Concentrations and sources of pesticides and PCBs in surficial sediments of the Red Sea coast, Egypt

AbstractSixteen surface sediments from the Egyptian coast of the Red Sea were collected and studied for organochlorine contamination. This research was endeavored to study sources, concentrations and risk factors of pesticides and PCBs in the surficial sediments collected from the studied locations. The sediments in the studied areas are predominantly sand. The most abundant PCB congeners detected in the investigated sediment samples of the Red Sea proper were a total of PCB 52 and a total of PCB 138 (225 and 465ngkg−1drywt., respectively). Meanwhile, in the Aqaba Gulf the most abundant PCB congener was a total of PCB 138 (226ngkg−1drywt.). At the Suez Gulf, the most abundant PCB congeners were a total of PCB 180 and 153 (127 and 103ngkg−1drywt., respectively). The input of direct industrial and domestic discharge in most of the contaminated zones of the studied area resulted in a larger concentration of total PCB 52, 138, 153 and 180. The results obtained showed fairly low levels of pesticide residues. The most dominant pollutants were the HCHs and DDTs, high proportions of α-HCH over γ-HCH isomer indicated less recent input of lindane. The α-HCH/γ-HCH ratios in most of the studied locations are slightly less than those in technical-grade HCH mixture (66.5% α isomer, 11.4% β isomer, 15.2% γ isomer (lindane), 6.4% δ isomer, and 0.5% other isomers) indicating that there was less input of lindane in the past several years. This study clearly indicates that PCB concentrations, DDTs, cyclodienes, HCHs were much lower than those recorded by the international organization

BACH ARRAY LINEAR GENERATOR FOR WAVE ENERGY CONVERTERS

linear generators have been proposed as a proper power takeoff system for direct-drive wave energy conversion. Coupled directly to a reciprocating wave energy device, it was declared that linear generators could be a valuable replacement for hydraulic and pneumatic systems. In this paper, the design and performance evaluation of permanent magnet linear generator that implements Halbach array arrangement is established. The designed generator is suitable for direct energy extraction from sea waves at small wave amplitude. The electromagnetic design is performed using finite element method and space harmonic analysis. A comparative study is performed between Halbach array and conventional air-cored linear generators to show the effectiveness of the proposed design. The equivalent circuit based model is utilized to investigate the dynamic performance of the Halbach array generator. The simulated dynamic performance of the designed generator clarifies that the implementation of Halbach array arrangement would improve energy extraction and voltage waveform

Optimal Sizing of Standalone PV-Wind Hybrid Energy System in Rural Area North Egypt

This paper studies the sizing of stand-alone renewable energy system applied in rural areas in the north of Egypt. The available renewable energy sources in these areas are investigated to be integrated to supply the different types of electrical loads. The quality and quantity of these sources over various weather and climate changes are studied to construct a robust energy system. The load demand in such areas is determined according to all activities require electrical energy. This study considers the different economic levels and technologies which affect the load demand value. The technique and economical indices required to obtain the optimal are investigated and applied in the various estimated cases. The genetic algorithm (GA) technique is applied to determine the size and number of photovoltaic panels and wind turbines. The obtained solution takes into account the loss of power supply probability and the minimization of system cost. This study presents an essential phase in the sustainable development of such rural areas

The Effect of Mineral Pigments on Mechanical Properties of Concrete

 Pigmented concrete exhibits artesian properties in addition to ordinary concrete properties, explicitly high strength, excellent durability, and weather resistance. However, the influence of several parameters that affect the characteristics of colored concrete should be studied; extensively. In this paper, the impact of the w/b (water/binder) ratio using color pigments on the mechanical properties such as compressive and flexural strengths of colored cement mortar prisms and cubes experimentally investigated. The experimental program included 21 mixes with six cubes and three flexural prisms specimens for assessing compressive and flexural strength, respectively. The blends included different water/binder ratios with values of 0.4, 0.5, and 0.6, in addition to several color pigments as a partial replacement of cement. The percentage of replacements altered between 0, 2.5%, 5% and 7.5% with two different shades of pigments consisting of red iron and green chromium oxide. Based on the experimental results, empirical expressions were generated based on Abram’s law to assess the relationship between the compressive strength of colored concrete and w/b ratio. The results revealed that the compressive and flexural strength of colored concrete is influenced by w/b ratio and partially replacement percentage of cement by color pigment not proportionally direct. Furthermore, the shade of pigments also has a different impact as well

