The world is experiencing an energy crisis and environmental issues due to the depletion of fossil fuels and the continuous increase in carbon dioxide concentrations. Microalgal biofuels are produced using sunlight, water, and simple salt minerals. Their high growth rate, photosynthesis, and carbon dioxide sequestration capacity make them one of the most important biorefinery platforms. Furthermore, microalgae's ability to alter their metabolism in response to environmental stresses to produce relatively high levels of high-value compounds makes them a promising alternative to fossil fuels. As a result, microalgae can significantly contribute to long-term solutions to critical global issues such as the energy crisis and climate change. The environmental benefits of algal biofuel have been demonstrated by significant reductions in carbon dioxide, nitrogen oxide, and sulfur oxide emissions. Microalgae-derived biomass has the potential to generate a wide range of commercially important high-value compounds, novel materials, and feedstock for a variety of industries, including cosmetics, food, and feed. This review evaluates the potential of using microalgal biomass to produce a variety of bioenergy carriers, including biodiesel from stored lipids, alcohols from reserved carbohydrate fermentation, and hydrogen, syngas, methane, biochar and bio-oils via anaerobic digestion, pyrolysis, and gasification. Furthermore, the potential use of microalgal biomass in carbon sequestration routes as an atmospheric carbon removal approach is being evaluated. The cost of algal biofuel production is primarily determined by culturing (77%), harvesting (12%), and lipid extraction (7.9%). As a result, the choice of microalgal species and cultivation mode (autotrophic, heterotrophic, and mixotrophic) are important factors in controlling biomass and bioenergy production, as well as fuel properties. The simultaneous production of microalgal biomass in agricultural, municipal, or industrial wastewater is a low-cost option that could significantly reduce economic and environmental costs while also providing a valuable remediation service. Microalgae have also been proposed as a viable candidate for carbon dioxide capture from the atmosphere or an industrial point source. Microalgae can sequester 1.3 kg of carbon dioxide to produce 1 kg of biomass. Using potent microalgal strains in efficient design bioreactors for carbon dioxide sequestration is thus a challenge. Microalgae can theoretically use up to 9% of light energy to capture and convert 513 tons of carbon dioxide into 280 tons of dry biomass per hectare per year in open and closed cultures. Using an integrated microalgal bio-refinery to recover high-value-added products could reduce waste and create efficient biomass processing into bioenergy. To design an efficient atmospheric carbon removal system, algal biomass cultivation should be coupled with thermochemical technologies, such as pyrolysis.
Organochlorine contamination in the Mediterranean coastal environment of Egypt was assessed based on 26 surface sediments samples collected from several locations on the Egyptian coast, including harbors, coastal lakes, bays, and estuaries. The distribution and potential ecological risk of contaminants is described. Organochlorine compounds (OCs) were widely distributed in the coastal environment of Egypt. Concentrations of PCBs, DDTs, and chloropyrifos ranged from 0.29 to 377 ng g−1 dw, 0.07 to 81.5 ng g−1 dw, and below the detection limit (DL) to 288 ng g−1 dw, respectively. Other organochlorinated pesticides (OCP) studied were 1–2 orders of magnitude lower. OCP and PCBs had higher concentrations at Burullus Lake, Abu Qir Bay, Alexandria Eastern Harbor, and El Max Bay compared to other sites. OCP and PCB contamination is higher in the vicinity of possible input sources such as shipping, industrial activities and urban areas. PCB congener profiles indicated they were derived from more than one commercially available mixture. The ratios of commercial chlordane and heptachlor metabolites indicate historical usage; however, DDT and HCHs inputs at several locations appear to be from recent usage. The concentrations of PCBs and DDTs are similar to those observed in sediments from coastal areas of the Mediterranean Sea. Ecotoxicological risk from DDTs and PCBs is greatest in Abu Qir Bay, Alexandria Harbor, and El-Max Bay. 相似文献
