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291.
以对硝基苯酚溶液为模拟废水,用自制的"Cu核-Cu2O壳"粒子对其进行光催化氧化试验,考察了光照时间、催化剂用量、对硝基苯酚的初始质量浓度、溶液的pH值和光源等对降解过程的影响。结果表明,对硝基苯酚溶液质量浓度为40 mg.L-1,催化剂投加量为2g.L-1,光照120min后降解率达到95%,降解反应符合一级反应动力学。与其他同类光催化剂相比,"Cu核-Cu2O壳"粒子具有较高的光催化活性,而且光催化过程中有氢氧自由基产生,对对硝基苯酚的降解较彻底。 相似文献
292.
293.
Robert Stottlemyer 《Journal of the American Water Resources Association》1997,33(4):767-779
ABSTRACT: Weekly precipitation and stream water samples were collected from small watersheds in Denali National Park, Alaska, the Fraser Experimental Forest, Colorado, Isle Royale National Park, Michigan, and the Calumet watershed on the south shore of Lake Superior, Michigan. The objective was to determine if stream water chemistry at the mouth and upstream stations reflected precipitation chemistry across a range of atmospheric inputs of H+, NH4+, NO3??, and SO42?. Volume-weighted precipitation H+, NH4+, NO3??, and SO42? concentrations varied 4 to 8 fold with concentrations highest at Calumet and lowest in Denali. Stream water chemistry varied among sites, but did not reflect precipitation chemistry. The Denali watershed, Rock Creek, had the lowest precipitation NO3?? and SO42? concentrations, but the highest stream water NO3?and SO42? concentrations. Among sites, the ratio of mean monthly upstream NO3?? concentration to precipitation NO3?- concentration declined (p < 0.001, R2= 0.47) as precipitation NO3?? concentration increased. The ratio of mean monthly upstream to precipitation SO42? concentration showed no significant relationship to change in precipitation SO42? concentration. Watersheds showed strong retention of inorganic N (> 90 percent inputs) across inputs ranging from 0.12 to > 6 kg N ha?1 y?1. Factors possibly accounting for the weak or non-existent signal between stream water and precipitation ion concentrations include rapid modification of meltwater and precipitation chemistry by soil processes, and the presence of unfrozen soils which permits winter mineralization and nitrification to occur. 相似文献
294.
Ag沉积对微弧氧化TiO2/Ti膜光催化性能的影响 总被引:1,自引:1,他引:0
以磷酸钠为电解液,采用微弧氧化技术在钛网上直接制备了TiO2膜.研究了硝酸银光沉积微弧氧化TiO2膜对直接耐晒蓝染料溶液的TiO2膜光催化活性,利用XRD、SEM和EDX对微弧氧化膜晶型、表面形貌和成分进行了分析.结果表明,微弧氧化TiO2膜主要由钛和锐钛矿TiO2组成,TiO2膜的光催化性能与电解时间有关.由于微弧氧化膜中锐钛矿TiO2含量相对较少,膜的光催化性能较差.光沉积银修饰微弧氧化TiO2膜可以改善膜的光催化性能,120 min对直接耐晒蓝溶液的光催化降解率由9.8%提高到26%. 相似文献
295.
Pt掺杂TiO2纳米粉体的制备及其光催化活性研究 总被引:3,自引:0,他引:3
以钛酸丁酯为前驱物,醋酸为酸催化剂,采用溶胶-凝胶法制备掺有不同质量分数Pt的纳米TiO2粉体.通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等现代分析手段对所制备的不同Pt/TiO2纳米粉体的微观结构进行了表征.并以甲基橙染料的光催化降解为模型反应,考察了不同条件下所制备的光催化剂的光催化活性,探讨了纳米粉体中Pt的掺杂量对其光催化活性的影响.实验结果表明,Pt质量分数为0.2%的纳米TiO2粉体的光催化活性最好,过低或者过高的掺Pt量无法提高TiO2的光催化活性,甚至会降低TiO2的光催化活性. 相似文献
296.
Chuan Lin Renzhi Hu Pinhua Xie Shengrong Lou Guoxian Zhang Jinzhao Tong Jianguo Liu Wenqing Liu 《环境科学学报(英文版)》2022,34(4):376-390
Comprehensive observations of the nocturnal atmospheric oxidation of NO3 and N2O5 were conducted at a suburban site in Changzhou in the YRD using cavity ring-down spectroscopy (CRDS) from 27 May to 24 June, 2019. High concentrations of NO3 precursors were observed, and the nocturnal production rate of NO3 was determined to be 1.7 ± 1.2 ppbv/hr. However, the nighttime NO3 and N2O5 concentrations were relatively low, with maximum values of 17.7 and 304.7 pptv, respectively, illustrating the rapid loss of NO3 and N2O5. It was found that NO3 dominated the nighttime atmospheric oxidation, accounting for 50.7%, while O3 and OH only contributed 34.1% and 15.2%, respectively. For the reactions of NO3 with volatile organic compounds (VOCs), styrene was found to account for 60.3%, highlighting its dominant role in the NO3 reactivity. In general, the contributions of the reactions between NO3 and VOCs and the N2O5 uptake to NO3 loss were found to be about 39.5% and 60.5%, respectively, indicating that N2O5 uptake also played an important role in the loss of NO3 and N2O5, especially under the high humidity conditions in China. The formation of nitrate at night mainly originated from N2O5 uptake, and the maximum production rate of NO3− reached 6.5 ppbv/hr. The average NOx consumption rate via NO3 and N2O5 chemistry was found to be 0.4 ppbv/h, accounting for 47.9% of the total NOx removal. The predominant roles of NO3 and N2O5 in nitrate formation and NOx removal in the YRD region was highlighted in this study. 相似文献
297.
