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371.
强化混凝处理城市纳污河污水运行过程中搅拌能量的影响 总被引:1,自引:1,他引:0
介绍了采用混凝技术大规模处理运河污水时所遇到的问题,并通过混凝试验分析了问题的原因。提出并初步探讨了混凝搅拌能量及其计算方式,利用混凝搅拌能量参数分析混凝反应效果的差异,说明在实际生产中混凝反应过程需要有足够的能量。 相似文献
372.
陕西省雷电灾害易损性分析、评估及易损度区划 总被引:7,自引:2,他引:5
根据2002~2007年陕西省10个市的雷暴日和雷电灾害统计资料,结合陕西各市的经济和人口密度特征,提出了雷暴日数、雷电灾害频度、生命易损模数及经济易损模数作为各市雷电灾害易损性评估指标,并在此基础上,给出了陕西各市雷电灾害易损度评估结构.采用四级分区法对上述雷电灾害易损性评估指标进行了分级,并赋予各等级如下定值:极高级为1.0、高级为0.8、中级为0.5、低级为0.2.将陕西省10市按照四个雷电灾害易损性评估指标的所属等级获取相应等级值,将各市四个评估指标的等级值累加得到平均值作为雷电灾害易损性评估的评价指数,并利用上述四级分区法形成陕西省雷电灾害易损度区划. 相似文献
373.
374.
受侧向土体位移斜桩的特性 总被引:1,自引:0,他引:1
通过三维有限单元法分析了斜桩受侧向土体位移的特性。变动柱和土体参数进行敏感性分析,得出桩的柔度、侧向土体位移的大小、桩顶约束条件、土体位移形状和土体移动层厚度等对斜桩的影响。刚性桩的挠度小于柔性桩,但弯矩和剪力大于柔性桩。斜桩非线性弹簧的土抗力—位移关系(p-y曲线)表现为双曲线特征,可基于直桩的Winkler地基反力法对斜桩进行简化计算分析,但应对直桩的极限土抗力值进行修正,以期更好的反映斜桩的特性。 相似文献
375.
Luo J Weber FA Cirpka OA Wu WM Nyman JL Carley J Jardine PM Criddle CS Kitanidis PK 《Journal of contaminant hydrology》2007,92(1-2):129-148
We present a travel-time based reactive transport model to simulate an in-situ bioremediation experiment for demonstrating enhanced bioreduction of uranium(VI). The model considers aquatic equilibrium chemistry of uranium and other groundwater constituents, uranium sorption and precipitation, and the microbial reduction of nitrate, sulfate and U(VI). Kinetic sorption/desorption of U(VI) is characterized by mass transfer between stagnant micro-pores and mobile flow zones. The model describes the succession of terminal electron accepting processes and the growth and decay of sulfate-reducing bacteria, concurrent with the enzymatic reduction of aqueous U(VI) species. The effective U(VI) reduction rate and sorption site distributions are determined by fitting the model simulation to an in-situ experiment at Oak Ridge, TN. Results show that (1) the presence of nitrate inhibits U(VI) reduction at the site; (2) the fitted effective rate of in-situ U(VI) reduction is much smaller than the values reported for laboratory experiments; (3) U(VI) sorption/desorption, which affects U(VI) bioavailability at the site, is strongly controlled by kinetics; (4) both pH and bicarbonate concentration significantly influence the sorption/desorption of U(VI), which therefore cannot be characterized by empirical isotherms; and (5) calcium-uranyl-carbonate complexes significantly influence the model performance of U(VI) reduction. 相似文献
376.
Küster A Pohl K Altenburger R 《Environmental science and pollution research international》2007,14(6):377-383
Background, Goals and Scope During the last years the miniaturization of toxicity test systems for rapid and parallel measurements of large quantities
of samples has often been discussed. For unicellular algae as well as for aquatic macrophytes, fluorescence-based miniaturized
test systems have been introduced to analyze photosystem II (PSII) inhibitors. Nevertheless, high-throughput screening should
also guarantee the effect detection of a broad range of toxicants in order to ensure routinely applicable, high-throughput
measuring device experiments which can cover a broad range of toxicants and modes of action others than PSII inhibition. Thus,
the aim of this study was to establish a fast and reproducible measuring system for non-PSII inhibitors for aquatic macrophyte
species to overcome major limitations for use.
