排序方式: 共有48条查询结果,搜索用时 15 毫秒
31.
Collins RN Saito T Aoyagi N Payne TE Kimura T Waite TD 《Journal of environmental quality》2011,40(3):731-741
Time-resolved laser fluorescence spectroscopy (TRLFS) is a useful means of identifying certain actinide species resulting from various biogeochemical processes. In general, TRLFS differentiates chemical species of a fluorescent metal ion through analysis of different excitation and emission spectra and decay lifetimes. Although this spectroscopic technique has largely been applied to the analysis of actinide and lanthanide ions having fluorescence decay lifetimes on the order of microseconds, such as UO , Cm, and Eu, continuing development of ultra-fast and cryogenic TRLFS systems offers the possibility to obtain speciation information on metal ions having room-temperature fluorescence decay lifetimes on the order of nanoseconds to picoseconds. The main advantage of TRLFS over other advanced spectroscopic techniques is the ability to determine in situ metal speciation at environmentally relevant micromolar to picomolar concentrations. In the context of environmental biogeochemistry, TRLFS has principally been applied to studies of (i) metal speciation in aqueous and solid phases and (ii) the coordination environment of metal ions sorbed to mineral and bacterial surfaces. In this review, the principles of TRLFS are described, and the literature reporting the application of this methodology to the speciation of actinides in systems of biogeochemical interest is assessed. Significant developments in TRLFS methodology and advanced data analysis are highlighted, and we outline how these developments have the potential to further our mechanistic understanding of actinide biogeochemistry. 相似文献
32.
Decolorization of oxygen-delignified bleaching effluent (abbreviated as OBE) and biobleaching of oxygen-delignified kraft pulp (OKP) were conducted using a non-white rot fungus Geotrichum candidum Dec 1 (abbreviated as Dec 1) which has ability to decolorize various synthetic dyes and molasses. Dec 1 decolorized up to 77% of OBE for 6 days. In addition, Dec 1 increased the brightness of OKP from 47.8% to 51.2% and decreased the kappa value of OKP from 12.4 to 10.4 points during a 6-day incubation period at a 25% of pulpconcentration. At 2% pulp-concentration, the brightness of OKP increased by 13% and the kappa value of OKP decreased by 4 points only for a 3-day incubation period. When the decolorized OBE was used for bleaching of OKP, the brightness of OKP increased to 62.7% under the shaking culture to a 2% pulp-concentration using culture fluid of decolorized OBE. It was revealed that Dec 1 is a potential to apply for decolorization of wastewater and biobleaching of pulp in paper-mills. 相似文献
33.
Hua ZHANG Zhiliang ZHU Noboru YOSHIKAWA 《Frontiers of Environmental Science & Engineering》2011,5(2):205-211
Microwave processing was used to stabilize copper ions in soil samples. Its effects on the stabilization efficiency were studied as a function of additive, microwave power, process time, and reaction atmosphere. The stabilization efficiency of the microwave process was evaluated based on the results of the toxicity characteristic leaching procedure (TCLP) test. The results showed that the optimal experimental condition contained a 700W microwave power, 20 min process time and 3 iron wires as the additive, and that the highest stabilization efficiency level was more than 70%. In addition, the different reaction atmospheres showed no apparent effect on the stabilization efficiency of copper in the artificially contaminated soil. According to the result of the Tessier sequential extraction, the partial species of copper in the contaminated soil was deduced to transform from unstable species to stable states after the microwave process. 相似文献
34.
Murayama H Moriyama N Mitobe H Mukai H Takase Y Shimizu Ki Kitayama Y 《Chemosphere》2003,52(5):825-833
A simple method for quantitative analyses of organic chlorine pesticides (OCPs) in environmental water samples such as rainwater, river water and seawater using activated carbon fiber filters (ACFF) is described. ACFF was used as adsorbent to collect the chemicals in water samples. The collection of OCPs was completed almost for one day by stirring the mixture of the sample and the ACFF chips at room temperature. The adsorbed OCPs on the ACFF could be extracted easily with toluene-ethanol (4:1) mixed solvent. The purified extract by a florisil column chromatograph was followed by the analysis using high-resolution gas chromatograph/high-resolution mass spectrometer. Recoveries of OCPs spiked to actual samples such as rainwater, river water and seawater samples were approximately more than 80%, and the coefficients of variations were within 10%. This method was applied to the actual samples and was confirmed to be applicable for monitoring sub-ng/l level OCPs in environmental water samples. 相似文献
35.