A multivariate statistical technique, cluster analysis, was used to assess the logged surface water quality at an irrigation project at Al-Fadhley, Eastern Province, Saudi Arabia. The principal idea behind using the technique was to utilize all available hydrochemical variables in the quality assessment including trace elements and other ions which are not considered in conventional techniques for water quality assessments like Stiff and Piper diagrams. Furthermore, the area belongs to an irrigation project where water contamination associated with the use of fertilizers, insecticides and pesticides is expected. This quality assessment study was carried out on a total of 34 surface/logged water samples. To gain a greater insight in terms of the seasonal variation of water quality, 17 samples were collected from both summer and winter seasons. The collected samples were analyzed for a total of 23 water quality parameters including pH, TDS, conductivity, alkalinity, sulfate, chloride, bicarbonate, nitrate, phosphate, bromide, fluoride, calcium, magnesium, sodium, potassium, arsenic, boron, copper, cobalt, iron, lithium, manganese, molybdenum, nickel, selenium, mercury and zinc. Cluster analysis in both Q and R modes was used. Q-mode analysis resulted in three distinct water types for both the summer and winter seasons. Q-mode analysis also showed the spatial as well as temporal variation in water quality. R-mode cluster analysis led to the conclusion that there are two major sources of contamination for the surface/shallow groundwater in the area: fertilizers, micronutrients, pesticides, and insecticides used in agricultural activities, and non-point natural sources. 相似文献
New comprehensive numerically solved 1D and 2D absorption rate/kinetics models have been developed, for the first time, to interpret the experimental kinetic data obtained with a laminar jet apparatus for the absorption of carbon dioxide (CO2) in CO2 loaded mixed solutions of mixed amine system of methyldiethanolamine (MDEA) and monoethanolamine (MEA). Three MDEA/MEA weight ratios ranging from 27/03 to 23/07, over a concentration range of 2.316–1.996 kmol/m3 for MDEA and of 0.490–1.147 kmol/m3 for MEA were studied. The models take into account the coupling between chemical equilibrium, mass transfer, and the chemical kinetics of all possible chemical reactions involved in the CO2 reaction with MDEA/MEA solvent. The partial differential equations of the 1D model were solved by two numerical techniques; the finite difference method (FDM) based on in-house coded Barakat–Clark scheme and the finite element method (FEM) based on COMSOL software. The FEM comprehensive model was then used to solve the set of partial differential equations in the 2D cylindrical coordinate system setting. Both FDM and FEM produced very accurate results for both the 1D and 2D models, which were much better than our previously published simplified model. The reaction rate constant obtained for MEA blended into MDEA at 298–333 K was kMEA = 5.127 × 108 exp(−3373.8/T). In addition, the 2D model, for the first time, has provided the concentration profiles of all the species in both the radial and axial directions of the laminar jet, thereby enabling an understanding of the correct sequence in which the reaction steps involved in the reactive absorption of CO2 in aqueous mixed amines occur. 相似文献
Landfills are sources of groundwater and soil pollution due to the production of leachate and its migration through refuse.
This study was conducted in order to determine the extent of groundwater and soil pollution within and around the landfill
of Seri Petaling located in the State of Selangor, Malaysia. The condition of nearby surface water was also determined. An
electrical resistivity imaging survey was used to investigate the leachate production within the landfill. Groundwater geochemistry
was carried out and chemical analysis of water samples was conducted upstream and downstream of the landfill. Surface water
was also analyzed in order to determine its quality.
Soil chemical analysis was performed on soil samples taken from different locations within and around the landfill in the
vadose zone (unsaturated zone) and below the water table (in the soil saturated zone). The resistivity image along line L–L1 indicated the presence of large zones of decomposed waste bodies saturated with highly conducting leachate. Analysis of trace
elements indicated their presence in very low concentrations and did not reflect any sign of heavy metal pollution of ground
and surface water or of soil.