Methods A newly developed imaging pulse-amplitude-modulated chlorophyll fluorometer (I-PAM) was applied as an effect detector in short-term
bioassays with the aquatic macrophyte species Lemna minor. This multiwell-plate based measuring device enabled the incubation and measurement of up to 24 samples in parallel. The
chemicals paraquat-dichloride, alizarine and triclosan were chosen as representatives for the toxicant groups of non-PSII
herbicides, polycyclic aromatic hydrocarbons (PAHs) and pharmaceuticals and personal care products (PPCPs), which are often
detected in the aquatic environment. The I-PAM was used (i) to establish and validate the sensitivity of the test system to
the three non-PSII inhibitors, (ii) to compare the test systems with standardized and established biotests for aquatic macrophytes,
and (iii) to define necessary time scales in aquatic macrophyte testing. For validation of the fluorescence-based assay, the
standard growth test with L. minor (ISO/DIS 20079) was performed in parallel for each chemical.
Results The results revealed that fluorescence-based measurements with the I-PAM allow rapid and parallel analysis of large amounts
of aquatic macrophyte samples. The I-PAM enabled the recording of concentration-effect-curves with L. minor samples on a 24-well plate with single measurements. Fluorescence-based concentration-effect-curves could be detected for
all three chemicals after only 1 h of incubation. After 4–5 h incubation time, the maximum inhibition of fluorescence showed
an 80–100% effect for the chemicals tested. The EC50 after 24 h incubation were estimated to be 0.06 mg/L, 0.84 mg/L and 1.69
mg/L for paraquatdichloride, alizarine and triclosan, respectively.
Discussion The results obtained with the I-PAM after 24 h for the herbicide paraquat-dichloride and the polycyclic aromatic hydrocarbon
alizarine were in good accordance with median effective concentrations (EC50s) obtained by the standardized growth test for
L. minor after 7 d incubation (0.09 mg/L and 0.79 mg/L for paraquat-dichloride and alizarine, respectively). Those results were in
accordance with literature findings for the two chemicals. In contrast, fluorescence-based EC50 of the antimicrobial agent
triclosan proved to be two orders of magnitude greater when compared to the standard growth test with 7 d incubation time
(0.026 mg/L) as well as with literature findings.
Conclusion Typically, aquatic macrophyte testing is very time consuming and relies on laborious experimental set-ups. The I-PAM measuring
device enabled fast effect screening for the three chemicals tested. While established test systems for aquatic macrophytes
need incubation times of ≥ 7 d, the I-PAM can detect inhibitory effects much earlier (24 h), even if inhibition of chemicals
is not specifically associated with PSII. Thus, the fluorescence-based bioassay with the I-PAM offers a promising approach
for the miniaturization and high-throughput testing of chemicals with aquatic macrophytes. For the chemical triclosan, however,
the short-term effect prediction with the I-PAM has been shown to be less sensitive than with long-term bioassays, which might
be due to physicochemical substance properties such as lipophilicity.
Recommendations and Perspectives The results of this study show that the I-PAM represents a promising tool for decreasing the incubation times of aquatic macrophyte
toxicity testing to about 24 h as a supplement to existing test batteries. The applicability of this I-PAM bioassay on emergent
and submerged aquatic macrophyte species should be investigated in further studies. Regarding considerations that physicochemical
properties of the tested substances might play an important role in microplate bioassays, the I-PAM bioassay should either
be accompanied by evaluating physicochemical properties modeled from structural information prior to an experimental investigation,
or by intensified chemical analyses to identify and determine nominal concentrations of the toxicants tested. The chemicals
paraquat-dichloride, alizarine and triclosan were chosen as representatives for the toxicant groups of non-PSII herbicides,
PAHs and PPCPs which are often detected in the aquatic environment. Nevertheless, in order to ensure a routinely applicable
measuring device, experiments with a broader range of toxicants and samples of surface and/or waste waters are necessary.
