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Microbial regeneration of spent activated carbon dispersed with organic contaminants: mechanism, efficiency, and kinetic models 全文
2011
Nath, Kaushik | Bhakhar, Mathurkumar S.
Background and purpose Regeneration of spent activated carbon assumes paramount importance in view of its economic reuse during adsorptive removal of organic contaminants. Classical thermal, chemical, or electrochemical regeneration methods are constrained with several limitations. Microbial regeneration of spent activated carbon provides a synergic combination of adsorption and biodegradation. Methods Microorganisms regenerate the surface of activated carbon using sorbed organic substrate as a source of food and energy. Aromatic hydrocarbons, particularly phenols, including their chlorinated derivatives and industrial waste water containing synthetic organic compounds and explosives-contaminated ground water are the major removal targets in adsorption-bioregeneration process. Popular mechanisms of bioregeneration include exoenzymatic hypothesis and biodegradation following desorption. Efficiency of bioregeneration can be quantified using direct determination of the substrate content on the adsorbent, the indirect measurement of substrate consumption by measuring the carbon dioxide production and the measurement of oxygen uptake. Modeling of bioregeneration involves the kinetics of adsorption/desorption and microbial growth followed by solute degradation. Some modeling aspects based on various simplifying assumptions for mass transport resistance, microbial kinetics and biofilm thickness, are briefly exposed. Results Kinetic parameters from various representative bioregeneration models and their solution procedure are briefly summarized. The models would be useful in predicting the mass transfer driving forces, microbial growth, substrate degradation as well as the extent of bioregeneration. Conclusions Intraparticle mass transfer resistance, incomplete regeneration, and microbial fouling are some of the problems needed to be addressed adequately. A detailed techno-economic evaluation is also required to assess the commercial aspects of bioregeneration.
显示更多 [+] 显示较少 [-]Potential influence of confounding factors (size, salinity) on biomarkers in the sentinel species Scrobicularia plana used in programmes monitoring estuarine quality 全文
2011
Tankoua, Olivia Fossi | Buffet, Pierre-Emmanuel | Amiard, J. C. | Amiard-Triquet, C. | Mouneyrac, Catherine | Berthet, Brigitte
INTRODUCTION: To use biomarkers in monitoring programmes, potential confounding factors must be considered. In the clam Scrobicularia plana, the influence of size and salinity on biomarkers at different levels of biological organisation has been examined. MATERIAL AND METHODS: Biochemical (glutathione-S-transferase, lactate dehydrogenase, acetylcholinesterase, digestive enzymes, metallothionein), physiological (energy reserves) and behavioural (burrowing) responses were compared (a) in specimens of different sizes from the Loire estuary; (b) in specimens from the Belon estuary at two sites with salinities of 30.1 or 11.5. RESULTS: Amongst the biomarkers able to reveal pollution effects, several are influenced by the size of the clams (Ag, Cu, Ni and glycogen concentrations, GST and AChE activities, condition indices). Salinity differences induced variations of the same order of magnitude (GST, AChE) or even higher (lactate dehydrogenase, digestive enzymes in the crystalline style) than contamination-induced variations. In burrowing tests, the number of burrowed specimens was similar at both salinities after an experiment time <3 h. CONCLUSIONS: Size is a factor necessarily but easily controlled. Because the weight may be different in clams of identical size, correction factors may be used to minimise the influence of weight changes on biomarkers. A correction factor taking into account salinity levels can also be used. The protein concentrations in the clams did not differ with salinity, a very favourable outcome since all enzyme activities are classically expressed by reference to total protein concentrations. For burrowing tests, the number of burrowed specimens at a particular time is an endpoint that is preferable to measures of burrowing speed.