Analyzing the spatial structure of a Sri Lankan tree species with multiple scales of clustering 总被引:5,自引:0,他引:5
Clustering at multiple critical scales may be common for plants since many different factors and processes may cause clustering. This is especially true for tropical rain forests for which theories explaining species coexistence and community structure rest heavily on spatial patterns. We used point pattern analysis to analyze the spatial structure of Shorea congestiflora, a dominant species in a 25-ha forest dynamics plot in a rain forest at Sinharaja World Heritage Site (Sri Lanka), which apparently shows clustering at several scales. We developed cluster processes incorporating two critical scales of clustering for exploring the spatial structure of S. congestiflora and interpret it in relation to factors such as competition, dispersal limitation, recruitment limitation, and Janzen-Connell effects. All size classes showed consistent large-scale clustering with a cluster radius of approximately 25 m. Inside the larger clusters, small-scale clusters with a radius of 8 m were evident for recruits and saplings, weak for intermediates, and disappeared for adults. The pattern of all trees could be divided into two independent patterns: a random pattern (nearest neighbor distance > 8 m) comprising approximately 12% of the trees and a nested double-cluster pattern. This finding suggests two independent recruitment and/or seed dispersal mechanisms. Saplings were several times as abundant as recruits and may accumulate several recruit generations. Recruits were only weakly associated with adults and occupied about half of the large-scale clusters, but saplings almost all. This is consistent with recruitment limitation. For approximately 70% (95%) of all juveniles the nearest adult was less than 26 m away (53 m), suggesting a dispersal limitation that may also be related to the critical large-scale clustering. Our example illustrates the manner in which the use of a specific and complex null hypothesis of spatial structure in point pattern analysis can help us better understand the biology of a species and generate specific hypotheses to be further investigated in the field. 相似文献
36.
Enhanced heavy metal immobilization in soil by grinding with addition of nanometallic Ca/CaO dispersion mixture 总被引:4,自引:0,他引:4
This study investigated the use of a nanometallic Ca and CaO dispersion mixture for the immobilization of heavy metals (As, Cd, Cr and Pb) in contaminated soil. Simple grinding achieved 85-90% heavy metal immobilization, but it can be enhanced further to 98-100% by addition of a nanometallic Ca/CaO dispersion mixture produced by grinding. Observations using SEM-EDS elemental maps and semi-quantitative analysis showed that the amounts of As, Cd, Cr, and Pb measurable on the soil particle surface decrease after nanometallic Ca/CaO treatment. The leachable heavy metal concentrations were reduced after nanometallic Ca/CaO treatment to concentrations lower than the Japan soil elution standard regulatory threshold: <0.01 mg L−1 for As, Cd, and Pb; and 0.05 mg L−1 for Cr. Effects of soil moisture and pH on heavy metal immobilization were not strongly influenced. The most probable mechanisms for the enhancement of heavy metal immobilization capacity with nanometallic Ca/CaO treatment might be due to adsorption and entrapment of heavy metals into newly formed aggregates, thereby prompting aggregation of soil particles and enclosure/binding with Ca/CaO-associated immobile salts. Results suggest that the nanometallic Ca/CaO mixture is suitable for use in immobilization of heavy-metal-contaminated soil under normal moisture conditions. 相似文献
37.
Naoko Yamano Atsuyoshi Nakayama Norioki Kawasaki Noboru Yamamoto Seiichi Aiba 《Journal of Polymers and the Environment》2008,16(2):141-146
We identified a biodegrading microorganism of polyamide (nylon) 4, a linear polymer of γ-aminobutyric acid (GABA). From activated
sludge, the biodegrading bacteria strains of Pseudomonas sp. were isolated and identified by their taxonomic characteristics and nucleotide sequences of 16S rDNA. One strain, ND-11,
was grown on a minimal medium containing polyamide 4 (PA4) as the sole carbon source. The strain produced GABA as a degradation
intermediate, as identified by analyzing the NMR spectra of degraded products. The culture supernatant of strain ND-11 degraded
the emulsified PA4 completely within one day. These results suggest that the ND-11 strain degraded PA4 using its extracellular
enzymes to hydrolyze amide bonds. 相似文献
38.