Major ions represented by Na, K, and Cl were found in anomalous concentrations in the groundwater of the downstream bore hole,
where they are 99.1%, 99.2%, and 99.4%, respectively, higher compared to the upstream bore hole. Electrical conductivity (EC)
was also found in anomalous concentration downstream. Ca and Mg ions represent the water hardness (which is comparatively
high downstream). There is a general trend of pollution towards the downstream area. Sulfates (SO4) and nitrates (NO3) are found in the area in low concentrations, even below the WHO standards for drinking water, but are significantly higher
in the surface water compared to the groundwater. Phosphate (PO4) and nitrite (NO2), although present in low levels, are significantly higher at the downstream. There is no significant difference in the amount
of fluoride (F) in the different locations. In the soil vadose zone, heavy metals were found to be in their typical normal
ranges and within the background concentrations. Soil exchangeable bases were significantly higher in the soil saturated zone
compared to the vadose zone, and no significant difference was obtained in the levels of inorganic pollutants. With the exception
of Cd, the concentration ranges of all trace elements (Cu, Zn, Cr, Pb, and Ni) of Seri Petaling landfill soils were below
the upper limits of baseline concentrations published from different sources. 相似文献
Catalytic activity of spinel ferrite in breaking down toxic dye materials are promising due to their uniqueness. In this study, aluminum-doped copper zinc ferrite, Cu0.4Zn0.6-xAlxFe2O4 (x = 0.0, 0.2, 0.4, 0.6), a catalyst for toxic dye degradation is synthesized through chemical co-precipitation route. The formation of the spinel ferrite catalyst is initially confirmed by Fourier transform infrared spectra, which shows the frequency of metal-oxygen bond vibration at 539 and 427 cm−1 attributed to the tetrahedral and octahedral sites respectively. Higher intensity sharp peak of X-ray diffraction for (311) plane is the evidence for the phase purity and the formation of spinel ferrite. The crystallite size is found to decrease with the increase of Al3+ ion. The surface structure of the obtained particles is investigated using a scanning electron microscope. Analyses of the material's magnetic characteristics using a vibrating sample magnetometer (VSM) revealed that it is, in fact, a soft magnet, as evidenced by the loop of its hysteresis, which is narrow. The catalytic degradation of methylene blue dye under the mechanism of the photo-Fenton process is studied with the obtained spinel ferrites and the result is found to be as high as 96.5%. The process follows pseudo-second order kinetics and the Langmuir isotherm. 相似文献
Summary The influence of pulsed magnetic fields (PMF) on the properties of nervous tissue was investigated. Hippocampal slices or
synaptosomes obtained from hippocampal tissue were used as model systems. The amplitude of potentials recorded in vitro from one of the hippocampal pathways (Schaffer collaterals that use glutamate as a neurotransmitter) was employed as a measure
of the influence of magnetic fields on synaptic efficiency. The synaptic glutamate turnover and radioactive calcium accumulation
were used as markers of the PMF influence on biochemistry of synaptic mechanisms. The exposure of hippocampal slices for 30
min to PMF amplified evoked potentials. While the frequency of 0.16 Hz exerted the strongest effect, lower (0.01, 0.07, 0.03
Hz) and higher (0.5 Hz) frequencies were much less effective. The enhancement of the neuronal excitability was correlated
with significant increase in the neuronal spontaneous activity mediated by electrical synapses. The PMF-induced changes in
the excitability of the tissue were accompanied by an increase in the synaptic turnover of glutamate. The release of radioactive
D-Aspartate (a glutamate analog used as a marker for glutamate turnover) from the slices, and its uptake by synaptosomes were
enhanced, and reduced respectively, following the stimulation with pulsed magnetic fields. The frequency which was the most
efficient in amplification of evoked potentials (0.16 Hz) was also the most effective in the modulation of the release and
uptake processes. The PMF-induced changes in neurotransmitter turnover coincided with an increase in 45Ca2+ accumulation observed in hippocampal slices exposed to PMF. 相似文献