Spotlight on mechanical properties of autogenic self-healing of concrete

Self-healing concrete is defined as the concrete ability to recover its cracks. Cracks in concrete are a common phenomenon that reveals adverse effects on a structure’s integrity, durability, and serviceability due to its relatively low tensile strength. Recently, self-healing techniques have been developed to ensure crack recovery and implemented in strategic structures to optimize maintenance costs. This study aims to highlight one self-healing technique type named the “autogenic self-healing technique”. Four mixes including the control were designed and established to examine the self-healing mechanism when using mineral admixtures such as fly ash and polyvinyl alcohol fiber (PVA fiber) at various percentiles. All mixes encountered 20% cement volume replacement by fly ash with various PVA fiber percentile additions: 1, 1.5, and 2%. Compressive, flexural, and tensile strengths were examined after cracking and failure. The cube prism and cylinder specimens were cracked and then cured at 28 days for testing to failure. The results showed that the compressive strength recovered in mixes with 1.5 and 2% PVA. This work provides promising insight on cracks healing or recovery to a certain extent

Comprehensive risk assessment of heavy metals in surface sediments along the Egyptian Red Sea coast

AbstractThe contamination of heavy metals (Fe, Zn, Mn, Cu, Ni, Pb, Cd, Co, Cr, and Hg) in 16 surface sediment samples collected from the Suez Gulf, Aqaba Gulf and the Red Sea Proper was studied to evaluate their distribution and potential ecological risk. The concentrations of the studied metals decreased in the order of Fe>Mn>Zn>Cr>Ni>Co>Pb>Cu>Cd>Hg (3490.2, 115.77, 28.66, 18.47, 11.40, 9.70, 3.26, 1.94, 6.10, 0.02μg/g dry weight). Based on the effect-range classification (ERL–ERM, TEL–PEL, LEL–SEL), the studied heavy metals did not pose any environmental risks for all investigated stations except Marsa Alam and El-Quseir stations, which may pose an environmental risk for Cr and Ni. The ecological risk assessment for metals in surface sediments was evaluated using the metal pollution index (MPI), geoaccumulation index (Igeo), and potential ecological risk index (ERI). Multivariate techniques including Pearson correlation, hierarchical cluster and principal components analysis were used to evaluate the metal sources

Techno-Economic Analysis of ZnO Nanoparticles Pretreatments for Biogas Production from Barley Straw

The aim of this study was to analyze the effect of ZnO nanoparticles (ZnO NPs) on the biogas production from mechanically treated barley straw and to perform a techno-economic analysis based on the costs assessment and on the results of biogas production. The structural changes of mechanically pretreated barley straw were observed using FTIR, XRD, TGA, and SEM. Additionally, both green ZnO NPs prepared from red alga (Antithamnion plumula) extract and chemically prepared ZnO NPs were characterized by FTIR, XRD, SEM, and TEM, surface area, and EDX. The results revealed that the biogas production was slightly improved by 14.9 and 13.2% when the barley straw of 0.4 mm was mechanically pretreated with 10 mg/L of both green and chemical ZnO NPs and produced 390.5 mL biogas/g VS and 385 mL biogas/g VS, respectively. On the other hand, the higher concentrations of ZnO NPs equal to 20 mg/L had an inhibitory effect on biogas production and decreased the biogas yield to 173 mL biogas/g VS, which was less than the half of previous values. It was also clear that the mechanically treated barley straw of 0.4 mm size presented a higher biogas yield of about 340 mL/g VS, in comparison to 279 mL biogas/g VS of untreated biomass. The kinetic study showed that the first order, modified Gompertz and logistic function models had the best fit with the experimental data. The results showed that the nanoparticles (NPs) of the mechanically treated barely straw are a suitable source of biomass for biogas production, and its yields are higher than the untreated barley straw. The results of the cost-benefit analysis showed that the average levelized cost of energy (LCOE), adopting the best treatments (0.4 mm + 10 mg/L ZnO), is 0.21 €/kWh, which is not competitive with the other renewable energy systems in the Egyptian energy market

