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Application of Fenton’s reagent combined with sawdust on the dewaterability of oily sludge 全文
2014
Guo, Hao | Feng, Suping | Jiang, Jun | Zhang, Miao | Lin, Hai | Zhou, Xiaoyan
Fenton’s reagent and sawdust were used on the dewaterability of the raw oily sludge in this study. The result shows that the combination of the two treatment processes is favorable, although the application of Fenton’s reagent only is not so good. The capillary suction time (CST) and specific resistance to filtration (SRF) were used to evaluate the effect of dewaterability of the raw oily sludge, and the CST and SRF values are reduced from 1,760 s and 13.8 × 10¹² m/kg to 185 s and 1.5 × 10¹² m/kg, respectively. The dry matter contents of sludge cakes and properties of the supernatant all gained when using only the Fenton’s reagent and when using the combined treatment with Fenton’s reagent and sawdust respectively were investigated. The results indicate that the oily sludge is more suitable for further treatment after combined process with Fenton’s reagent and sawdust.
显示更多 [+] 显示较少 [-]Long-term microphytoplankton variability patterns using multivariate analyses: ecological and management implications 全文
2014
Feki-Sahnoun, Wafa | Hamza, Asma | Mahfoudi, Mabrouka | Rebai, Ahmed | Hassen, Malika Bel
Microphytoplankton data along the southern Tunisian coasts have been monitored weekly since 1995. This study used the data collected during the period 2000–2007 to determine the temporal variability patterns and to characterize the geographical structures of microphytoplankton populations. The methodological approach consisted in isolating the temporal variability common to all sampled sites and in analyzing the “residual” site-specific component. Multivariate ordination methods were used to determine the seasonal and interannual variability. The temporal pattern shared by all sites was highlighted and the seasonal cycle of the most frequent phytoplankton communities contrasted the diatoms winter-spring species to the dinoflagellates summer-fall species. Multitable comparison allowed the identification of three areas exhibiting similar phytoplankton population variability. The results, despite the coastal location of sampling sites, indicated that hydrodynamic and geomorphologic properties of the different areas as well as anthropogenic activities play a key role in the structure of the phytoplankton communities.
显示更多 [+] 显示较少 [-]Weighing empirical and hypothetical evidence for assessing potential invasive species range limits: a review of the case of Burmese pythons in the USA 全文
2014
Engeman, Richard | Avery, Michael L. | Jacobson, Elliott
Range expansion potential is an important consideration for prioritizing management actions against an invasive species. Understanding the potential for range expansion by invasive reptiles such as the Burmese python can be challenging, because the lack of knowledge on fundamental physiological and behavioral constraints initially forces reliance on modeling to predict hypothetical invasive range potential. Hypothetical predictions for Burmese python range limits in the USA have been highly divergent, from only extreme South Florida and the extreme southern Gulf edge of Texas to a broad swath over the southern third of the continental USA. Empirical observations on python thermal tolerances and behavioral abilities to cope with more temperate temperatures became evident during a cold spell in December 2009–January 2010. We review and highlight important considerations for improving invasive range estimation methodology, deciding between competing range predictions, and the importance of having, and applying, empirical data to aid in decision making.
显示更多 [+] 显示较少 [-]The local and regional atmospheric oxidants at Athens (Greece) 全文
2014
Varotsos, C. A. | Ondov, J. M. | Efstathiou, M. N. | Cracknell, A. P.
In the present study, the investigation of the levels of the local and regional oxidants concentration at Athens, Greece, is attempted by analyzing the observations obtained at an urban and a rural station, during 2001–2011 and 2007–2011, respectively. A progressive increase of the daytime and nighttime average of [NO₂]/[Oₓ] versus [NOₓ] is observed showing a larger proportion of Oₓin the form of NO₂when the level of NOₓincreases. Similar results are observed when studying the variation of mean values of [NO₂]/[NOₓ] versus [NOₓ]. The results obtained when compared with those that have earlier detected elsewhere, revealed similarities and discrepancies that are discussed in detail. The parameterized curves that are presented for the first time in this paper may be used by the air quality planners to track the trends in other cities also, and to understand what is or was driving them.
显示更多 [+] 显示较少 [-]Aerosol optical and physical properties during winter monsoon pollution transport in an urban environment 全文
2014
Verma, S. | Bhanja, S. N. | Pani, S. K. | Misra, A.