ABSTRACTThis article aims to study the influence of the addition of graphene oxide nanoparticles (GO) to diesel/higher alcohols blends on the combustion, emission, and exergy parameters of a CI engine under various engine loads. The higher alcohols mainly n-butanol, n-heptanol, and n-octanol are blended with diesel at a volume fraction of 50%. Then, the 25 and 50 mg/L concentrations of GO are dispersed into diesel/higher alcohols blends using an ultrasonicator. The GO structures are examined using TEM, TGA, XRD and FTIR. The findings show that there is a reduction in pmax. and HRR when adding higher alcohols with diesel fuel. Regarding engine emission, there is a significant improvement in emissions formation with adding higher alcohols. The addition of GO into diesel/higher alcohols blends improves the brake thermal efficiency by 15%. Moreover, the pmax. and HRR are both enhanced by 4%. The CO, UHC and smoke formation are reduced considerably by 40%, 50 and 20%, respectively, while NOx level is increased by 30% with adding GO. Finally, adding high percentages of n-butanol, n-heptanol, and n-octanol with diesel fuel with the presence of GO has the potential to achieve ultra-low CO, UHC, and smoke formation meanwhile keeping high thermal efficiency level. 相似文献
Incinerator bottom ash (IBA) is a residual produced from incinerating municipal solid waste. In the past, IBA presented a big waste disposal problem; however, various recycling approaches have been adopted in recent years to mitigate this problem, as well as to provide a useful alternative to using primary aggregate resources. The use of IBA as an alternative to conventional aggregates in different civil engineering construction applications helps to conserve premium grade aggregate supplies; however, when IBA is in contact with water in the field, as a consequence of precipitation events or changes in water table, elements, such as salts and heavy metals, may be released to the soil and ground water. In this work, IBA waste was mixed with limestone aggregate to produce a blend with acceptable mechanical properties and minimum environmental risks for use as road foundation. The study focused on evaluating potential environmental impacts of some constituents, including sulphate, chloride, sodium, copper, zinc and lead in IBA blends using a lysimeter as a large scale leaching tool. Moreover, a specific scenario simulating field conditions was adopted in the lysimeter to assess the potential impact of changing conditions, such as IBA content in the blend, liquid to solid ratio (L/S) and pH value, on long-term release of heavy metals and salts. Then, numerical modelling was used to predict the release of the aforementioned constituents from IBA based on initial measurement of intrinsic material properties and the kinetic desorption process concept. Experimental results showed that zinc and lead were released in very low concentrations but sodium and sulphate were in high concentrations. The control limestone only blend also demonstrated low release concentrations of constituents in comparison to IBA blends, where constituent concentrations increased with increase in IBA content. Experimental results were compared with numerical results obtained using a non-equilibrium desorption model. Good agreement was found between the two sets of data. 相似文献
In natural environment, semiochemicals are involved in many interactions between the different trophic levels involving insects, plants and hosts for parasitoids or prey for predators. These volatile compounds act as messengers within or between insect species, inducing particular behaviours, such as the localisation of a source of food, the orientation to an adequate oviposition site, the selection of a suitable breeding site and the localisation of hosts or prey. In this sense, bacteria have been shown to play an important role in the production of volatile compounds which ones act as semiochemicals. This review, focusing on the semiochemically mediated interactions between bacteria and insects, highlights that bacterial semiochemicals act as important messengers for insects. Indeed, in most of the studies reported here, insects respond to specific volatiles emitted by specific bacteria hosted by the insect itself (gut, mouthparts, etc.) or present in the natural environment where the insect evolves. Particularly, bacteria from the families Enterobacteriaceae, Pseudomonaceae and Bacillaceae are involved in many interactions with insects. Because semiochemicals naturally produced by bacteria could be a very interesting option for pest management, advances in this field are discussed in the context of biological control against insect pests. 相似文献