显示更多 [+] 显示较少 [-]Impact of long-range transport and under-cloud scavenging on precipitation chemistry in East China 全文
2011
Li, Yuhua | Wang, Yan | Ding, Aijun | Liu, Xiaohuan | Guo, Jia | Li, Penghui | Sun, Minghu | Ge, Fuling | Wang, Wenxing
INTRODUCTION: Two hundred twenty-five precipitation samples were collected at high- (summit, 1,534 m ASL) and low-elevation (base, 218 m ASL) sites between 2005 and 2008 in eastern China. The present work focused on the roles of long-range transport and under-cloud/boundary layer scavenging on chemical composition of precipitation collected at the two sites. METHODS: Ionic and trace species were analyzed in 225 precipitation samples. A total of 72 precipitation events occurring simultaneously at the summit and base sites were further examined. Positive matrix factorization (PMF) and backward air mass trajectories were used to identify the sources of precipitation pollutants. RESULTS: Low pH and high concentrations of ionic and trace species were measured at both sites. Inter-correlations for the simultaneous samples at the two sites were poor for trace elements (−0.07~0.47). A several fold increase in major ion (122~546%) and trace element (261~3,302%) concentrations occurred as the rain fell. Approximately 89% of the air masses responsible for the summit precipitation events were of distance origin. Marine salt, crustal material, fossil fuel burning plus secondary products, and metallic-industry-related factors were identified by PMF, contributing 9.7%, 22.8%, 41.8%, and 25.6%, respectively, to the precipitation pollutants at the summit and 13.3%, 31.9%, 39.6%, and 15.2%, respectively, at the base. CONCLUSIONS: Long-range atmospheric transport primarily influenced the high and the low site precipitation was strongly influenced by the under-cloud scavenging process of local boundary layer pollutants. Crustal material and fossil fuel burning plus secondary products were the predominant pollution sources in this region.
显示更多 [+] 显示较少 [-]Biologic impact on the coastal belt of the province of Venice (Italy, Northern Adriatic Sea): preliminary analysis for the characterization of the bathing water profile 全文
2011
Ostoich, Marco | Aimo, Emilia | Fassina, Daniel | Barbaro, Jvan | Vazzoler, Marina | Soccorso, Corrado | Rossi, Chiara
Background, aim and scope This paper presents a preliminary study of the water profile with reference to microbiological parameters, required by Directive 2006/07/EC (European Community 2006) concerning the management of bathing water quality, in the coastal belt of the Province of Venice (Italy, Northern Adriatic Sea). A historical database has been implemented with monitoring data for the period 2000-2006 (data on rivers, bathing and marine coastal waters and on the characterization of Wastewater Treatment Plant (WWTP) discharges) from the institutional activity of Veneto Regional Environmental Prevention and Protection Agency (ARPAV). An integrated areal analysis for the microbiological investigation of homogeneous stretches along the coast of the Province of Venice was performed for a preliminary characterization of the bathing water profile considering water quality status and existing pressure sources. Materials and methods ARPAV is the institutional body responsible for environmental monitoring and control activities. Data were produced from monitoring and controls made available by the Regional Environmental Informative System and extracted and elaborated for the period of interest (2000−2006). Sampling and analysis of microbiological parameters were executed following the official Italian methods in accordance with international procedures (APHA et al. 1998). For the purpose of this study, the coast was divided into eight stretches, which were considered to be homogeneous according to their physical and geographical characteristics. An ANOVA statistical assessment has been performed on stretches I, V and VIII. Results and discussion From the integrated areal analysis of microbiological parameters in the homogeneous stretches along the coast of all the investigated matrices, high mean levels of faecal contamination were found in some cases. The most critical situation amongst the stretches evaluated is to be found in stretch VIII--Ca' Roman, Sottomarina and Isola Verde shores (Southern part of the Province). These results can be widely attributed to pressure sources