We analysed aerosol optical and physical properties in an urban environment (Kolkata) during winter monsoon pollution transport from nearby and far-off regions. Prevailing meteorological conditions, viz. low temperature and wind speed, and a strong downdraft of air mass, indicated weak dispersion and inhibition of vertical mixing of aerosols. Spectral features of WinMon aerosol optical depth (AOD) showed larger variability (0.68–1.13) in monthly mean AOD at short-wavelength (SW) channels (0.34–0.5 μm) compared to that (0.28–0.37) at long-wavelength (LW) channels (0.87–1.02 μm), thereby indicating sensitivity of WinMon AOD to fine aerosol constituents and the predominant contribution from fine aerosol constituents to WinMon AOD. WinMon AOD at 0.5 μm (AOD₀. ₅) and Angstrom parameter ( α) were 0.68–0.82 and 1.14–1.32, respectively, with their highest value in December. Consistent with inference from spectral features of AOD, surface aerosol loading was primarily constituted of fine aerosols (size 0.23–3 μm) which was 60–70 % of aerosol 10- μm (size 0.23–10 μm) concentration. Three distinct modes of aerosol distribution were obtained, with the highest WinMon concentration at a mass median diameter (MMD) of 0.3 μm during December, thereby indicating characteristics of primary contribution related to anthropogenic pollutants that were inferred to be mostly due to contribution from air mass originating in nearby region having predominant emissions from biofuel and fossil fuel combustion. A relatively higher contribution from aerosols in the upper atmospheric layers than at the surface to WinMon AOD was inferred during February compared to other months and was attributed to predominant contribution from open burning emissions arising from nearby and far-off regions. A comparison of ground-based measurements with Moderate Resolution Imaging Spectroradiometer (MODIS) data showed an underestimation of MODIS AOD and α values for most of the days. Discrepancy in relative distribution of fine and coarse mode of MODIS AOD was also inferred.
显示更多 [+] 显示较少 [-]Sorption behavior of dibutyl phthalate and dioctyl phthalate by aged refuse 全文
2014
Fang, Cheng-ran | Long, Yu-yang | Shen, Dong-sheng
Sorption is a fundamental process controlling the transformation, fate, degradation, and biological activity of hydrophobic organic contaminants in the environment. We investigated the kinetics, isotherms, and potential mechanisms for the sorption of two phthalic acid esters (PAEs), dibutyl phthalate (DBP) and dioctyl phthalate (DOP), on aged refuse. A two-compartment first-order model performed better than a one-compartment first-order model in describing the kinetic sorption of PAEs, with a fast sorption process dominating. Both the Freundlich and Dubinin–Astakhov (DA) models fit the sorption isotherms of DBP and DOP, with the DA model being of a better fit over the range of apparent equilibrium concentrations. The values of the fitting parameters (n, b, E) of the PAEs suggest nonlinear sorption characteristics. Higher predicted partition coefficient values and saturated sorption capacity existed in refuse containing larger quantities of organic matter. The sorption capacity of DOP was significantly higher than that of DBP. PAE sorption was dependent on liquid phase pH. Desorption hysteresis occurred in PAE desorption experiments, especially for the long-chain DOP. PAEs may therefore be a potential environmental risk in landfill.
显示更多 [+] 显示较少 [-]A comparative study of metal pollution and potential eco-risk in the sediment of Chaohu Lake (China) based on total concentration and chemical speciation 全文
2014
Liu, Enfeng | Shen, Ji
Total and extractable concentrations of Cu, Pb, and Zn were determined in surface sediments of west Chaohu Lake (China) by HCl-HNO₃-HF-HClO₄digestion and an optimized BCR sequential extraction procedure, respectively. The metal pollution was evaluated by the enrichment factor approach, and the potential eco-risk was evaluated by the sediment quality guideline (SQG) and risk assessment code (RAC) assessments. The results indicated that both total and extractable metal concentrations were highly variable and were affected by sediment properties, even though the sediments were predominantly composed of <63-μm particles (>89 %). Enrichment factors of the metals based on the total and extractable concentrations all showed higher values in the northern lake area and decreasing values towards the south. This distribution indicated an input of anthropogenic metals via the Nanfei River. Anthropogenic Cu, Pb, and Zn in surface sediments showed comparable values for each metal based on the total and extractable concentrations, suggesting that anthropogenic Cu, Pb, and Zn resided predominantly in the extractable fractions. Sediment Cu had low eco-risk, and Pb and Zn had medium eco-risk by the SQG assessment, whereas the eco-risk rankings of Cu, Pb, and Zn were medium, low, and low–high, respectively, by the RAC assessment. Referencing to the labile (dilute acid soluble) metal concentrations, we deduced that the eco-risk of Cu may be largely overestimated by the RAC assessment, and the eco-risk of Pb may be largely overestimated by the SQG assessment. Overall, sediments Cu and Pb may pose low eco-risk, and Zn may pose low–high eco-risk.