Reddy MS Okuda T Nakai S Nishijima W Okada M 《Waste management (New York, N.Y.)》2011,31(8):1848-1851
Wet gravity separation technique has been regularly practiced to separate the polypropylene (PP) and polyethylene (PE) (light plastic films) from chlorinated plastic films (CP films) (heavy plastic films). The CP films including poly vinyl chloride (PVC) and poly vinylidene chloride (PVDC) would float in water even though its density is more than 1.0 g/cm3. This is because films are twisted in which air is sometimes entrapped inside the twisted CP films in real existing recycling plant. The present research improves the current process in separating the PP and PE from plastic packaging waste (PPW), by reducing entrapped air and by increasing the hydrophilicity of the CP films surface with ozonation. The present research also measures the hydrophilicity of the CP films.In ozonation process mixing of artificial films up to 10 min reduces the contact angle from 78° to 62°, and also increases the hydrophilicity of CP films. The previous studies also performed show that the artificial PVDC films easily settle down by the same. The effect of ozonation after the wet gravity separation on light PPW films obtained from an actual PPW recycling plant was also evaluated. Although actual light PPW films contained 1.3% of CP films however in present case all the CP films were removed from the PPW films as a settled fraction in the combination process of ozonation and wet gravity separation. The combination process of ozonation and wet gravity separation is the more beneficial process in recovering of high purity PP and PE films from the PPW films. 相似文献
39.
北京清华园采暖前与采暖期PM10中含碳组分的理化特征 总被引:4,自引:1,他引:3
采用美国rp公司生产的Series5400大气颗粒物碳质组分监测仪对清华园PM10中的碳质组分进行了连续在线监测(2002年9月~11月)。结合PM2.5中碳质组分浓度、PM10的浓度和气象数据,分析了碳质组分的污染特征。结果表明,采样期间清华园大气PM10中有机碳(OC)、元素碳(EC)的日平均质量浓度分别在4.07~65.81μg/m3、0.96~26.14μg/m3之间变化,平均值分别为20.8±12.1和7.0±5.1μg/m3。OC在总碳(TC)中占有很大比例,OC/TC平均值为75.84%;TC在PM10中的含量平均为25.0%。本文对9~10月份(秋季)和11月份(初冬)OC、EC的相关性分别进行了分析,结果表明OC、EC之间具有良好的相关性,9月份和10月份相关性系数(R2)为0.83;11月份为0.90。二次生成的OC(OCsec)浓度估算结果表明,9、10月份OCsec在OC中的比例(60.7%)比11月份(38.5%)大。碳质组分主要集中在细颗粒物中,PM10中的OC有70.3%存在于细颗粒物PM2.5中,TC则有58.6%存在于PM2.5中。 相似文献
40.
Noboru Okuda Tomohiro Takeyama Yasunobu Yanagisawa 《Behavioral ecology and sociobiology》1997,41(6):363-369
Entire-brood cannibalism by mouthbrooding males of the cardinal fish Apogon doederleini was investigated in temperate waters of southern Japan during two breeding seasons. The rate of cannibalism was 17–18% in
each season and did not differ among age-groups. However, the seasonal pattern of cannibalism differed markedly among age-groups:
young (1- and 2-year-old) males frequently cannibalized early broods, especially the first brood, of the season, whereas cannibalism
by middle-aged (3- and 4-year-old) and old (5- and 6-year-old) males mainly occurred late in the breeding season. We explain
this difference in terms of trade-offs between current and future reproduction. Young males, whose future reproductive success
is enhanced by the growth increment, may allocate more time and energy to growth by cannibalizing early broods. In contrast,
for older males who have had more breeding cycles and grow little, cannibalism could be a way to reverse the deterioration
in their somatic condition that occurs as the breeding season progresses. It is also likely that the current reproductive
loss entailed by the cannibalism is effectively compensated by quick re-mating with another female.
Received: 24 February 1997 / Accepted after revision: 20 July 1997 相似文献