Ballschmite K Hackenberg R Jarman WM Looser R 《Environmental science and pollution research international》2002,9(4):274-288
Members of the United Nations Economic Commission for Europe (UN-ECE) signed a legally binding protocol on persistent organic pollutants (POPs) in February 1998 under the Convention on Long-Range Transboundary Air Pollution. A treaty that intends to control the production, import, export, disposal and use of toxic chemicals that persist for decades in the environment has been formally signed at a conference in May 2001 in Stockholm. The 2001 POP treaty, like the 1998 LRTAP POP protocol, contains a provision on adding further chemicals to the initial group of twelve or fifteen. The occurrence of a compound or a group of compounds in so called remote and pristine areas, e.g. in the Artic or in the Southern Hemisphere, proves its stability under the chemical and biological conditions of the environment. Compounds identified in this way, in samples taken primarily in very remote regions of the planet, are classified by their environmental fate and global distribution as persistent organic pollutants (POPs), regardless of any political assessments. 相似文献
298.
Gordon Brent Ingram 《Environmental management》1992,16(5):585-595
Islands with large tracts of primary rain forest constitute a distinct complex of terrestrial and marine ecosystems with global
significance because of high levels of biological richness or, in the case of oceanic islands, the evolutionary distinctiveness
of the organisms that they support. The myriad of small habitat units makes these settings particularly prone to fragmentation
and thus problematic for the conservation of biological diversity. Most of the remaining examples of islands with primary
rain forest are in the Pacific Rim, particularly in Indonesia, and there are threats from intensive timber harvesting, mining,
tourism, and dismemberment of traditional convervation systems. Prospects for inventorying, monitoring, and protecting the
remaining islands with relatively pristine successional mosaics of humid forest and shallow marine habitats within a framework
global monitoring are explored. Recommendations are made for a program of expanded use of the biosphere reserve designation
for rain forest islands and adjacent marine areas. 相似文献
299.
Since 1972, 10 benthic surveys and 9 static fish bioassays have been conducted to assess the impact of AVTEX Fibers, Inc. effluent on the lower South Fork of the Shenandoah River. AVTEX (formerly FMC Corp.) is a rayon and polyester fibers plant located in Front Royal, Virginia. Benthic samples were taken at four stations, one above and three below the plant discharges. Single surveys in 1972 and 1973 indicated a severe impact on the benthic community along the right side of the river, below the plant, as a result of the channelized effluent. Diversity values (¯d) were low (0–2.42) and numbers of taxa and organisms were reduced. A fish bioassay in 1973 indicated the effluent to be acutely toxic at the 34.5% level (mixture of effluent and river water). In early 1974, FMC Corp. constructed an activated sludge treatment system to reduce BOD and supplement the neutralization and chemical precipitation (zinc hydroxide and liquid-solid separation) facilities that had been used to treat waste waters since 1948. After the new equipment was placed in operation, the previously stressed area became more stable. In 1975 and 1976 the stressed area exhibited greater ¯d values (1.19–3.39) and an increased number of taxa and organisms. Bioassays showed the effluent to be acutely toxic to fish only once since 1973. The major improvements in the effluent were a 70% reduction in BOD5 and a 60% reduction in the amount of zinc entering the river. Community conditions in 1977 indicated a partial remission of improvement, probably due to drought conditions.The rehabilitation of damaged ecosystems is a process important to all biologists. An important factor in encouraging industry to participate in this activity is evidence that improved waste treatment will often have demonstrable biological benefits rather soon. As data accumulate on the recovery process it may be possible to predict the degree of rehabilitation and time required more precisely. 相似文献
300.
P. A. Glancy A. S. Van Denburgh S. M. Born 《Journal of the American Water Resources Association》1972,8(6):1157-1172
The Truckee River heads in the Sierra Nevada at Lake Tahoe, and terminates in Pyramid Lake. During the 1969 water year, flow about 9 miles upstream from the mouth (974,000 acre-ft) was almost four times the long-term average, due mainly to heavy winter rains and spring snowmelt. A short period of low-altitude rainfall produced the highest concentrations of suspended sediment, whereas a much longer subsequent period of snowmelt yielded a much greater total quantity of material. The upper 90 percent of the basin yielded about 260 acre-feet (630,000 tons) of sediment at the Nixon gage, whereas an estimated 2,800 acre-feet (6.8 million tons) was contributed by erosion of about 200 acres of river bank below the gage. Solute content at the gage ranged from 80 to 450 mg/l, dominated by calcium, sodium, and bicarbonate, plus silica in the most dilute snowmelt and chloride in the most concentrated low flows. Solute load totaled about 130,000 tons, of which the principal constituents in Pyramid Lake-sodium plus equivalent bicarbonate and chloride-amounted to almost 40,000 tons. The total solute load during a year of average flow may be 45,000-55,000 tons, including 18,000-22,000 tons of principal lake constituents. 相似文献