显示更多 [+] 显示较少 [-]Effects of Cutrine-Plus® algaecide and predators on wood frog (Lithobates sylvaticus) tadpole survival and growth 全文
2014
Christenson, Tia A. | Horton, Marisa E. | Jackson, Brian C. | Smith, G. R. (Geoffrey R.) | Rettig, Jessica E.
Copper contamination is increasing in many aquatic ecosystems. One mode by which copper can be introduced into aquatic ecosystems is as an algaecide, such as Cutrine-Plus®. Using a mesocosm experiment, we examined the effects of Cutrine-Plus® on wood frog (Lithobates sylvaticus) tadpoles. In addition, we examined how the presence of a nonnative predator the Western mosquitofish (Gambusia affinis) may interact with exposure to Cutrine-Plus®. Exposure to our low and high Cutrine-Plus® treatments had a strong negative effect on the wood frog tadpoles, and survivorship was greatly decreased in the low treatment, and no tadpoles survived in the high treatment. Additionally, the tadpoles that survived the low treatment were significantly smaller than those in the control treatment. Mosquitofish had no effect on the survivorship or growth of wood frog tadpoles, and mosquitofish presence did not have a significant interaction with the Cutrine-Plus® treatments. Cutrine-Plus® clearly had a negative effect on wood frog tadpoles at the concentrations used in our experiment, which were at and below the label-recommended dosages, suggesting that the use of Cutrine-Plus® in natural ponds may have negative consequences for wood frog populations and possibly other amphibians.
显示更多 [+] 显示较少 [-]Industrial metabolism of chlorine: a case study of a chlor-alkali industrial chain 全文
2014
Han, Feng | Li, Wenfeng | Yu, Fei | Cui, Zhaojie
Substance flow analysis (SFA) is applied to a case study of chlorine metabolism in a chlor-alkali industrial chain. A chain-level SFA model is constructed, and eight indices are proposed to analyze and evaluate the metabolic status of elemental chlorine. The primary objectives of this study are to identify low-efficiency links in production processes and to find ways to improve the operational performance of the industrial chain. Five-year in-depth data collection and analysis revealed that system production efficiency and source efficiency continued increasing since 2008, i.e., when the chain was first formed, at average annual growth rates of 21.01 % and 1.01 %, respectively. In 2011, 64.15 % of the total chlorine input was transformed into final products. That is, as high as 98.50 % of the chlorine inputs were utilized when other by-products were counted. Chlorine loss occurred mostly in the form of chloride ions in wastewater, and the system loss rate was 0.54 %. The metabolic efficiency of chlorine in this case was high, and the chain system had minimal impact on the environment. However, from the perspectives of processing depth and economic output, the case study of a chlor-alkali industrial chain still requires expansion.
显示更多 [+] 显示较少 [-]Performance of ANFIS versus MLP-NN dissolved oxygen prediction models in water quality monitoring 全文
2014
Najah, A. | El-Shafie, A. | Karim, O. A. | El-Shafie, Amr H.
We discuss the accuracy and performance of the adaptive neuro-fuzzy inference system (ANFIS) in training and prediction of dissolved oxygen (DO) concentrations. The model was used to analyze historical data generated through continuous monitoring of water quality parameters at several stations on the Johor River to predict DO concentrations. Four water quality parameters were selected for ANFIS modeling, including temperature, pH, nitrate (NO₃) concentration, and ammoniacal nitrogen concentration (NH₃-NL). Sensitivity analysis was performed to evaluate the effects of the input parameters. The inputs with the greatest effect were those related to oxygen content (NO₃) or oxygen demand (NH₃-NL). Temperature was the parameter with the least effect, whereas pH provided the lowest contribution to the proposed model. To evaluate the performance of the model, three statistical indices were used: the coefficient of determination (R ²), the mean absolute prediction error, and the correlation coefficient. The performance of the ANFIS model was compared with an artificial neural network model. The ANFIS model was capable of providing greater accuracy, particularly in the case of extreme events.
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