from the Brenta and Adige rivers, rather than to local contributions. Stretches VI and VII, which correspond to the area from Punta Sabbioni (Cavallino shore N-E) to the Pellestrina shore (S-W), present the best conditions for faecal contamination parameters (low pollution levels). These situations can probably be explained given that WWTPs 7 and 8 have two submarine outfalls at a distance of about 4 km from the coastline and therefore a discharge point which is distant from the bathing and marine coastal monitoring stations; there are also no river mouths in these two stretches. Due to lack of data, it was not possible to implement seasonal assessments. Conclusions This study aimed to develop an integrated areal analysis for biological parameters along the coast over the period 2000-2006 for the identified homogeneous stretches in order to develop a preliminary approach for the characterization of the water profile, as requested by directive 2006/7/EC. From the integrated analysis of the stretches, it is evident that in some cases there are high levels of faecal contamination along the coast which can be caused by river flows which heavily condition the quality of coastal waters as verified with the statistical assessment. Recommendations and perspectives From the preliminary analysis, the submarine outfalls seem to be the best solution to guarantee good bathing water quality on the coast. Nevertheless, it must be observed that this solution cannot overlook the possible impact of the discharges on seawaters intended for a specific use, such as mussel farms with reference to coastal hydrodynamics. Therefore, a sound wastewater dispersion analysis on the discharges of the WWTPs for the identification of the interested area and the level of contamination must be performed; a modelling study on pollution dispersion is complementary to this study (Scroccaro et al. 2009). This analysis highlights the critical stretches as being numbers II and, above all, VIII with particular correlation with the main river mouths. Thus, it is evident that the issue of microbiological impact must be studied following a river basin approach according to the influence of river loads on coastal areas.
显示更多 [+] 显示较少 [-]Petroleum hydrocarbon concentrations in ten commercial fish species along Tamilnadu coast, Bay of Bengal, India 全文
2011
Veerasingam, S. | Venkatachalapathy, R. | Rājjā. | Sudhākar, Es | Rajeswari, V. | Asanulla, R Mohamed | Mohan, R. | Sutharsan, P.
Background, aim, and scope The aim of the present study was to evaluate the distribution of petroleum hydrocarbons in ten commercial fish species and water samples in three estuaries along Tamilnadu coast, Bay of Bengal, India. Materials and methods Fish and water samples collected from Tamilnadu coast, India, were extracted and analyzed for petroleum hydrocarbons by ultraviolet fluorescence (UVF) spectroscopy. Results The petroleum hydrocarbon concentration (PHC) in coastal waters and fish species varied between 2.28 and 14.02 μg/l and 0.52 and 2.05 μg/g, respectively. The highest PHC concentration was obtained in Uppanar estuarine waters (14.02 ± 0.83) and the lowest was observed in Vellar estuarine waters (2.28 ± 0.25). Discussion Among the ten fish species, Sardinella longiceps have high PHC concentration from all the locations. This study suggests that S. longiceps can be used as a good biological indicator for petroleum hydrocarbon pollution in water. Conclusions The concentration of petroleum hydrocarbons in coastal waters along Tamilnadu coast is markedly higher than that in the background, but there is no evidence for its increase in fish of this region. From a public health point, petroleum hydrocarbon residue levels in all fish samples analyzed in this study are considerably lower than the hazardous levels. Recommendations and perspectives At present, as Tamilnadu coastal area is in a rapid development stage of new harbour, chemical industries, power plants, oil exploration and other large-scale industries, further assessment of petroleum hydrocarbons and the various hydrodynamic conditions acting in the region are to be studied in detail and continuous pollution monitoring studies should be conducted for improving the aquatic environment. The results will also be useful for pollution monitoring program along the coastal region and also to check the levels of petroleum hydrocarbons.