Silica fume and crumb rubber as partial replacement of cement and fine aggregate concrete

This study investigated nine mixes containing 0 or 15% silica fume as the cement replacement and 0 or 10% treated and untreated crumb rubber as the fine aggregate replacement. The fresh and mechanical properties of these concrete mixes were correlated with non-destructive test results including rebound hammer and Ultrasonic Pulse velocity (UPV). One curing scheme was adopted here in this study which was normal curing. Microstructure characterization was carried out using X-ray diffraction Analysis (XRD) and Scanning Electron Microscope (SEM). The XRD showed that the crumb rubber must be washed in clean water after pretreatment with sodium hydroxide (NaOH) to avoid ettringite formation in the concrete pores. The results showed that combining the silica fume and crumb rubber enhanced the compressive strength of the rubberized concrete. The rebound hammer numbers were closely correlated linearly with the compressive strength of the test mixes

Mechanical properties and air permeability of concrete containing waste tires extracts

The safe disposal of waste tires has been seen as having a negative impact on the environment. To mitigate this impact, the components of waste tires can be used in the production of green concrete. This study explores the effects of the curing and drying regime on the mechanical properties and permeation characteristics of concrete containing both crumbed rubber and steel fibers that are removed from waste tires. Five concrete mixes were designed, and concrete cubes, cylinders, and prisms were cast using waste tires extracts. Crumb rubber was treated by submersion in sodium hydroxide and then used to partially replace 10% and 30% of fine aggregates in the concrete mix. Extracted steel fibers were added at the rate of 1% and 2% per volume of each mix. Compressive and indirect splitting tensile as well as flexural strengths were conducted after normal curing while observing several drying conditions. Additionally, air permeability was assessed using a portable apparatus that was developed to assess permeability easily. For the concrete test specimens containing 10% partial replacement of fine aggregate by crumb rubber and 1% steel fibers, it was discovered that the splitting tensile strength and flexural strength were higher than that of the control mix by 21% and 22.6%, respectively. For specimens that included the 10% crumb rubber and 1% steel fibers, when exposed to oven drying at 105°C for 12 h, the compressive strength results increased by 17% compared with the control specimens exposed to the same conditions. Unlike the compressive strength results, the splitting tensile and flexural strength results decreased after exposing the specimens to elevated temperature. The addition of crumb rubber and steel fibers as a partial fine-aggregate replacement resulted in increasing the air permeability of the concrete to different degrees depending on the percentages used. The oven-drying curing regime improved the permeability by reducing it in specimens containing the 10% crumb rubber and 1% steel fibers as indicated by increasing their permeability time index by 15% when compared with air-dried specimens. Using waste tire extracts as a partial replacement of concrete fine aggregate can be recommended for both indoor and outdoor applications. This study showed that this was a viable, economic, and environmentally friendly method for reducing carbon footprint

PERMEATION CHARACTERISTICS AND DURABILITY ASPECTS FOR SUSTAINABLE CONCRETE

This study investigates the durability indicators for sustainable concrete produced by adding both crumbed rubber and steel fibres that are removed from waste tyres to the concrete mixes. Crumb rubber was treated by submersion in sodium hydroxide and then used to partially replace 10% and 30% of fine aggregates in the concrete mix. Extracted steel fibres were added at the rate of 1% and 2% per volume of each mix. The compressive strength was recorded, and a non-destructive air permeability test was used to assess permeation characteristics of studied specimens and to correlate the results with compressive strength results. It was found that with the increase in the steel fibres percentage while keeping the rubber content constant resulted in increased compressive strength of concrete. Rubberized concrete of 10% crumb rubber and 1% steel fibres exposed to oven drying at 105°C for 12 hours exhibited an increase in compressive strength. The addition of crumb rubber and steel fibres as a partial fine aggregate replacement resulted in increasing the air permeability of the concrete to different degrees depending on the percentages used. This study showed that waste tyres extracts can be a viable, economic, and environmentally friendly method for obtaining durable and sustainable concrete