ESS-Submission Editor: Dr. Markus Hecker (MHecker@Entrix.com) 相似文献
377.
Aerobic degradation of bisphenol A by Achromobacter xylosoxidans strain B-16 isolated from compost leachate of municipal solid waste 总被引:3,自引:0,他引:3
A novel bacterium designated strain B-16 was isolated from the compost leachate of the municipal solid waste (MSW) in a laboratory reactor. This strain was identified as a gram-negative bacterium, Achromobacter xylosoxidans that could grow on bisphenol A (BPA, a representative endocrine disruptor) as a sole carbon source under aerobic condition. BPA-degrading characteristics of strain B-16 were investigated in liquid cultures. The results show that BPA degradation was influenced by several factors (e.g. inoculum size, substrate concentration, temperature and pH, etc). The half-lives, optimum temperature and pH were found to be 0.58-3.1d, 35 degrees C and 7.0, respectively. BPA-degrading activity and cell growth were inhibited at high substrate concentration. Metabolic intermediates detected during the degradation process were identified as p-hydroxybenzaldehyde, p-hydroxybenzoic acid and p-hydroquinone, respectively. Metabolic pathway of BPA degradation was proposed in this study. 相似文献
378.
Rothenberg SE Du X Zhu YG Jay JA 《Environmental pollution (Barking, Essex : 1987)》2007,149(2):246-251
The impact of sewage irrigation on the uptake and translocation of mercury (Hg) in corn plants (Zea mays) was investigated. Corn plants were harvested the same day from two nearby fields in suburban Beijing, one irrigated historically with sewage effluent, and one irrigated solely with groundwater. Hg content was analyzed in the soil, roots and stems, while percent moisture and soil organic content were analyzed in the soil samples. The concentration of Hg in the soil and roots, and the soil organic content were not significantly different between the two fields, despite the historic practice of sewage irrigation. Hg content in roots was positively correlated with soil Hg concentration (r=0.95, n=6). The transfer coefficients between roots and stems were significantly higher in the control site (control: 2.06, sewage-irrigated: 0.44, p<0.05), indicating that the barrier effect of the roots was not consistent between the two fields. 相似文献
379.
During the second half of the 20th century, the Ganga River ecosystem has been continuously altered by several ongoing anthropogenic
processes, accommodating multi-dimensional pressure due to increase of nearly four-fold human population. For solution of
any environmental issues of the river, the Earth System Science approach is required to have maximum socio-economic benefits
to millions of people living in Indian and Bangladesh. A bibliography containing more than 250 references on environmental
studies of the Ganga River was prepared to preserve its ecosystem by providing the baseline support in this regard. 相似文献
380.
Wen-Cheng Liu Jan-Tai Kuo Chih-Chieh Young Ming-Ching Wu 《Environmental Modeling and Assessment》2007,12(3):201-211
Numerical models are often used to evaluate the potential impact of human alternation of natural water bodies and to help
the design of the alternation to mitigate its impacts. In the past decade, three-dimensional hydrodynamic and reactive transport
modeling has matured from a research subject to a practical analysis technology. This paper presents a practical study in
which a three-dimensional hydrodynamic and water quality model [hydrodynamic eutrophication model (HEM-3D)] was applied to
determine the optimal location for treated wastewater discharged from marine outfall system in the Keelung harbor and the
adjacent coastal sea. First, model validation was conducted with respect to surface elevation, current, and water quality
variables measured in the Keelung harbor station and its coastal sea. The overall performance of the model was in qualitative
agreement with the available field data. The model was then used to evaluate several scenarios of the locations from marine
outfall system. Based on model simulation results, a location at the northeast of Ho-Ping Island was recommended for adoption
because the environmental impact is smaller than any other alternative.
相似文献
Wen-Cheng LiuEmail: |