kinetic data could be better fitted by the pseudo-second-order model, and the adsorption was controlled by multidiffusion. Current study showed that activated porous calcium silicate has a good adsorption of Cs+/Sr2+ for their removal. However, other characteristics, such as selectivity because of coexisting cations, elution and regeneration, thermal stability, and acid resistance, should be discussed carefully before using it in an actual field.
Implications:Removing 137Cs+/90Sr2+ from radioactive wastewater is one of the tough issues that has been attracting more and more attention world widely, which is the same as fly ash. For recycling high-alumina fly ash, in which Al is extracted to produce Al2O3, a huge amount of activated porous calcium silicate is generated year by year. In this paper, this by-product was successfully used as an absorbent to remove 137Cs+/90Sr2+ from radioactive wastewater for the first time. Factors that affect the absorbability and the mechanisms were discussed in details, providing a possible choice for disposal of 137Cs+/90Sr2+-containing radioactive wastewater. 相似文献
40.
Treatment of coking wastewater by an advanced Fenton oxidation process using iron powder and hydrogen peroxide 总被引:5,自引:0,他引:5
In this study the treatment of coking wastewater was investigated by an advanced Fenton oxidation process using iron powder and hydrogen peroxide. Particular attention was paid to the effect of initial pH, dosage of H2O2 and to improvement in biodegradation. The results showed that higher COD and total phenol removal rates were achieved with a decrease in initial pH and an increase in H2O2 dosage. At an initial pH of less than 6.5 and H2O2 concentration of 0.3 M, COD removal reached 44-50% and approximately 95% of total phenol removal was achieved at a reaction time of 1 h. The oxygen uptake rate of the effluent measured at a reaction time of 1 h increased by approximately 65% compared to that of the raw coking wastewater. This indicated that biodegradation of the coking wastewater was significantly improved. Several organic compounds, including bifuran, quinoline, resorcinol and benzofuranol were removed completely as determined by GC-MS analysis. The advanced Fenton oxidation process is an effective pretreatment method for the removal of organic pollutants from coking wastewater. This process increases biodegradation, and may be combined with a classical biological process to achieve effluent of high quality. 相似文献