显示更多 [+] 显示较少 [-]Toxic effect of tetracycline exposure on growth, antioxidative and genetic indices of wheat (Triticum aestivum L.) 全文
2011
Xie, Xiujie | Zhou, Qixing | Lin, Dasong | Guo, Jianmian | Bao, Yanyu
Introduction More attention has been paid to tetracycline contamination in view of its rapid increasing concentration in the environment. Therefore, it is important to set up rapid, simple, and accurate methods for monitoring tetracycline ecotoxicity. Methods In the present study, a hydroponics experiment was conducted to examine toxic effects of tetracycline at the concentration range of 0.5 to 300 mg L⁻¹ on growth, antioxidative, and genetic indices of wheat (Triticum aestivum L.). Results The results indicated that tetracycline at 0.5-10 mg L⁻¹ could stimulate seed germination, cell mitotic division, and growth of wheat seedlings and did not induce a significant increase in the activity of antioxidative enzymes. However, tetracycline at the high concentrations (10-300 mg L⁻¹) could significantly inhibit these parameters in the concentration-dependent manner, including germination percentage (≥100 mg L⁻¹), shoot height (≥100 mg L⁻¹), root length (≥50 mg L⁻¹), and mitotic index (≥50 mg L⁻¹), and increased the activity of antioxidative enzymes (≥25 mg L⁻¹) in the dose-dependent manner, including superoxide dismutase, catalase, and peroxidase. Tetracycline at 5 mg L⁻¹ and above significantly augmented chromosome aberration frequency and malondialdehyde (MDA) content. On the other hand, MDA has positive correlation with the inhibition rates of seed germination, root length, shoot length, mitotic index, and antioxidative enzyme activities. Conclusion Tetracycline may have potential physiological, biochemical, and genetic toxicity to plant cells, and chromosome aberration and MDA might be sensitive bioindicators for tetracycline contamination than the other plant characteristics.
显示更多 [+] 显示较少 [-]Effect of nuclear power on CO₂ emission from power plant sector in Iran 全文
2011
Kargari, Nargess | Mastouri, Reza
INTRODUCTION: It is predicted that demand for electricity in Islamic Republic of Iran will continue to increase dramatically in the future due to the rapid pace of economic development leading to construction of new power plants. At the present time, most of electricity is generated by burning fossil fuels which result in emission of great deal of pollutants and greenhouse gases (GHG) such as SO₂, NOₓ, and CO₂. The power industry is the largest contributor to these emissions. Due to minimal emission of GHG by renewable and nuclear power plants, they are most suitable replacements for the fossil-fueled power plants. However, the nuclear power plants are more suitable than renewable power plants in providing baseload electricity. The Bushehr Nuclear Power Plant, the only nuclear power plant of Iran, is expected to start operation in 2010. This paper attempts to interpret the role of Bushehr nuclear power plant (BNPP) in CO₂ emission trend of power plant sector in Iran. MATERIALS AND METHODS: In order to calculate CO₂ emissions from power plants, National CO₂ coefficients have been used. The National CO₂ emission coefficients are according to different fuels (natural gas, fuels gas, fuel oil). RESULTS AND DISCUSSION: By operating Bushehr Nuclear Power Plant in 2010, nominal capacity of electricity generation in Iran will increase by about 1,000 MW, which increases the electricity generation by almost 7,000 MWh/year (it is calculated according to availability factor and nominal capacity of BNPP). CONCLUSIONS: Bushehr Nuclear Power Plant will decrease the CO₂ emission in Iran power sector, by about 3% in 2010.
显示更多 [+] 显示较少 [-]Interpreting methamphetamine levels in a high-use community 全文
2011
Chiaia-Hernandez, Aurea C. | Banta-Green, Caleb J. | Field, Jennifer A.
INTRODUCTION: Illicit drug use is a largely hidden phenomenon, and population measures are notoriously problematic. Reliable and valid data for local, regional, and national public health and other interventions are needed. METHODS: To address this information, we examined temporal trends within and across weeks in methamphetamine (MA) in a single location in order to inform a sampling plan for understanding long-term trends in MA use based on sampling raw influent to wastewater treatment plants. The measured concentrations in the wastewater are used to estimate the total mass of MA consumed rather than the number of doses due to the uncertainty surrounding methamphetamine purity, mass of MA per dose, and the number of doses used per day. RESULTS: Results from a region with high levels of MA use indicate that MA levels do not differ significantly between weekdays and weekends (p = 0.1), consistent with a predominately regular, daily use pattern use. The potential contribution of legal sales of D: - and L: -MA to the mass of MA consumed within the community was estimated to range from 3–8%. Limitations and uncertainties associated with estimating the mass of MA consumption include small contributions of prescription and over-the-counter drugs that are metabolized to MA as well as measurement and sampling variability.
显示更多 [+] 显示较少 [-]An approach to determining potential surrogates for analyzing ecological patterns of planktonic ciliate communities in marine ecosystems 全文
2011
Xu, Henglong | Jiang, Yong | Zhang, Wei | Zhu, Mingzhuang | Al-Rasheid, Khaled A. S.
INTRODUCTION: In order to identify a potential surrogate of planktonic ciliate communities for marine bioassessments and evaluating biological conservations, the different taxonomic/numerical resolutions and taxa as surrogates were studied in Jiaozhou Bay, northern China during a 1-year cycle (June 2007–May 2008). MATERIALS AND METHODS: Samples were collected biweekly from a depth of 1 m at each of five sites. A range of physicochemical parameters were also measured in order to determine water quality. RESULTS: The genus- and family-level resolutions maintained sufficient information to evaluate the ecological patterns of the ciliate communities in response to environmental status. The non-loricate oligotrichous ciliate assemblages in both abundance and occurrence may be used as a surrogate of planktonic ciliate communities. Heavy data transformations were an optimal strategy for the species level of planktonic ciliates, while mild data transformations were for the higher. The ordination patterns based on species biomass, occurrence, and biomass/abundance ratio matrices were significantly consistent with that of species abundance data. CONCLUSION: The results suggest that the use of simplifications at both taxonomic and numerical resolutions are time-efficient and would allow improving sampling strategies of large spatial/temporal scale monitoring programs and biological conservation researches in the marine ecosystem with a relative paucity of scientists.
显示更多 [+] 显示较少 [-]Chlorpyrifos degradation by the cyanobacterium Synechocystis sp. strain PUPCCC 64 全文
2011
Singh, D. P. | Khattar, J. I. S. | Nadda, J. | Singh, Y. | Garg, A. | Kaura, Ainna. | Gulati, A.
BACKGROUND, AIM, AND SCOPE: Indiscriminate use of insecticides leads to environmental problems and poses a great threat to beneficial microorganisms. The aim of the present work was to study chlorpyrifos degradation by a rice field cyanobacterium Synechocystis sp. strain PUPCCC 64 so that the organism is able to reduce insecticide pollution in situ. MATERIAL AND METHODS: The unicellular cyanobacterium isolated and purified from a rice field was identified by partial 16S rRNA gene sequence as Synechocystis sp. strain PUPCCC 64. Tolerance limit of the organism was determined by studying its growth in graded concentrations (2.5–20 mg/L) of chlorpyrifos. Chlorpyrifos removal was studied by its depletion from the insecticide supplemented growth medium, and its biodegradation products were identified in the cell extract, biomass wash, and growth medium. RESULTS AND DISCUSSION: The organism tolerated chlorpyrifos up to 15 mg/L. Major fraction of chlorpyrifos was removed by the organism during the first day followed by slow uptake. Biomass, pH, and temperature influenced the insecticide removal and the organism exhibited maximum chlorpyrifos removal at 100 mg protein/L biomass, pH 7.0, and 30°C. The cyanobacterium metabolized chlorpyrifos producing a number of degradation products as evidenced by GC-MS chromatogram. One of the degradation products was identified as 3,5,6-trichloro-2-pyridinol. CONCLUSION AND RECOMMENDATIONS: Present study reports the biodegradation of chlorpyrifos by Synechocystis sp. Biodegradation of the insecticide by the cyanobacterium is significant as it can be biologically removed from the environment. The cyanobacterium may be used for bioremediation of chlorpyrifos-contaminated soils.
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